Publications by authors named "Gideon Wolfaardt"

43 Publications

A two-year study of emerging micro-pollutants and drugs of abuse in two Western Cape wastewater treatment works (South Africa).

Chemosphere 2021 Jul 7;285:131460. Epub 2021 Jul 7.

Department of Microbiology, Stellenbosch University, Stellenbosch, 7600, South Africa; Department of Chemistry and Biology, Ryerson University, Toronto, ON, M5B 2K3, Canada. Electronic address:

This study evaluated the occurrence and fate of fourteen contaminants of emerging concern (CECs) at two South African wastewater treatment works (WWTW). Daily loads of the drug targets were calculated in the aqueous phase of influent- and effluent wastewater to evaluate their fate at the treatment works, along with population-normalised daily loads in raw influent wastewater to identify community-wide substance use patterns in the two study areas. Environmental risk characterisation of the CECs at WWTW effluent discharge was done using conventional risk quotient (RQ) estimations. A significant reduction of most CECs was observed at both WWTW locations, except for some that have been previously recorded to persist through various WWTW processes globally, including the illicit drug methaqualone that was reported here for the first time to evaluate its fate during wastewater treatment, substance use trends, and potential toxicological risk. Moderate-to high-RQs were estimated for several target CECs during the sampling period for both treatment facilities. The results presented here suggest the need for a multi-disciplinary approach to WWTW monitoring of CECs and highlight the need for further refinement of risk assessment approaches to mitigate recalcitrant- or pseudo-persistent CECs in wastewater discharge. Such refinement should include: (1) identifying the potential ecological risk on a wider range of sentinel indicators, (2) interaction of CECs with various biochemical pathways (including sub-lethal toxicity responses), (3) identifying the persistence and toxicological risks of breakdown products and (4) partitioning of CECs in the aqueous environment and/or bioaccumulation in freshwater biota.
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http://dx.doi.org/10.1016/j.chemosphere.2021.131460DOI Listing
July 2021

Draft Genome Sequence of sp. Strain 260, Isolated from a Uranium Tailings Management Facility in Northern Saskatchewan, Canada.

Microbiol Resour Announc 2021 Jul 1;10(26):e0036021. Epub 2021 Jul 1.

Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

The 3.9-Mbp draft genome sequence of sp. strain 260, which was isolated from a uranium tailings management facility, is reported. The sequence may help determine the bioremediation potential of this strain and facilitate further research aimed at a better understanding of the hypertolerance of this genus to extreme conditions.
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http://dx.doi.org/10.1128/MRA.00360-21DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8248859PMC
July 2021

Interaction between CO2-consuming autotrophy and CO2-producing heterotrophy in non-axenic phototrophic biofilms.

PLoS One 2021 15;16(6):e0253224. Epub 2021 Jun 15.

Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada.

As the effects of climate change become increasingly evident, the need for effective CO2 management is clear. Microalgae are well-suited for CO2 sequestration, given their ability to rapidly uptake and fix CO2. They also readily assimilate inorganic nutrients and produce a biomass with inherent commercial value, leading to a paradigm in which CO2-sequestration, enhanced wastewater treatment, and biomass generation could be effectively combined. Natural non-axenic phototrophic cultures comprising both autotrophic and heterotrophic fractions are particularly attractive in this endeavour, given their increased robustness and innate O2-CO2 exchange. In this study, the interplay between CO2-consuming autotrophy and CO2-producing heterotrophy in a non-axenic phototrophic biofilm was examined. When the biofilm was cultivated under autotrophic conditions (i.e. no organic carbon), it grew autotrophically and exhibited CO2 uptake. After amending its growth medium with organic carbon (0.25 g/L glucose and 0.28 g/L sodium acetate), the biofilm rapidly toggled from net-autotrophic to net-heterotrophic growth, reaching a CO2 production rate of 60 μmol/h after 31 hours. When the organic carbon sources were provided at a lower concentration (0.125 g/L glucose and 0.14 g/L sodium acetate), the biofilm exhibited distinct, longitudinally discrete regions of heterotrophic and autotrophic metabolism in the proximal and distal halves of the biofilm respectively, within 4 hours of carbon amendment. Interestingly, this upstream and downstream partitioning of heterotrophic and autotrophic metabolism appeared to be reversible, as the position of these regions began to flip once the direction of medium flow (and hence nutrient availability) was reversed. The insight generated here can inform new and important research questions and contribute to efforts aimed at scaling and industrializing algal growth systems, where the ability to understand, predict, and optimize biofilm growth and activity is critical.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0253224PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8205120PMC
June 2021

Evaluating CO emissions from continuous flow and batch growth systems under autotrophic mode: Implications for GHG accounting of biological nutrient removal.

J Environ Manage 2021 Sep 8;294:112928. Epub 2021 Jun 8.

Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto, ON, M5B 2K3, Canada; Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa. Electronic address:

The oxidation of ammonia by autotrophic bacteria is a central part of the nitrogen cycle and a fundamental aspect of biological nutrient removal (BNR) during wastewater treatment. Autotrophic ammonia oxidation produces protons and results in net-CO production due to the neutralizing effect of bicarbonate alkalinity. Attention must be paid to the propensity for this produced CO to be transferred to the atmosphere where it can act as a greenhouse gas (GHG). In the context of BNR systems, bicarbonate-derived CO emissions should be considered distinct from the biogenic CO that arises from cellular respiration, though this distinction is not made in current GHG accounting practices. The aim of this study was to evaluate the performance of two experimental systems operated under autotrophic mode and buffered with bicarbonate, to investigate the relationship between ammonia removal and gaseous CO emissions. The first system consisted of continuously aerated lab-scale batch reactors, which were effective in demonstrating the important link between ammonia oxidizer activity, pH, and gaseous CO production. Depletion of the buffer system always led to a rapid decline in system pH and cessation of CO emissions when the pH fell below 7.0. The second system was a tubular continuous-flow biofilm reactor which permitted comparison of ammonia removal and CO emission rates. A linear relationship between ammonia removal and CO emissions was demonstrated and the quantified CO production was relatively close to that which was predicted based on the stoichiometry of nitrification, with this CO being detected in the gas phase. It was apparent that this system offered minimal resistance to the mass transfer of CO from the liquid to gas, which is an important factor that determines how much of the bicarbonate-derived CO may contribute to greenhouse gas emissions in engineered systems such as those used for BNR.
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http://dx.doi.org/10.1016/j.jenvman.2021.112928DOI Listing
September 2021

Comparison of phytoplankton control measures in reducing cyanobacteria assemblage of reservoirs found in the arid region of Southern Africa.

