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Molecular Microbiology

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https://www.readbyqxmd.com/read/28214340/molecular-tiling-on-the-surface-of-a-bacterial-spore-the-exosporium-of-the-bacillus-anthracis-cereus-thuringiensis-group
#1
Cassandra Terry, Shuo Jiang, David S Radford, Wan Qiang, Svetomir Tzokov, Anne Moir, Per A Bullough
Bacteria of the genera Bacillus and Clostridium form highly resistant spores, which in the case of some pathogens act as the infectious agents. An exosporium forms the outermost layer of some spores; it plays roles in protection, adhesion, dissemination, host targeting in pathogens, and germination control. The exosporium of the Bacillus cereus group, including the anthrax pathogen, contains a 2D-crystalline basal layer, overlaid by a hairy nap. BclA and related proteins form the hairy nap, and require ExsFA (BxpB) for their localisation on the basal layer...
February 18, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28213898/nuclear-localization-of-a-putative-phytophthora-sojae-bzip1-transcription-factor-is-mediated-by-multiple-targeting-motifs
#2
Yufeng Fang, Brett M Tyler
Oomycetes are fungal-like eukaryotic microbes in the kingdom Stramenopila. We recently found that the oomycete plant pathogen Phytophthora sojae uses nuclear localization signals (NLSs) for translocation of proteins into the nucleus that differ from conventional well-characterized NLSs from mammals and yeast. Here we have characterized in depth the nuclear localization signals of a P. sojae basic leucine zipper transcription factor, PsbZIP1. Nuclear localization of PsbZIP1 was determined by a central conserved region overlapping the DNA binding domain...
February 18, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28211111/regulation-of-nrf-operon-expression-in-pathogenic-enteric-bacteria-sequence-divergence-reveals-new-regulatory-complexity
#3
Rita E Godfrey, David J Lee, Stephen J W Busby, Douglas F Browning
The Escherichia coli K-12 nrf operon encodes a periplasmic nitrite reductase, the expression of which is driven from a single promoter, pnrf. Expression from pnrf is activated by the FNR transcription factor in response to anaerobiosis and further increased in response to nitrite by the response regulator proteins, NarL and NarP. FNR-dependent transcription is suppressed by the binding of two nucleoid associated proteins, IHF and Fis. As Fis levels increase in cells grown in rich medium, the positioning of its binding site, overlapping the promoter -10 element, ensures that pnrf is sharply repressed...
February 17, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28207180/assembly-of-the-outermost-spore-layer-pieces-of-the-puzzle-are-coming-together
#4
George C Stewart
Certain endospore-forming soil dwelling bacteria are important human, animal, or insect pathogens. These organisms produce spores containing an outer layer, the exosporium. The exosporium is the site of interactions between the spore and the soil environment and between the spore and the infected host during the initial stages of infection. The composition and assembly process of the exosporium are poorly understood. This is partly due to the extreme stability of the exosporium that has proven to be refractive to existing methods to deconstruct the intact structure into its component parts...
February 16, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28196402/pimelic-acid-the-first-precursor-of-the-bacillus-subtilis-biotin-synthesis-pathway-exists-as-the-free-acid-and-is-assembled-by-fatty-acid-synthesis
#5
Miglena Manandhar, John E Cronan
Biotin synthetic pathways are readily separated into two stages, synthesis of the seven carbon α, ω-dicarboxylic acid pimelate moiety and assembly of the fused heterocyclic rings. The biotin pathway genes responsible for pimelate moiety synthesis vary widely among bacteria whereas the ring synthesis genes are highly conserved. Bacillus subtilis seems to have redundant genes, bioI and bioW, for generation of the pimelate intermediate. Largely consistent with previous genetic studies we found that deletion of bioW caused a biotin auxotrophic phenotype whereas deletion of bioI did not...
