Publications by authors named "Hilário Cuquetto Mantovani"

29 Publications

  • Page 1 of 1

Bovicin HC5 and nisin reduce cell viability and the thermal resistance of Alicyclobacillus acidoterrestris endospores in fruit juices.

J Sci Food Agric 2022 Jan 8. Epub 2022 Jan 8.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, Brazil.

Background: Alicyclobacillus acidoterrestris is an important thermoacidophilic spore-forming bacterium in fruit-juice deterioration, and alternative non-thermal methods have been investigated to control fruit juice spoilage. This work aimed to evaluate the capacity of bovicin HC5 and nisin to inhibit the growth of vegetative cells and reduce the thermal resistance of endospores of A. acidoterrestris inoculated (10 CFU mL ) in different fruit juices. The number of viable cells was determined after 12 h incubation at 43 °C in the presence and absence of nisin or bovicin HC5 (10-100 AU mL ). The exposure time (min) required to kill 90% of the initial population (reduction of one log factor) at 90 ºC (D ) was used to assess the thermal resistance of A. acidoterrestris endospores exposed (80 AU mL ) or non-exposed to the bacteriocins. Additionally, the effect of bovicin and nisin on the morphology and cell structure of A. acidoterrestris was evaluated by atomic force microscopy (AFM).

Results: Bovicin HC5 and nisin were bactericidal against A. acidoterrestris inoculated in fruit juices and reduced the D values up to 30-fold. AFM topographical images revealed substantial structural changes in the cellular framework of vegetative cells upon treatment with bovicin HC5 or nisin.

Conclusions: These results emphasize the potential application of lantibiotics as additional hurdles in food processing to control thermoacidophilic spoilage bacteria in fruit juices. © 2022 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.11747DOI Listing
January 2022

Protein expression profiling of Staphylococcus aureus in response to the bacteriocin bovicin HC5.

Appl Microbiol Biotechnol 2021 Oct 23;105(20):7857-7869. Epub 2021 Sep 23.

Departamento de Microbiologia, Universidade Federal de Viçosa, Av. P.H. Rolfs, Viçosa, MG, 36570-000, Brazil.

Alternative strategies to antibiotic treatment are required to inhibit pathogens, including Staphylococcus aureus. Bacteriocins, such as the lantibiotic bovicin HC5, have shown potential to control pathogens. This study aims to evaluate the stress response of S. aureus to bovicin HC5 using a proteomic approach. Sublethal concentrations of the bacteriocin repressed the synthesis of 62 cytoplasmic proteins, whereas 42 proteins were induced in S. aureus COL. Specifically, synthesis of several proteins involved in amino acid biosynthesis, mainly products of ilv-leu operon, and DNA metabolism, such as DNA polymerase I, decreased following bovicin treatment while proteins involved in catabolism, mainly tricarboxylic acid cycle metabolism, and chaperones were over-expressed. The levels of CodY and CcpA, important regulators involved in the stationary phase adaptation and catabolite repression, respectively, also increased in the presence of the bacteriocin. These results indicate that stress caused by the sublethal concentration of bovicin HC5 in the cell membrane results in growth reduction, reduced protein synthesis, and, at the same time, enhanced the levels of chaperones and enzymes involved in energy-efficient catabolism in an attempt to restore energy and cell homeostasis. These results bring relevant information to amplify the knowledge concerning the bacterial physiological changes in response to the stress caused by the cell exposition to bovicin HC5. New potential targets for controlling this pathogen can also be determined from the new protein expression pattern presented. KEY POINTS: • Bovicin HC5 changed the synthesis of cytoplasmic proteins of S. aureus. • Bovicin HC5 interfered in the synthesis of proteins of amino acids biosynthesis. • Synthesis of chaperones enhanced in the presence of sublethal dosage of bovicin HC5.
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http://dx.doi.org/10.1007/s00253-021-11594-3DOI Listing
October 2021

Assessing the relationship between the rumen microbiota and feed efficiency in Nellore steers.

J Anim Sci Biotechnol 2021 Jul 15;12(1):79. Epub 2021 Jul 15.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, MG, 36570-900, Brazil.

Background: Ruminants rely upon a complex community of microbes in their rumen to convert host-indigestible feed into nutrients. However, little is known about the association between the rumen microbiota and feed efficiency traits in Nellore (Bos indicus) cattle, a breed of major economic importance to the global beef market. Here, we compare the composition of the bacterial, archaeal and fungal communities in the rumen of Nellore steers with high and low feed efficiency (FE) phenotypes, as measured by residual feed intake (RFI).

Results: The Firmicutes to Bacteroidetes ratio was significantly higher (P < 0.05) in positive-RFI steers (p-RFI, low feed efficiency) than in negative-RFI (n-RFI, high feed efficiency) steers. The differences in bacterial composition from steers with high and low FE were mainly associated with members of the families Lachnospiraceae, Ruminococcaceae and Christensenellaceae, as well as the genus Prevotella. Archaeal community richness was lower (P < 0.05) in p-RFI than in n-RFI steers and the genus Methanobrevibacter was either increased or exclusive of p-RFI steers. The fungal genus Buwchfawromyces was more abundant in the rumen solid fraction of n-RFI steers (P < 0.05) and a highly abundant OTU belonging to the genus Piromyces was also increased in the rumen microbiota of high-efficiency steers. However, analysis of rumen fermentation variables and functional predictions indicated similar metabolic outputs for the microbiota of distinct FE groups.

Conclusions: Our results demonstrate that differences in the ruminal microbiota of high and low FE Nellore steers comprise specific taxa from the bacterial, archaeal and fungal communities. Biomarker OTUs belonging to the genus Piromyces were identified in animals showing high feed efficiency, whereas among archaea, Methanobrevibacter was associated with steers classified as p-RFI. The identification of specific RFI-associated microorganisms in Nellore steers could guide further studies targeting the isolation and functional characterization of rumen microbes potentially important for the energy-harvesting efficiency of ruminants.
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http://dx.doi.org/10.1186/s40104-021-00599-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8281616PMC
July 2021

Effect of the ingestion of vegetable oils associated with energy-restricted normofat diet on intestinal microbiota and permeability in overweight women.

Food Res Int 2021 01 7;139:109951. Epub 2020 Dec 7.