Water Environ Res 2021 Apr 3. Epub 2021 Apr 3.

Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.

Ecological restorations of reservoirs are implemented worldwide; however, minimal successes are reported and understood for warmer African lakes like Swakoppoort Dam, Namibia. The objectives of the study were (a) to establish the effectiveness of the two control measures in reducing cyanobacteria growths in comparison with untreated control areas and (b) to compare the results generated before and after control measures with the reference Von Bach Dam. During Phoslock treatment, the average cyanobacteria cells and total phosphate (TP) were 90,521 cells/ml and 0.3 mg/L in the treated area and 55,338 cells/ml and 0.1 mg/L in the control area. During Solar Powered Circulation (SPC) treatment, the average cyanobacteria cells were on average 906,420 cells/ml in the treated areas and 121,891 cells/ml in the control area. The TP on average was 0.3 mg/L during SPC treatment, while during the combined treatment, the average cyanobacteria cells, TP, and total nitrogen (TN) were 18,387,226 cells/ml, 0.27 mg/L, and 2.41 mg/L before and 22,836,511 cells/ml, 0.42 mg/L, and 1.50 mg/L after treatment. This was higher compared to the reference site. PCA triplot indicates no grouping pattern, and the repeated-measures mixed model analyses indicate that treatment had no significant effect on cyanobacteria cells. It was evident that the two control measures were ineffective in reducing cyanobacterial cells. PRACTITIONER POINTS: Key findings of the article: Two phytoplankton control measures were found ineffective to reduce the cyanobacterial cell numbers. High cell numbers of cyanobacteria were recorded at the treatment areas compared to untreated control areas during both treatments. The combined effect of the two control measures was ineffective as more cyanobacterial cells were recorded during the treatment. During control measure treatment, the Swakoppoort Dam was hypertrophic, which could be due to a malfunctioned WWTP upstream. The inefficiency of the control measures could be due to small treatment area, higher nutrients, or treatment period. The implications of the results to water/wastewater practice: The selection of appropriate mitigation measures considering treatment area for dams with high nutrient situated in warmer arid environments. There is a need to understand the trophic relationships, climatic conditions, and the sources of the internal and external nutrients to manage water quality. Focus on point and non-point sources of nutrients as the root causes of the degradation of Swakoppoort Dam water.
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http://dx.doi.org/10.1002/wer.1564DOI Listing
April 2021

Canary in the coliform mine: Exploring the industrial application limits of a microbial respiration alarm system.

PLoS One 2021 4;16(3):e0247910. Epub 2021 Mar 4.

Water Institute and Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa.

Fundamental ecological principles of ecosystem-level respiration are extensively applied in greenhouse gas and elemental cycle studies. A laboratory system termed CEMS (Carbon Dioxide Evolution Measurement System), developed to explore microbial biofilm growth and metabolic responses, was evaluated as an early-warning system for microbial disturbances in industrial settings: in (a) potable water system contamination, and (b) bioreactor inhibition. Respiration was detected as CO2 production, rather than O2 consumption, including aerobic and anaerobic metabolism. Design, thresholds, and benefits of the remote CO2 monitoring technology were described. Headspace CO2 correlated with contamination levels, as well as chemical (R2 > 0.83-0.96) and microbiological water quality indicators (R2 > 0.78-0.88). Detection thresholds were limiting factors in monitoring drinking water to national and international standards (0 CFU/100 mL fecal coliforms) in both open- (>1500 CFU/mL) and closed-loop CO2 measuring regimes (>100 CFU/100 mL). However, closed-loop detection thresholds allow for the detection of significant contamination events, and monitoring less stringent systems such as irrigation water (<100 CFU/mL). Whole-system respiration was effectively harnessed as an early-warning system in bioreactor performance monitoring. Models were used to deconvolute biological CO2 fluctuations from chemical CO2 dynamics, to optimize this real-time, sustainable, low-waste technology, facilitating timeous responses to biological disturbances in bioreactors.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0247910PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7932117PMC
March 2021

Disinfectant, Soap or Probiotic Cleaning? Surface Microbiome Diversity and Biofilm Competitive Exclusion.

Microorganisms 2020 Nov 4;8(11). Epub 2020 Nov 4.

Environmental Microbiology Laboratory, Water Institute, Department of Microbiology, Stellenbosch University, 7602 Stellenbosch, South Africa.

This study extends probiotic cleaning research to a built environment. Through an eight-month cleaning trial, we compared the effect of three cleaning products (disinfectant, plain soap, and a probiotic cleaner containing a patented spore consortium), and tap water as the control, on the resident microbiome of three common hospital surfaces (linoleum, ceramic, and stainless steel). Pathogens, and were deposited and desiccated, and competitive exclusion was assessed for each microbiome. Cell survival was shown to be an incomplete tool for measuring microbial competitive exclusion. Biofilm competition offered a fuller understanding of competitive dynamics. A test for culturable cell survival showed that both plain soap and probiotic cleaner regimes established a surface microbiome that outcompeted the two pathogens. A different picture emerged when observing biofilms with a deposited and desiccated GFP-labeled pathogen, . Competitive exclusion was again demonstrated. On surfaces cleaned with disinfectant the pathogen outcompeted the microbiomes. On surfaces cleaned with plain soap, the microbiomes outcompeted the pathogen. However, on surfaces cleaned with probiotic cleaner, despite the exponentially higher surface microbial loads, the microbiome did not completely outcompete the pathogen. Thus, the standard culturable cell test for survival on a surface confirmed the competitive advantage that is typically reported for probiotic cleaners. However, observation of competition in biofilms showed that the more diverse microbiome (according to alpha and beta indices) established on a surface cleaned with plain soap had a better competitive advantage than the monoculture established by the probiotic cleaner. Therefore, microbial diversity appears to be as critical to the competitive exclusion principle as cell numbers. The study showed that both plain soap and probiotic cleaner fostered competitive exclusion far more effectively than disinfectant. Probiotic cleaners with microbial diversity could be worth considering for hospital cleaning.
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http://dx.doi.org/10.3390/microorganisms8111726DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694204PMC
November 2020

Biofilm dynamics: linking in situ biofilm biomass and metabolic activity measurements in real-time under continuous flow conditions.

NPJ Biofilms Microbiomes 2020 10 21;6(1):42. Epub 2020 Oct 21.

Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa.

The tools used to study biofilms generally involve either destructive, end-point analyses or periodic measurements. The advent of the internet of things (IoT) era allows circumvention of these limitations. Here we introduce and detail the development of the BioSpec; a modular, nondestructive, real-time monitoring system, which accurately and reliably track changes in biofilm biomass over time. The performance of the system was validated using a commercial spectrophotometer and produced comparable results for variations in planktonic and sessile biomass. BioSpec was combined with the previously developed carbon dioxide evolution measurement system (CEMS) to allow simultaneous measurement of biofilm biomass and metabolic activity and revealed a differential response of these interrelated parameters to changing environmental conditions. The application of this system can facilitate a greater understanding of biofilm mass-function relationships and aid in the development of biofilm control strategies.
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http://dx.doi.org/10.1038/s41522-020-00153-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7578832PMC
October 2020

A Novel System for Real-Time, In Situ Monitoring of CO Sequestration in Photoautotrophic Biofilms.

Microorganisms 2020 Jul 31;8(8). Epub 2020 Jul 31.

Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto, ON M5B 2K3, Canada.

Climate change brought about by anthropogenic CO emissions has created a critical need for effective CO management solutions. Microalgae are well suited to contribute to efforts aimed at addressing this challenge, given their ability to rapidly sequester CO coupled with the commercial value of their biomass. Recently, microalgal biofilms have garnered significant attention over the more conventional suspended algal growth systems, since they allow for easier and cheaper biomass harvesting, among other key benefits. However, the path to cost-effectiveness and scaling up is hindered by a need for new tools and methodologies which can help evaluate, and in turn optimize, algal biofilm growth. Presented here is a novel system which facilitates the real-time in situ monitoring of algal biofilm CO sequestration. Utilizing a CO-permeable membrane and a tube-within-a-tube design, the CO sequestration monitoring system (CSMS) was able to reliably detect slight changes in algal biofilm CO uptake brought about by light-dark cycling, light intensity shifts, and varying amounts of phototrophic biomass. This work presents an approach to advance our understanding of carbon flux in algal biofilms, and a base for potentially useful innovations to optimize, and eventually realize, algae biofilm-based CO sequestration.
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http://dx.doi.org/10.3390/microorganisms8081163DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7464137PMC
July 2020

Investigating (anti)estrogenic activities within South African wastewater and receiving surface waters: Implication for reliable monitoring.

Environ Pollut 2020 Aug 29;263(Pt A):114424. Epub 2020 Mar 29.

Scientific Services, East Rand Water Care Company (ERWAT), Kempton Park, 1631, South Africa.

Natural and synthetic steroid hormones and many persistent organic pollutants are of concern for their endocrine-disrupting activities observed in receiving surface waters. Apart from the demonstrated presence of estrogen- and estrogen-mimicking compounds in surface waters, antagonistic (anti-estrogenic) responses originating from wastewater effluent have been reported but are less known. Estrogenicity and anti-estrogenicity were assessed using recombinant yeast estrogen receptor binding assays (YES/YAES) at ten South African wastewater treatment works (WWTWs) and receiving rivers in two separate sampling campaigns during the summer- and winter periods in the area. Four WWTWs were then further investigated to show daily variation in estrogenic endocrine-disrupting activities during the treatment process. Although estrogenicity was notably reduced at most of the WWTWs, some treated effluent and river water samples were shown to be above effect-based trigger values posing an endocrine-disrupting risk for aquatic life and potential health risks for humans. Furthermore, estrogenicity recorded in samples collected upstream from some WWTW discharge points also exceeded some calculated risk trigger values, which highlights the impact of alternative pollution sources contributing towards endocrine disrupting contaminants (EDCs) in the environment. The YAES further showed variable anti-estrogenic activities in treated wastewater. The current study highlights a variety of factors that may affect bioassay outcomes and conclusions drawn from the results for risk decision-making. For example, mismatches were found between estrogenic and anti-estrogenic activity, which suggests a potential masking effect in WWTW effluents and highlights the complexity of environmental samples containing chemical mixtures having variable endocrine-disrupting modes of action. Although the recombinant yeast assay is not without its limitations to show endocrine-disrupting modulation in test water systems, it serves as a cost-effective tier-1 scoping assay for further risk characterisation and intervention.
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http://dx.doi.org/10.1016/j.envpol.2020.114424DOI Listing
August 2020

Species Interaction and Selective Carbon Addition During Antibiotic Exposure Enhances Bacterial Survival.

Front Microbiol 2019 29;10:2730. Epub 2019 Nov 29.

Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada.

Biofilms are multifaceted and robust microbiological systems that enable microorganisms to withstand a multitude of environmental stresses and expand their habitat range. We have shown previously that nutritional status alters antibiotic susceptibility in a mixed-species biofilm. To further elucidate the effects of nutrient addition on inter-species dynamics and whole-biofilm susceptibility to high-dose streptomycin exposures, a CO Evolution Measurement System was used to monitor the metabolic activity of early steady state pure-culture and mixed-species biofilms containing and , with and without added carbon. Carbon supplementation was needed for biofilm recovery from high-dose streptomycin exposures when was either the dominant community member in a mixed-species biofilm (containing predominantly and ) or as a pure culture. By contrast, biofilms could recover from high-dose streptomycin exposures without the need for carbon addition during antibiotic exposure. Metagenomic analysis revealed that even when inocula were dominated by , the relative abundance of increased upon biofilm development to ultimately become the dominant species post-streptomycin exposure. The combined metabolic and metagenomic results demonstrated the relevance of inter-species influence on survival and that nutritional status has a strong influence on the survival of dominated biofilms.
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http://dx.doi.org/10.3389/fmicb.2019.02730DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6895500PMC
November 2019

Bacterial diversity and production of sulfide in microcosms containing uncompacted bentonites.

Heliyon 2018 Aug 9;4(8):e00722. Epub 2018 Aug 9.

Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, Canada.

Aims: This study examined the diversity and sulfide-producing activity of microorganisms in microcosms containing commercial clay products (, MX-80, Canaprill and National Standard) similar to materials which are currently considered for use in the design specifications for deep geologic repositories (DGR) for spent nuclear fuel.

