Journal of Bacteriology

The Research Publications track research that is published across national and international peer-reviewed journals. The most recent articles are available ahead of print and searchable by Journal Title, Subject, USDA Grant Funding Agencies or FDA Grant Funding Agencies. The research publications are tracked across five subject areas: Bacterial Pathogens, Chemical Contaminants, Natural Toxins, Parasites, and Viruses.

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...
Tue, 01/14/2020 - 03:23
The marine bacterium and human pathogen Vibrio parahaemolyticus rapidly colonizes surfaces by using swarming motility and forming robust biofilms. Entering either colonization program, swarming motility or sessility, involves differential regulation of many genes resulting in a dramatic shift in physiology and behavior. V. parahaemolyticus has evolved complex regulation to control these two...
Tue, 12/24/2019 - 03:23
Quorum Sensing (QS) are mechanisms of synthesis and detection of signaling molecules to regulate gene expression and coordinate behaviors in bacterial populations. In Bacillus subtilis (Bs), multiple paralog Rap-Phr QS systems (receptor-signaling peptide) are highly redundant and multifunctional, interconnecting the regulation of differentiation processes such as sporulation and competence....
Tue, 12/24/2019 - 03:23
The intrinsic resistance of Pseudomonas aeruginosa to many antibiotics limits treatment options for pseudomonal infections. P. aeruginosa's outer membrane is highly impermeable and decreases antibiotic entry into the cell. We used an unbiased, high-throughput approach to examine mechanisms underlying outer membrane-mediated antibiotic exclusion. Insertion Sequencing (INSeq) identified genes that...
Tue, 12/03/2019 - 03:45
Bacterial lipopolysaccharides are major components and contributors to the integrity of Gram-negative outer membranes. The more conserved lipid A-core part of this complex glycolipid is synthesized separately from the hypervariable O-antigenic polysaccharide (OPS) part and they are joined in the periplasm prior to translocation to the outer membrane. Three different biosynthesis strategies are...
Wed, 11/13/2019 - 03:24
The Na+ - ion translocating NADH:quinone oxidoreductase (NQR) from Vibrio cholerae is a membrane bound respiratory enzyme which harbors flavins and Fe-S clusters as redox centers. The NQR is the main producer of sodium motive force (SMF) and drives energy-dissipating processes such as flagellar rotation, substrate uptake, ATP synthesis and cation-proton antiport. The NQR requires for its...
Tue, 10/29/2019 - 03:26
Cytochrome bd quinol oxidases, which have greater affinity for oxygen than heme-copper cytochrome oxidases (HCOs), promote bacterial respiration and fitness in low-oxygen environments such as host tissues. Here, we show that in addition to the CydA and CydB subunits, the small protein CydX is required for the assembly and function of the cytochrome bd complex in the enteric pathogen Salmonella...
Tue, 10/22/2019 - 03:28
Background: Mycobacterium tuberculosis nicotinamidase/pyrazinamidase (PZAse) is a metalloenzyme that catalyzes conversion of nicotinamide/pyrazinamide to nicotinic acid/pyrazinoic acid. This study investigated whether a metallochaperone is required for optimal PZAse activity.Methods: M. tuberculosis and E.coli PZAses (PZAse-MT and PZAse-EC respectively) were inactivated by metal depletion (giving...
Tue, 10/15/2019 - 03:33
Escherichia coli O157:H7 is a foodborne pathogen, implicated in various multi-state outbreaks. It encodes Shiga toxin on a prophage, and Shiga toxin production is linked to phage induction. An E. coli strain, designated 0.1229, was identified that amplified Stx2a production when co-cultured with E. coli O157:H7 strain PA2. Growth of PA2 in 0.1229 cell-free supernatants had a similar effect, even...
Tue, 10/08/2019 - 03:28
The gene designated BAB_RS23470 in the Brucella abortus 2308 genome encodes an ortholog of the cation diffusion facilitator family protein EmfA which has been linked to resistance to Mn toxicity in Rhizobium etli. A B. abortus emfA null mutant derived from strain 2308 displays increased sensitivity to elevated levels of Mn in the growth medium compared to the parent strain, but wild-type...
Tue, 09/24/2019 - 03:27
Cyclic di-GMP (c-di-GMP) is a bacterial second messenger molecule that is important in the biology of Vibrio cholerae, but the molecular mechanisms by which this molecule regulates downstream phenotypes have not been fully characterized. We have previously shown that the Vc2 c-di-GMP-binding riboswitch, encoded upstream of the gene tfoY, functions as an off-switch in response to c-di-GMP. However...