Laboratory of Studies in Food Ingestion, Department of Nutrition and Health, Federal University of Vicosa, Avenida PH Rolfs, s/n, CEP 36570-900 Vicosa, Minas Gerais, Brazil. Electronic address:

Previous studies suggest that the type of dietary fatty acid may modulate the intestinal bacterial ecosystem. However, this effect is still inconclusive. Thus, the aim of this study was to investigate the effect of the intake of vegetable oils rich in different types of fatty acids, associated with energy-restricted normofat diets, on the composition of intestinal microbiota and permeability, on LPS concentrations, and fecal short chain fatty acids and pH. This was a 9 consecutive weeks (±5 days), randomized, parallel, double-blind clinical trial. Overweight women received daily breakfast containing 25 mL of one of the test oils: soybean oil (n = 17), extra virgin olive oil (n = 19) or coconut oil (n = 16). Blood, fecal and urine samples were collected on the first and last day of the experiment for the analysis of the variables of interest. The consumption of the three oils did not affect the diversity and relative abundance of intestinal bacteria. We observed an increase in bacterial richness estimated by the Chao 1 index, and a reduction in the concentration of isovaleric fatty acid in the group that ingested soybean oil. Paracellular and transcellular permeability increased after the ingestion of extra virgin olive oil and coconut oil. However, LPS concentrations remained unchanged. The intake of different types of fatty acids associated with the energy-restricted normofat diet modestly affected the intestinal microbiota and permeability, without resulting in metabolic endotoxemia in overweight women.
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http://dx.doi.org/10.1016/j.foodres.2020.109951DOI Listing
January 2021

Chemoprevention of DMH-Induced Early Colon Carcinogenesis in Male BALB/c Mice by Administration of DTA81.

Microorganisms 2020 Dec 14;8(12). Epub 2020 Dec 14.

Department of General Biology, Av. Peter Henry Rolfs, s/n, Campus Universitario, Universidade Federal de Vicosa, 36570-900 Vicosa, Brazil.

We evaluated the effects of the probiotic candidate DTA81 (DTA81) on liver oxidative stress, colonic cytokine profile, and gut microbiota in mice with induced early colon carcinogenesis (CRC) by 1,2-dimethylhydrazine (DMH). Animals were divided into four different groups ( = 6) and received the following treatments via orogastric gavage for 8 weeks: Group skim milk (GSM): 300 mg/freeze-dried skim milk/day; Group DTA81 (DTA81): 3 × 10 colony-forming units (CFU)/day; Group GG (LGG): 3 × 10 CFU/day; Group non-intervention (GNI): 0.1 mL/water/day. A single DMH dose (20 mg/kg body weight) was injected intraperitoneally (i.p), weekly, in all animals (seven applications in total). At the end of the experimental period, DTA81 intake reduced hepatic levels of carbonyl protein and malondialdehyde (MDA). Moreover, low levels of the pro-inflammatory cytokines Interleukin-6 (IL-6) and IL-17, as well as a reduced expression level of the proliferating cell nuclear antigen (PCNA) were observed in colonic homogenates. Lastly, animals who received DTA81 showed an intestinal enrichment of the genus and increased concentrations of caecal acetic acid and total short-chain fatty acids. In conclusion, this study indicates that the administration of the probiotic candidate DTA81 can have beneficial effects on the initial stages of CRC development.
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http://dx.doi.org/10.3390/microorganisms8121994DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7765108PMC
December 2020

Teaching-learning: a mutual exchange between high school and graduate students in the field of microbiology.

FEMS Microbiol Lett 2020 Dec 3. Epub 2020 Dec 3.

Departamento de Biologia Geral, Universidade Federal de Viçosa, Viçosa, 36570-000, Brazil.

The teaching-learning process becomes more attractive when practical classes are used as part of methodological tools. Aiming (i) to stimulate the interest of high school students in the microbiological world and (ii) to provide didactic experience for microbiology graduate students, practical classes were undertaken. These classes were carried out during the years 2016 and 2017, using the infrastructure held at Universidade Federal de Viçosa. Briefly, laboratory classes were prepared and taught by microbiology graduate students and an evaluation questionnaire was answered by the participants after the classes. Approximately 95% of the high school students, from both years, evaluated the experience outside of the school routine as very good and good. A total of 90.09% (2016) and 100% (2017) of graduate students evaluated this experience as very good and good. The relationship between high school and graduate students also increased the curiosity of the former regarding the university environment. Accordingly, the information retention regarding the 'microbiology world' was verified after one year and the students were able to remember important terms related to the microbiology class. In addition, this work allowed graduate students and high school students to build a closer relationship and created an excellent teaching-learning strategy for both.
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http://dx.doi.org/10.1093/femsle/fnaa199DOI Listing
December 2020

Stimulation of Bovicin HC5 Production and Selection of Improved Bacteriocin-Producing Streptococcus equinus HC5 Variants.

Probiotics Antimicrob Proteins 2021 06;13(3):899-913

Departamento de Microbiologia, Universidade Federal de Viçosa, Vicosa, MG, 36570-900, Brazil.

Bovicin HC5 is a peptide that has inhibitory activity against various pathogenic microorganisms and food spoilage bacteria. Aiming to improve the productivity of this bacteriocin, we evaluated several potential factors that could stimulate the synthesis of bovicin HC5 and selected variants of Streptococcus equinus (Streptococcus bovis) HC5 with enhanced bacteriocin production by adaptive laboratory evolution (ALE). The highest production of the bacteriocin (1.5-fold) was observed when Strep. equinus HC5 was cultivated with lactic acid (100 mmol/L). For the ALE experiment, Strep. equinus HC5 cells were subjected to acid-shock (pH 3.0 for 2 h) and maintained in continuous culture for approximately 140 generations (40 days) in media with lactic acid (100 mmol/L) and pH-controlled at 5.5 ± 0.2. An adapted variant was selected showing a distinct phenotype (sedimentation, pigmentation) compared with the parental strain. Bacteriocin production increased 2-fold in this adapted Strep. equinus HC5 variant, which appears to be associated with changes in the cell envelope of the adapted variant and enhanced bacteriocin release into the culture media. In addition, the adapted variant showed higher levels of expression of all bovicin HC5 biosynthetic genes compared with the parental strain during the early and late stages of growth. Results presented here indicate that ALE is a promising strategy for selecting strains of lactic acid bacteria with increased production of bacteriocins.
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http://dx.doi.org/10.1007/s12602-020-09703-1DOI Listing
June 2021

Morphology and composition of the midgut bacterial community of Scaptocoris castanea Perty, 1830 (Hemiptera: Cydnidae).

