Journal of Bacteriology

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...
Mon, 08/19/2019 - 11:10
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...
Mon, 08/12/2019 - 12:29
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...
Mon, 07/29/2019 - 11:30
Vibrio parahaemolyticus RIMD2210633 secretes both chitinase and chitin oligosaccharide deacetylase and produces β-N-acetyl-d-glucosaminyl-(1,4)-d-glucosamine (GlcNAc-GlcN) from chitin. Previously, we reported that GlcNAc-GlcN induces chitinase production by several strains of Vibrio harboring chitin oligosaccharide deacetylase genes (Hirano et al. Glycobiology 19:1049-1053, 2009). The...
Mon, 07/22/2019 - 11:21
Outer membrane vesicles (OMVs) are continuously produced by Gram-negative bacteria, and are increasingly recognized as ubiquitous mediators of bacterial physiology. In particular, OMVs are powerful effectors in inter-organismal interactions, driven largely by their molecular contents. These impacts have been studied extensively in bacterial pathogenesis, but have not been well documented within...
Mon, 07/01/2019 - 11:32
In open environments such as water, enterohemorrhagic Escherichia coli O157:H7 responds to inorganic phosphate (Pi) starvation by inducing the Pho regulon controlled by PhoB. This activates the phosphate-specific transport (Pst) system that contains a high-affinity Pi transporter. In the pst mutant, PhoB is constitutively activated and regulates the expression of genes in the Pho regulon. Here we...
Mon, 07/01/2019 - 11:32
Salmonella enterica serovar Typhimurium induces inflammatory diarrhea and bacterial uptake into intestinal epithelial cells using the Salmonella pathogenicity island 1 (SPI1) type III secretion system (T3SS). HilA activates transcription of the SPI1 structural components and effector proteins. Expression of hilA is activated by HilD, HilC, and RtsA, which act in a complex feed-forward regulatory...
Mon, 06/24/2019 - 11:16
Enteroaggregative Escherichia coli (EAEC) from the O104:H4 specific serotype caused a large outbreak of bloody diarrhea with some complicated cases of hemolytic uremic syndrome (HUS) in Europe in 2011. The outbreak strain consisted in an EAEC capable to produce the Shiga toxin (Stx) subtype 2a, a characteristic from enterohemorrhagic E. coli (EHEC). QseBC 2-component system detects AI-3/Epi/NE...
Mon, 06/10/2019 - 12:53
Salmonella must rapidly adapt to various niches in the host during infection. Relevant virulence factors must be appropriately induced, and systems that are detrimental in a particular environment must be turned off. Salmonella infects intestinal epithelial cells using a type 3 secretion system (T3SS) encoded on Salmonella pathogenicity island 1 (SPI1). The system is controlled by three AraC-like...
Mon, 06/10/2019 - 12:53
Salmonella virulence requires the initial invasion of host cells followed by the modulation of the intracellular environment for survival and replication. In an effort to characterize the role of small RNAs in Salmonella pathogenesis, we inadvertently identified a 5 kD protein named YshB that is involved in the intracellular survival of Salmonella. We show here that yshB expression is upregulated...
Mon, 05/20/2019 - 11:20
The Zur-regulon is central to zinc homeostasis in the zinc-resistant bacterium Cupriavidus metallidurans. It comprises the transcription regulator Zur, the zinc importer ZupT, and three members of the COG0523 family of metal-chaperoning G3E-type GTPases, annotated as CobW1, CobW2, and CobW3. The operon structures of the zur and cobW1 loci were determined. To analyze the interplay between the Zur...
Mon, 04/29/2019 - 11:34
Vibrio cholerae, the facultative pathogen responsible for cholera disease, continues to pose a global health burden. Its persistence can be attributed to a flexible genetic toolkit that allows for adaptation to different environments with distinct carbon sources, including the six-carbon sugar alcohol mannitol. V. cholerae takes up mannitol through the transporter protein MtlA, whose production...
Mon, 04/29/2019 - 11:34
Capsular polysaccharides (CPSs) are virulence factors for many important pathogens. In Escherichia coli, CPSs are synthesized via two distinct pathways, but both require proteins from the outer membrane polysaccharide export (OPX) family to complete CPS export from the periplasm to the cell surface. In this study, we compare the properties of the OPX proteins from the prototypical group 1 (Wzy-...
Mon, 04/22/2019 - 11:14
The bacterial flagellum is a sophisticated self-assembling nanomachine responsible for motility in many bacterial pathogens including Pseudomonas aeruginosa, Vibrio spp., and Salmonella enterica. The bacteria flagellum has been studied extensively in the model systems Escherichia coli and Salmonella Typhimurium, yet the range of variation in flagellar structure and assembly remains incompletely...