February 14, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28196401/systematic-genetic-dissection-of-pts-in-vibrio-cholerae-uncovers-a-novel-glucose-transporter-and-a-limited-role-for-pts-during-infection-of-a-mammalian-host
#6
Chelsea A Hayes, Triana N Dalia, Ankur B Dalia
A common mechanism for high affinity carbohydrate uptake in microbial species is the phosphoenolpyruvate-dependent phosphotransferase system (PTS). This system consists of a shared component, EI, which is required for all PTS transport, and numerous carbohydrate uptake transporters. In V. cholerae, there are 13 distinct PTS transporters. Due to genetic redundancy within this system, the carbohydrate specificity of each of these transporters is not currently defined. Here, using multiplex genome editing by natural transformation (MuGENT), we systematically dissect PTS transport in V...
February 14, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28196397/evolved-distal-tail-carbohydrate-binding-modules-of-lactobacillus-phage-j-1-a-novel-type-of-anti-receptor-widespread-among-lactic-acid-bacteria-phages
#7
Maria-Eugenia Dieterle, Silvia Spinelli, Irina Sadovskaya, Mariana Piuri, Christian Cambillau
Bacteriophage replication requires specific host-recognition. Some siphophages harbour a large complex, the baseplate, at the tip of their non-contractile tail. This baseplate holds receptor binding proteins (RBPs) that can recognize the host cell-wall polysaccharide (CWPS) and specifically attach the phage to its host. While most phages possess a dedicated RBP, the phage J-1 that infects Lactobacillus casei seemed to lack one. We have shown that the phage J-1 distal tail protein (Dit) plays a role in host recognition and that its sequence comprises two inserted modules compared to "classical" Dits...
February 14, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28188651/the-torc1-sch9-rim15-signaling-pathway-represses-yeast-to-hypha-transition-in-response-to-glycerol-availability-in-the-oleaginous-yeast-yarrowia-lipolytica
#8
Shu-Heng Liang, Heng Wu, Rui-Rui Wang, Qiang Wang, Tao Shu, Xiang-Dong Gao
The yeast-to-hypha dimorphic transition is important for survival under nutrient starvation in fungi. The oleaginous yeast Yarrowia lipolytica grows in the oval-shaped yeast form in glycerol media whereas it adopts a filamentous form in glucose media. It is not clear why this yeast responds differently to glycerol and glucose. Here, we show that glycerol blocks dimorphic transition even in the presence of glucose whereas glycerol depletion induces filamentous growth, suggesting that dimorphic transition is repressed in response to glycerol availability...
February 11, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28187498/structural-modeling-and-functional-analysis-of-the-essential-ribosomal-processing-protease-prp-from-staphylococcus-aureus
#9
Erin A Wall, Adam L Johnson, Darrell L Peterson, Gail E Christie
In Firmicutes and related bacteria, ribosomal large subunit protein L27 is encoded with a conserved N-terminal extension that is removed to expose residues critical for ribosome function. Bacteria encoding L27 with this N-terminal extension also encode a sequence-specific cysteine protease, Prp, which carries out this cleavage. In this work we demonstrate that L27 variants with an un-cleavable N-terminal extension, or lacking the extension ("pre-cleaved"), are unable to complement an L27 deletion in Staphylococcus aureus...
February 10, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28187496/post-translational-modification-directs-nuclear-and-hyphal-tip-localization-of-c-albicans-mrna-binding-protein-slr1
#10
Chaiyaboot Ariyachet, Christian Beißel, Xiang Li, Selena Lorrey, Olivia Mackenzie, Patrick M Martin, Katharine O'Brien, Tossapol Pholcharee, Sue Sim, Heike Krebber, Anne E McBride
The morphological transition of the opportunistic fungal pathogen Candida albicans from budding to hyphal growth has been implicated in its ability to cause disease in animal models. Absence of SR-like RNA-binding protein Slr1 slows hyphal formation and decreases virulence in a systemic candidiasis model, suggesting a role for post-transcriptional regulation in these processes. SR (serine-arginine)-rich proteins influence multiple steps in mRNA metabolism and their localization and function are frequently controlled by modification...