Cell Tissue Res 2020 Nov 23;382(2):337-349. Epub 2020 May 23.

Departamento de Biologia Geral, Universidade Federal de Viçosa, Vicosa, Minas Gerais, 36570-000, Brazil.

The burrower bug Scaptocoris castanea is an important soybean and pasture pest in Brazil, with an underground habit feeding directly on the sap of the roots. Underground habit hinders control and knowledge of the biology and physiology of this pest. This study describes the anatomy, histology, ultrastructure and symbionts of the midgut of S. castanea. The midgut of S. castanea is anatomically divided into five regions (ventricles). Ventricles 1-3 are similar between males and females, with cells specialized in digestion and absorption of nutrients, water transport and homeostasis. Ventricle 4 has squamous epithelium forming crypts and harboring bacteria in the lumen. Ventricle 5 of males is small with cells containing apical microvilli and broad basal folds with many openings for hemocoel, while in females, this region of the midgut is well developed and colonized by intracellular bacteria, characterizing bacteriocytes. The main bacteria are Gammaproteobacteria. The results show sexual dimorphism in ventricle 5 of the midgut of S. castanea, with formation of bacteriocytes in the females, while the other regions are involved in digestive processes in both sexes.
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http://dx.doi.org/10.1007/s00441-020-03197-7DOI Listing
November 2020

Characterization of antibiotic resistance genes in the species of the rumen microbiota.

Nat Commun 2019 11 20;10(1):5252. Epub 2019 Nov 20.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.

Infections caused by multidrug resistant bacteria represent a therapeutic challenge both in clinical settings and in livestock production, but the prevalence of antibiotic resistance genes among the species of bacteria that colonize the gastrointestinal tract of ruminants is not well characterized. Here, we investigate the resistome of 435 ruminal microbial genomes in silico and confirm representative phenotypes in vitro. We find a high abundance of genes encoding tetracycline resistance and evidence that the tet(W) gene is under positive selective pressure. Our findings reveal that tet(W) is located in a novel integrative and conjugative element in several ruminal bacterial genomes. Analyses of rumen microbial metatranscriptomes confirm the expression of the most abundant antibiotic resistance genes. Our data provide insight into antibiotic resistange gene profiles of the main species of ruminal bacteria and reveal the potential role of mobile genetic elements in shaping the resistome of the rumen microbiome, with implications for human and animal health.
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http://dx.doi.org/10.1038/s41467-019-13118-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6868206PMC
November 2019

The Bacterial and Fungal Microbiota of Nelore Steers Is Dynamic Across the Gastrointestinal Tract and Its Fecal-Associated Microbiota Is Correlated to Feed Efficiency.

Front Microbiol 2019 25;10:1263. Epub 2019 Jun 25.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, Brazil.

The ruminant gastrointestinal tract (GIT) microbiome plays a major role in the health, physiology and production traits of the host. In this work, we characterized the bacterial and fungal microbiota of the rumen, small intestine (SI), cecum and feces of 27 Nelore steers using next-generation sequencing and evaluated biochemical parameters within the GIT segments. We found that only the bacterial microbiota clustered according to each GIT segment. Bacterial diversity and richness as well as volatile fatty acid concentration was lowest in the SI. Taxonomic grouping of bacterial operational taxonomic units (OTUs) revealed that (24.61 ± SD 6.58%) and (20.87 ± SD 4.22%) were the two most abundant taxa across the GIT. For the fungi, the family dominated in all GIT segments, with the genus being the most abundant. Twenty-eight bacterial and six fungal OTUs were shared across all GIT segments in at least 50% of the steers. We also evaluated if the fecal-associated microbiota of steers showing negative and positive residual feed intake (n-RFI and p-RFI, respectively) was associated with their feed efficiency phenotype. Diversity indices for both bacterial and fungal fecal microbiota did not vary between the two feed efficiency groups. Differences in the fecal bacterial composition between high and low feed efficiency steers were primarily assigned to OTUs belonging to the families and and to the genus . The fungal OTUs shared across the GIT did not vary between feed efficiency groups, but 7 and 3 OTUs were found only in steers with positive and negative RFI, respectively. These results provide further insights into the composition of the Nelore GIT microbiota, which could have implications for improving animal health and productivity. Our findings also reveal differences in fecal-associated bacterial OTUs between steers from different feed efficiency groups, suggesting that fecal sampling may represent a non-invasive strategy to link the bovine microbiota with productivity phenotypes.
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http://dx.doi.org/10.3389/fmicb.2019.01263DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6603086PMC
June 2019

Bacupari (Garcinia brasiliensis) extract modulates intestinal microbiota and reduces oxidative stress and inflammation in obese rats.

Food Res Int 2019 08 8;122:199-208. Epub 2019 Apr 8.

Department of Nutrition and Health, Federal University of Viçosa, Avenida P.H. Rolfs, University Campus S/N, Viçosa, MG 36570-900, Brazil. Electronic address:

The objective of this study was to evaluate the effects of an ethanolic extract of the bark of bacupari (Garcinia brasiliensis - EEB) on the abundance of intestinal microbiota, concentration of short-chain fatty acids (SCFAs), oxidative stress, and inflammation in obese rats fed a high-fat diet (HFD). Male Wistar rats were divided into three groups: an HFD-fed obese control group, a group fed HFD plus EEB (BHFD) at a dose of 300 mg per animal per day (42 mg 7-epiclusianone and 10.76 mg morelloflavone), and a lean control group fed an AIN-93 M diet for 8 weeks. EEB decreased (p < 0.05) the abundance of organisms belonging to the phyla Firmicutes and Proteobacteria, and increased (p < 0.05) the concentration of propionic acid. Liver concentrations of malondialdehyde, nitric oxide, resistin, and p65 nuclear factor-kappa B p65(NF-κB) decreased (p < 0.05), while the expression of heat shock protein (HSP)72 and catalase increased (p < 0.05) with the consumption of EEB. Moreover, computational molecular modeling studies involving molecular docking between the main constituents of EEB, 7-epiclusianone and morelloflavone, and NF-κB suggested its inhibitory activity, thus corroborating the experimental results. The consumption of EEB may therefore be a promising strategy for the beneficial dietary modulation of the intestinal ecosystem, thereby countering oxidative stress and inflammation in obese rats. This activity is attributable to the presence of bioactive compounds that act individually or synergistically in the scavenging of free radicals or in the inflammatory process.
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http://dx.doi.org/10.1016/j.foodres.2019.04.012DOI Listing
August 2019

Synbiotic meal decreases uremic toxins in hemodialysis individuals: A placebo-controlled trial.

