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Molecular Microbiology

Tomoya Maeda, Yuya Tanaka, Masayuki Inui
The Corynebacterium glutamicum R grtA (cgR_2936), grtB (cgR_2934), and grtC (cgR_2933) genes were identified as paralogs encoding glutamine-rich toxic proteins. We also identified a new antisense small RNA AsgR (antisense sRNA for grtA) that overlaps the 3' end of the grtA gene. Single over-expressions of grtA, grtB, and grtC resulted in complete inhibition of Escherichia coli cell growth. This growth was rescued by co-expression of AsgR. Similar effects were observed in C. glutamicum, although the toxicities of these proteins were moderate...
March 14, 2018: Molecular Microbiology
Woo Cheol Lee, Min-Cheol Jeong, Yeongjoon Lee, Chulhee Kwak, Jee-Young Lee, Yangmee Kim
Originally annotated as the initiator of fatty acid synthesis (FAS), β-ketoacyl-acyl carrier protein synthase III (KAS III) is a unique component of the bacterial FAS system. Novel variants of KAS III have been identified that promote the de novo use of additional extracellular fatty acids by FAS. These KAS III variants prefer longer acyl-groups, notably octanoyl-CoA. Acinetobacter baumannii, a clinically important nosocomial pathogen, contains such a multifunctional KAS III (AbKAS III). To characterize the structural basis of its substrate specificity, we determined the crystal structures of AbKAS III in the presence of different substrates...
March 12, 2018: Molecular Microbiology
Matthew H Foley, Eric C Martens, Nicole M Koropatkin
The Bacteroides thetaiotaomicron starch utilization system (Sus) is a model system for nutrient acquisition by gut Bacteroidetes, a dominant phylum of gut bacteria. The Sus includes SusCDEFG, which assemble on the cell surface to capture, degrade and import starch. While SusD is an essential starch-binding protein, the precise role(s) of the partially homologous starch-binding proteins SusE and SusF has remained elusive. We previously reported that a non-binding version of SusD (SusD*) supports growth on starch when other members of the multi-protein complex are present...
March 12, 2018: Molecular Microbiology
Cameron S Runte, Umang Jain, Landon J Getz, Sabrina Secord, Asaomi Kuwae, Akio Abe, Jason J LeBlanc, Andrew W Stadnyk, James B Kaper, Anne-Marie Hansen, Nikhil A Thomas
Enteropathogenic Escherichia coli (EPEC) use a type 3 secretion system (T3SS) for injection of effectors into host cells and intestinal colonization. Here, we demonstrate that the multicargo chaperone CesT has two strictly conserved tyrosine phosphosites, Y152 and Y153, that regulate differential effector secretion in EPEC. Conservative substitution of both tyrosine residues to phenylalanine strongly attenuated EPEC type 3 effector injection into host cells, and limited Tir effector mediated intimate adherence during infection...
March 6, 2018: Molecular Microbiology
Matthew L Blank, Michelle L Parker, Raghavendran Ramaswamy, Cameron J Powell, Elizabeth D English, Yaw Adomako-Ankomah, Lena F Pernas, Sean D Workman, John C Boothroyd, Martin J Boulanger, Jon P Boyle
The Toxoplasma gondii locus mitochondrial association factor 1 (MAF1) encodes multiple paralogs, some of which mediate host mitochondrial association (HMA). Previous work showed that HMA was a trait that arose in T. gondii through neofunctionalization of an ancestral MAF1 ortholog. Structural analysis of HMA-competent and incompetent MAF1 paralogs (MAF1b and MAF1a, respectively) revealed that both paralogs harbor an ADP ribose binding macro domain, with comparatively low (micromolar) affinity for ADP ribose...
March 5, 2018: Molecular Microbiology
Stéphane L Benoit, Ashley A Holland, Michael K Johnson, Robert J Maier
Helicobacter pylori is anomalous among non-nitrogen fixing bacteria in containing an incomplete NIF system for Fe-S cluster assembly comprising two essential proteins, NifS (cysteine desulfurase) and NifU (scaffold protein). Although nifU deletion strains cannot be obtained via the conventional gene replacement, a NifU-depleted strain was constructed and shown to be more sensitive to oxidative stress compared to wild-type (WT) strains. The hp1492 gene, encoding a putative Nfu-type Fe-S cluster carrier protein, was disrupted in three different H...