Methods And Results: In anoxic microcosms incubated for minimum of 60 days with 10 g l NaCl, sulfide production varied with temperature, electron donor and bentonite type. Maximum specific sulfide production rates of 0.189 d, 0.549 d and 0.157 d occurred in lactate-fed MX-80, Canaprill and National Standard microcosms, respectively. In microcosms with 50 g l NaCl, sulfide production was inhibited. Denaturing gradient gel electrophoresis (DGGE) profiling of microcosms revealed the presence of bacterial classes and . Spore-forming and non-spore-forming bacteria were confirmed in microcosms using high-throughput 16S rRNA gene sequencing. Sulfate-reducing bacteria of the genus predominated in MX-80 microcosms; whereas, and genera contributed to sulfate-reduction in National Standard and Canaprill microcosms.

Conclusions: Commercial clays microcosms harbour a sparse bacterial population dominated by spore-forming microorganisms. Detected sulfate- and sulfur-reducing bacteria presumably contributed to sulfide accumulation in the different microcosm systems.

Significance And Impact Of Study: The use of carbon-supplemented, clay-in-water microcosms offered insights into the bacterial diversity present in as-received clays, along with the types of metabolic and sulfidogenic reactions that might occur in regions of a DGR (, interfaces between the bulk clay and host rock, cracks, fissures, ) that fail to attain target parameters necessary to inhibit microbial growth and activity.
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http://dx.doi.org/10.1016/j.heliyon.2018.e00722DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090518PMC
August 2018

Survival of Planktonic and Sessile Cells of Lactobacillus rhamnosus and Lactobacillus reuteri upon Exposure to Simulated Fasting-State Gastrointestinal Conditions.

Probiotics Antimicrob Proteins 2019 06;11(2):594-603

Department of Microbiology, University of Stellenbosch, Private Bag X1, Matieland 7602, Stellenbosch, 7600, South Africa.

In this study, we report on the formation and resilience of Lactobacillus reuteri HFI-LD5 and Lactobacillus rhamnosus HFI-K2 biofilms cultivated in a CO evolution measurement system (CEMS) and exposed to biologically relevant, fasting-state gastrointestinal fluids under continuous flow conditions. For comparative purposes, planktonic and sessile populations of L. reuteri HFI-LD5 and L. rhamnosus HFI-K2 were each exposed to fasting-state gastric fluid (FSGF, pH 2.0) for 2 h, fasting-state intestinal fluid (FSIF, pH 7.5) for 6 h, and simulated colonic fluid (SCoF, pH 7.0) for 24 h. Planktonic cell numbers of L. reuteri HFI-LD5 declined from 6.6 log CFU/mL to 3.2 log CFU/mL and L. rhamnosus HFI-K2 from 6.6 log CFU/mL to undetectable levels after exposure to FSGF. Limited loss in viability was observed when free-floating cells were exposed to FSIF and SCoF. Sessile populations of both strains survived and recovered from the sequential exposure to all three gastric fluids despite observed detachment of biofilm biomass and a temporary decrease in metabolic activity to below detection limits, as recorded by changes in whole-biofilm CO production rates. The planktonic cell-focused gut microbiome-related research has most likely caused an underestimation in the overall survival ability of microorganisms in the gastrointestinal tract. Sessile cells of L. reuteri HFI-LD5 were metabolically inactive when exposed to gastric (FSGF) and intestinal (FSIF) fluids, suggesting that biofilms are formed in the small intestinal tract as survival mechanism. In the case of L. rhamnosus HFI-K2, cells were released from biofilms when suddenly exposed to pH 2.0.
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http://dx.doi.org/10.1007/s12602-018-9426-7DOI Listing
June 2019

UV-Curable Contact Active Benzophenone Terminated Quaternary Ammonium Antimicrobials for Applications in Polymer Plastics and Related Devices.

ACS Appl Mater Interfaces 2017 Aug 10;9(33):27491-27503. Epub 2017 Aug 10.

Department of Chemistry and Biology, Ryerson University , 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada.

A series of UV active benzophenone ([CHCOCH-O-(CH)-NMeR][X]; 4, R = CH, n = 3, X = Br; 5a-c, R = CH, n = 3, X = Cl, Br, I; 6a-c, R = CH, n = 4, X = Cl, Br, I; 7a-c, R = CH, n = 6, X = Cl, Br, I) terminated C and C quaternary ammonium salts (QACs) were prepared by thermal or microwave-driven Menshutkin protocols of the appropriate benzophenone alkyl halide (1a-c, 2a-c, 3a-c) with the corresponding dodecyl- or octadecyl N,N-dimethylamine. All new compounds were characterized by NMR spectroscopy, HRMS spectrometry, and, in one instance (4), by single-crystal X-ray crystallography. Representative C and C benzophenone QACs were formulated into 1% (w/v) water or water/ethanol-based aerosol spray coatings and then UV-cured onto plastic substrates (polypropylene, polyethylene, polystyrene, polyvinyl chloride, and polyether ether ketone) with exposure to low to moderate doses of UV (20-30 J cm). Confirmation as to the presence of the coatings was detected by advancing water contact angle measurements, which revealed a more hydrophilic surface after coating. Further confirmation was gained by X-ray photoelectron spectroscopy analysis, time of flight secondary ion mass spectrometry, and bromophenol blue staining, all of which showed the presence of the attached quaternary ammonium molecule. Analysis of surfaces treated with the C benzophenone 5b by atomic force microscopy and surface profilometry revealed a coating thickness of ∼350 nm. The treated samples along with controls were then evaluated for their antimicrobial efficacy against Gram-positive (Arthrobacter sp., Listeria monocytogenes) and Gram-negative (Pseudomonas aeruginosa) bacteria at a solid/air interface using the large drop inoculum protocol; this technique gave no evidence for cell adhesion after a 3 h time frame. These antimicrobial materials show promise for their use as coatings on plastic biomedical devices with the aim of preventing biofilm formation and preventing the spread of hospital acquired infections.
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http://dx.doi.org/10.1021/acsami.7b07363DOI Listing
August 2017

The fate of pharmaceuticals and personal care products (PPCPs), endocrine disrupting contaminants (EDCs), metabolites and illicit drugs in a WWTW and environmental waters.

Chemosphere 2017 May 26;174:437-446. Epub 2017 Jan 26.

Department of Microbiology, University of Stellenbosch, Stellenbosch 7602, South Africa; Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B 2K3, Canada.

