Research Publications (Food Safety)

Multi-drug resistance (MDR) is a serious threat to public health, making the development of new antimicrobials an urgent necessity. Pyocins are protein antibiotics produced by Pseudomonas aeruginosa strains to kill closely related cells during intraspecific competition. Here, we report an in depth biochemical, microbicidal and structural characterization of a new S-type pyocin, named S8. Initially, we described the domain organization and secondary structure of S8.

Uropathogenic Escherichia coli (UPEC) are the leading cause of human urinary tract infections (UTIs) and many patients experience recurrent infection after successful antibiotic treatment. The source of recurrent infections may be persistent bacterial reservoirs in vivo that are in a quiescent state and thus are not susceptible to antibiotics. Here, we show that multiple UPEC strains require a quorum to proliferate in vitro with glucose as the carbon source.

Cohesion of biofilms made by Yersinia pestis and Yersinia pseudotuberculosis (Yptb) has been attributed solely to an extracellular polysaccharide matrix encoded by the hms genes (Hms-ECM). However, mutations in the Yptb BarA/UvrY/CsrB regulatory cascade enhance biofilm stability without dramatically increasing Hms-ECM production.

RNases are key regulatory components in prokaryotes, responsible for the degradation and maturation of specific RNA molecules at precise times. Specifically, RNases allow cells to cope with changes in their environment through rapid alteration of gene expression. To date, few RNases have been characterized in the mammalian pathogen Brucella abortus. In the present work, we sought to investigate several RNases in B. abortus and determine what role, if any, they have in pathogenesis.

A mutant of Salmonella Typhimurium was isolated that simultaneously affected two metabolic pathways: NAD metabolism and DNA repair. The mutant was isolated as resistant to a nicotinamide analog and as temperature-sensitive for growth on minimal glucose medium. In this mutant, Salmonella's 94 kb virulence plasmid pSLT had recombined into the chromosome upstream of the NAD salvage pathway gene pncA.

Listeria monocytogenes is a fastidious bacterial pathogen that can utilize only a limited number of nitrogen sources for growth. Both glutamine and ammonium are common nitrogen sources used in listerial defined growth media, but little is known about the regulation of their uptake or utilization. The functional role of L.

Vibrio cholerae biofilm biogenesis, which is important for survival, dissemination, and persistence, requires multiple genes in the Vibrio polysaccharides (vps) operons I and II as well as the cluster of ribomatrix (rbm) genes. Transcriptional control of these genes is a complex process that requires several activators/repressors and the ubiquitous signaling molecule, cyclic di-GMP (c-di-GMP).

Both fermentative and respiratory processes contribute to bacterial metabolic adaptations to low oxygen tension (hypoxia). In the absence of O2 as a respiratory electron sink, many bacteria utilize alternative electron acceptors such as nitrate (NO3-). During canonical NO3- respiration, NO3- is reduced in a stepwise manner to N2 by a dedicated set of reductases.

Clostridioides difficile is an aetiological agent for antibiotic-associated diarrhoeal disease. C. difficile produces a phenolic compound, para-cresol, which selectively targets gammaproteobacteria in the gut, facilitating dysbiosis. C. difficile decarboxylates para-hydroxyphenylacetate (p-HPA) to produce p-cresol by the action of the HpdBCA decarboxylase encoded by the hpdBCA operon.

The Pseudomonas aeruginosa type III secretion system (T3SS) needle comprised of multiple PscF subunits is essential for the translocation of effector toxins into human cells, facilitating the establishment and dissemination of infection. Mutations in the pscF gene provide resistance to the phenoxyacetamide (PhA) series of T3SS inhibitory chemical probes.

Biofilms exist in complex environments including the intestinal tract as a part of the gastrointestinal microbiota. The interaction of planktonic bacteria with biofilms can be influenced by material properties of the biofilm. During previous confocal studies, we observed amyloid curli-containing Salmonella Typhimurium and Escherichia coli biofilms appeared rigid. In these studies, Enterococcus faecalis, which lacks curli-like protein, showed more fluid movement.

Salmonella Typhimurium uses a type three secretion system (T3SS) encoded on the Salmonella pathogenicity island 1 (SPI1) to invade intestinal epithelial cells and induce inflammatory diarrhea. The SPI1 T3SS is regulated by numerous environmental and physiological signals, integrated to either activate or repress invasion.

Current mouse models for evaluating the efficacy of live oral cholera vaccines (OCVs) have important limitations. Conventionally raised adult mice are resistant to intestinal colonization by Vibrio cholerae, but germ free mice can be colonized and have been used to study OCV immunogenicity.