March 2, 2018: Molecular Microbiology
Lindsey Haggett, Archna Bhasin, Priyanka Srivastava, Masaya Fujita
In starving Bacillus subtilis cells, the accDA operon encoding two subunits of the essential acetyl-CoA carboxylase (ACC) has been proposed to be tightly regulated by direct binding of the master regulator Spo0A to a cis element (0A box) in the promoter region. When the 0A box is mutated, biofilm formation and sporulation have been reported to be impaired. Here, we present evidence that two 0A boxes, one previously known (0A-1) and another newly discovered (0A-2) in the accDA promoter region are positively and negatively regulated by Spo0A∼P, respectively...
February 28, 2018: Molecular Microbiology
Ching-Chung Ko, Graham F Hatfull
Bacteriophages engage in complex dynamic interactions with their bacterial hosts and with each other. Bacteria have numerous mechanisms to resist phage infection, and phages must co-evolve by overcoming bacterial resistance or by choosing an alternative host. Phages also compete with each other, both during lysogeny by prophage-mediated defense against viral attack, and by superinfection exclusion during lytic replication. Phages are enormously diverse genetically and are replete with small genes of unknown function, many of which are not required for lytic growth, but which may modulate these bacteria-phage and phage-phage dynamics...
February 28, 2018: Molecular Microbiology
Timothy J Brickman, Sandra K Armstrong
The classical Bordetella species use amino acids as carbon sources and can catabolize organic acids and tricarboxylic acid cycle intermediates. They are also auxotrophic for nicotinamide adenine dinucleotide (NAD) pathway precursors such as nicotinic acid. Bordetellae have a putative nicotinate catabolism gene locus highly similar to that characterized in Pseudomonas putida KT2440. This study determined the distribution of the nic genes among Bordetella species and analyzed the regulation of this nicotinic acid degradation system...
February 27, 2018: Molecular Microbiology
Chang Su, Jing Yu, Qiangqiang Sun, Qian Liu, Yang Lu
Candida albicans can switch between yeast and hyphae growth forms, which is critical for its pathogenesis. Diluting from saturated cells into fresh medium at 37°C is routinely used to induce hyphae, which depends on the cAMP-PKA pathway-activated transcriptional down-regulation of NRG1 and degradation of Nrg1 protein triggered by inoculation. It is reported that N-acetylglucosamine (GlcNAc), serum or neutral pH could stimulate filamentation in log phase cells, whereas how C. albicans develops hyphae without inoculation remains unknown...
February 27, 2018: Molecular Microbiology
Devon M Fitzgerald, Carol Smith, Pascal Lapierre, Joseph T Wade
In Escherichia coli, one Sigma factor recognizes the majority of promoters, and six "alternative" Sigma factors recognize specific subsets of promoters. The alternative Sigma factor FliA (σ28 ) recognizes promoters upstream of many flagellar genes. We previously showed that most E. coli FliA binding sites are located inside genes. However, it was unclear whether these intragenic binding sites represent active promoters. Here, we construct and assay transcriptional promoter-lacZ fusions for all 52 putative FliA promoters previously identified by ChIP-seq...
February 24, 2018: Molecular Microbiology
Sébastien Bontemps-Gallo, Kevin A Lawrence, Crystal L Richards, Frank C Gherardini
Polyamines are an essential class of metabolites found throughout all kingdoms in life. Borrelia burgdorferi harbors no enzymes to synthesize or degrade polyamines yet does contain a polyamine uptake system, potABCD. In this report, we describe the initial characterization of this putative transport system. After several unsuccessful attempts to inactivate potABCD, we placed the operon under the control of an inducible LacI promoter expression system. Analyses of this construct confirmed that potABCD was required for in vitro survival...
February 24, 2018: Molecular Microbiology
Joseph T Wade, David C Grainger
The histone-like nucleoid structuring (H-NS) protein and its analogues bind large stretches of horizontally acquired AT-rich DNA in a broad range of bacterial species. Binding by H-NS silences the promoters within such DNA that would otherwise deplete the cellular pool of RNA polymerase. Selective de-repression can occur when sequence-specific DNA-binding proteins locally disrupt H-NS function; this mechanism is important for the regulation of many virulence genes. In this issue of Molecular Microbiology, Rangarajan and Schnetz show that when transcription from a neighbouring region invades an H-NS-bound locus, it can disrupt local H-NS repression...
February 23, 2018: Molecular Microbiology
Kaitlynne Bohm, Steffen Porwollik, Weiping Chu, John A Dover, Eddie B Gilcrease, Sherwood R Casjens, Michael McClelland, Kristin N Parent
Bacteriophages rely on their hosts for replication, and many host genes critically determine either viral progeny production or host success via phage resistance. A random insertion transposon library of 240,000 mutants in Salmonella enterica serovar Typhimurium was used to monitor effects of individual bacterial gene disruptions on bacteriophage P22 lytic infection. These experiments revealed candidate host genes that alter the timing of phage P22 propagation. Using a False Discovery Rate of <0.1, mutations in 235 host genes either blocked or delayed progression of P22 lytic infection, including many genes for which this role was previously unknown...