Food Res Int 2019 02 9;116:241-248. Epub 2018 Aug 9.

Nutrition and Health Department, Federal University of Viçosa, PH Rolfs Avenue, s/n, Viçosa 36.570-900, Minas Gerais, Brazil.

Generation of uremic toxins p-cresylsulfate (p-CS), indoxyl sulfate (IS) and indole 3-acetic acid (IAA) in hemodialysis (HD) individuals may be associated with the gut flora and recognized markers of disease progression. This study investigated the effect of synbiotic meal on uremic toxins in HD individuals. We conducted randomized singleblind and placebo-controlled intervention study with 58 HD subjects (20F/38M, 63.1 ± 10.9-old) who were randomly allocated in synbiotic group (SG, 40 g of extruded sorghum plus 100 mL of unfermented probiotic milk) or control group (CG, 40 g of extruded corn plus 100 mL of pasteurized milk), during 7-wk Metabolic markers and uremic toxins, fecal concentration of short chain fatty acid and pH value was determined. The SG group had decreased serum p-CS and IS, as well as decreased urea concentration (p < .05) compared to CG. SG showed higher fecal butyric acid and lower pH compared to baseline and SC (p < .05). In addition, serum p-CS and fecal pH were positively correlated to urea concentration in SG participants at the endpoint. The consumption of the synbiotic meal during 7-wk reduced colonic pH, and reduced serum uremic (p-CS and IS) toxins and urea in HD subjects.
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http://dx.doi.org/10.1016/j.foodres.2018.08.024DOI Listing
February 2019

Effects of grain processing methods on the expression of genes involved in volatile fatty acid transport and pH regulation, and keratinization in rumen epithelium of beef cattle.

PLoS One 2018 14;13(6):e0198963. Epub 2018 Jun 14.

Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.

Two experiments were carried out to evaluate the effects of corn and sorghum with different processing methods on the expression of genes involved in volatile fatty acids transport and pH regulation, and ruminal keratinization in rumen epithelium of finishing bulls. For Exp. 1, five rumen cannulated Nellore bulls were used in a 5x5 Latin square arrangement, with 14 d for adaptation and 9 d for sample collection. Treatments were: dry ground corn, dry ground sorghum, reconstituted corn, reconstituted sorghum, and control (forage-based diet). Samples of rumen epithelium from ventral sac were excised, rinsed, snap-frozen and stored at -80°C until total RNA isolation and quantitative real-time PCR analysis. In the Exp. 2, 24 Nellore bulls were assigned to a completely randomized design lasting 168 d. Experimental treatments were similar to those at Exp. 1, but without the control treatment. After the experimental period, bulls were slaughtered and rumen epithelium samples were rapidly excised for further histological analysis. Rumen epithelial tissue from animals fed reconstituted corn had lower expression of downregulated-in-adenoma (P = 0.03) and Na+/H+ exchanger 2 (trend; P = 0.09). The expression of Na+/ H+ exchanger 1 (P = 0.10) and putative anion transporter (P = 0.06) tended to be lower in rumen epithelium of bulls fed reconstituted grains. Ruminal concentration of valerate was greater for animals fed reconstituted grain (P = 0.01). Likewise, animals fed reconstituted corn tended to have greater butyrate ruminal concentration (P = 0.08). Keratinized layer thickness did not differ among treatments (P > 0.10). Therefore, reconstituted grains (especially corn) decrease the mRNA expression of genes involved in volatile fatty acids transport and pH control in the rumen epithelium.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0198963PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6002044PMC
December 2018

Bacterial Community Dynamics across the Gastrointestinal Tracts of Dairy Calves during Preweaning Development.

Appl Environ Microbiol 2018 05 16;84(9). Epub 2018 Apr 16.

Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA

Microbial communities play critical roles in the gastrointestinal tracts (GIT) of preruminant calves by influencing performance and health. However, little is known about the establishment of microbial communities in the calf GIT or their dynamics during development. In this study, next-generation sequencing was used to assess changes in the bacterial communities of the rumen, jejunum, cecum, and colon in 26 crossbred calves at four developmental stages (7, 28, 49, and 63 days old). Alpha diversity differed among GIT regions with the lowest diversity and evenness in the jejunum, whereas no changes in alpha diversity were observed across developmental stage. Beta diversity analysis showed both region and age effects, with low numbers of operational taxonomic units (OTUs) shared between regions within a given age group or between ages in a given region. Taxonomic analysis revealed that several taxa coexisted in the rumen, jejunum, cecum, and colon but that their abundances differed considerably by GIT region and age. As calves aged, we observed lower abundances of taxa such as , , and with higher abundances of and in the rumen. The jejunum also displayed taxonomic changes with increases in and taxa in older calves. In the lower gut, taxa such as , , and decreased and S24-7, , and increased as calves aged. These data support a model whereby early and successive colonization by bacteria occurs across the GIT of calves and provides insights into the temporal dynamics of the GIT microbiota of dairy calves during preweaning development. The gastrointestinal tracts (GIT) of ruminants, such as dairy cows, house complex microbial communities that contribute to their overall health and support their ability to produce milk. For example, the rumen microbiota converts feed into usable nutrients, while the jejunal microbiota provides access to protein. Thus, establishing a properly functioning GIT microbiota in dairy calves is critical to their productivity as adult cows. However, little is known about the establishment, maintenance, and dynamics of the calf GIT microbiota in early life. In this study, we evaluated the bacterial communities in the rumen, jejunum, cecum, and colon in dairy calves across preweaning development and show that they are highly variable early on in life before transitioning to a stable community. Understanding the dairy calf GIT microbiota has implications for ensuring proper health during early life and will aid in efforts to develop strategies for improving downstream production.
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http://dx.doi.org/10.1128/AEM.02675-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5930334PMC
May 2018

Antioxidant, antiproliferative, and immunostimulatory effects of cell wall α-d-mannan fractions from Kluyveromyces marxianus.

