Publications by authors named "Benjamin Beck"

96 Publications

Toxicity of recombinant PirA and PirB derived from Vibrio parahaemolyticus in shrimp.

Microb Pathog 2021 Apr 27;155:104886. Epub 2021 Apr 27.

Aquatic Animal Health Research Unit, Agricultural Research Service, USDA 990 Wire Road, Auburn, AL, 36832, USA.

Acute hepatopancreatic necrosis disease (AHPND), caused by emerging strains of Vibrio Parahaemolyticus, is of concern in shrimp aquaculture. Secreted proteins PirA and PirB, encoded by a plasmid harbored in V. parahaemolyticus, were determined to be the major virulence factors that induce AHPND. To better understand pathogenesis associated with PirA and PirB, recombinant proteins rPirA and rPirB were produced to evaluate their relative toxicities in shrimp. By challenging shrimp at concentration of 3 μM with reverse gavage method, rPirA and rPirB (approximately 0.4 and 1.5 μg per g of body weight, respectively) caused 27.8 ± 7.8% and 33.3 ± 13.6% mortality, respectively; combination of 3 μM rPirA and rPirB resulted in 88.9 ± 7.9% mortality. Analysis of protein mobility in native gel revealed that rPirB was apparently in the form of monomer while rPirA was oligomerized as an octamer-like macromolecule, suggesting that inter- and intra-molecular interactions between rPirA and rPirB enhanced the toxic effect. An attempt to block or reduce rPirA activity with a putative receptor, N-acetyl-galactosamine, was unsuccessful, implying that remodeling analysis of PirA molecule, such as the octamer observed in this study, is necessary. Results of this study provided new insight into toxic mechanism of PirA and PirB and shall help design strategic antitoxin methods against AHPND in shrimp.
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http://dx.doi.org/10.1016/j.micpath.2021.104886DOI Listing
April 2021

Reactivation of the Hedgehog pathway in esophageal progenitors turns on an embryonic-like program to initiate columnar metaplasia.

Cell Stem Cell 2021 Apr 14. Epub 2021 Apr 14.

IRIBHM, ULB/Faculty of Medicine, 808 route de Lennik, 1070 Brussels, Belgium; WELBIO/FNRS Principal Investigator at IRIBHM, ULB/Faculty of Medicine, 808 route de Lennik, 1070 Brussels, Belgium. Electronic address:

Columnar metaplasia of the esophagus is the main risk factor for esophageal adenocarcinoma. There is a lack of evidence to demonstrate that esophageal progenitors can be the source of columnar metaplasia. In this study, using transgenic mouse models, lineage tracing, single-cell RNA sequencing, and transcriptomic and epigenetic profiling, we found that the activation of the Hedgehog pathway in esophageal cells modifies their differentiation status in vivo. This process involves an initial step of dedifferentiation into embryonic-like esophageal progenitors. Moreover, a subset of these cells undergoes full squamous-to-columnar conversion and expresses selected intestinal markers. These modifications of cell fate are associated with remodeling of the chromatin and the appearance of Sox9. Using a conditional knockout mouse, we show that Sox9 is required for columnar conversion but not for the step of dedifferentiation. These results provide insight into the mechanisms by which esophageal cells might initiate columnar metaplasia.
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http://dx.doi.org/10.1016/j.stem.2021.03.019DOI Listing
April 2021

Principled Design and Implementation of Steerable Detectors.

IEEE Trans Image Process 2021 21;30:4465-4478. Epub 2021 Apr 21.

We provide a complete pipeline for the detection of patterns of interest in an image. In our approach, the patterns are assumed to be adequately modeled by a known template, and are located at unknown positions and orientations that we aim at retrieving. We propose a continuous-domain additive image model, where the analyzed image is the sum of the patterns to localize and a background with self-similar isotropic power-spectrum. We are then able to compute the optimal filter fulfilling the SNR criterion based on one single template and background pair: it strongly responds to the template while being optimally decoupled from the background model. In addition, we constrain our filter to be steerable, which allows for a fast template detection together with orientation estimation. In practice, the implementation requires to discretize a continuous-domain formulation on polar grids, which is performed using quadratic radial B-splines. We demonstrate the practical usefulness of our method on a variety of template approximation and pattern detection experiments. We show that the detection performance drastically improves when we exploit the statistics of the background via its power-spectrum decay, which we refer to as spectral-shaping. The proposed scheme outperforms state-of-the-art steerable methods by up to 50% of absolute detection performance.
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http://dx.doi.org/10.1109/TIP.2021.3072499DOI Listing
April 2021

PER2 Circadian Oscillation Sensitizes Esophageal Cancer Cells to Chemotherapy.

Biology (Basel) 2021 Mar 26;10(4). Epub 2021 Mar 26.

Institute of Interdisciplinary Research (IRIBHM), Faculty of Medicine, Erasme Campus of Université Libre de Bruxelles (ULB), 808 Route de Lennik, 1070 Brussels, Belgium.

Esophageal squamous cell carcinoma (eSCC) accounts for more than 85% cases of esophageal cancer worldwide and the 5-year survival rate associated with metastatic eSCC is poor. This low survival rate is the consequence of a complex mechanism of resistance to therapy and tumor relapse. To effectively reduce the mortality rate of this disease, we need to better understand the molecular mechanisms underlying the development of resistance to therapy and translate that knowledge into novel approaches for cancer treatment. The circadian clock orchestrates several physiological processes through the establishment and synchronization of circadian rhythms. Since cancer cells need to fuel rapid proliferation and increased metabolic demands, the escape from circadian rhythm is relevant in tumorigenesis. Although clock related genes may be globally repressed in human eSCC samples, PER2 expression still oscillates in some human eSCC cell lines. However, the consequences of this circadian rhythm are still unclear. In the present study, we confirm that PER2 oscillations still occur in human cancer cells in vitro in spite of a deregulated circadian clock gene expression. Profiling of eSCC cells by RNAseq reveals that when PER2 expression is low, several transcripts related to apoptosis are upregulated. Consistently, treating eSCC cells with cisplatin when PER2 expression is low enhances DNA damage and leads to a higher apoptosis rate. Interestingly, this process is conserved in a mouse model of chemically-induced eSCC ex vivo. These results therefore suggest that response to therapy might be enhanced in esophageal cancers using chronotherapy.
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http://dx.doi.org/10.3390/biology10040266DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8065910PMC
March 2021

Naked mole rat TRF1 safeguards glycolytic capacity and telomere replication under low oxygen.

