Journal of Bacteriology

Tue, 11/24/2020 - 10:01
Lysozyme is an important component of the innate immune system. It functions by hydrolysing the peptidoglycan (PG) layer of bacteria. The human pathogen Listeria monocytogenes is intrinsically lysozyme resistant. The peptidoglycan N-deacetylase PgdA and O-acetyltransferase OatA are two known factors contributing to its lysozyme resistance. Furthermore, it was shown that the absence of components...
Tue, 11/17/2020 - 10:01
Vibrio parahaemolyticus rapidly colonizes surfaces using swarming motility. Surface contact induces the surface sensing regulon including lateral flagellar genes, spurring dramatic shifts in physiology and behavior. The bacterium can also adopt a sessile, surface-associated lifestyle and form robust biofilms. These alternate colonization strategies are influenced reciprocally by the second...
Wed, 11/04/2020 - 10:02
To initiate their life cycle, phages must specifically bind to the surface of their bacterial hosts. Long-tailed phages often interact with the cell surface using fibers, which are elongated intertwined trimeric structures. The folding and assembly of these complex structures generally requires the activity of an intra- or intermolecular chaperone protein. Tail fiber assembly (Tfa) proteins are a...
Tue, 10/27/2020 - 10:02
An essential feature of the pathogenesis of Salmonella enterica serovar Enteritidis (S. Enteritidis; wild type (WT)) is its ability to survive in diverse micro-environmental stress conditions such as encountering antimicrobial peptides (AMPs), glucose and micronutrient starvation. These stress factors trigger virulence genes encoded on Salmonella pathogenicity islands (SPIs) and determine the...
Tue, 10/06/2020 - 10:01
Cyclic-di-AMP (c-di-AMP) is an essential and ubiquitous second messenger among bacteria. C-di-AMP regulates many cellular pathways through direct binding to several molecular targets in bacterial cells. C-di-AMP depletion is well known to destabilize the bacterial cell wall, resulting in increased bacteriolysis and enhanced susceptibility to cell wall targeting antibiotics. Using the human...
Tue, 09/29/2020 - 10:01
Shigella flexneri is a major causative agent of bacillary dysentery in developing countries where serotype 2a2 is the prevalent strain. To date, approximately 30 serotypes have been identified for S. flexneri and the major contribution to the emergence of new serotypes is chemical modifications of the lipopolysaccharide (LPS) component O antigen (Oag). Glucosylation, O-acetylation and...
Tue, 09/15/2020 - 10:01
Members of the small multidrug resistant (SMR) efflux pump family known as SugE (more recently renamed to Gdx) are known for their narrow substrate selectivity to small guanidinium (Gdm+) compounds and disinfectant quaternary ammonium compounds (QACs). Gdx members have been identified on multidrug resistant plasmids in Gram-negative bacilli, but their functional role remains unclear as few have...
Wed, 09/09/2020 - 10:01
YggS (COG0325) is a pyridoxal 5'-phosphate (PLP)-binding protein proposed to be involved in homeostasis of B6 vitamers. In Salmonella enterica, lack of yggS resulted in phenotypes that were distinct, and others that were similar, to those of a yggS mutant of Escherichia coli. Like other organisms, yggS mutants of S. enterica accumulate endogenous pyridoxine 5'-phosphate (PNP). Data herein show...
Wed, 09/09/2020 - 10:01
Pathogenic Vibrios use many different approaches to subvert, attack, and undermine the host response. The toxins they produce are often responsible for the devastating effects associated with their diseases. These toxins target a variety of host proteins, which leads to deleterious effects including dissolution of cell organelle integrity and inhibition of protein secretion. Becoming increasingly...
Wed, 09/09/2020 - 10:01
Phenotypic testing for drug susceptibility of Mycobacterium tuberculosis is critical to basic research and managing the evolving problem of antimicrobial resistance in tuberculosis management, but remains a specialized technique to which access is severely limited. Here, we report on the development and validation of an improved phage-mediated detection system for M. tuberculosis. We incorporated...
Tue, 09/01/2020 - 10:02
Motility is required for many bacterial pathogens to reach and colonize target sites. Vibrio cholerae traverses a thick mucus barrier coating the small intestine to reach the underlying epithelium. We screened a transposon library in motility media containing mucin to identify factors that influence mucus transit. Lesions in structural genes of the Type VI Secretion System (T6SS) were among those...
Tue, 08/25/2020 - 10:02
The Gram-negative enterobacterium Erwinia amylovora causes fire blight disease in apple and pear trees. Lipopolysaccharides and the exopolysaccharide amylovoran are essential E. amylovora virulence factors. We found that mutations to rfbX disrupted amylovoran production and virulence in apple fruits and tree shoots, and that deletion of yibD suppressed the rfbX mutant phenotype. Expression of...
Tue, 08/18/2020 - 10:01
Fluctuations in osmolarity are one of the most prevalent stresses to which bacteria must adapt, both hypo- and hyper-osmotic conditions. Most bacteria cope with high osmolarity by accumulating compatible solutes (osmolytes) in the cytoplasm to maintain the turgor pressure of the cell. Vibrio parahaemolyticus, a halophile, utilizes at least six compatible solute transporters for the uptake of...
Tue, 08/18/2020 - 10:01
To adapt to changing and potentially hostile environments, bacteria can activate the transcription of genes under the control of alternative sigma factors, such as SigB, a master regulator of the general stress response in several Gram-positive species. Bacillus thuringiensis is a Gram-positive spore-forming invertebrate pathogen whose lifecycle includes a variety of environments, including...
Tue, 08/18/2020 - 10:01
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....
Tue, 08/11/2020 - 10:02
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...
Tue, 08/11/2020 - 10:02
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. We found that treatment with proteinase K enzyme effectively...