Int J Biol Macromol 2018 Apr 11;109:837-846. Epub 2017 Nov 11.

Department of Biochemistry, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte, 59,078-970, Brazil. Electronic address:

This study evaluated the antioxidant, antiproliferative, and immunostimulatory properties of cell wall α-d-mannan fractions from yeast Kluyveromyces marxianus CCT7735. Filter centrifugation was used to obtain four fractions (KMM-1, KMM-2, KMM-3, and KMM-4) with molecular weight ranging from 7.6 to 75.1kDa. KMM-1 and KMM-2 comprised D-mannose with traces of D-glucose, whereas other fractions contained only D-mannose. Total sugar found in samples ranged from 85.9% to 96.1%, while protein and phenolic contents were 1.21% and 0.41%, respectively. Although only KMM-1 was able to scavenge superoxide radicals, all fractions presented total antioxidant capacity as well as reducing power, hydroxyl-radical scavenging, and copper- and iron-chelating activities. No fraction was cytotoxic to HeLa cells. However, all samples inhibited the proliferation of the tumor cell Hep-G2 and presented minor cytotoxicity against normal 3T3 cells. All fractions showed mitogenic activity in macrophages and all, except KMM-4, induced nitric oxide production in macrophages, suggestive of their immunostimulatory effects.
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http://dx.doi.org/10.1016/j.ijbiomac.2017.11.053DOI Listing
April 2018

Bacteriocins from lactic acid bacteria and their potential in the preservation of fruit products.

Crit Rev Biotechnol 2017 Nov 3;37(7):852-864. Epub 2017 Jan 3.

a Departamento de Morfologia , Universidade Federal de Sergipe , São Cristóvão , Sergipe , Brazil.

Bacteriocins produced by lactic acid bacteria (LAB) are well-recognized for their potential as natural food preservatives. These antimicrobial peptides usually do not change the sensorial properties of food products and can be used in combination with traditional preservation methods to ensure microbial stability. In recent years, fruit products are increasingly being associated with food-borne pathogens and spoilage microorganisms, and bacteriocins are important candidates to preserve these products. Bacteriocins have been extensively studied to preserve foods of animal origin. However, little information is available for their use in vegetable products, especially in minimally processed ready-to-eat fruits. Although, many bacteriocins possess useful characteristics that can be used to preserve fruit products, to date, only nisin, enterocin AS-48, bovicin HC5, enterocin 416K1, pediocin and bificin C6165 have been tested for their activity against spoilage and pathogenic microorganisms in these products. Among these, only nisin and pediocin are approved to be commercially used as food additives, and their use in fruit products is still limited to certain countries. Considering the increasing demand for fresh-tasting fruit products and concern for public safety, the study of other bacteriocins with biochemical characteristics that make them candidates for the preservation of these products are of great interest. Efforts for their approval as food additives are also important. In this review, we discuss why the study of bacteriocins as an alternative method to preserve fruit products is important; we detail the biotechnological approaches for the use of bacteriocins in fruit products; and describe some bacteriocins that have been tested and have potential to be tested for the preservation of fruit products.
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http://dx.doi.org/10.1080/07388551.2016.1262323DOI Listing
November 2017

Chemical structure, antiproliferative and antioxidant activities of a cell wall α-d-mannan from yeast Kluyveromyces marxianus.

Carbohydr Polym 2017 Feb 5;157:1298-1305. Epub 2016 Nov 5.

Department of Biochemistry, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte 59.078-970, Brazil. Electronic address:

Cell wall polysaccharides from filamentous fungi and yeasts have been reported as antioxidant and antiproliferative polymers. Thus, we evaluated these activities from cell wall polysaccharides from Kluyveromyces marxianus CCT7735. By using a centrifugal filter, a 203kDa α-d-mannan (KMM-5) was obtained. KMM-5 exhibited no effect on HeLa cells and a weak antiproliferative activity against Hep-G2 cells. In addition, at higher concentrations, it presented a cytotoxicity to the normal cell line, 3T3. However, KMM-5 showed copper- and iron-chelating abilities, the latter of which presented improved activity. By using 2D-NMR COSY, HSQC edited and HMBC experiments, a structure arrangement was proposed. The main chain was formed by 6)-α-d-Manp-(1→6) units substituted at the 2-O-position by non-reducing terminals α-d-Manp-(1→2) and by a branched tetrasaccharide. The latter was formed by an internal 2)-α-d-Manp-(1→2) unit with linked to it a 2,3)-α-d-Manp-(1→2) unit substituted at the 2-O-position by a non-reducing terminal α-d-Manp-(1→2), and at the 3-O-position by a non-reducing terminal α-d-Manp-(1→3). In conclusion, we considered K. marxianus CCT7735 a source of natural and renewable polysaccharides with pharmacological properties.
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http://dx.doi.org/10.1016/j.carbpol.2016.11.015DOI Listing
February 2017

Tithonia diversifolia as a Supplementary Feed for Dairy Cows.

PLoS One 2016 1;11(12):e0165751. Epub 2016 Dec 1.

The University of Sydney, Faculty of Veterinary Science, School of Life and Environmental Sciences, Sydney, NSW, Australia.

The objective of this study was to examine the effects of Tithonia diversifolia as a supplementary forage on dairy cow performance and methane production. Nine lactating Holstein × Zebu dairy cows (519 ± 53.3 kg of body weight and 66 ± 13.3 d in milk) were paired by milk yield (21.3 ± 2.34 kg/d) and body weight and randomly assigned to three dietary treatments in a Latin square design with 21-d experimental periods (14 d for diet adaptation and 7 d for measurements and sample collection). The dietary treatments included the control diet consisting of fresh sugar cane plus concentrate (44:56, % of diet DM), and two treatment diets containing different levels of fresh T. diversifolia (6.5 and 15.4%, DM basis) which partially replaced both sugarcane and concentrates. Methane production was measured using the sulphur hexafluoride (SF6) technique from d 16 to d 21 of each experimental period. Analysis of the gas samples was performed by gas chromatography. The inclusion of T. diversifolia at 15.4% DM had no effects on DM intake, milk production, nitrogen balance or methane production. There was no effect on the concentrations of total saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) in milk fat (P ≥ 0.28), though individual milk fatty acids were affected. Serum concentrations of glucose, urea nitrogen (BUN), triglycerides, β-hydroxybutyrate (BHBA), and cholesterol were unaffected by the dietary treatments (P ≥ 0.13). There was a time (2 and 6 h post-feeding) and dietary treatment effect (P < 0.01) on the acetate to propionate ratio in the rumen. A denaturing gradient gel electrophoresis analysis of the archaeal community showed distinct clustering of the archaea populations for control and treatment diets. Taken together, our results indicate the potential of T. diversifolia as a supplementary forage for dairy cattle in the tropics.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0165751PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5132235PMC
July 2017

Acyl homoserine lactone-based quorum sensing stimulates biofilm formation by Salmonella Enteritidis in anaerobic conditions.