Sci Adv 2021 Feb 19;7(8). Epub 2021 Feb 19.

Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.

The naked mole rat (NMR), a long-lived and cancer-resistant rodent, is highly resistant to hypoxia. Here, using robust cellular models wherein the mouse telomeric protein TRF1 is substituted by NMR TRF1 or its mutant forms, we show that TRF1 supports maximal glycolytic capacity under low oxygen, shows increased nuclear localization and association with telomeres, and protects telomeres from replicative stress. We pinpoint this evolutionary gain of metabolic function to specific amino acid changes in the homodimerization domain of this protein. We further find that NMR TRF1 accelerates telomere shortening. These findings reveal an evolutionary strategy to adapt telomere biology for metabolic control under an extreme environment.
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http://dx.doi.org/10.1126/sciadv.abe0174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7895426PMC
February 2021

Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture.

BMC Microbiol 2021 Jan 6;21(1). Epub 2021 Jan 6.

Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA.

Background: Hypervirulent Aeromonas hydrophila (vAh) is an emerging pathogen in freshwater aquaculture that results in the loss of over 3 million pounds of marketable channel catfish, Ictalurus punctatus, and channel catfish hybrids (I. punctatus, ♀ x blue catfish, I. furcatus, ♂) each year from freshwater catfish production systems in Alabama, U.S.A. vAh isolates are clonal in nature and are genetically unique from, and significantly more virulent than, traditional A. hydrophila isolates from fish. Even with the increased virulence, natural infections cannot be reproduced in aquaria challenges making it difficult to determine modes of infection and the pathophysiology behind the devastating mortalities that are commonly observed. Despite the intimate connection between environmental adaptation and plastic response, the role of environmental adaption on vAh pathogenicity and virulence has not been previously explored. In this study, secreted proteins of vAh cultured as free-living planktonic cells and within a biofilm were compared to elucidate the role of biofilm growth on virulence.

Results: Functional proteolytic assays found significantly increased degradative activity in biofilm secretomes; in contrast, planktonic secretomes had significantly increased hemolytic activity, suggesting higher toxigenic potential. Intramuscular injection challenges in a channel catfish model showed that in vitro degradative activity translated into in vivo tissue destruction. Identification of secreted proteins by HPLC-MS/MS revealed the presence of many putative virulence proteins under both growth conditions. Biofilm grown vAh produced higher levels of proteolytic enzymes and adhesins, whereas planktonically grown cells secreted higher levels of toxins, porins, and fimbrial proteins.

Conclusions: This study is the first comparison of the secreted proteomes of vAh when grown in two distinct ecological niches. These data on the adaptive physiological response of vAh based on growth condition increase our understanding of how environmental niche partitioning could affect vAh pathogenicity and virulence. Increased secretion of colonization factors and degradative enzymes during biofilm growth and residency may increase bacterial attachment and host invasiveness, while increased secretion of hemolysins, porins, and other potential toxins under planktonic growth (or after host invasion) could result in increased host mortality. The results of this research underscore the need to use culture methods that more closely mimic natural ecological habitat growth to improve our understanding of vAh pathogenesis.
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http://dx.doi.org/10.1186/s12866-020-02065-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7788984PMC
January 2021

A novel paper-based and pH-sensitive intelligent detector in meat and seafood packaging.

Talanta 2021 Mar 23;224:121913. Epub 2020 Nov 23.

Alabama Center for Paper and Bioresource Engineering (AC-PABE), Department of Chemical Engineering, Auburn University, AL, USA. Electronic address:

The annual amount of food waste or loss is about one-third of the total edible food globally produced for human consumption. Continuous and real-time monitoring by spoilage detectors can significantly reduce food waste. A novel paper-based pH-sensitive meat spoilage detector was developed. A mixture of soybean hulls (SBHs) (hydrothermally-treated in an acidic environment), bentonite, and bromocresol purple (BCP) was coated on paper to produce the detector. The resultant meat spoilage detector was evaluated as a real-time freshness and spoilage indicator of catfish fillets (Ictalurus punctatus). Freshness and spoilage of fish meat with varying weights and headspace were determined by tailoring the detector's pH. Elemental, structural, and functional analysis verified the formation of a packed SBH-bentonite matrix with enhanced gas adsorption capacity and effective BCP-immobilization. Binder nanofibrillation increased the overall visual color vibrancy and decreased the binder demand in the coating formulation. Headspace volume in the studied range (40 and 160 cm) did not affect the activation time of the detectors. However, increasing fish weight decreased the detectors' optimum activation time and pH. The findings of this study show that the developed detectors can be tailored for a wide range of sample and packaging sizes by simply adjusting the pH of the detector.
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http://dx.doi.org/10.1016/j.talanta.2020.121913DOI Listing
March 2021

Draft Genome Sequences of Cetobacterium somerae 2G Large and Two Novel Isolates from Intestines of Channel Catfish ().

Microbiol Resour Announc 2020 Oct 29;9(44). Epub 2020 Oct 29.

School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, Alabama, USA.