February 10, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28164413/the-botrytis-cinerea-pak-kinase-bccla4-mediates-morphogenesis-growth-and-cell-cycle-regulating-processes-downstream-of-bcrac
#11
Anna Minz-Dub, Amir Sharon
Rac proteins are involved in a variety of cellular processes. Effector proteins that interact with active Rac convey the GTPase-generated signal to downstream developmental cascades and processes. Here we report on the analysis of the main effector and signal cascade downstream of BcRac, the Rac homolog of the grey mold fungus Botrytis cinerea. Several lines of evidence highlighted the p21-activated kinase Cla4 as an important effector of Rac in fungi. Analysis of Δbccla4 strains revealed that the BcCla4 protein was sufficient to mediate all of the examined BcRac-driven processes, including hyphal growth and morphogenesis, conidia production and pathogenicity...
February 6, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28164393/importance-of-the-e-coli-dinj-antitoxin-carboxy-terminus-for-toxin-suppression-and-regulated-proteolysis
#12
Ajchareeya Ruangprasert, Tatsuya Maehigashi, Stacey J Miles, Christine M Dunham
Toxin-antitoxin genes play important roles in the regulation of bacterial growth during stress. One response to stress is selective proteolysis of antitoxin proteins which releases their cognate toxin partners causing rapid inhibition of growth. The features of toxin-antitoxin complexes that are important to inhibit toxin activity as well as to release the active toxin remain elusive. Furthermore, it is unclear how antitoxins are selected for proteolysis by cellular proteases. Here, we test the minimal structural requirements of the E...
February 6, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28164388/exclusion-of-assembled-mreb-by-anionic-phospholipids-at-cell-poles-confers-cell-polarity-for-bidirectional-growth
#13
Takuma Kawazura, Kanon Matsumoto, Koki Kojima, Fumiya Kato, Tomomi Kanai, Hironori Niki, Daisuke Shiomi
Cell polarity determines the direction of cell growth in bacteria. MreB actin spatially regulates peptidoglycan synthesis to enable cells to elongate bidirectionally. MreB densely localizes in the cylindrical part of the rod cell and not in polar regions in Escherichia coli. When treated with A22, which inhibits MreB polymerization, rod-shaped cells became round and MreB was diffusely distributed throughout the cytoplasmic membrane. A22 removal resulted in restoration of the rod shape. Initially, diffuse MreB started to re-assemble, and MreB-free zones were subsequently observed in the cytoplasmic membrane...
February 6, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28164386/a-class-c-radical-s-adenosylmethionine-methyltransferase-synthesizes-8-methylmenaquinone
#14
Sascha Hein, Oliver Klimmek, Markus Polly, Melanie Kern, Jörg Simon
The membranous quinone/quinol pool is essential to the majority of life forms and has been widely used as an important biomarker in microbial taxonomy. In the anaerobic world, the most important quinones are menaquinone (MK) and a methylated form of MK, designated methylmenaquinone (MMK), which is anticipated to serve specifically in low-potential electron transport chains involved in anaerobic respiration. However, it has remained unclear how MMK is generated. Here we show that a novel enzyme homologous to class C radical SAM methyltransferases (RSMTs) synthesizes MMK using MK as substrate...
February 6, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28164379/peptide-nucleotide-antibiotic-microcin-c-is-a-potent-inducer-of-stringent-response-and-persistence-in-both-sensitive-and-producing-cells
#15
Julia Piskunova, Etienne Maisonneuve, Elsa Germain, Kenn Gerdes, Konstantin Severinov
Microcin C (McC) is a peptide-nucleotide antibiotic that inhibits aspartyl-tRNA synthetase. Here, we show that McC is a strong inducer of persistence in Escherichia coli. Persistence induced by McC is mediated by (p)ppGpp and requires chromosomally encoded toxin-antitoxin modules. McC-producing cells have increased persistence levels due to a combined effect of McC imported from the cultured medium and intracellularly synthesized antibiotic. McC-producing cells also induce persistence in sensitive cells during co-cultivation, underscoring complex interactions in bacterial communities where an antagonistic compound produced by one community member can benefit other members by increasing their ability to withstand antibiotics...