Arch Microbiol 2017 Apr 12;199(3):475-486. Epub 2016 Nov 12.

Department of Microbiology, Universidade Federal de Viçosa, Viçosa, Minas Gerais, 36570-900, Brazil.

Quorum sensing regulates a variety of phenotypes in bacteria including the production of virulence factors. Salmonella spp. have quorum sensing systems mediated by three autoinducers (AI-1, AI-2, and AI-3). The AI-1-mediated system is incomplete in that the bacterium relies on the synthesis of signaling molecules by other microorganisms. This study aimed to evaluate the influence of the AI-1 N-dodecanoyl-DL-homoserine lactone (C12-HSL) on the growth, motility, adhesion, and biofilm formation of Salmonella enterica serovar Enteritidis PT4 578 on a polystyrene surface. Experiments were conducted at 37 °C in anaerobic tryptone soy broth supplemented with C12-HSL and/or a mixture of four synthetic furanones, at the concentration of 50 nM each. The planktonic growth, adhesion, swarming, and twitching motility were not altered in the presence of C12-HSL and/or furanones under anaerobic conditions. However, C12-HSL induced biofilm formation after 36 h of cultivation as determined by quantification of biofilm formation, by enumeration of adhered cells to polystyrene coupons, and finally by imaging the presence of multilayered cells on an epifluorescence microscope. When furanones were present in the medium, an antagonistic effect against C12-HSL on the biofilm development was observed. The results demonstrate an induction of biofilm formation in Salmonella Enteritidis by AI-1 under anaerobic conditions. Considering that Salmonella does not produce AI-1 but respond to it, C12-HSL synthesized by other bacterial species could trigger biofilm formation by this pathogen in conditions that are relevant for its pathogenesis.
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http://dx.doi.org/10.1007/s00203-016-1313-6DOI Listing
April 2017

A central composite rotatable design (CCRD) approach to study the combined effect of antimicrobial agents against bacterial pathogens.

World J Microbiol Biotechnol 2015 Sep 17;31(9):1361-7. Epub 2015 Jun 17.

Departamento de Microbiologia, Universidade Federal de Viçosa, Av. PH Rolfs s/n - Campus Universitário, Viçosa, Minas Gerais, CEP 36570-900, Brazil.

The combination of antimicrobial agents has been proposed as a therapeutic strategy to control bacterial diseases and to reduce the emergence of antibiotic-resistant strains in clinical environments. In this study, the interaction between the lantibiotic bovicin HC5 with chloramphenicol, gentamicin, nisin, lysostaphin and hydrogen peroxide against Staphylococcus aureus O46 was evaluated by MIC assays. The central composite rotatable design (CCRD), a robust and economic statistical design, was used to combine concentration levels of different antimicrobials agents with distinct mechanisms of action and the presence of significant interactions among the antimicrobials was determined by regression analysis. According to the adjusted model, there were no significant interactions between bovicin HC5 and gentamicin, lysostaphin, nisin or hydrogen peroxide. However, bovicin HC5 showed a significant interaction (P < 0.02) with chloramphenicol. This is the first study applying the CCRD approach to evaluate the combined effect of antimicrobials against S. aureus. Based on our results, this approach is an effective strategy to determine synergistic interactions between antimicrobial agents applied in human and veterinary medicine against bacterial pathogens.
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http://dx.doi.org/10.1007/s11274-015-1884-4DOI Listing
September 2015

Biochemical and genetic diversity of carbohydrate-fermenting and obligate amino acid-fermenting hyper-ammonia-producing bacteria from Nellore steers fed tropical forages and supplemented with casein.

BMC Microbiol 2015 Feb 14;15:28. Epub 2015 Feb 14.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.

Background: Dietary protein plays a major role in ruminant nutrition, and protein supplementation is a widespread practice among farmers in the tropics. Ruminal bacteria are the main agents of dietary protein and amino acid degradation, yet few studies have focused on the isolation and characterization of hyper-ammonia-producing bacteria in animals fed tropical diets or supplemented with rumen-degradable proteins. This work investigated the bacterial community diversity of the rumen of Nellore steers fed tropical forages, with or without casein supplementation. We also isolated and characterized ruminal bacteria showing high levels of ammonia production.

Results: Polymerase chain reaction-denaturing gradient gel electrophoresis analysis indicated no differences in the ruminal bacterial community composition between the control and supplemented animals. Amino acid-fermenting bacteria (n = 250) were isolated from crossbred Nellore steers fed Tifton 85 (Cynodon sp.) using trypticase as the sole carbon and organic nitrogen source in the enrichment and isolation media. The deamination rates in isolates obtained from steers supplemented with casein showed a higher incidence of deamination rates >350 nmol NH3 mg protein(-1) min(-1) (P < 0.05), whereas isolates obtained from steers without supplementation showed deamination rates <200 nmol NH3 mg protein(-1) min(-1). Although most isolates (84%) could ferment carbohydrates, none could hydrolyze proteins or use urea to sustain growth. All isolates were sensitive to lasalocid and monensin (1 μmol l(-1)), and similarity analysis of the 16S rRNA sequences indicated a predominance of bacteria from the order Clostridiales, with variable homology (73-99%) to known bacterial species.

Conclusions: These results expand what is known about the biochemical and genetic diversity of hyper-ammonia-producing bacteria, and emphasize the role of carbohydrate-fermenting bacteria in ammonia production in the rumen.
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http://dx.doi.org/10.1186/s12866-015-0369-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4332921PMC
February 2015

Bovicin HC5 and nisin reduce Staphylococcus aureus adhesion to polystyrene and change the hydrophobicity profile and Gibbs free energy of adhesion.

