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Journal of Bacteriology

Matthew Z Tien, Benjamin J Stein, Sean Crosson
GsrN is a conserved small RNA that is under transcriptional control of the general stress sigma factor, σT , and that functions as a post-transcriptional regulator of Caulobacter crescentus survival under multiple stress conditions. We have defined features of GsrN structure that determine survival under hyperosmotic stress, and have applied transcriptomic and proteomic methods to identify regulatory targets of GsrN under hyperosmotic conditions. The 5' end of GsrN, which includes a conserved cytosine-rich stem loop structure, is necessary for cell survival after osmotic upshock...
July 16, 2018: Journal of Bacteriology
Thomas D Mand, Gargi Kulkarni, William W Metcalf
The methanogenic archaeon Methanosarcina barkeri encodes three distinct types of hydrogenase, whose functions vary depending on the growth substrate. These include the F420-dependent (Frh), methanophenazine-dependent (Vht), and ferredoxin-dependent (Ech) hydrogenases. To investigate their physiological roles, we characterized a series of mutants lacking each hydrogenase in various combinations. Mutants lacking Frh, Vht, or Ech in any combination failed to grow on H2 /CO2 , whereas only Vht and Ech were essential for growth on acetate...
July 16, 2018: Journal of Bacteriology
Floricel Gonzalez, Richard F Helm, Katherine M Broadway, Birgit E Scharf
Bacteriophage 7-7-1, a member of the Myoviridae family, infects the soil bacterium Agrobacterium sp. H13-3. Infection requires attachment to actively rotating bacterial flagellar filaments, with flagellar number, length, and rotation speed being important determinants for infection efficiency. To identify secondary receptor(s) on the cell surface, we isolated motile, phage-resistant Agrobacterium sp. H13-3 transposon mutants. Transposon insertion sites were pinpointed using arbitrary-primed polymerase chain reaction and bioinformatics analyses...
July 16, 2018: Journal of Bacteriology
Anne-Sophie Godeux, Agnese Lupo, Marisa Haenni, Simon Guette-Marquet, Gottfried Wilharm, Maria-Halima Laaberki, Xavier Charpentier
Acinetobacter baumannii is a nosocomial agent with a high propensity for developing resistance to antibiotics. This ability relies on horizontal gene transfer mechanisms occurring in the Acinetobacter genus, including natural transformation. To study natural transformation in bacteria, the most prevalent method uses selection for the acquisition of an antibiotic resistance marker in a target chromosomal locus by the recipient cell. Most clinical isolates of A. baumannii are resistant to multiple antibiotics limiting the use of such selection-based method...
July 16, 2018: Journal of Bacteriology
Mark L Guillotte, Joseph J Gillespie, Courtney E Chandler, M Sayeedur Rahman, Robert K Ernst, Abdu F Azad
Members of the Rickettsia genus are obligate intracellular, Gram-negative coccobacilli that infect mammalian and arthropod hosts. Several rickettsial species are human pathogens and are transmitted by blood-feeding arthropods. As Gram-negative parasites, the outer membrane (OM) sits at the nexus of host-pathogen interaction and is rich in lipopolysaccharide (LPS). The lipid A component of LPS anchors the molecule to the bacterial surface and is an endotoxic agonist of Toll-like receptor 4 (TLR4). Despite the apparent importance of lipid A in maintaining OM integrity, as well as its inflammatory potential during infection, this molecule is poorly characterized in Rickettsia pathogens...
July 16, 2018: Journal of Bacteriology
Imène Kouidmi, Laura Alvarez, Jean François Collet, Felipe Cava, Catherine Paradis-Bleau
Peptidoglycan (PG) is the main structural component of bacterial envelopes. It protects bacterial cells against variations in osmotic pressure and cell lysis. The newly discovered Escherichia coli factor ElyC was shown to be important for peptidoglycan biosynthesis at low temperature. PG production in Δ elyC mutant cells is totally blocked after few hours of growth at 21°C, which triggers cell lysis. In this study, we took a candidate approach to identify genetic suppressors of the Δ elyC mutant cell lysis phenotype...
July 16, 2018: Journal of Bacteriology
Zachary R DeMars, Jeffrey L Bose
Staphylococcus aureus is capable of phosphorylating exogenous fatty acids via the fatty acid kinase FakA for incorporation into the bacterium's membrane. Additionally, FakA plays a significant role in virulence factor regulation and skin infections. We previously showed that a fakA mutant displays altered growth kinetics in vitro, observed during late-exponential phase of growth. Here, we demonstrate that the absence of FakA leads to key metabolic changes. First, the fakA mutant has an altered acetate metabolism with acetate being consumed at an increased rate than the wild-type strain...