We report the draft genome sequences of 2G Large and two isolates, 2A and 8H, which may represent novel species. The isolates were recovered from the intestines of catfish, and the genomes will assist in research to understand their potential use as probiotics in aquaculture.
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http://dx.doi.org/10.1128/MRA.01006-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595949PMC
October 2020

Proteome analysis of virulent Aeromonas hydrophila reveals the upregulation of iron acquisition systems in the presence of a xenosiderophore.

FEMS Microbiol Lett 2020 11;367(20)

United States Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Unit, 990 Wire Road, Auburn, AL, 36832 USA.

The Gram-negative bacterium, Aeromonas hydrophila, has been responsible for extensive losses in the catfish industry for over a decade. Due to this impact, there are ongoing efforts to understand the basic mechanisms that contribute to virulent A. hydrophila (vAh) outbreaks. Recent challenge models demonstrated that vAh cultured in the presence of the iron chelating agent deferoxamine mesylate (DFO) were more virulent to channel catfish (Ictalurus punctatus). Interestingly, differential gene expression of select iron acquisition genes was unremarkable between DFO and non-DFO cultures, posing the question: why the increased virulence? The current work sought to evaluate growth characteristics and protein expression of vAh after the addition of DFO. A comparative proteome analysis revealed differentially expressed proteins among tryptic soy broth (TSB) and TSB + DFO treatments. Upregulated proteins identified among the TSB + DFO treatment were enriched for gene ontology groups including iron ion transport, siderophore transport and siderophore uptake transport, all iron acquisition pathways. Protein-protein interactions were also evaluated among the differentially expressed proteins and predicted that many of the upregulated iron acquisition proteins likely form functional physiological networks. The proteome analysis of the vAh reveals valuable information about the basic biological processes likely leading to increased virulence during iron restriction in this organism.
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http://dx.doi.org/10.1093/femsle/fnaa169DOI Listing
November 2020

Differential susceptibility of white bass (Morone chrysops), striped bass (Morone saxatilis) and hybrid striped bass (M. chrysops × M. saxatilis) to Flavobacterium columnare and effects of mucus on bacterial growth and biofilm development.

J Fish Dis 2021 Feb 2;44(2):161-169. Epub 2020 Oct 2.

Harry K. Dupree Stuttgart National Aquaculture Research Center, United States Department of Agriculture, Agricultural Research Service, Stuttgart, AR, USA.

Columnaris disease generates substantial losses of many freshwater fish species; one is the hybrid striped bass. The ubiquitous aquatic bacterium Flavobacterium columnare can be highly effective in biofilm formation on fish skin and gills. Previous research showed a difference between columnaris disease susceptibility of hybrid striped bass (Morone saxatilis × M. chrysops) and white bass (M. chrysops). To understand these differential susceptibilities and possible mucosal relationship, we assessed total bacterial growth and biofilm formation with mucus derived from each moronid parental species: white bass and striped bass (M. saxatilis). Differential susceptibility was confirmed of the other parent species, the striped bass (M. saxatilis). In addition to intraspecies investigations, individual hybrid striped bass mucosal affects were also studied for deferential responses to bacterial growth and biofilm formation. Species- and concentration-dependent differences were detected in the total growth of the bacteria to host mucus. Our data suggest that bass mucus can significantly affect biofilm formation with the F. columnare isolate tested. There appears to be a correlation between the bacteria's response of growth and biofilms and bass species susceptibility. This study provides insight into our understanding of the host-pathogen interaction between F. columnare and moronids.
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http://dx.doi.org/10.1111/jfd.13272DOI Listing
February 2021

Dose effects of a DNA vaccine encoding immobilization antigen on immune response of channel catfish against Ichthyophthirius multifiliis.

Fish Shellfish Immunol 2020 Nov 14;106:1031-1041. Epub 2020 Aug 14.

United States Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Unit, 990 Wire Road, Auburn, AL, 36832-4352, USA.

Channel catfish (Ictalurus punctatus) vaccinated with pcDNA3.1-IAg52b plasmid DNA vaccine encoding immobilization antigen genes of Ichthyophthirius multifiliis (Ich) produced anti-Ich antibodies and were partially protected (20% survival) in a previous study. Here we evaluated whether a higher dose or two doses of pcDNA3.1-IAg52b vaccine could provide better protection for catfish against Ich. Fish were distributed into 6 groups and vaccinated using following schemes: 1.10 μg pcDNA3.1-IAg52b fish, 2.20 μg pcDNA3.1-IAg52b fish, 3. two doses of 10 μg pcDNA3.1-IAg52b fish with 7 days between doses, 4.20 μg pcDNA3.1 fish (mock-vaccinated control), 5.15,000 live theronts fish (positive control), and 6. non-vaccinated and non-challenge control. Parasite infection levels, serum anti-Ich antibody levels, fish mortality and immune-related gene expression were determined during the trial. Fish vaccinated with a single dose of 20 μg pcDNA3.1-IAg52b fish or two doses of 10 μg fish had higher anti-Ich antibody levels than fish receiving a single dose of 10 μg fish. Survival was significantly higher in fish receiving 20 μg vaccine fish (35.6%) or 2 doses of 10 μg fish (48.9%) than fish injected with a single dose of 10 μg fish (15.6%) or mock-vaccinated control (0%). Fish vaccinated at the dose 20 μg fish had higher expression of vaccine DNA in muscle than fish vaccinated with 10 μg fish. Fish vaccinated with the DNA vaccine showed higher up-regulation than mock-vaccinated control in the expression of IgM, CD4, MHC I and TcR-α genes during most of time points after vaccination. Further studies are needed to improve efficacy of DNA vaccines by using multiple antigens in the DNA vaccines.
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http://dx.doi.org/10.1016/j.fsi.2020.07.063DOI Listing
November 2020

EasyParallel: A GUI platform for parallelization of STRUCTURE and NEWHYBRIDS analyses.

PLoS One 2020 24;15(4):e0232110. Epub 2020 Apr 24.

School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United States of America.