Mon, 04/15/2019 - 11:36
Bacterial lipoproteins are globular proteins anchored to the extracytoplasmic surfaces of cell membranes through lipidation at a conserved N-terminal cysteine. Lipoproteins contribute to an array of important cellular functions for bacteria, as well as being a focal point for innate immune system recognition through binding to Toll-like receptor 2 (TLR2) heterodimer complexes. Although...
Mon, 04/08/2019 - 11:17
Typhoid fever, a human-specific disease, is primarily caused by the pathogen Salmonella enterica serovar Typhi (S. Typhi). It is estimated that 3-5% of people infected with typhoid fever become chronic carriers. Studies have demonstrated that a mechanism of chronic carriage involves biofilm formation on gallstone surfaces. In the course of a previous study using a chronic carriage mouse model, a...
Mon, 04/01/2019 - 11:50
Typhoid fever is caused primarily by Salmonella enterica serovar Typhi (S. Typhi). Approximately 3-5% of individuals infected with S. Typhi become chronic carriers with the gallbladder (GB) as the site of persistence, as gallstones within the GB are a platform on which the bacteria form a biofilm. S. Typhi is a human-restricted pathogen; therefore, asymptomatic carriers represent a critical...
Mon, 04/01/2019 - 11:50
The Gram-negative cell envelope is a remarkable structure with core components that include an inner membrane, an outer membrane, and a peptidoglycan layer in the periplasmic space between. Multiple molecular systems function to maintain integrity of this essential barrier between the interior of the cell and its surrounding environment. We show that a conserved DUF1849-family protein, EipB, is...
Mon, 03/25/2019 - 11:20
The Type VI secretion system (T6SS) is an injection apparatus that uses a spring-like mechanism for effector delivery. The contractile tail is composed of a needle tipped by a sharpened spike and wrapped by the sheath that polymerizes in an extended conformation on the assembly platform or baseplate. Contraction of the sheath propels the needle and effectors associated with it into target cells....
Mon, 03/18/2019 - 11:18
Elongation factor P (EF-P) facilitates the translation of certain peptide motifs, including those with multiple proline residues. EF-P must be post-translationally modified for full functionality; in Enterobacteria this is accomplished by two enzymes, EpmA and EpmB, which catalyze the β-lysylation of EF-P at a conserved lysine position. Mutations to efp or its modifying enzymes produce...
Mon, 03/11/2019 - 11:32
Korormicin is an antibiotic, produced by some Pseudoalteromonads, which selectively kills gram negative bacteria that express the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR.) We show that, although korormicin is an inhibitor of Na+-NQR, the antibiotic action is not a direct result of inhibiting enzyme activity. Instead, perturbation of electron transfer inside the enzyme promotes a reaction...
Mon, 03/11/2019 - 11:32
Conjugative plasmids of the IncC group, formerly known as A/C2, disseminate antibiotic resistance genes globally in diverse pathogenic species of Gammaproteobacteria. Salmonella genomic island 1 (SGI1) can be mobilized by IncC plasmids and was recently shown to reshape the conjugative type IV secretion system (T4SS) encoded by these plasmids to evade entry exclusion. Entry exclusion blocks DNA...
Mon, 03/11/2019 - 11:32
The phage shock protein (Psp) system is a stress response pathway that senses and responds to inner membrane damage. The genetic components of the Psp system are present in several clinically relevant Gram-negative bacteria, including Vibrio cholerae. However, most of the current knowledge about the Psp response stems from in vitro studies in Escherichia coli and Yersinia enterocolitica. In fact...
Tue, 02/19/2019 - 11:27
Prophage mediated horizontal gene transfer (HGT) plays a key role in the evolution of bacteria, enabling access to new environmental niches, including pathogenicity. Citrobacter rodentium is a host-adapted intestinal mouse pathogen and important model organism for attaching and effacing (A/E) pathogens including the clinically significant enterohaemorrhagic (EHEC) and enteropathogenic (EPEC)...
Mon, 02/11/2019 - 11:14
Coxiella burnetii, the etiological agent of Q fever, undergoes a unique biphasic developmental cycle where bacteria transition from a replicating (exponential phase) large cell variant (LCV) form to a non-replicating (stationary phase) small cell variant (SCV) form. The alternative sigma factor RpoS is an essential regulator of stress responses and stationary phase physiology in several bacterial...
Mon, 02/11/2019 - 11:14
Bacteria deploy global programs of gene expression, including components of the SOS-response, to counteract the cytotoxic and genotoxic effects of environmental DNA damaging factors. Here, we report that genetic damage promoted by hexavalent chromium elicited the SOS-response in Bacillus subtilis, as evidenced by the induction of transcriptional uvrA-lacZ, recA-lacZ and PrecA-gfp fusions....