July 16, 2018: Journal of Bacteriology
William J MacCain, Suresh Kannan, Dannah Z Jameel, Jerry M Troutman, Kevin D Young
The peptidoglycan exoskeleton shapes bacteria and protects them against osmotic forces, making its synthesis the target of many current antibiotics. Peptidoglycan precursors are attached to a lipid carrier and flipped from the cytoplasm into the periplasm to be incorporated into the cell wall. In Escherichia coli, this carrier is undecaprenyl phosphate (Und-P), which is synthesized as a diphosphate by the enzyme UppS. E. coli MG1655 exhibits wild type morphology at all temperatures, but one of our laboratory strains (CS109) was highly aberrant when grown at 42°C...
July 9, 2018: Journal of Bacteriology
Steve P Bernier, Susie Son, Michael G Surette
Antibiotic resistance is a threat to our modern society and new strategies leading to the identification of new molecules or targets to combat multidrug-resistant pathogens are needed. Species of the genus Burkholderia , including Burkholderia cepacia complex (Bcc), Burkholderia pseudomallei , and Burkholderia mallei can be highly pathogenic and are intrinsically resistant to multiple classes of antibiotics. Bcc species are nonetheless sensitive to extracellular products released by Pseudomonas aeruginosa in interspecies competition...
July 9, 2018: Journal of Bacteriology
Juni Sarkar, Daniel P Miller, Lee D Oliver, Richard T Marconi
Periodontal disease (PD) results from a shift in the composition of the microbial community of the subgingival crevice. As the bacterial population transitions from Gram- positive bacteria to predominantly Gram-negative anaerobes and spirochetes, dramatic changes occur in the physiological and immunological environment at diseased sites. Treponema denticola thrives in periodontal pockets, indicating that it has a unique ability to adapt to the changing environmental conditions. Hpk2 (tde1970), a PAS domain containing histidine kinase (HK), is part of the T...
July 9, 2018: Journal of Bacteriology
Michał Dmowski, Marcin Gołębiewski, Izabela Kern-Zdanowicz
Plasmid conjugative transfer systems comprise type IV secretion systems (T4SS) coupled to DNA processing and replication. The T4SSs are divided into two phylogenetic subfamilies, namely, IVA and IVB or based on the phylogeny of the VirB4 ATPase into eight groups. The conjugation system of the IncM group plasmid pCTX-M3, from Citrobacter freundii , is classified in the IVB subfamily and in the MPFI group, as are the conjugation systems of IncI1 group plasmids. Although the majority of the conjugative genes of the IncM and IncI1 plasmids display conserved synteny, there are several differences...
July 9, 2018: Journal of Bacteriology
Dawn A Manias, Gary M Dunny
It was shown previously that disruption of the ahrC gene encoding a predicted ArgR family transcription factor results in a severe defect in biofilm formation in vitro, as well as significant attenuation of virulence of E. faecalis OG1RF in multiple experimental infection models. Using RNA-seq, we observed ahrC -dependent changes in expression of over 20 genes. AhrC-repressed genes included predicted determinants of arginine catabolism and several other metabolic genes and predicted transporters, while AhrC-activated genes included determinants involved in production of surface protein adhesins...
July 9, 2018: Journal of Bacteriology
Kristin Little, Murray J Tipping, Karine A Gibbs
Individual cells of the bacterium Proteus mirabilis can elongate up to 40-fold on surfaces before engaging in a cooperative surface-based motility termed swarming. How cells regulate this dramatic morphological remodeling remains an open question. In this paper, we move forward the understanding of this regulation by demonstrating that P. mirabilis requires the gene rffG for swarmer cell elongation and subsequent swarm motility. The rffG gene encodes a protein homologous to the dTDP-glucose 4,6-dehydratase protein of Escherichia coli , which contributes to Enterobacterial Common Antigen biosynthesis...