A large number of emerging contaminants (ECs) are known to persist in surface waters, and create pressure on wastewater treatment works (WWTW) for their effective removal. Although a large database for the levels of these pollutants in water systems exist globally, there is still a lack in the correlation of the levels of these pollutants with possible long-term adverse health effects in wildlife and humans, such as endocrine disruption. The current study detected a total of 55 ECs in WWTW influent surface water, 41 ECs in effluent, and 40 ECs in environmental waters located upstream and downstream of the plant. A list of ECs persisted through the WWTW process, with 28% of all detected ECs removed by less than 50%, and 18% of all ECs were removed by less than 25%. Negative mass balances of some pharmaceuticals and metabolites were observed within the WWTW, suggesting possible back-transformation of ECs during wastewater treatment. Three parental illicit drug compounds were detected within the influent of the WWTW, with concentrations ranging between 27.6 and 147.0 ng L for cocaine, 35.6-120.6 ng L for mephedrone, and 270.9-450.2 ng L for methamphetamine. The related environmental risks are also discussed for some ECs, with particular reference to their ability to disrupt endocrine systems. The current study propose the potential of the pharmaceuticals carbamazepine, naproxen, diclofenac and ibuprofen to be regarded as priority ECs for environmental monitoring due to their regular detection and persistence in environmental waters and their possible contribution towards adverse health effects in humans and wildlife.
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http://dx.doi.org/10.1016/j.chemosphere.2017.01.101DOI Listing
May 2017

Microbes at Surface-Air Interfaces: The Metabolic Harnessing of Relative Humidity, Surface Hygroscopicity, and Oligotrophy for Resilience.

Front Microbiol 2016 30;7:1563. Epub 2016 Sep 30.

Department of Microbiology, University of Stellenbosch, Cape TownSouth Africa; Department of Chemistry and Biology, Ryerson University, Toronto, ONCanada.

The human environment is predominantly not aqueous, and microbes are ubiquitous at the surface-air interfaces with which we interact. Yet microbial studies at surface-air interfaces are largely survival-oriented, whilst microbial metabolism has overwhelmingly been investigated from the perspective of liquid saturation. This study explored microbial survival and metabolism under desiccation, particularly the influence of relative humidity (RH), surface hygroscopicity, and nutrient availability on the interchange between these two phenomena. The combination of a hygroscopic matrix (i.e., clay or 4,000 MW polyethylene glycol) and high RH resulted in persistent measurable microbial metabolism during desiccation. In contrast, no microbial metabolism was detected at (a) hygroscopic interfaces at low RH, and (b) less hygroscopic interfaces (i.e., sand and plastic/glass) at high or low RH. Cell survival was conversely inhibited at high RH and promoted at low RH, irrespective of surface hygroscopicity. Based on this demonstration of metabolic persistence and survival inhibition at high RH, it was proposed that biofilm metabolic rates might inversely influence whole-biofilm resilience, with 'resilience' defined in this study as a biofilm's capacity to recover from desiccation. The concept of whole-biofilm resilience being promoted by oligotrophy was supported in desiccation-tolerant spp. biofilms, but not in desiccation-sensitive biofilms. The ability of microbes to interact with surfaces to harness water vapor during desiccation was demonstrated, and potentially to harness oligotrophy (the most ubiquitous natural condition facing microbes) for adaptation to desiccation.
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http://dx.doi.org/10.3389/fmicb.2016.01563DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5043023PMC
September 2016

USMB-induced synergistic enhancement of aminoglycoside antibiotics in biofilms.

Ultrasonics 2016 07 31;69:182-90. Epub 2016 Mar 31.

Department of Physics, Ryerson University, Toronto, Ontario, Canada. Electronic address:

This study evaluated the effect of combining antibiotics with ultrasound and microbubbles (USMB) toward the eradication of biofilms. Pseudomonas aeruginosa PAO1 biofilms were treated with the antibiotics gentamicin sulfate or streptomycin sulfate, or a combination of USMB with the respective antibiotics. Biofilm structure was quantified using confocal laser scanning microscopy with COMSTAT analysis, while activity was measured as whole-biofilm CO2 production in a continuous-flow biofilm model. The combined antibiotic-USMB treatment significantly impacted biofilm biomass, thickness and surface roughness compared to antibiotics alone (p<0.05). USMB exposure caused the formation of craters (5-20μm in diameter) in the biofilms, and when combined with gentamicin, activity was significantly lower, compared to gentamicin, USMB or untreated controls, respectively. Interestingly, the CO2 production rate following combined streptomycin-USMB treatment was higher than after streptomycin alone, but significantly lower than USMB alone and untreated control. These results show strong evidence of a synergistic effect between antibiotics and USMB, although the varied response to different antibiotics emphasize the need to optimize the USMB exposure conditions to maximize this synergism and ultimately transfer this technology into clinical or industrial practice.
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http://dx.doi.org/10.1016/j.ultras.2016.03.017DOI Listing
July 2016

Measuring microbial metabolism in atypical environments: Bentonite in used nuclear fuel storage.

J Microbiol Methods 2016 Jan 11;120:79-90. Epub 2015 Nov 11.

Department of Chemistry and Biology, Ryerson University, Toronto, Ontario, Canada; Department of Microbiology, University of Stellenbosch, South Africa. Electronic address:

Genomics enjoys overwhelming popularity in the study of microbial ecology. However, extreme or atypical environments often limit the use of such well-established tools and consequently demand a novel approach. The bentonite clay matrix proposed for use in Deep Geological Repositories for the long-term storage of used nuclear fuel is one such challenging microbial habitat. Simple, accessible tools were developed for the study of microbial ecology and metabolic processes that occur within this habitat, since the understanding of the microbiota-niche interaction is fundamental to describing microbial impacts on engineered systems such as compacted bentonite barriers. Even when genomic tools are useful for the study of community composition, techniques to describe such microbial impacts and niche interactions should complement these. Tools optimised for assessing localised microbial activity within bentonite included: (a) the qualitative use of the resazurin-resorufin indicator system for redox localisation, (b) the use of a CaCl2 buffer for the localisation of pH, and (c) fluorometry for the localisation of precipitated sulphide. The use of the Carbon Dioxide Evolution Monitoring System was also validated for measuring microbial activity in desiccated and saturated bentonite. Finally, the buffering of highly-basic bentonite at neutral pH improved the success of isolation of microbial populations, but not DNA, from the bentonite matrix. Thus, accessible techniques were optimised for exploring microbial metabolism in the atypical environments of clay matrices and desiccated conditions. These tools have application to the applied field of used nuclear fuel management, as well as for examining the fundamental biogeochemical cycles active in sedimentary and deep geological environments.
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http://dx.doi.org/10.1016/j.mimet.2015.11.006DOI Listing
January 2016

Effect of carbon on whole-biofilm metabolic response to high doses of streptomycin.