Int J Food Microbiol 2014 Nov 9;190:1-8. Epub 2014 Aug 9.

Departamento de Microbiologia, Universidade Federal de Viçosa, Av. P.H. Rolfs, 36570-000 Viçosa, Brazil. Electronic address:

Staphylococcus aureus is an opportunistic pathogen often multidrug-resistant that not only causes a variety of human diseases, but also is able to survive on biotic and abiotic surfaces through biofilm communities. The best way to inhibit biofilm establishment is to prevent cell adhesion. In the present study, subinhibitory concentrations of the bacteriocins bovicin HC5 and nisin were tested for their capability to interfere with the adhesion of S. aureus to polystyrene. Subinhibitory dosages of the bacteriocins reduced cell adhesion and this occurred probably due to changes in the hydrophobicity of the bacterial cell and polystyrene surfaces. After treatment with bovicin HC5 and nisin, the surfaces became more hydrophilic and the free energy of adhesion (∆G(adhesion)) between bacteria and the polystyrene surface was unfavorable. The transcriptional level of selected genes was assessed by RT-qPCR approach, revealing that the bacteriocins affected the expression of some important biofilm associated genes (icaD, fnbA, and clfB) and rnaIII, which is involved in the quorum sensing mechanism. The conditioning of food-contact surfaces with bacteriocins can be an innovative and powerful strategy to prevent biofilms in the food industry. The results are relevant for food safety as they indicate that bovicin HC5 and nisin can inhibit bacterial adhesion and consequent biofilm establishment, since cell adhesion precedes biofilm formation.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2014.08.004DOI Listing
November 2014

Safety evaluation of the antimicrobial peptide bovicin HC5 orally administered to a murine model.

BMC Microbiol 2013 Mar 27;13:69. Epub 2013 Mar 27.

Background: Bovicin HC5 is an antimicrobial peptide that shows a broad spectrum of activity and potential for biotechnological and therapeutic applications. To gain insight about the safety of bovicin HC5 application, the histological and immunostimulatory effects of orally administrated bovicin HC5 to BALB/c mice were evaluated. BALB/c mice were divided into three groups: negative control (NC group); mice given purified bovicin HC5 (Bov group); mice given ovalbumin (positive control, PC group; a murine model of enteropathy). The mice were initially pre-sensitized, and PBS, bovicin HC5 or ovalbumin were administered for 30 days by daily gavages. Histological and morphometric analysis were performed and the relative expression of cytokines was analyzed by real-time RT-PCR.

Results: The oral administration of bovicin HC5 to BALB/c mice reduced weight gain and caused alterations in the small intestine, although absorptive changes have not been detected. The number of total goblet cells and the mucopolysaccharides production were not affected by bovicin HC5 administration. A hypertrophy of Paneth cells and an increase in the number of mitotic cells were observed in Bov group, while the number of mast cells remained unaltered. Increased expression of TNF-α, INF-γ and IL-12 was observed in the small intestine upon bovicin HC5 administration.

Conclusion: Bovicin HC5 has only minor effects on intestinal permeability and did not elicit an allergenic response upon oral administration to animal models. Considering the low in vivo toxicity of bovicin HC5, it might be a good candidate for enteral applications.
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http://dx.doi.org/10.1186/1471-2180-13-69DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3639230PMC
March 2013

AiiA quorum-sensing quenching controls proteolytic activity and biofilm formation by Enterobacter cloacae.

Curr Microbiol 2012 Dec 18;65(6):758-63. Epub 2012 Sep 18.

Department of Microbiology, Federal University of Viçosa, Viçosa, MG 36570-000, Brazil.

The aim of this work was to evaluate a quorum-quenching approach to identify functions regulated by quorum sensing in Enterobacter cloacae. We employed an aiiA transconjugant strain of E. cloacae that synthesizes a lactonase enzyme that hydrolyzes N-acyl homoserine lactone signaling molecules to compare bacterial phenotypes in the presence and absence of quorum signals. The aiiA-expressing strain displayed increased proteolytic activity and intensity of a milk-clotting reaction when compared to the wild-type strain. Although both strains growing on polystyrene plates in rich media and a minimal medium of salts formed biofilms, the wild-type strain exhibited a higher number of adhered cells. On the surface of stainless steel coupons that were submerged in culture media, the number of adhered cells of the wild type contained up to one log more cells compared with the aiiA transconjugant. However, after 48 h of incubation, there was no significant difference between the strains. The results demonstrated that the quorum-sensing system negatively regulates proteolytic activity and is likely involved in the early steps of biofilm formation by E. cloacae 067.
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http://dx.doi.org/10.1007/s00284-012-0226-0DOI Listing
December 2012

Toxicity of bovicin HC5 against mammalian cell lines and the role of cholesterol in bacteriocin activity.

Microbiology (Reading) 2012 Nov 6;158(Pt 11):2851-2858. Epub 2012 Sep 6.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.

Bacteriocins are ribosomally synthesized antimicrobial peptides produced by Bacteria and some Archaea. The assessment of the toxic potential of antimicrobial peptides is important in order to apply these peptides on an industrial scale. The aim of the present study was to investigate the in vitro cytotoxic and haemolytic potential of bovicin HC5, as well as to determine whether cholesterol influences bacteriocin activity on model membranes. Nisin, for which the mechanism of action is well described, was used as a reference peptide in our assays. The viability of three distinct eukaryotic cell lines treated with bovicin HC5 or nisin was analysed by using the MTT assay and cellular morphological changes were determined by light microscopy. The haemolytic potential was evaluated by using the haemoglobin liberation assay and the role of cholesterol on bacteriocin activity was examined by using model membranes composed of DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) and DPoPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine). The IC(50) of bovicin HC5 and nisin against Vero cells was 65.42 and 13.48 µM, respectively. When the MTT assay was performed with MCF-7 and HepG2 cells, the IC(50) obtained for bovicin HC5 was 279.39 and 289.30 µM, respectively, while for nisin these values were 105.46 and 112.25 µM. The haemolytic activity of bovicin HC5 against eukaryotic cells was always lower than that determined for nisin. The presence of cholesterol did not influence the activity of either bacteriocin on DOPC model membranes, but nisin showed reduced carboxyfluorescein leakage in DPoPC membranes containing cholesterol. In conclusion, bovicin HC5 only exerted cytotoxic effects at concentrations that were greater than the concentration needed for its biological activity, and the presence of cholesterol did not affect its interaction with model membranes.
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http://dx.doi.org/10.1099/mic.0.062190-0DOI Listing
November 2012

Bactericidal activity of ethanolic extracts of propolis against Staphylococcus aureus isolated from mastitic cows.