The software programs STRUCTURE and NEWHYBRIDS are widely used population genetic programs useful in addressing questions related to genetic structure, admixture, and hybridization. These programs usually require a large number of independent runs with many iterations to provide robust data for downstream analyses, thus significantly increasing computation time. Programs such as Structure_threader and parallelnewhybrid were previously developed to address this problem by processing tasks in parallel on a multi-threaded processor; however some programming knowledge (e.g., R, Bash) is required to run these programs. We developed EasyParallel as a community resource to facilitate practical and routine population structure and hybridization analyses. The multi-threaded parallelization of EasyParallel allows processing of large genetic datasets in a very efficient way, with its point-and-click GUI providing ready access to users who have little experience in script programming. Performance evaluation of EasyParallel using simulated datasets showed similar speed-up and parallel execution time when compared to Structure_threader and Parallelnewhybrid. EasyParallel is written in Python 3 and freely available on the GitHub site https://github.com/hzz0024/EasyParallel.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0232110PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7182190PMC
July 2020

Development of a perforated plate underwater acoustic ground cloak.

J Acoust Soc Am 2019 Oct;146(4):2303

The Applied Research Laboratory at the Pennsylvania State University, State College, Pennsylvania 16801, USA.

One of the commonly investigated transformation acoustic device is the ground cloak, which conceals a scattering object on a reflecting surface. Multiple studies have numerically simulated acoustic ground cloaks, but because of the challenges associated with realizing a homogeneous anisotropic metamaterial, only two acoustic ground cloaks have been built and tested. Perforated plastic plates in air were used to construct two and three dimensional ground cloaks and alternating layers of brass and water were used to construct an extended area ground cloak underwater. With underwater mass density anisotropy previously demonstrated for perforated steel plates, the primary focus of this article is to build and evaluate an underwater ground cloak with perforated steel plates. The cloak was evaluated at a water-air pressure release reflecting surface. The cloak successfully concealed the scattering object over a broad frequency range of 7-12 kHz.
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http://dx.doi.org/10.1121/1.5127844DOI Listing
October 2019

Phosphoinositide 5-phosphatases SKIP and SHIP2 in ruffles, the endoplasmic reticulum and the nucleus: An update.

Adv Biol Regul 2020 01 7;75:100660. Epub 2019 Oct 7.

IRIBHM, Campus Erasme, ULB Bâtiment C, 808 Route de Lennik, 1070, Bruxelles, Belgium. Electronic address:

Phosphoinositides (PIs) are phosphorylated derivatives of phosphatidylinositol. They act as signaling molecules linked to essential cellular mechanisms in eukaryotic cells, such as cytoskeleton organization, mitosis, polarity, migration or invasion. PIs are phosphorylated and dephosphorylated by a large number of PI kinases and PI phosphatases acting at the 5-, 4- and 3- position of the inositol ring. PI 5-phosphatases i.e. OCRL, INPP5B, SHIP1/2, Synaptojanin 1/2, INPP5E, INPP5J, SKIP (INPP5K) are enzymes that dephosphorylate the 5-phosphate position of PIs. Several human genetic diseases such as the Lowe syndrome, some congenital muscular dystrophy and opsismodysplasia are due to mutations in PI phosphatases, resulting in loss-of-function. The PI phosphatases are also up or down regulated in several human cancers such as glioblastoma or breast cancer. Their cellular localization, that is dynamic and varies in response to stimuli, is an important issue to understand function. This is the case for two members of the PI 5-phosphatase SKIP and SHIP2. Both enzymes are in ruffles, plasma membranes, the endoplasmic reticulum, a situation that is unique for SKIP, and the nucleus. Following localization, PI 5-phosphatases act on specific cellular pools of PIs, which in turn interact with target proteins. Nuclear PIs have emerged as regulators of genome functions in different area of cell signaling. They often localize to nuclear speckles, as do several PI metabolizing kinases and phosphatases. We asked whether SKIP and SHIP2 could have an impact on nuclear PI(4,5)P2. In two glioblastoma cell models, lowering SKIP expression had an impact on nuclear PI(4,5)P2. In a model of SHIP2 deletion in MCF-7 cells, no change in nuclear PI(4,5)P2 was observed. Finally, we present evidence of an anti-tumoral role of SKIP in vivo, in xenografts using as model U87shSKIP cells.
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http://dx.doi.org/10.1016/j.jbior.2019.100660DOI Listing
January 2020

Immune response of channel catfish (Ictalurus punctatus) against Ichthyophthirius multifiliis post vaccination using DNA vaccines encoding immobilization antigens.

Fish Shellfish Immunol 2019 Nov 28;94:308-317. Epub 2019 Aug 28.

United States Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Unit, 990 Wire Road, Auburn, AL, 36832-4352, USA.

The channel catfish (Ictalurus punctatus) immune response against Ichthyophthirius multifiliis (Ich) after vaccination using plasmid DNA vaccines pcDNA3.1-IAg52a and pcDNA3.1-IAg52b, encoding Ich immobilization antigen genes was studied. Parasite infection level, serum anti-Ich antibodies level, fish mortality after theront challenge, and immune-related gene expression were measured. After in vitro transfection of walking catfish gill cells (G1b) with both pcDNA3.1-IAg52a and pcDNA3.1-IAg52b, antigens IAG52A and IAG52B were detected. During the vaccination trial, 76-fold increase in the Iag52b gene expression was observed in the vaccinated fish group h4 post vaccination. Administration of DNA vaccines by IM injection induced significant gene up-regulation in the head kidney, including immunoglobulin M (IgM), cluster of differentiation 4 (CD4), major histocompatibility I (MHC I), and T cell receptor α (TcR-α) from h4 to d5 post immunization. Fish vaccinated with DNA vaccines or theronts showed increased gene expression of the cytokine interferon (IFN-γ), complement component 3 (C3), and toll-like receptor-1 (TLR-1). Anti-Ich antibodies were detected in fish received pcDNA3.1-IAg52a, pcDNA3.1-IAg52b and the combination of both vaccines d10 post vaccination. Fish vaccinated with pcDNA3.1-IAg52b showed mild parasite infection level, partial survival (20%) and longer mean day to death (MDD) after theront challenge. By contrast, a heavy parasite load, 0% survival and short MDD were observed in the sham vaccinated control fish that received pcDNA3.1 (plasmid without genes encoding Ich immobilization antigen). Further research is needed to improve DNA vaccines for Ich that can induce strong protective immunity in fish. Suggested studies include improved transfection efficiency, use of appropriate adjuvants and including additional parasite antigen genes in the plasmid.
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http://dx.doi.org/10.1016/j.fsi.2019.08.071DOI Listing
November 2019