Front Microbiol 2015 11;6:953. Epub 2015 Sep 11.

Department of Chemistry and Biology, Ryerson University, Toronto ON, Canada ; Department of Microbiology, Stellenbosch University Stellenbosch, South Africa.

Biofilms typically exist as complex communities comprising multiple species with the ability to adapt to a variety of harsh conditions. In clinical settings, antibiotic treatments based on planktonic susceptibility tests are often ineffective against biofilm infections. Using a CO2 evolution measurement system we delineated the real-time metabolic response in continuous flow biofilms to streptomycin doses much greater than their planktonic susceptibilities. Stable biofilms from a multispecies culture (containing mainly Pseudomonas aeruginosa and Stenotrophomonas maltophilia), Gram-negative environmental isolates, and biofilms formed by pure culture P. aeruginosa strains PAO1 and PAO1 ΔMexXY (minimum planktonic inhibitory concentrations between 1.5 and 3.5 mg/l), were exposed in separate experiments to 4000 mg/l streptomycin for 4 h after which growth medium resumed. In complex medium, early steady state multispecies biofilms were susceptible to streptomycin exposure, inferred by a cessation of CO2 production. However, multispecies biofilms survived high dose exposures when there was extra carbon in the antibiotic medium, or when they were grown in defined citrate medium. The environmental isolates and PAO1 biofilms showed similar metabolic profiles in response to streptomycin; ceasing CO2 production after initial exposure, with CO2 levels dropping toward baseline levels prior to recovery back to steady state levels, while subsequent antibiotic exposure elicited increased CO2 output. Monitoring biofilm metabolic response in real-time allowed exploration of conditions resulting in vulnerability after antibiotic exposure compared to the resistance displayed following subsequent exposures.
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http://dx.doi.org/10.3389/fmicb.2015.00953DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4566048PMC
October 2015

Live-streaming: Time-lapse video evidence of novel streamer formation mechanism and varying viscosity.

Biomicrofluidics 2015 Jul 6;9(4):041101. Epub 2015 Aug 6.

Département de Chimie, Université Laval , Québec, Canada.

Time-lapse videos of growing biofilms were analyzed using a background subtraction method, which removed camouflaging effects from the heterogeneous field of view to reveal evidence of streamer formation from optically dense biofilm segments. In addition, quantitative measurements of biofilm velocity and optical density, combined with mathematical modeling, demonstrated that streamer formation occurred from mature, high-viscosity biofilms. We propose a streamer formation mechanism by sudden partial detachment, as opposed to continuous elongation as observed in other microfluidic studies. Additionally, streamer formation occurred in straight microchannels, as opposed to serpentine or pseudo-porous channels, as previously reported.
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http://dx.doi.org/10.1063/1.4928296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4529438PMC
July 2015

Influence of wave action on the partitioning and transport of unattached and floc-associated bacteria in fresh water.

Can J Microbiol 2015 Aug 11;61(8):584-96. Epub 2015 Jun 11.

a Ryerson University, Department of Chemistry and Biology, Toronto, ON M5B 2K3, Canada.

The dynamic interaction of bacteria within bed sediment and suspended sediment (i.e., floc) in a wave-dominated beach environment was assessed using a laboratory wave flume. The influence of shear stress (wave energy) on bacterial concentrations and on the partitioning and transport of unattached and floc-associated bacteria was investigated. The study showed that increasing wave energy (0.60 and 5.35 N/s) resulted in a 0.5 to 1.5 log increase in unattached cells of the test bacterium Pseudomonas sp. strain CTO7::gfp-2 in the water column. There was a positive correlation between the bacterial concentrations in water and the total suspended solids, with the latter increasing from values of near 0 to up to 200 mg/L over the same wave energy increase. The median equivalent spherical diameter of flocs in suspension also increased by an order of magnitude in all experimental trials. Under both low (0.60 N/s) and high (5.35 N/s) energy regime, bacteria were shown to preferentially associate with flocs upon cessation of wave activity. The results suggest that collecting water samples during periods of low wave action for the purpose of monitoring the microbiological quality of water may underestimate bacterial concentrations partly because of an inability to account for the effect of shear stress on the erosion and mobilization of bacteria from bed sediment to the water column. This highlights the need to develop a more comprehensive beach analysis strategy that not only addresses presently uncharacterized shores and sediments but also recognizes the importance of eroded flocs as a vector for the transport of bacteria in aquatic environments.
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http://dx.doi.org/10.1139/cjm-2014-0815DOI Listing
August 2015

Bioenergy and African transformation.

Biotechnol Biofuels 2015 12;8:18. Epub 2015 Feb 12.

Department of Microbiology, University of Stellenbosch, Stellenbosch, South Africa.

Among the world's continents, Africa has the highest incidence of food insecurity and poverty and the highest rates of population growth. Yet Africa also has the most arable land, the lowest crop yields, and by far the most plentiful land resources relative to energy demand. It is thus of interest to examine the potential of expanded modern bioenergy production in Africa. Here we consider bioenergy as an enabler for development, and provide an overview of modern bioenergy technologies with a comment on application in an Africa context. Experience with bioenergy in Africa offers evidence of social benefits and also some important lessons. In Brazil, social development, agricultural development and food security, and bioenergy development have been synergistic rather than antagonistic. Realizing similar success in African countries will require clear vision, good governance, and adaptation of technologies, knowledge, and business models to myriad local circumstances. Strategies for integrated production of food crops, livestock, and bioenergy are potentially attractive and offer an alternative to an agricultural model featuring specialized land use. If done thoughtfully, there is considerable evidence that food security and economic development in Africa can be addressed more effectively with modern bioenergy than without it. Modern bioenergy can be an agent of African transformation, with potential social benefits accruing to multiple sectors and extending well beyond energy supply per se. Potential negative impacts also cut across sectors. Thus, institutionally inclusive multi-sector legislative structures will be more effective at maximizing the social benefits of bioenergy compared to institutionally exclusive, single-sector structures.
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http://dx.doi.org/10.1186/s13068-014-0188-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4337098PMC
February 2015

Micropatterned biofilm formations by laminar flow-templating.

Lab Chip 2014 Aug 11;14(15):2666-72. Epub 2014 Apr 11.