World J Microbiol Biotechnol 2012 Feb 17;28(2):485-91. Epub 2011 Jul 17.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa-MG, 36570-000, Brazil.

Staphylococcus aureus is an important pathogen for both humans and animals, and it has been an ubiquitous etiological agent of bovine mastitis in dairy farms worldwide. Elimination of S. aureus with classic antibiotics is difficult, and the current study aimed to evaluate the efficacy of ethanolic extracts of propolis (EEP) against S. aureus cultivated in complex media or milk. EEP (0-0.5 mg ml(-1)) decreased growth of S. aureus in BHI media and 1 mg ml(-1) was bactericidal against washed cell suspensions (10(7) CFU ml(-1)). Propolis extracts also killed S. aureus cells resuspended in milk, but the bactericidal dose was at least 20-fold greater. Cultures that were transferred for at least 60 generations with sub-lethal doses of propolis did not change much their sensibility to EEP. Atomic force microscopy images revealed changes in morphology and cell size of S. aureus cells exposed to EEP (0.5 mg ml(-1)). Our results indicate that propolis extracts might be effective against mastitis-causing S. aureus strains in vivo, but milk constituents affect the inhibitory activity of propolis. Considering that propolis-resistance appears to be a phenotype not easily selected, the use of EEP combined or not with other antimicrobial agents might be useful for mastitis control in vivo.
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http://dx.doi.org/10.1007/s11274-011-0839-7DOI Listing
February 2012

Interaction with lipid II induces conformational changes in bovicin HC5 structure.

Antimicrob Agents Chemother 2012 Sep 11;56(9):4586-93. Epub 2012 Jun 11.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.

Bovicin HC5 is a lantibiotic produced by Streptococcus bovis HC5 that targets the cell wall precursor lipid II. An understanding of the modes of action against target bacteria can help broadening the clinical applicability of lantibiotics in human and veterinary medicine. In this study, the interaction of bovicin HC5 with lipid II was examined using tryptophan fluorescence and circular dichroism spectroscopy with model membrane systems that do or do not allow pore formation by bovicin HC5. In the presence of lipid II, a blue-shift of 12 nm could be observed for the fluorescence emission maximum of the tryptophan residue for all of the membrane systems tested. This change in fluorescence emission was paralleled by a decrease in accessibility toward acrylamide and phospholipids carrying a spin-label at the acyl chain; the tryptophan residue of bovicin HC5 was located near the twelfth position of the membrane phospholipid acyl chains. Moreover, the binding of lipid II by bovicin HC5 induced remarkable conformational changes in the bovicin HC5 structure. The interaction of bovicin HC5 with lipid II was highly stable even at pH 2.0. These results indicate that bovicin HC5 interacts directly with lipid II and that the topology of this interaction changes under different conditions, which is relevant for the biological activity of the peptide. To our knowledge, bovicin HC5 is the only bacteriocin described thus far that is able to interact with its target in extreme pH values, and this fact might be related to its unique structure and stability.
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http://dx.doi.org/10.1128/AAC.00295-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3421850PMC
September 2012

Role of lipid II and membrane thickness in the mechanism of action of the lantibiotic bovicin HC5.

Antimicrob Agents Chemother 2011 Nov 29;55(11):5284-93. Epub 2011 Aug 29.

Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil

Lantibiotics are antimicrobial peptides produced by Gram-positive bacteria, nisin being the most well-known member. Nisin inhibits peptidoglycan synthesis and forms pores at sensitive membranes upon interaction with lipid II, the essential bacterial cell wall precursor. Bovicin HC5, a bacteriocin produced by Streptococcus bovis HC5, has the putative N-terminal lipid II binding motif, and we investigated the mode of action of bovicin HC5 using both living bacteria and model membranes, with special emphasis on the role of lipid II. Bovicin HC5 showed activity against Staphylococcus cohnii and Staphylococcus warneri, but bovicin HC5 hardly interfered with the membrane potential of S. cohnii. In model membranes, bovicin HC5 was not able to cause carboxyfluorescein release or proton influx from DOPC vesicles containing lipid II. Bovicin HC5 blocked lipid II-dependent pore formation activity of nisin, and a high-affinity interaction with lipid II was observed (apparent binding constant [K(a)] = 3.1 × 10(6) M(-1)), with a 1:1 stoichiometry. In DOPC vesicles containing lipid II, bovicin HC5 was able to assemble with lipid II into a prepore-like structure. Furthermore, we observed pore formation activity of bovicin HC5, which was stimulated by the presence of lipid II, in thin membranes. Moreover, bovicin HC5 induced the segregation of lipid II into domains in giant model membrane vesicles. In conclusion, bovicin HC5 has a primary mode of action similar to that of nisin, but some differences regarding the pore-forming capacity were demonstrated.
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http://dx.doi.org/10.1128/AAC.00638-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3195046PMC
November 2011

Biofilm formation and acyl homoserine lactone production in Hafnia alvei isolated from raw milk.

Biol Res 2009 29;42(4):427-36. Epub 2010 Jan 29.

Research National Center of Cassava and Tropical Fruits, Brazilian Company of Agricultural Research, Cruz das Almas, BA, Brazil.

The objective of this study was to detect the presence of acyl homoserine lactones (AHLs), signal molecules of the quorum sensing system in biofilm formed by Hafnia alvei strains. It also evaluated the effect of synthetic quorum sensing inhibitors in biofilm formation. AHLs were assayed using well diffusion techniques, thin layer chromatography (TLC) and detection directly in biofilm with biomonitors. The extracts obtained from planktonic and sessile cell of H. alvei induced at least two of three monitor strains evaluated. The presence of AHLs with up to six carbon atoms was confirmed by TLC. Biofilm formation by H. alvei was inhibited by furanone, as demonstrated by 96-well assay of crystal violet in microtitre plates and by scanning electron microscopy. The H. alvei 071 hall mutant was deficient in biofilm formation. All these results showed that the quorum sensing system is probably involved in the regulation of biofilm formation by H. alvei.
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http://dx.doi.org//S0716-97602009000400004DOI Listing
September 2010
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