Tue, 09/24/2019 - 03:27
Brucella are intracellular pathogens that cause a disease known as brucellosis. Though the genus is highly monomorphic at the genetic level, species have animal host preferences and some defining physiologic characteristics. Of note is the requirement for CO2 supplementation to cultivate particular species, which confounded early efforts to isolate B. abortus from diseased cattle. Differences in...
Tue, 09/24/2019 - 03:27
Colicin U is a protein produced by the bacterium Shigella boydii (serovars 1 and 8). It exerts antibacterial activity against strains of the enterobacterial genera Shigella and Escherichia. Here we report that colicin U forms voltage-dependent pores in planar lipid membranes; its single-pore conductance was found to be about 22 pS in 1M KCl, at pH 6 under 80 mV in asolectin bilayers. In agreement...
Sun, 09/22/2019 - 03:22
Germination of Bacillus spores is triggered by the binding of specific nutrients to germinant receptors (GRs) located in the spore's inner membrane. The GRs typically consist of A, B and C subunits, encoded by tricistronic ger operons. The Bacillus licheniformis genome contains the gerA family operons gerA, ynd and gerK. In contrast to the ABC (D) organization that characterizes gerA operons of...
Sun, 09/22/2019 - 03:22
Staphylococcus aureus has evolved a complex regulatory network that controls a multitude of defense mechanisms against the deleterious effects of oxidative stress stimuli subsequently leading to the pathogen's survival and persistence in the hosts. Previously, we characterized the msaABCR operon as a regulator of virulence, antibiotic resistance, and the formation of persister cells in S. aureus...
Sun, 09/22/2019 - 03:22
Production of flagella is costly and subject to global, multi-layered regulation. This is reflected in the hierarchical control of flagellar production in many bacterial species. For Salmonella enterica serovar Typhimurium and its relatives, global regulation of flagellar production primarily occurs through control of flhDC transcription and mRNA translation. In this study, the role of the...
Sun, 09/22/2019 - 03:22
Coxiella burnetii is an obligate intracellular gammaproteobacterium and zoonotic agent of Q fever. We previously identified 15 small non-coding RNAs (sRNAs) of C. burnetii. One of them, CbsR12 (Coxiella b urnetii small RNA 12), is highly transcribed during axenic growth and becomes more prominent during infection of cultured mammalian cells. Secondary structure predictions of CbsR12 revealed four...
Sun, 09/22/2019 - 03:22
Macrophage parasitism by Coxiella burnetii, the cause of human Q fever, requires translocation of proteins with effector functions directly into the host cell cytosol via a Dot/Icm type 4B secretion system (T4BSS). Secretion by the analogous Legionella pneumophila T4BSS involves signal sequences within C-terminal and internal domains of effector proteins. The cytoplasmic chaperone pair IcmSW...
Mon, 09/09/2019 - 11:22
Production of flagella is costly and subject to global, multi-layered regulation. This is reflected in the hierarchical control of flagellar production in many bacterial species. For Salmonella enterica serovar Typhimurium and its relatives, global regulation of flagellar production primarily occurs through control of flhDC transcription and mRNA translation. In this study, the role of the...
Mon, 09/09/2019 - 11:22
Macrophage parasitism by Coxiella burnetii, the cause of human Q fever, requires translocation of proteins with effector functions directly into the host cell cytosol via a Dot/Icm type 4B secretion system (T4BSS). Secretion by the analogous Legionella pneumophila T4BSS involves signal sequences within C-terminal and internal domains of effector proteins. The cytoplasmic chaperone pair IcmSW...
Tue, 09/03/2019 - 11:50
Brucella are intracellular pathogens that cause a disease known as brucellosis. Though the genus is highly monomorphic at the genetic level, species have animal host preferences and some defining physiologic characteristics. Of note is the requirement for CO2 supplementation to cultivate particular species, which confounded early efforts to isolate B. abortus from diseased cattle. Differences in...
Mon, 08/26/2019 - 12:33
Coxiella burnetii is an obligate intracellular gammaproteobacterium and zoonotic agent of Q fever. We previously identified 15 small non-coding RNAs (sRNAs) of C. burnetii. One of them, CbsR12 (Coxiella b urnetii small RNA 12), is highly transcribed during axenic growth and becomes more prominent during infection of cultured mammalian cells. Secondary structure predictions of CbsR12 revealed four...

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