July 2, 2018: Journal of Bacteriology
Genki Akanuma, Kotaro Yamazaki, Yuma Yagishi, Yuka Iizuka, Morio Ishizuka, Fujio Kawamura, Yasuyuki Kato-Yamada
Individually, the ribosomal proteins L1, L23, L36 and S6 are not essential for cell proliferation of B. subtilis , but the absence of any one of these ribosomal proteins causes a defect in the formation of the 70S ribosomes and a reduced growth rate. In mutant strains individually lacking these ribosomal proteins, the cellular Mg2+ content was significantly reduced. The deletion of YhdP, an exporter of Mg2+ , and overexpression of MgtE, the main importer of Mg2+ , increased the cellular Mg2+ content and restored the formation of 70S ribosomes in these mutants...
July 2, 2018: Journal of Bacteriology
Amber B Sauder, Melissa M Kendall
To adapt to ever-changing environments, pathogens quickly alter gene expression. This can occur through transcriptional, post-transcriptional, or post-translational regulation. Historically, transcriptional regulation has been thoroughly studied to understand pathogen niche adaptation, whereas post-transcriptional and post-translational gene regulation have only been relatively recently appreciated to play a central role in bacterial pathogenesis. Post-transcriptional regulation may involve chaperones, nucleases, and/or non-coding small RNAs (sRNAs) and typically controls gene expression by altering the stability and/or translation of the target mRNA...
July 2, 2018: Journal of Bacteriology
James A Budnick, Lauren M Sheehan, Lin Kang, Pawel Michalak, Clayton C Caswell
Elucidating the function of proteins less 50 amino acids in length is no small task. Nevertheless, small proteins can play vital roles in the lifestyle of bacteria and influence the virulence of pathogens; thus, the investigation of the small proteome is warranted. Recently our group identified the Brucella abortus protein VtlR as a transcriptional activator of four genes, one of which is the well-studied small regulatory RNA, AbcR2, while the other three genes encode hypothetical small proteins, two of which are highly conserved among the order Rhizobiales This study provides evidence that all three genes encode authentic small proteins and all three are highly expressed under oxidative stress, low pH, and stationary phase growth conditions...
July 2, 2018: Journal of Bacteriology
Mei G Lei, Chia Y Lee
Capsule is one of many virulence factors produced by Staphylococcus aureus and its expression is highly regulated. Here, we report the repression of capsule by direct interaction of XdrA and CodY with the capsule promoter region. We found, by footprinting analyses, that XdrA repressed capsule by binding to a broad region that extended from upstream of the -35 region of the promoter to the coding region of capA , the first gene of the 16-gene cap operon. Footprinting analyses also revealed that CodY bound to a large region that overlapped extensively with that of XdrA...
July 2, 2018: Journal of Bacteriology
Krithika Rajagopalan, Jonathan Dworkin
In bacteria, signaling phosphorylation is thought to occur primarily on His and Asp residues. However, phosphoproteomic surveys in phylogenetically diverse bacteria over the past decade have identified numerous proteins that are phosphorylated on Ser and/or Thr residues. Consistently, genes encoding Ser/Thr kinases are present in many bacterial genomes such as E. coli , which encodes at least three Ser/Thr kinases. Since Ser/Thr phosphorylation is a stable modification, a dedicated phosphatase is necessary to allow reversible regulation...
July 2, 2018: Journal of Bacteriology
David R Cameron, Yue Shan, Eliza A Zalis, Vincent Isabella, Kim Lewis
Persisters are a small subpopulation of cells within a bacterial culture that are tolerant to killing by antibiotics. Persisters have been linked to recalcitrant infections caused by numerous bacterial pathogens including Pseudomonas aeruginosa. A classic example is the incurable infection of the airways for patients with cystic fibrosis. The genetic mediators of persister formation for P. aeruginosa are poorly understood. We generated a high-density transposon insertion library of P. aeruginosa PAO1 and determined the relative frequency of each insertion following fluoroquinolone treatment using sequencing (Tn-seq)...
June 25, 2018: Journal of Bacteriology
Justin L Batte, Gyan S Sahukhal, Mohamed O Elasri
Staphylococcus aureus has a complex regulatory network for controlling the production of capsule polysaccharide. In S. aureus , capsule production is controlled by several regulators in response to various environmental stimuli. Previously, we described MsaB as a new regulator that specifically binds to the cap promoter in a growth-phase or nutrient-dependent manner. In addition to MsaB, several other regulators have also been shown to bind the same region. In this study, we examined the interactions between MsaB and other nutrient-sensing regulators (CodY and CcpE) with respect to binding to the cap promoter in a nutrient-dependent manner...
June 25, 2018: Journal of Bacteriology
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