Département de Chimie, Université Laval, 1045 Avenue de la Médecine, Québec, QC G1V 0A6, Canada.

We present a microfluidic device capable of patterning linear biofilm formations using a flow templating approach. We describe the design considerations and fabrication methodology of a two level flow-templating micro-bioreactor (FT-μBR), which generates a biofilm growth stream surrounded on 3 sides by a growth inhibiting confinement stream. Through a combination of experiments and simulations we comprehensively evaluate and exploit control parameters to manipulate the biofilm growth template stream dimensions. The FT-μBR is then used to grow biofilm patterns with controllable dimensions. A proof-of-principle study using the device demonstrates its utility in conducting biofilm growth rate measurements under different shear stress environments. This opens the way for quantitative studies into the effects of the local shear environment on biofilm properties and for the synthesis of a new generation of functional biomaterials with controllable properties.
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http://dx.doi.org/10.1039/c4lc00084fDOI Listing
August 2014

Synthesis, structures and properties of self-assembling quaternary ammonium dansyl fluorescent tags for porous and non-porous surfaces.

J Mater Chem B 2014 Mar 5;2(11):1509-1520. Epub 2014 Feb 5.

Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B-2K3.

A series of HO and/or EtOH soluble, self-assembling quaternary ammonium salts containing a dansyl (DNS) fluorescent moiety suitable for attachment to both porous ([DNS-NH-(CH)-NMe-R][X] (2; R = -Si(OMe), X = Cl) and non-porous (3a; R = -PO(OEt), 3b; -PO(Oi-Pr), 3c; -(PO(OH), X = Br), 4; ([DNS-NH-(CH)-NMe-(CH)-NH(CHPO(OEt)) ][Br], 5; R = -((CH)SCOCH, X = Cl), 6a; (R = -(CH)O(CH)CO(CH), n = 3, X = Br, 6b; n = 3, X = Cl, 6c; n = 3, X = I, 6d; n = 4, X = Br, 6e; n = 4, X = I, 6f; n = 6, X = Br, 6g; n = 6, X = Cl, 6h; n = 6, X = I), 7; (R = -CH-CH[double bond, length as m-dash]CH, X = Br) surfaces were prepared from the precursor dansyl amine (1; DNS-NH-(CH)-NMe). Compounds 1-7 were characterized by NMR (H, C, Si (2), P (3a-c, 4)) spectroscopy, HRMS, UV-Vis and fluorescence spectroscopy. Additional characterization of compounds 1 and 7 were carried out by X-ray structure determinations. Physical attachment of compound 2 to cotton surfaces after immersion in solutions containing fluorescent dyes was verified by exposure to UV light and by complexation with bromo-phenol blue that rendered the surfaces visibly blue in colour. Phosphorus containing dansyl fluorescent dye, 3c, was attached to a stainless steel surface by exposure to an aqueous solution containing this dye, resulting in the formation of a self-assembled fluorescent monolayer. UV cure of plastic surfaces (polypropylene, silicon medical tubing) coated with compound 6a resulted in the covalent attachment of the dyes.
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http://dx.doi.org/10.1039/c3tb21633kDOI Listing
March 2014

Integration and proliferation of Pseudomonas aeruginosa PA01 in multispecies biofilms.

Microb Ecol 2014 Jul 1;68(1):121-31. Epub 2014 Mar 1.

Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada.

Despite an increased awareness of biofilm formation by pathogens and the role of biofilms in human infections, the potential role of environmental biofilms as an intermediate stage in the host-to-host cycle is poorly described. To initiate infection, pathogens in biofilms on inanimate environmental surfaces must detach from the biofilm and be transmitted to a susceptible individual in numbers large enough to constitute an infectious dose. Additionally, while detachment has been recognized as a discrete event in the biofilm lifestyle, it has not been studied to the same extent as biofilm development or biofilm physiology. Successful integration of Pseudomonas aeruginosa strain PA01 expressing green fluorescent protein (PA01GFP), employed here as a surrogate pathogen, into multispecies biofilm communities isolated and enriched from sink drains in public washrooms and a hospital intensive care unit is described. Confocal laser scanning microscopy indicated that PA01GFP cells were most frequently located in the deeper layers of the biofilm, near the attachment surface, when introduced into continuous flow cells before or at the same time as the multispecies drain communities. A more random integration pattern was observed when PA01GFP was introduced into established multispecies biofilms. Significant numbers of single PA01GFP cells were continuously released from the biofilms to the bulk liquid environment, regardless of the order of introduction into the flow cell. Challenging the multispecies biofilms containing PA01GFP with sub-lethal concentrations of an antibiotic, chelating agent and shear forces that typically prevail at distances away from the point of treatment showed that environmental biofilms provide a suitable habitat where pathogens are maintained and protected, and from where they are continuously released.
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http://dx.doi.org/10.1007/s00248-014-0398-1DOI Listing
July 2014

Tracking the cellulolytic activity of Clostridium thermocellum biofilms.

Biotechnol Biofuels 2013 Nov 29;6(1):175. Epub 2013 Nov 29.

Department of Chemistry and Biology, Ryerson University, 350 Victoria St,, Toronto, ON M5B 2K3, Canada.

Background: Microbial cellulose conversion by Clostridium thermocellum 27405 occurs predominantly through the activity of substrate-adherent bacteria organized in thin, primarily single cell-layered biofilms. The importance of cellulosic surface exposure to microbial hydrolysis has received little attention despite its implied impact on conversion kinetics.

Results: We showed the spatial heterogeneity of fiber distribution in pure cellulosic sheets, which made direct measurements of biofilm colonization and surface penetration impossible. Therefore, we utilized on-line measurements of carbon dioxide (CO2) production in continuous-flow reactors, in conjunction with confocal imaging, to observe patterns of biofilm invasion and to indirectly estimate microbial accessibility to the substrate's surface and the resulting limitations on conversion kinetics. A strong positive correlation was found between cellulose consumption and CO2 production (R2 = 0.996) and between surface area and maximum biofilm activity (R2 = 0.981). We observed an initial biofilm development rate (0.46 h-1, 0.34 h-1 and 0.33 h-1) on Whatman sheets (#1, #598 and #3, respectively) that stabilized when the accessible surface was maximally colonized. The results suggest that cellulose conversion kinetics is initially subject to a microbial limitation period where the substrate is in excess, followed by a substrate limitation period where cellular mass, in the form of biofilms, is not limiting. Accessible surface area acts as an important determinant of the respective lengths of these two distinct periods. At end-point fermentation, all sheets were digested predominantly under substrate accessibility limitations (e.g., up to 81% of total CO2 production for Whatman #1). Integration of CO2 production rates over time showed Whatman #3 underwent the fastest conversion efficiency under microbial limitation, suggestive of best biofilm penetration, while Whatman #1 exhibited the least recalcitrance and the faster degradation during the substrate limitation period.