February 22, 2018: Molecular Microbiology
Anja Seybert, Luis Gonzalez-Gonzalez, Margot P Scheffer, Maria Lluch-Senar, Ana M Mariscal, Enrique Querol, Franziska Matthaeus, Jaume Piñol, Achilleas S Frangakis
The terminal organelle of Mycoplasma genitalium is responsible for bacterial adhesion, motility and pathogenicity. Localized at the cell tip, it comprises an electron-dense core that is anchored to the cell membrane at its distal end and to the cytoplasm at its proximal end. The surface of the terminal organelle is also covered with adhesion proteins. We performed cellular cryo-electron tomography on deletion mutants of eleven proteins that are implicated in building the terminal organelle, in order to systematically analyse the ultrastructural effects...
February 22, 2018: Molecular Microbiology
Duncan C Krause, Songye Chen, Jian Shi, Ashley Jensen, Edward S Sheppard, Grant J Jensen
The Mycoplasma pneumoniae terminal organelle functions in adherence and gliding motility and is comprised of at least eleven substructures. We used electron cryotomography to correlate impaired gliding and adherence function with changes in architecture in diverse terminal organelle mutants. All eleven substructures were accounted for in the prkC, prpC, and P200 mutants, and variably so for the HMW3 mutant. Conversely, no terminal organelle substructures were evident in HMW1 and HMW2 mutants. The P41 mutant exhibits a terminal organelle detachment phenotype and lacked the bowl element normally present at the terminal organelle base...
February 22, 2018: Molecular Microbiology
Mohd Farid Abdul Halim, Ronald Rodriguez, Jonathan D Stoltzfus, Iain G Duggin, Mechthild Pohlschroder
Proper protein anchoring is key to the biogenesis of prokaryotic cell surfaces, dynamic, resilient structures that play crucial roles in various cell processes. A novel surface protein anchoring mechanism in Haloferax volcanii depends upon the peptidase archaeosortaseA (ArtA) processing C-termini of substrates containing C-terminal tripartite structures and anchoring mature substrates to the cell membrane via intercalation of lipid-modified C-terminal amino acid residues. While this membrane protein lacks clear homology to soluble sortase transpeptidases of Gram-positive bacteria, which also process C-termini of substrates whose C-terminal tripartite structures resemble those of ArtA substrates, archaeosortases do contain conserved cysteine, arginine, and arginine/histidine/asparagine residues, reminiscent of His-Cys-Arg residues of sortase catalytic sites...
February 21, 2018: Molecular Microbiology
Hongliang Qian, Qingqing Yao, Cui Tai, Zixin Deng, Jianhua Gan, Hong-Yu Ou
A type II toxin-antitoxin (TA) system, in which the toxin contains a Gcn5-related N-acetyltransferase (GNAT) domain, has been characterized recently. GNAT toxin acetylates aminoacyl-tRNA and blocks protein translation. It is abolished by the cognate antitoxin that contains the ribbon-helix-helix (RHH) domain. Here, we present an experimental demonstration of the interaction of the GNAT-RHH complex with TA promoter DNA. First, the GNAT-RHH TA locus kacAT was found in Klebsiella pneumoniae HS11286, a strain resistant to multiple antibiotics...
February 20, 2018: Molecular Microbiology
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February 20, 2018: Molecular Microbiology
Natasha Weatherspoon-Griffin, Michael A Picker, Krystle L Pew, Hiromichi S Park, Daren Ginete, Monika M Karney, Pashtana Usufzy, Maria I Castellanos, Juan Carlos Duhart, Dustin J Harrison, Jillian N Socea, Alexander D Karabachev, Christopher T Hensley, Amber J Howerton, Rosa Ojeda-Daulo, Joy A Immak, Helen J Wing
Transcriptional silencing and anti-silencing mechanisms modulate bacterial physiology and virulence in many human pathogens. In Shigella species, many virulence plasmid genes are silenced by the histone-like nucleoid structuring protein H-NS and anti-silenced by the virulence gene regulator VirB. Despite the key role that these regulatory proteins play in Shigella virulence, their mechanisms of transcriptional control remain poorly understood. Here, we characterize the regulatory elements and their relative spacing requirements needed for the transcriptional silencing and anti-silencing of icsP, a locus that requires remotely located regulatory elements for both types of transcriptional control...
February 17, 2018: Molecular Microbiology
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