Evidence that the stress hormone cortisol regulates biofilm formation differently among Flavobacterium columnare isolates.

Vet Res 2019 Apr 11;50(1):24. Epub 2019 Apr 11.

Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, Ghent University, Ghent, 9000, Belgium.

The impact of cortisol on Flavobacterium columnare biofilm formation was explored. Firstly, the dynamics of biofilm formation by one highly (HV) and one low virulent (LV) F. columnare isolate with and without the stress hormone cortisol under microfluidic flow conditions was characterized. This to confirm that F. columnare cells could form biofilm under cortisol supplementation, and to compare the temporal and structural differences between different treatment groups. One trial revealed that in both isolates cell aggregates resembling biofilms occurred within 7-h post-inoculation. Consequently, cell clusters were sloughed away, followed by a rebuilding of bacterial cell aggregates, suggestive for a high spreading capacity. While the HV isolate revealed cell aggregates formed upstream at all time-points, for the LV isolate this was only seen upon cortisol supplementation. Secondly, the transcriptional effect of genes (gldK, gldL, gldM, gldN, sprA, sprE, sprT, and porV) belonging to the Type IX secretion system involved in gliding motility was investigated in planktonic and biofilm cells of a HV and LV isolate to which no, a low (LD) or high (HD) dose of cortisol was added. Significantly lower expression of gliding genes gldK, gldL, gldM and gldN, and of protein secretion regulator porV was seen in the LV isolate planktonic cells supplemented with a HD-cortisol. The LV isolate biofilm cells treated with the HD-cortisol showed a significant upregulation of sprT, encoding mobile surface adhesion important in bacterial colonization. This is the first evidence for the co-regulatory effect of cortisol on biofilm formation and F. columnare gliding gene expression.
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http://dx.doi.org/10.1186/s13567-019-0641-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458827PMC
April 2019

Antimicrobial activity of the biopolymer chitosan against Streptococcus iniae.

J Fish Dis 2019 Mar 15;42(3):371-377. Epub 2019 Jan 15.

School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, Alabama.

The antimicrobial activity and mode of action of chitosan were evaluated against Streptococcus iniae, a pathogenic Gram-positive bacterium of fish worldwide. Cell proliferation kinetics were examined following exposure to varying concentrations of chitosan. The action of chitosan on S. iniae was also investigated by measuring agglutination activity, conductivity, and extracellular and intracellular bacterial adenosine triphosphate (ATP) levels. Chitosan exhibited antibacterial activity against S. iniae at concentrations of 0.1% and above and was lethal at a concentration of 0.4% and higher. The mechanism of antibacterial activity of chitosan at the inhibitory level of bacterial growth appears to hinge upon the interaction between chitosan and the oppositely charged bacterial surface. This interplay causes agglutination, which was readily observed grossly and microscopically. After interacting with the cell surface via adsorption, an efflux of intracellular ATP was documented, which suggests that chitosan disrupts the bacterial cell causing leakage of cytosolic contents and ultimately cell death. Results suggest chitosan may be worth evaluating as a natural alternative to antibiotic against S. iniae infection of fish.
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http://dx.doi.org/10.1111/jfd.12938DOI Listing
March 2019

Organoids from pituitary as a novel research model toward pituitary stem cell exploration.

J Endocrinol 2019 02;240(2):287-308

Department of Development and Regeneration, Cluster of Stem Cell and Developmental Biology, Unit of Stem Cell Research, KU Leuven (University of Leuven), Leuven, Belgium.

The pituitary is the master endocrine gland, harboring stem cells of which the phenotype and role remain poorly characterized. Here, we established organoids from mouse pituitary with the aim to generate a novel research model to study pituitary stem cell biology. The organoids originated from the pituitary cells expressing the stem cell marker SOX2 were long-term expandable, displayed a stemness phenotype during expansive culture and showed specific hormonal differentiation ability, although limited, after subrenal transplantation. Application of the protocol to transgenically injured pituitary harboring an activated stem cell population, resulted in more numerous organoids. Intriguingly, these organoids presented with a cystic morphology, whereas the organoids from undamaged gland were predominantly dense and appeared more limited in expandability. Transcriptomic analysis revealed distinct epithelial phenotypes and showed that cystic organoids more resembled the pituitary phenotype, at least to an immature state, and displayed in vitro differentiation, although yet moderate. Organoid characterization further exposed facets of regulatory pathways of the putative stem cells of the pituitary and advanced new injury-activated markers. Taken together, we established a novel organoid research model revealing new insights into the identity and regulation of the putative pituitary stem cells. This organoid model may eventually lead to an interesting tool to decipher pituitary stem cell biology in both healthy and diseased gland.
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http://dx.doi.org/10.1530/JOE-18-0462DOI Listing
February 2019

Analysis of agglutinants elicited by antiserum of channel catfish immunized with extracellular proteins of virulent Aeromonas hydrophila.

Fish Shellfish Immunol 2019 Mar 16;86:223-229. Epub 2018 Nov 16.

