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Molecular Microbiology

Julio C Ayala, Hongxia Wang, Jorge A Benitez, Anisia J Silva
VieA is a cyclic diguanylate phosphodiesterase that modulates biofilm development and motility in Vibrio cholerae O1 of the classical biotype. vieA is part of an operon encoding the VieSAB signal transduction pathway that is nearly silent in V. cholerae of the El Tor biotype. A DNA pull-down assay for proteins interacting with the vieSAB promoter identified the LysR-type regulator LeuO. We show that in classical biotype V. cholerae, LeuO cooperates with the nucleoid-associated protein H-NS to repress vieSAB transcription...
November 20, 2017: Molecular Microbiology
Koichi Toyoda, Inui Masayuki
Mycolates are α-branched, β-hydroxylated, long-chain fatty acid specifically synthesized in bacteria in the suborder Corynebacterineae of the phylum Actinobacteria. They form an outer membrane, which functions as a permeability barrier and confers pathogenic mycobacteria to resistance to antibiotics. Although the mycolate biosynthetic pathway has been intensively studied, knowledge of transcriptional regulation of genes involved in this pathway is limited. Here we report that the extracytoplasmic function sigma factor σ(D) is a key regulator of the mycolate synthetic genes in Corynebacterium glutamicum in the suborder...
November 17, 2017: Molecular Microbiology
Darrell W Cockburn, Carolyn Suh, Krizia Perez Medina, Rebecca M Duvall, Zdzislaw Wawrzak, Bernard Henrissat, Nicole M Koropatkin
Gut bacteria recognize accessible glycan substrates within a complex environment. Carbohydrate binding modules (CBMs) of cell-surface glycoside hydrolases often drive binding to the target substrate. Eubacterium rectale, an important butyrate-producing organism in the gut, consumes a limited range of substrates, including starch. Host consumption of resistant starch increases the abundance of E. rectale in the intestine, likely because it successfully captures the products of resistant starch degradation by other bacteria...
November 15, 2017: Molecular Microbiology
Ke Huang, Yan Xu, Charles Packianathan, Fan Gao, Chuan Chen, Jun Zhang, Qirong Shen, Barry P Rosen, Fang-Jie Zhao
Arsenic (As) biomethylation is an important component of the As biogeochemical cycle that can influence As toxicity and mobility in the environment. Biomethylation of As is catalyzed by the enzyme arsenite (As(III)) S-adenosylmethionine methyltransferase (ArsM). To date, all identified ArsM orthologs with As(III) methylation activities have four conserved cysteine residues, which are thought to be essential for As(III) methylation. Here, we isolated an As(III)-methylating bacterium, Bacillus sp. CX-1, and identified a gene encoding a S-adenosylmethionine methyltranserase termed BlArsM with low sequence similarities (≤ 39%) to other ArsMs...
November 14, 2017: Molecular Microbiology
Roman Mortuza, Htin Lin Aung, George Taiaroa, Helen K Opel-Reading, Torsten Kleffmann, Gregory M Cook, Kurt L Krause
Glutamate racemase (MurI) has been proposed as a target for anti-tuberculosis drug development based on the inability of ΔmurI mutants of Mycobacterium smegmatis to grow in the absence of d-glutamate. In this communication, we identify ΔmurI suppressor mutants that are detected during prolonged incubation. Whole genome sequencing of these ΔmurI suppressor mutants identified the presence of a SNP, located in the promoter region of MSMEG_5795. RT-qPCR and transcriptional fusion analyses revealed that the ΔmurI suppressor mutant overexpressed MSMEG_5795 14-fold compared to the isogenic wild-type...
November 14, 2017: Molecular Microbiology
Trevor Starr, A Pedro Gonçalves, Neeka Meshgin, N Louise Glass
Filamentous fungi are native secretors of lignocellulolytic enzymes and are used as protein-producing factories in the industrial biotechnology sector. Despite the importance of these organisms in industry, relatively little is known about the filamentous fungal secretory pathway or how it might be manipulated for improved protein production. Here we use Neurospora crassa as a model filamentous fungus to interrogate the requirements for trafficking of cellulase enzymes from the endoplasmic reticulum to the Golgi...
November 13, 2017: Molecular Microbiology
Connor B Pogue, Tianyi Zhou, Beiyan Nan
The rod-shaped bacterium Myxococcus xanthus moves on surfaces along its long cell axis and reverses its moving direction regularly. Current models propose that the asymmetric localization of a Ras-like GTPase, MglA, to leading cell poles determines the moving direction of cells. However, cells are still motile in the mutants where MglA localizes symmetrically, suggesting the existence of additional regulators that control moving direction. In this study, we identified PlpA, a PilZ-like protein that regulates the direction of motility...