Core genome multilocus sequence typing (cgMLST) has gained popularity in recent years in epidemiological research and subspecies level classification. cgMLST retains the intuitive nature of traditional MLST but offers much greater resolution by utilizing significantly larger portions of the genome. Here, we introduce a cgMLST scheme for Vibrio cholerae, a bacterium abundant in marine and freshwater environments and the etiologic agent of cholera. A set of 2,443 core genes ubiquitous in V.

Pterins are ubiquitous biomolecules with diverse functions including roles as cofactors, pigments, and redox mediators. Recently, a novel pterin-dependent signaling pathway that controls biofilm formation was identified in the plant pathogen, Agrobacterium tumefaciens. A key player in this pathway is a pteridine reductase termed PruA, where its enzymatic activity has been shown to control surface attachment and limit biofilm formation.

Naturally occurring free fatty acids (FFAs) are recognized as potent antimicrobial agents that also affect the production of virulence factors in bacterial pathogens. In the foodborne pathogen Listeria monocytogenes, some medium- and long-chain FFAs act as antimicrobial agents as well as signaling compounds, causing repression of transcription of virulence genes.

Flagellar gene expression is bimodal in Salmonella enterica. Under certain growth conditions, some cells express the flagellar genes whereas others do not. This results in mixed populations of motile and non-motile cells. In the present study, we found that two independent mechanisms control bimodal expression of the flagellar genes. One was previously found to result from a double negative-feedback loop involving the flagellar regulators RflP and FliZ.

Phage tail-like bacteriocins (tailocins) are bacterially-produced protein toxins that mediate competitive interactions between co-colonizing bacteria. Both theoretical and experimental research has shown there are intransitive interactions between bacteriocin-producing, bacteriocin-sensitive, and bacteriocin-resistant populations, whereby producers outcompete sensitive, sensitive outcompete resistant, and resistant outcompete producers.

LtrR is a LysR-type regulator involved in the positive expression of ompR to promote ompC and ompF expression. This regulatory network is fundamental in the control of bacterial transformation and in resistance to the bile salt sodium deoxycholate in Salmonella enterica serovar Typhi. In this work, the transcriptional regulation of ltrR was characterized, revealing that the use of alternative promoters results in two transcripts.

Listeria monocytogenes is a model facultative intracellular pathogen. Tight regulation of virulence proteins is essential for a successful infection, and the gene encoding the annotated thioredoxin YjbH was identified in two forward genetic screens as required for virulence factor production. Accordingly, an L. monocytogenes strain lacking yjbH is attenuated in a murine model of infection. However, the function of YjbH in L. monocytogenes has not been investigated.

Dps, a DNA-binding protein from starved cells in E. coli, is part of the bacterial defense system that protects DNA against various cellular stresses. Our lab previously demonstrated that a novel antimicrobial peptide, wrwycr, enhances acid-induced killing of enterohemorrhagic Escherichia coli (EHEC) and ameliorates infection in a Citrobacter rodentium mouse model of EHEC infection. Wrwycr has previously been shown to compromise DNA damage repair and increase chelatable iron within the cell.

In response to nutrient depletion, the RelA and SpoT proteins generate the signaling molecule (p)ppGpp, which then controls a number of downstream effectors to modulate cell physiology. In Acinetobacter baumannii strain AB5075, a relA ortholog (ABUW_3302) was identified by a transposon insertion that conferred an unusual colony phenotype. An in-frame deletion in relA (relA) failed to produce detectable levels of ppGpp when amino acid starvation was induced with serine hydroxamate.

Bacteriocins are ribosomally synthesized proteinaceous antibacterial peptides. They selectively interfere with the growth of other bacteria. The production and secretion of bacteriocins confer a distinct ecological advantage to the producer in competing against other bacteria that are present in the same ecological niche. Streptococcus mutans, a significant contributor to the development of dental caries, is one of the most prolific producer of bacteriocins, known as mutacins in S. mutans.

While alternating between insects and mammals during its lifecycle, Yersinia pestis, the flea transmitted bacterium that causes plague, regulates its gene expression appropriately to adapt to these two physiologically disparate host environments. In fleas competent to transmit Y. pestis, low GC content genes y3555, y3551 and y3550 are highly transcribed, suggesting that these genes have a highly prioritized role in flea infection.

The capacity of Listeria monocytogenes to adapt to environmental changes is facilitated by a large number of regulatory proteins encoded within its genome. Among these proteins are the uncharacterized LysR-type transcriptional regulators (LTTRs). LTTRs can work as positive and/or negative transcription regulators at both local and global genetic levels.