Aquatic Animal Health Research Unit, USDA-ARS, 990 Wire Road, Auburn, AL, 36832, USA.

Motile Aeromonas septicemia (MAS), caused by new virulent Aeromonas hydrophila (vAh) strains, has been one of the major diseases in channel catfish in recent years. Previous studies showed that channel catfish developed immunity against vAh infection after immunization with the pathogen's extracellular proteins (ECP). To understand the mechanisms associated with the immunity, anti-ECP fish serum (antiserum) was analyzed in this study. Our results revealed that the antiserum elicited agglutination of both ECP and cells of vAh. Five fish proteins were identified in ECP agglutinants, including two innate immunity associated proteins (serotransferrin and rhamnose-binding lectin), two immunoglobulin M (IgM) molecules (IgM heavy chain and light chain) and a constitutively-produced protein (warm temperature acclimation protein). More than 68 vAh proteins in ECP were recognized and caused to aggregate by IgM in the antiserum. IgM was isolated from vAh cell agglutinants and the native IgM was shown to form a tetramer that was responsible for bacterial agglutination. Immunoblotting analysis indicated that the isolated native IgM was able to recognize some proteins in ECP, such as aerolysin and hemolysin (in the form of a high molecular weight heterologous polymer). Gene expression analysis by quantitative PCR showed that fish immunized with vAh ECP had more transcripts of genes coding for IgM, serotransferrin and rhamnose binding lectin than mock-immunized fish. Both innate and antibody-mediated immune responses in serum and expressed genes contributed to fish immunity upon immunization with ECP. Results of this study shed light on the versatility of vAh antigens and catfish IgM, which would help identify specific antigens for vaccine development and antigen specific antibodies in catfish.
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http://dx.doi.org/10.1016/j.fsi.2018.11.033DOI Listing
March 2019

Examining the interplay between Streptococcus agalactiae, the biopolymer chitin and its derivative.

Microbiologyopen 2019 05 1;8(5):e00733. Epub 2018 Oct 1.

Aquatic Animal Health Research Unit, United States Department of Agriculture, Agricultural Research Service, Auburn, Alabama.

Streptococcus agalactiae is a highly pathogenic bacterium of aquatic species and terrestrial animals worldwide, whereas chitin and its derivative chitosan are among the most abundant biopolymers found in nature, including the aquatic milieu. The present investigation focused on the capability of S. agalactiae to degrade and utilize these polymers. Growth of S. agalactiae in the presence of colloid chitin, chitosan, or N-acetyl-glucosamine (GlcNAc) was evaluated. Chitosanase production was measured daily over 7 days of growth period and degraded products were evaluated with thin later chorography. Chitin had no effect on the growth of S. agalactiae. Degraded chitin, however, stimulated the growth of S. agalactiae. S. agalactiae cells did not produce chitinase to degrade chitin; however, they readily utilize GlcNAc (product of degraded chitin) as sole source of carbon and nitrogen for growth. Chitosan at high concentrations had antibacterial activities against S. agalactiae, while in the presence of lower than the inhibitory level of chitosan in the medium, S. agalactiae secrets chitosanase to degrade chitosan, and utilizes it to a limited extent to benefit growth. The interaction of S. agalactiae with chitin hydrolytes and chitosan could play a role in the diverse habitat distribution and pathogenicity of S. agalactiae worldwide.
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http://dx.doi.org/10.1002/mbo3.733DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6528556PMC
May 2019

Immersion vaccination with an inactivated virulent Aeromonas hydrophila bacterin protects hybrid catfish (Ictalurus punctatus X Ictalurus furcatus) from motile Aeromonas septicemia.

Fish Shellfish Immunol 2018 Nov 18;82:239-242. Epub 2018 Aug 18.

United States Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Unit, Auburn, AL, USA. Electronic address:

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http://dx.doi.org/10.1016/j.fsi.2018.08.040DOI Listing
November 2018

Influence of native catfish mucus on Flavobacterium columnare growth and proteolytic activity.

J Fish Dis 2018 Sep 11;41(9):1395-1402. Epub 2018 Jun 11.

U.S. Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Unit, Auburn, Alabama.

Flavobacterium columnare causes columnaris disease of farmed and wild freshwater fish. Skin mucus is an important factor in early stages of columnaris pathogenesis, albeit little studied. Our objectives were to (a) characterize the terminal glycosylation pattern (TGP) of catfish mucus, (b) determine the growth of F. columnare in formulated water (FW)-containing channel catfish (Ictalurus punctatus) or hybrid catfish (Ictalurus punctatus X Ictalurus furcatus) mucus and (c) examine extracellular protease activity of two F. columnare isolates differing in virulence. The TGP of catfish mucus by lectin binding was as follows: alpha-D-mannose/alpha-D-glucose >N-acetyl-beta-D-glucosamine >N-acetyl-beta-D-glucosamine/N-acetylneuraminic acid >N-acetyl-D-galactosamine >alpha-D-galactose/N-acetyl-alpha-D-galactosamine >beta-D-galactose = alpha-L-fucose. Virulence studies demonstrated isolate AL-02-36 was highly virulent in channel catfish fry (0.1 g) with cumulative mortality of 90%-100% versus 60% for isolate ALG-00-530 at equivalent doses (~3 × 10 CFU/ml); a similar result was observed in larger (0.7 g) catfish. In multiple experiments, F. columnare replicated (2-3 logs) and survived (28 days) in formulated water-containing catfish mucus. Highly virulent isolate AL-02-36 possessed at least 2.5- to fivefold higher protease activity following growth in mucus than the less virulent ALG-00-530. Flavobacterium columnare utilized catfish mucus as a nutrient source and mucus presence modulated extracellular protease production.
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http://dx.doi.org/10.1111/jfd.12833DOI Listing
September 2018

l-rhamnose-binding lectins (RBLs) in Nile tilapia, Oreochromis niloticus: Characterization and expression profiling in mucosal tissues.