February 6, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28152228/transporters-as-information-processors-in-bacterial-signalling-pathways
#16
REVIEW
Hannah Piepenbreier, Georg Fritz, Susanne Gebhard
Transporters are essential players in bacterial growth and survival, since they are key for uptake of nutrients on the one hand, and for defence against endogenous and environmental stresses on the other hand. Remarkably, in addition to their primary role in substrate translocation, it has become clear that some transporters have acquired a secondary function as sensors and information processors in signalling pathways. In this review, we describe recent advances in our understanding of the role of transporters in such signalling cascades, and discuss some of the emergent dynamic behaviour found in hallmark examples...
February 2, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28142206/mycobacterium-tuberculosis-virulence-regulator-phop-interacts-with-alternative-sigma-factor-sige-during-acid-stress-response
#17
Roohi Bansal, Vijjamarri Anil Kumar, Ritesh Rajesh Sevalkar, Prabhat Ranjan Singh, Dibyendu Sarkar
The ability to sense acid stress and mount an appropriate adaptive response by M. tuberculosis, which adapts a long term residence in the macrophage phagosome remains one of the critical features that defines mycobacterial physiology and its intracellular location. To understand the mechanistic basis of adaptation of the intracellular pathogen, we studied global regulation of M. tuberculosis gene expression in response to acid stress. Although recent studies indicate a role for the virulence-associated phoP locus in pH-driven adaptation, in this study, we discovered a strikingly novel regulatory mechanism which controls acid-stress homeostasis...
January 31, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28142193/staphylococcus-aureus-biofilm-a-complex-developmental-organism
#18
REVIEW
Derek E Moormeier, Kenneth W Bayles
Chronic biofilm-associated infections caused by Staphylococcus aureus often lead to significant increases in morbidity and mortality, particularly when associated with indwelling medical devices. This has triggered a great deal of research attempting to understand the molecular mechanisms that control S. aureus biofilm formation and the basis for the recalcitrance of these multicellular structures to antibiotic therapy. The purpose of this review is to summarize our current understanding of S. aureus biofilm development, focusing on the description of a newly-defined, five-stage model of biofilm development and the mechanisms required for each stage...
January 31, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28142188/phosphatidylserine-synthase-2-and-phosphatidylserine-decarboxylase-are-essential-for-aminophospholipid-synthesis-in-trypanosoma-brucei
#19
Luce Farine, Jennifer Jelk, Jae-Yeon Choi, Dennis R Voelker, Jon Nunes, Terry K Smith, Peter Bütikofer
Phosphatidylethanolamine (PE) and phosphatidylserine (PS) are ubiquitously expressed and metabolically interconnected glycerophospholipids in eukaryotes and prokaryotes. In Trypanosoma brucei, PE synthesis has been shown to occur mainly via the Kennedy pathway, one of the three routes leading to PE synthesis in eukaryotes, while PS synthesis has not been studied experimentally. We now reveal the importance of T. brucei PS synthase 2 (TbPSS2) and T. brucei PS decarboxylase (TbPSD), two key enzymes involved in aminophospholipid synthesis, for trypanosome viability...
January 31, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28142187/spatial-regulation-of-the-kh-domain-rna-binding-protein-rnc1-mediated-by-a-crm1-independent-nuclear-export-system-in-schizosaccharomyces-pombe
#20
Ryosuke Satoh, Yasuhiro Matsumura, Akitomo Tanaka, Makoto Takada, Yuna Ito, Kanako Hagihara, Masahiro Inari, Ayako Kita, Akira Fukao, Toshinobu Fujiwara, Shinya Hirai, Tokio Tani, Reiko Sugiura
RNA-binding proteins (RBPs) play important roles in the posttranscriptional regulation of gene expression, including mRNA stability, transport, and translation. Fission yeast rnc1(+) encodes a K Homology (KH)-type RBP, which binds and stabilizes the Pmp1 MAPK phosphatase mRNA thereby suppressing the Cl(-) hypersensitivity of calcineurin deletion and MAPK signaling mutants. Here, we analyzed the spatial regulation of Rnc1 and discovered a putative nuclear export signal (NES)Rnc1 , which dictates the cytoplasmic localization of Rnc1 in a Crm1-independent manner...
January 31, 2017: Molecular Microbiology
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