Conclusion: The results showed that the specific biofilm development rate of cellulolytic bacteria such as C. thermocellum has a notable effect on overall reactor kinetics during the period of microbial limitation, when ca. 20% of cellulose conversion occurs. The study further demonstrated the utility of on-line CO2 measurements as a method to assess biofilm development and substrate digestibility pertaining to microbial solubilization of cellulose, which is relevant when considering feedstock pre-treatment options.
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http://dx.doi.org/10.1186/1754-6834-6-175DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4176736PMC
November 2013

Biofilms' role in planktonic cell proliferation.

Int J Mol Sci 2013 Nov 6;14(11):21965-82. Epub 2013 Nov 6.

Department of Chemistry and Biology, 350 Victoria Street, Ryerson University, Toronto, ON M5B 2K3, Canada.

The detachment of single cells from biofilms is an intrinsic part of this surface-associated mode of bacterial existence. Pseudomonas sp. strain CT07gfp biofilms, cultivated in microfluidic channels under continuous flow conditions, were subjected to a range of liquid shear stresses (9.42 mPa to 320 mPa). The number of detached planktonic cells was quantified from the effluent at 24-h intervals, while average biofilm thickness and biofilm surface area were determined by confocal laser scanning microscopy and image analysis. Biofilm accumulation proceeded at the highest applied shear stress, while similar rates of planktonic cell detachment was maintained for biofilms of the same age subjected to the range of average shear rates. The conventional view of liquid-mediated shear leading to the passive erosion of single cells from the biofilm surface, disregards the active contribution of attached cell metabolism and growth to the observed detachment rates. As a complement to the conventional conceptual biofilm models, the existence of a biofilm surface-associated zone of planktonic cell proliferation is proposed to highlight the need to expand the traditional perception of biofilms as promoting microbial survival, to include the potential of biofilms to contribute to microbial proliferation.
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http://dx.doi.org/10.3390/ijms141121965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3856045PMC
November 2013

Interspecies interaction extends bacterial survival at solid-air interfaces.

Biofouling 2013 17;29(9):1087-96. Epub 2013 Sep 17.

a Department of Chemistry and Biology , Ryerson University , Toronto , ON , Canada .

Despite the ubiquity of biofilms in natural and man-made environments, research on surface-associated cells has focused primarily on solid-liquid interfaces. This study evaluated the extent to which bacterial cells persist on inanimate solid-air interfaces. The desiccation tolerance of bacterial strains isolated from indoor air, as well as of a test strain (Pseudomonas aeruginosa), was determined at different levels of relative humidity (RH) using the large droplet inoculation method in an aerosol chamber. The cells survived longer at lower (25 and 42%) than at high RH (95%). Four of the seven indoor strains selected for further study showed extended period of survival following deposition as 0.05-0.1 ml of washed culture followed by desiccation, each with different effects on the survival of the test strain, P. aeruginosa. A strain closely related to Arthrobacter species afforded the highest level of protection to the test strain. Even though the desiccation-tolerant strains survived when they were deposited as bioaerosols, the protective role towards the test strain was not observed when the latter was deposited as a bioaerosol. These, which are often-unculturable, bacteria may go undetected during routine monitoring of biofouling, thereby allowing them to act as reservoirs and extending the habitat range of undesired microorganisms.
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http://dx.doi.org/10.1080/08927014.2013.829820DOI Listing
April 2014

Bacterial diversity and composition of an alkaline uranium mine tailings-water interface.

J Microbiol 2013 Oct 14;51(5):558-69. Epub 2013 Sep 14.

Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK, Canada.

The microbial diversity and biogeochemical potential associated with a northern Saskatchewan uranium mine water-tailings interface was examined using culture-dependent and -independent techniques. Morphologically-distinct colonies from uranium mine water-tailings and a reference lake (MC) obtained using selective and non-selective media were selected for 16S rRNA gene sequencing and identification, revealing that culturable organisms from the uranium tailings interface were dominated by Firmicutes and Betaproteobacteria; whereas, MC organisms mainly consisted of Bacteroidetes and Gammaproteobacteria. Ion Torrent (IT) 16S rRNA metagenomic analysis carried out on extracted DNA from tailings and MC interfaces demonstrated the dominance of Firmicutes in both of the systems. Overall, the tailings-water interface environment harbored a distinct bacterial community relative to the MC, reflective of the ambient conditions (i.e., total dissolved solids, pH, salinity, conductivity, heavy metals) dominating the uranium tailings system. Significant correlations among the physicochemical data and the major bacterial groups present in the tailings and MC were also observed. Presence of sulfate reducing bacteria demonstrated by culture-dependent analyses and the dominance of Desulfosporosinus spp. indicated by Ion Torrent analyses within the tailings-water interface suggests the existence of anaerobic microenvironments along with the potential for reductive metabolic processes.
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http://dx.doi.org/10.1007/s12275-013-3075-zDOI Listing
October 2013

A versatile and robust aerotolerant microbial community capable of cellulosic ethanol production.

Bioresour Technol 2013 Feb 16;129:156-63. Epub 2012 Nov 16.

Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada.

The use of microbial communities in the conversion of cellulosic materials to bio-ethanol has the potential to improve the economic competitiveness of this biofuel and subsequently lessen our dependency on fossil fuel-based energy sources. Interactions between functionally different microbial groups within a community can expand habitat range, including the creation of anaerobic microenvironments. Currently, research focussing on exploring the nature of the interactions occurring during cellulose degradation and ethanol production within mixed microbial communities has been limited. The aim of this study was to enrich and characterize a cellulolytic bacterial community, and determine if ethanol is a major soluble end-product. Cellulolytic activity by the community was observed in both non-reduced and pre-reduced media, with ethanol and acetate being major fermentation products. Similar results were obtained when sterile wastewater extract was provided as nutrient. Several community members showed high similarity to Clostridium species with overlapping metabolic capabilities, suggesting clostridial functional redundancy.
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http://dx.doi.org/10.1016/j.biortech.2012.10.164DOI Listing
February 2013
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