November 11, 2017: Molecular Microbiology
Patrick J Lariviere, Piotr Szwedziak, Christopher R Mahone, Jan Löwe, Erin D Goley
During bacterial division, polymers of the tubulin-like GTPase FtsZ assemble at midcell to form the cytokinetic Z-ring, which coordinates peptidoglycan (PG) remodeling and envelope constriction. Curvature of FtsZ filaments promotes membrane deformation in vitro, but its role in division in vivo remains undefined. Inside cells, FtsZ directs PG insertion at the division plane, though it is unclear how FtsZ structure and dynamics are mechanistically coupled to PG metabolism. Here we study FzlA, a division protein that stabilizes highly curved FtsZ filaments, as a tool for assessing the contribution of FtsZ filament curvature to constriction...
November 9, 2017: Molecular Microbiology
Patrick J Woida, Karla J F Satchell
Bacteria often coordinate virulence factors to fine-tune the host response during infection. These coordinated events can include toxins counteracting or amplifying effects of another toxin or though regulating the stability of virulence factors to remove their function once it is no longer needed. Multifunctional autoprocessing repeats-in toxin (MARTX) toxins are effector delivery toxins that form a pore into the plasma membrane of a eukaryotic cell to deliver multiple effector proteins into the cytosol of the target cell...
November 8, 2017: Molecular Microbiology
Matthew Joseph Powers, M Stephen Trent
Asymmetry in the outer membrane has long defined the cell envelope of Gram-negative bacteria. This asymmetry, with lipopolysaccharide (LPS) or lipooligosaccharide (LOS) exclusively in the outer leaflet of the membrane, establishes an impermeable barrier that protects the cell from a number of stressors in the environment. Work done over the past 5 years has shown that Acinetobacter baumannii has the remarkable capability to survive with inactivated production of lipid A biosynthesis and the absence of LOS in its outer membrane...
November 8, 2017: Molecular Microbiology
Theodore B Verhey, Mildred Castellanos, George Chaconas
The Lyme disease spirochete evades the host immune system by combinatorial variation of VlsE, a surface antigen. Antigenic variation occurs via segmental gene conversion from contiguous silent cassettes into the vlsE locus. Because of the high degree of similarity between switch variants and the size of vlsE, short-read NGS technologies have been unsuitable for sequencing vlsE populations. Here we use PacBio sequencing technology coupled with the first fully-automated software pipeline (VAST) to accurately process NGS data by minimizing error frequency, eliminating heteroduplex errors and accurately aligning switch variants...
November 4, 2017: Molecular Microbiology
Robert Davis, Ana Écija-Conesa, Julia Gallego-Jara, Teresa de Diego, Ekaterina V Filippova, Gina Kuffel, Wayne F Anderson, Bradford W Gibson, Birgit Schilling, Manuel Canovas, Alan J Wolfe
Transcriptional regulation is the key to ensuring that proteins are expressed at the proper time and the proper amount. In Escherichia coli, the transcription factor cAMP receptor protein (CRP) is responsible for much of this regulation. Questions remain, however, regarding the regulation of CRP activity itself. Here, we demonstrate that a lysine (K100) on the surface of CRP has a dual function: to promote CRP activity at Class II promoters, and to ensure proper CRP steady state levels. Both functions require the lysine's positive charge; intriguingly, the positive charge of K100 can be neutralized by acetylation using the central metabolite acetyl phosphate as the acetyl donor...
November 4, 2017: Molecular Microbiology
Sarah K Wilson, Laura J Knoll
Emerging lipidomic technologies have enabled researchers to dissect the complex roles of phospholipases in lipid metabolism, cellular signaling, and immune regulation. Host phospholipase products are involved in stimulating and resolving the inflammatory response to pathogens. While many pathogen-derived phospholipases also manipulate the immune response, they have recently been shown to be involved in lipid remodeling and scavenging during replication. Animal and plant hosts as well as many pathogens contain a family of patatin-like phospholipases, which have been shown to have phospholipase A2 activity...
November 1, 2017: Molecular Microbiology
Elizabeth Ward, Thibaud T Renault, Eun A Kim, Marc Erhardt, Kelly T Hughes, David F Blair
During assembly of the bacterial flagellum, protein subunits that form the exterior structures are exported through a specialized secretion apparatus energized by the proton gradient. This category of protein transport, together with the similar process that occurs in the injectisomes of gram-negative pathogens, is termed type-III secretion. The membrane-embedded part of the flagellar export apparatus contains five essential proteins: FlhA, FlhB, FliP, FliQ, and FliR. Here, we have undertaken a variety of experiments that together support the proposal that the protein-conducting conduit is formed primarily, and possibly entirely, by FliP...