Fish Shellfish Immunol 2018 Jan 10;72:426-435. Epub 2017 Nov 10.

School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL 36849, USA. Electronic address:

Rhamnose-binding lectins (RBLs) are crucial elements associated with innate immune responses to infections and have been characterized from a variety of teleost fishes. Given the importance of RBL in teleost fishes, we sought to study the diversity and expression profiles of RBLs in an important cultured fish, Nile tilapia (Oreochromis niloticus) following experimental infection with Streptococcus agalactiae, a major cause of streptococcosis in farmed tilapia. In this study, four predicted RBL genes were identified from Nile tilapia and were designated as OnRBL3a, OnRBL3b, OnRBL3c, and OnRBL3d. These OnRBLs were composed of two tandem-repeated type five carbohydrate recognition domains (CRDs), classified as type IIIc, and all clustered together phylogenetically. OnRBL-CRDs shared conserved topology of eight cysteine residues, characteristic peptide motifs of -YGR- and -DPC- (or -FGR- and -DTC-), and similar exon/intron organization. OnRBLs had the highest expression in immune-related tissues, gills, intestine or liver. However, the changes of OnRBL expression in the gills and intestine at 2 h, 4 h and 24 h post S. agalactiae challenge were modest, suggesting that tilapia may not mediate the entry or confront the infection of S. agalactiae through induction of RBL genes. The observed expression pattern may be related to the RBL type and CRD composition, S. agalactiae pathogenesis, the accessibility of ligands on the bacterial surface, and/or the species of fish. OnRBLs characterized in this study were the first RBL members identified in Nile tilapia and their characterization will expand our knowledge of RBLs in immunity.
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http://dx.doi.org/10.1016/j.fsi.2017.11.015DOI Listing
January 2018

More than just antibodies: Protective mechanisms of a mucosal vaccine against fish pathogen Flavobacterium columnare.

Fish Shellfish Immunol 2017 Dec 5;71:160-170. Epub 2017 Oct 5.

School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL 36849, USA. Electronic address:

A recently developed attenuated vaccine for Flavobacterium columnare has been demonstrated to provide superior protection for channel catfish, Ictalurus punctatus, against genetically diverse columnaris isolates. We were interested in examining the mechanisms of this protection by comparing transcriptional responses to F. columnare challenge in vaccinated and unvaccinated juvenile catfish. Accordingly, 58 day old fingerling catfish (28 days post-vaccination or unvaccinated control) were challenged with a highly virulent F. columnare isolate (BGSF-27) and gill tissues collected pre-challenge (0 h), and 1 h and 2 h post infection, time points previously demonstrated to be critical in early host-pathogen interactions. Following RNA-sequencing and transcriptome assembly, differential expression (DE) analysis within and between treatments revealed several patterns and pathways potentially underlying improved survival of vaccinated fish. Most striking was a pattern of dramatically higher basal expression of an array of neuropeptides (e.g. somatostatin), hormones, complement factors, and proteases at 0 h in vaccinated fish. Previous studies indicate these are likely the preformed mediators of neuroendocrine cells and/or eosinophilic granular (mast-like) cells within the fish gill. Following challenge, these elements fell to almost undetectable levels (>100-fold downregulated) by 1 h in vaccinated fish, suggesting their rapid release and/or cessation of synthesis following degranulation. Concomitantly, levels of pro-inflammatory cytokines (IL-1b, IL-8, IL-17) were induced in unvaccinated fish. In contrast, in vaccinated catfish, we observed widespread induction of genes needed for collagen deposition and tissue remodeling. Taken together, our results indicate an important component of vaccine protection in fish mucosal tissues may be the sensitization, proliferation and arming of resident secretory cells in the period between primary and secondary challenge.
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http://dx.doi.org/10.1016/j.fsi.2017.10.001DOI Listing
December 2017

White Bass (Morone chrysops) Preferentially Retain n-3 PUFA in Ova When Fed Prepared Diets with Varying FA Content.

Lipids 2017 Oct 3;52(10):823-836. Epub 2017 Aug 3.

United States Department of Agriculture, Agriculture Research Service, Harry K. Dupree Stuttgart National Aquaculture Research Center, P.O. Box 1050, 2955 Highway 130 East, Stuttgart, AR, 72160, USA.

We evaluated the fatty acid (FA) composition of broodstock white bass ova fed one of six commercial diets with increasing polyunsaturated FA content (n-6/n-3 ratio; 0.36, 0.39, 0.46, 0.83, 1.07, 1.12) eight weeks prior to sampling. Fatty acid profiles of ova from brooders fed each of the six diets were significantly altered according to canonical discriminant analysis. Ova FA profiles resulting from the 0.39 diet separated those from the 0.36 diet based on lower 18:2n-6 (LNA) and higher 20:1n-9 concentrations from the 0.36 diet. Ova profiles were further separated based on lower concentrations of 22:5n-3 (DPA) from the 0.46 diet, lower concentrations of 20:5n-3 (EPA) in the 1.12 and 0.83 diets, and lower concentrations of 22:6n-3 (DHA) in all other diets relative to the 0.46 diet. Changes in ova FA profile at four and eight weeks were consistent with dietary intake with an approximate 2% increase in any given FA class with increasing time on individual diet. There was no correlation between dietary ARA concentrations (0.7-1.1 mol%), or dietary EPA/ARA ratios (7-15), and the concentrations (1.4-1.7 mol%) or ratios (3.3-4.4) found in the ova by diet. Our results suggest that white bass females have the ability to preferentially incorporate n-3 PUFA, particularly DHA, suggesting mobilization of this FA from other tissues for ova deposition or preferential dietary incorporation of PUFA into ova. These results will add to the limited FA information available in white bass and enable nutritionists to formulate broodstock diets that maximize reproductive potential in this species.
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http://dx.doi.org/10.1007/s11745-017-4281-yDOI Listing
October 2017

Expression of immune genes in systemic and mucosal immune tissues of channel catfish vaccinated with live theronts of Ichthyophthirius multifiliis.