Tue, 08/04/2020 - 10:01
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...
Tue, 08/04/2020 - 10:01
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...
Tue, 07/21/2020 - 10:01
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. monocytogenes GlnR, the transcriptional regulator of nitrogen metabolism...
Tue, 07/14/2020 - 10:01
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)....
Tue, 07/07/2020 - 10:01
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. Vibrio cholerae, the etiological...
Tue, 07/07/2020 - 10:01
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. Herein, we...
Tue, 06/30/2020 - 10:01
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. To better understand PscF functions and...
Tue, 06/30/2020 - 10:01
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...
Tue, 06/23/2020 - 10:01
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. Transcription of hilA, encoding the transcriptional activator of the SPI1...
Tue, 06/16/2020 - 10:01
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. However, germ free animals have impaired immune systems and intestinal physiology; also, live OCVs colonize...
Tue, 06/16/2020 - 10:01
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...
Tue, 06/02/2020 - 03:35
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...
Tue, 05/12/2020 - 03:32
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. We previously observed that the...
Tue, 04/21/2020 - 03:33
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...
Tue, 04/21/2020 - 03:33
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-...
Tue, 04/14/2020 - 03:24
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...
Tue, 04/07/2020 - 03:41
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....
Tue, 03/31/2020 - 03:24
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...
Tue, 03/31/2020 - 03:24
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...
Tue, 03/31/2020 - 03:24
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...
Tue, 03/24/2020 - 03:39
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...
Tue, 03/17/2020 - 03:24
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. Previously, our group determined by...
Tue, 03/17/2020 - 03:24
Listeria monocytogenes is a Gram-positive pathogen able to cause severe human infections. Its major virulence regulator is the transcriptional activator PrfA, a member of the Crp/Fnr family of transcriptional regulators. To establish a successful L. monocytogenes infection, the PrfA protein needs to be in an active conformation, either by binding the cognate inducer glutathione (GSH) or by...
Tue, 03/10/2020 - 03:23
The type VI secretion system (T6SS) is a weapon widespread in Gram-negative bacteria that delivers effectors into target cells. The T6SS is a highly versatile machine as it can target both eukaryotic and prokaryotic cells, and it has been proposed that T6SS are adapted to the specific needs of each bacterium. The expression of T6SS gene clusters and the activation of the secretion apparatus are...
Tue, 03/03/2020 - 03:32
Shigella species, the causal agents of bacillary dysentery, use a type III secretion system (T3SS) to inject two waves of virulence proteins, known as effectors, into the colonic epithelium to subvert host cell machinery. Prior to host cell contact and secretion of the first wave of T3SS effectors, OspD1, an effector and anti-activator protein, prevents premature production of the second wave of...
Tue, 02/25/2020 - 03:27
In Listeria monocytogenes the full details of how stress signals are integrated into the B regulatory pathway are not yet available. To help shed light on this question we investigated a collection of transposon mutants that were predicted to have compromised activity of the alternative sigma factor B (B). These mutants were tested for acid tolerance, a trait that is known to be under B...
Tue, 02/11/2020 - 03:25
Salmonella enterica serovar Typhimurium colonizes and invades host intestinal epithelial cells using the Type Three Secretion System (T3SS) encoded on Salmonella Pathogenicity Island 1 (SPI1). The level of SPI1 T3SS gene expression is controlled by the transcriptional activator HilA, encoded on SPI1. Expression of hilA is positively regulated by three homologous transcriptional regulators, HilD,...
Tue, 01/28/2020 - 03:26
The physiological relevance of bacterial iron efflux has only recently been appreciated. The Bacillus subtilis P1B4-type ATPase PfeT (peroxide-induced ferrous efflux transporter) was one of the first iron efflux pumps to be characterized, and cells lacking pfeT accumulate high levels of intracellular iron. The pfeT promoter region has binding sites for both PerR, a peroxide sensing Fur-family...
Tue, 01/28/2020 - 03:26
Exoelectrogens are able to transfer electrons extracellularly, enabling them to respire on insoluble terminal electron acceptors. Extensively studied exoelectrogens like Geobacter sulfurreducens and Shewanella oneindensis are Gram-negative, but more recently it has been reported that Gram-positive bacteria like Listeria monocytogenes and Enterococcus faecalis also exhibit the ability to transfer...
Wed, 01/22/2020 - 03:24
Listeria monocytogenes is a Gram-positive Firmicute that causes food-borne infections, in part due to its ability to use multiple strategies, including biofilm formation, to survive adverse growth conditions. As a potential way to screen for genes required for biofilm formation we harnessed the ability of bacteria to accumulate mutations in the genome over time, diverging the properties of...
Wed, 01/22/2020 - 03:24
Transition metals are essential for life, but are toxic when in excess. Metal ion intoxication may result from the mismetallation of essential metal-dependent enzymes with a non-cognate metal. To begin to identify enzymes and processes that are susceptible to mismetallation, we have selected for strains with increased resistance to Mn(II) and Co(II). In Bacillus subtilis, cells lacking the MntR...
Tue, 01/14/2020 - 03:23
Campylobacter jejuni causes acute gastroenteritis world-wide and is transmitted primarily through poultry, in which it is often a commensal member of the intestinal microbiota. Previous RNASeq experiments showed that transcripts from an operon encoding a high affinity phosphate transporter (PstSCAB) of C. jejuni were among the most abundant when grown in chickens. Elevated levels of the pstSCAB...
Tue, 01/14/2020 - 03:23
Enterococcus faecalis cells are known to have ferric reductase activity and the ability to transfer electrons generated in metabolism to the external environment. We have isolated mutants defective in ferric reductase activity and studied their electron transfer properties to electrodes mediated by ferric ions and an osmium complex modified redox polymer (OsRP), respectively. Electron transfer...

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