Mon, 02/11/2019 - 11:14
Bacteria sense environmental chemicals using chemosensor proteins, most of which are present in the cytoplasmic membrane. Canonical chemoreceptors bind their specific ligands in their periplasmic domain, and the ligand binding creates a molecular stimulus that is transmitted into the cytoplasm, leading to various cellular responses, such as chemotaxis and specific gene expression. Vibrio cholerae...
Mon, 02/04/2019 - 12:19
H-NS-mediated repression of acquired genes and the subsequent adaptation of regulatory mechanisms that counteract this repression have played a central role in the Salmonella pathogenicity evolution. The Salmonella pathogenicity island 2 (SPI-2) is an acquired chromosomal region containing genes necessary for Salmonella to colonize and replicate in different niches of hosts. The ssrAB operon,...
Mon, 01/28/2019 - 15:58
Campylobacter jejuni and Campylobacter coli are the most common cause of bacterial gastroenteritis in the world. Ganglioside mimicry by C. jejuni lipooligosaccharide (LOS) is the triggering factor of Guillain-Barré syndrome (GBS), an acute polyneuropathy. Sialyltransferases from the glycosyltransferase (GT) family 42 are essential for the expression of ganglioside mimics in C. jejuni....
Mon, 01/14/2019 - 12:47
Lag is a temporary period of non-replication seen in bacteria that are introduced to new media. Despite latency being described by Müller in 1895, until only recently have we gained insights into the cellular processes characterizing lag phase. This review covers literature to date on the transcriptomic, proteomic, metabolomic, physiological, biochemical, and evolutionary features of...
Mon, 12/17/2018 - 11:19
The flagellar lipoprotein FlgP has been identified in several species of bacteria and, its absence provokes different phenotypes. In this work we show that in the α proteobacterium Rhodobacter sphaeroides, a flgP mutant is unable to assemble the hook and the filament. In contrast, the MS ring and the flagellar rod appear to be assembled. In the absence of FlgP a severe defect in the...
Mon, 12/03/2018 - 11:34
The Salmonella Typhimurium RcsCDB system regulates the synthesis of colanic acid and flagellum as well as the expression of virulence genes. We previously demonstrated that the rcsC11 mutant, which constitutively activates the RcsB regulator, attenuates Salmonella virulence in an animal model. This attenuated phenotype could be also produced by deletion of the slyA gene. In this work, we...
Mon, 11/12/2018 - 11:43
Escherichia coli and many other bacterial species can enter into a viable but nonculturable (VBNC) state, which is a survival strategy adopted by cells exposed to adverse environmental conditions. Pyruvate is known to be one factor that promotes resuscitation of VBNC cells. Here we studied the role of a pyruvate-sensing network, composed of the two histidine kinase/response regulator systems BtsS...
Mon, 10/22/2018 - 12:48
The histidine ATP-binding cassette (ABC) transporter of Salmonella enterica serovar Typhimurium is among the best-studied type I ABC import systems. The transporter consists of two transmembrane subunits, HisQ and HisM, and a homodimer of the nucleotide-binding subunit, HisP. Substrates are delivered by two periplasmic solute binding proteins, HisJ and LAO, with preferences for histidine and...
Mon, 10/01/2018 - 11:39
Pyruvate kinase plays a central role in glucose catabolism in bacteria, and efficient utilization of this hexose has been linked to the virulence of Brucella strains in mice. The brucellae produce a single pyruvate kinase which is an ortholog of the Bradyrhizobium manganese (Mn)-dependent pyruvate kinase PykM. Biochemical analysis of the Brucella pyruvate kinase and phenotypic analysis of a B....
Mon, 09/24/2018 - 11:46
Cyclic-di-GMP (c-di-GMP) is a bacterial second messenger that regulates processes such as biofilm formation and virulence. During degradation, c-di-GMP is first linearized to pGpG and subsequently hydrolyzed to two GMPs by a previously unknown enzyme, which was recently identified in Pseudomonas aeruginosa as the 3' to 5' exoribonuclease Oligoribonuclease (Orn). Mutants of orn accumulated pGpG,...
Mon, 09/17/2018 - 11:20
Vibrio cholerae controls the pathogenicity of interactions with arthropod hosts via the activity of the CrbS/R two component system. This signaling pathway regulates the consumption of acetate, which in turn, alters the relative virulence of interactions with arthropods, including Drosophila melanogaster. CrbS is a histidine kinase that links a transporter-like domain to its signaling apparatus...
Mon, 09/10/2018 - 11:28
The 54 regulon in Salmonella enterica serovar Typhimurium includes a predicted RNA repair operon, encoding homologs of the metazoan Ro60 protein (Rsr), Y RNAs (YrlBA), RNA ligase (RtcB), and RNA 3'-phosphate cyclase (RtcA). Transcription from 54-dependent promoters requires that a cognate bacterial enhancer binding protein (bEBP) be activated by a specific environmental or cellular signal; the...

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