Fish Shellfish Immunol 2017 Jul 22;66:540-547. Epub 2017 May 22.

United States Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Unit, 990 Wire Road, Auburn, AL, 36832-4352, USA.

Ichthyophthiriasis caused by Ichthyophthirius multifiliis (Ich) has a worldwide distribution and affects most freshwater fishes. Fish surviving natural infection and/or immunized with Ich develop strong innate and adaptive immune responses. However, there is a lack of the knowledge regarding immune gene expression patterns in systemic and mucosal immune tissues, and how immune genes interact and lead to innate and adaptive immune protection against Ich infection in fish. The objective of this study was to investigate the expression of innate and adaptive immune-related genes in systemic (liver, spleen) and mucosal (gill, intestine) tissues of channel catfish over time following vaccination with live Ich theronts. The vaccinated fish showed significantly higher antibody titers and survival (95%) than those of mock immunized fish. Expression of IgM and IgD heavy chain genes exhibited a rapid increase from 4 h (h4) to 2 days (d2) post-vaccination in systemic immune tissues. Immune cell receptor genes (CD4, CD8-α, MHC I, MHC II β, TcR-α, and TcR-β) were more highly upregulated and remained upregulated for longer duration in systemic tissues than in mucosal tissues of the vaccinated fish. The cytokine genes IL-1βa and IFN-γ were rapidly upregulated in both systemic and mucosal tissues of vaccinated fish, with peak expression from h4 to d1 post-vaccination. Toll-like receptor genes TLR-1 and TLR-9 showed relatively stable upregulation in the gill of immunized fish following vaccination. Results of this study revealed the molecular immune responses in mucosal and systemic tissues of vaccinated fish and demonstrated that Ich vaccination resulted in innate and adaptive immune responses against Ich infection.
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http://dx.doi.org/10.1016/j.fsi.2017.05.051DOI Listing
July 2017

Chitin degradation and utilization by virulent Aeromonas hydrophila strain ML10-51K.

Arch Microbiol 2017 May 28;199(4):573-579. Epub 2016 Dec 28.

Aquatic Animal Health Research Unit, USDA-ARS, 990 Wire Road, Auburn, AL, 36832, USA.

Virulent Aeromonas hydrophila (vAh) is one of the most important bacterial pathogens that causes persistent outbreaks of motile Aeromonas septicemia in warm-water fishes. The survivability of this pathogen in aquatic environments is of great concern. The aim of this study was to determine the capability of the vAh strain ML10-51K to degrade and utilize chitin. Genome-wide analysis revealed that ML10-51K encodes a suite of proteins for chitin metabolism. Assays in vitro showed that four chitinases, one chitobiase and one chitin-binding protein were secreted extracellularly and participated in chitin degradation. ML10-51K was shown to be able to use not only N-acetylglucosamine and colloidal chitin but also chitin flakes as sole carbon sources for growth. This study indicates that ML10-51K is a highly chitinolytic bacterium and suggests that the capability of effective chitin utilization could enable the bacterium to attain high densities when abundant chitin is available in aquatic niches.
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http://dx.doi.org/10.1007/s00203-016-1326-1DOI Listing
May 2017

Cell-Type-Specific Chromatin States Differentially Prime Squamous Cell Carcinoma Tumor-Initiating Cells for Epithelial to Mesenchymal Transition.

Cell Stem Cell 2017 02 23;20(2):191-204.e5. Epub 2016 Nov 23.

Université libre de Buxelles (ULB), Institut de recherche interdisciplinaire en biologie humaine et moléculaire (IRIBHM), 808 route de Lennik, 1070 Brussels, Belgium; WELBIO, Université Libre de Bruxelles (ULB), 1070 Bruxelles, Belgium. Electronic address:

Epithelial to mesenchymal transition (EMT) in cancer cells has been associated with metastasis, stemness, and resistance to therapy. Some tumors undergo EMT while others do not, which may reflect intrinsic properties of their cell of origin. However, this possibility is largely unexplored. By targeting the same oncogenic mutations to discrete skin compartments, we show that cell-type-specific chromatin and transcriptional states differentially prime tumors to EMT. Squamous cell carcinomas (SCCs) derived from interfollicular epidermis (IFE) are generally well differentiated, while hair follicle (HF) stem cell-derived SCCs frequently exhibit EMT, efficiently form secondary tumors, and possess increased metastatic potential. Transcriptional and epigenomic profiling revealed that IFE and HF tumor-initiating cells possess distinct chromatin landscapes and gene regulatory networks associated with tumorigenesis and EMT that correlate with accessibility of key epithelial and EMT transcription factor binding sites. These findings highlight the importance of chromatin states and transcriptional priming in dictating tumor phenotypes and EMT.
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http://dx.doi.org/10.1016/j.stem.2016.10.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5939571PMC
February 2017

Draft Genome Sequence of Pseudomonas mosselii Gil3, Isolated from Catfish and Antagonistic against Hypervirulent Aeromonas hydrophila.

Genome Announc 2016 Nov 17;4(6). Epub 2016 Nov 17.

Aquatic Animal Health Research Unit, USDA-ARS, Auburn, Alabama, USA.

Pseudomonas mosselii Gil3 was isolated from a catfish that survived from lethal challenge with hypervirulent Aeromonas hydrophila (vAh). When assayed in vitro, the bacterium showed antagonism against vAh. Sequence analysis revealed that the genome of P. mosselii Gil3 encodes numerous aromatic metabolism pathways and proteins for biosynthesis of antimicrobial compounds.
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http://dx.doi.org/10.1128/genomeA.01305-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5114387PMC
November 2016