October 27, 2017: Molecular Microbiology
Lauren M Sheehan, Clayton C Caswell
The AbcR small RNAs (sRNAs) are a fascinating example of two highly conserved sRNAs that differ tremendously at the functional level amongst organisms. From their transcriptional activation to their regulatory capabilities, the AbcR sRNAs exhibit varying characteristics in three well-studied bacteria belonging to the Rhizobiales order: the plant symbiont Sinorhizobium meliloti, the plant pathogen Agrobacterium tumefaciens, and the animal pathogen Brucella abortus. This review outlines the similarities and differences of the AbcR sRNAs between each of these organisms, and discusses reasons as to why this group of sRNAs has diverged in their genetic organization and regulatory functions across species...
October 27, 2017: Molecular Microbiology
Eun Young Yu, Min Hsu, William K Holloman, Neal F Lue
Homologous recombination and repair factors are known to promote both telomere replication and recombination-based telomere extension. Herein we address the diverse contributions of several recombination/repair proteins to telomere maintenance in Ustilago maydis, a fungus that bears strong resemblance to mammals with respect to telomere regulation and recombination mechanisms. In telomerase-positive U. maydis, deletion of rad51 and blm separately caused shortened but stably maintained telomeres, whereas deletion of both engendered similar telomere loss, suggesting that the repair proteins help to resolve similar problems in telomere replication...
October 20, 2017: Molecular Microbiology
Rama R Yakubu, Louis M Weiss, Natalie C Silmon de Monerri
Parasites of the Apicomplexa phylum, such as Plasmodium spp. and Toxoplasma gondii., undergo complex life cycles involving multiple stages with distinct biology and morphologies. Posttranslational modifications (PTMs), such as phosphorylation, acetylation and glycosylation, regulate numerous cellular processes, playing a role in every aspect of cell biology. PTMs can occur on proteins at any time in their lifespan and through alterations of target protein activity, localization, protein-protein interactions, among other functions, dramatically increase proteome diversity and complexity...
October 20, 2017: Molecular Microbiology
Justin L Luebke, Daniel S Eaton, Joseph R Sachleben, Sean Crosson
Bacterial signal transduction systems commonly use receiver (REC) domains, which regulate adaptive responses to the environment as a function of their phosphorylation state. REC domains control cell physiology through diverse mechanisms, many of which remain understudied. We have defined structural features that underlie activation of the multi-domain REC protein, PhyR, which functions as an anti-anti-σ factor and regulates transcription of genes required for stress adaptation and host-microbe interactions in Alphaproteobacteria...
October 20, 2017: Molecular Microbiology
Nathaniel Lazar, Allison Fay, Madhumitha Nandakumar, Kerry E Boyle, Joao Xavier, Kyu Rhee, Michael S Glickman
Biotin is an essential cofactor utilized by all domains of life, but only synthesized by bacteria, fungi and plants, making biotin biosynthesis a target for antimicrobial development. To understand biotin biosynthesis in mycobacteria, we executed a genetic screen in Mycobacterium smegmatis for biotin auxotrophs and identified pyruvate carboxylase (Pyc) as required for biotin biosynthesis. The biotin auxotrophy of the pyc::tn strain is due to failure to transcriptionally induce late stage biotin biosynthetic genes in low biotin conditions...
October 20, 2017: Molecular Microbiology
Yun Heacock-Kang, Zhenxin Sun, Jan Zarzycki-Siek, Ian A McMillan, Michael H Norris, Andrew P Bluhm, Darlene Cabanas, Dawson Fogen, Hung Vo, Stuart P Donachie, Bradley R Borlee, Christopher D Sibley, Shawn Lewenza, Michael J Schurr, Herbert P Schweizer, Tung T Hoang
Bacterial cooperative associations and dynamics in biofilm microenvironments are of special interest in recent years. Knowledge of localized gene-expression and corresponding bacterial behaviors within the biofilm architecture at a global scale has been limited, due to a lack of robust technology to study limited number of cells in stratified layers of biofilms. With our recent pioneering developments in single bacterial cell transcriptomic analysis technology, we generated herein an unprecedented spatial transcriptome map of the mature in vitro Pseudomonas aeruginosa biofilm model, revealing contemporaneous yet altered bacterial behaviors at different layers within the biofilm architecture (i...
October 14, 2017: Molecular Microbiology
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