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Molecular Microbiology

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https://www.readbyqxmd.com/read/27935200/probing-bacterial-cell-biology-using-image-cytometry
#1
Julie A Cass, Stella Stylianidou, Nathan J Kuwada, Beth Traxler, Paul A Wiggins
Advances in automated fluorescence microscopy have made snapshot and time-lapse imaging of bacterial cells commonplace, yet fundamental challenges remain in analysis. The vast quantity of data collected in high-throughput experiments requires a fast and reliable automated method to analyze fluorescence intensity and localization, cell morphology and proliferation as well as other descriptors. Inspired by effective yet tractable methods of population-level analysis using flow cytometry, we have developed a framework and tools for facilitating analogous analyses in image cytometry...
December 9, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27935141/evolution-of-a-multi-step-phosphorelay-signal-transduction-system-in-ensifer-recruitment-of-the-sigma-factor-rpon-and-a-novel-enhancer-binding-protein-triggers-acid-activated-gene-expression
#2
Rui Tian, Stephan Heiden, Wan A M Osman, Julie K Ardley, Euan K James, Margaret M Gollagher, Ravi Tiwari, Rekha Seshadri, Nikos C Kyrpides, Wayne G Reeve
Most Ensifer strains are comparatively acid sensitive, compromising their persistence in low pH soils. In the acid-tolerant strain E. medicae WSM419, the acid-activated expression of lpiA is essential for enhancing survival in lethal acidic conditions. Here we characterise a multi-step phosphorelay signal transduction pathway consisting of TcsA, TcrA, FsrR, RpoN and its cognate enhancer binding protein EbpA, which is required for the induction of lpiA and the downstream acvB gene. The fsrR, tcrA, tcsA, and rpoN genes were constitutively expressed, whereas lpiA and acvB were strongly acid-induced...
December 9, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27902860/genetic-and-biochemical-interactions-between-the-bacterial-replication-initiator-dnaa-and-the-nucleoid-associated-protein-rok-in-bacillus-subtilis
#3
Charlotte A Seid, Janet L Smith, Alan D Grossman
We identified interactions between the conserved bacterial replication initiator and transcription factor DnaA and the nucleoid-associated protein Rok of Bacillus subtilis. DnaA binds directly to clusters of DnaA boxes at the origin of replication and elsewhere, including the promoters of several DnaA-regulated genes. Rok, an analog of H-NS from gamma-proteobacteria that affects chromosome architecture and Lsr2 from Mycobacteria, binds A+T-rich sequences throughout the genome and represses expression of many genes...
November 30, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27893179/ctra-controls-cell-division-and-outer-membrane-composition-of-the-pathogen-brucella-abortus
#4
Nayla Francis, Katy Poncin, Antonella Fioravanti, Victoria Vassen, Kevin Willemart, Thi Anh Phuong Ong, Luca Rappez, Jean-Jacques Letesson, Emanuele G Biondi, Xavier De Bolle
Brucella abortus is a pathogen infecting cattle, able to survive, traffic and proliferate inside host cells. It belongs to the Alphaproteobacteria, a phylogenetic group comprising bacteria with free living, symbiotic and pathogenic lifestyles. An essential regulator of cell cycle progression named CtrA was described in the model bacterium Caulobacter crescentus. This regulator is conserved in many alphaproteobacteria, but the evolution of its regulon remains elusive. Here we identified promoters that are CtrA targets using ChIP-seq and we found that CtrA binds to promoters of genes involved in cell cycle progression, in addition to numerous genes encoding outer membrane components involved in export of membrane proteins and synthesis of lipopolysaccharide...
November 28, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27888610/camp-independent-signal-pathways-stimulate-hyphal-morphogenesis-in-candida-albicans
#5
Salvatore M Parrino, Haoyu Si, Shamoon Naseem, Kevin Groudan, Justin Gardin, James B Konopka
The fungal pathogen Candida albicans can transition from budding to hyphal growth, which promotes biofilm formation and invasive growth into tissues. Stimulation of adenylyl cyclase to form cAMP induces hyphal morphogenesis. The failure of cells lacking adenylyl cyclase (cyr1Δ) to form hyphae has suggested that cAMP signaling is essential for hyphal growth. However, cyr1Δ mutants also grow slowly and have defects in morphogenesis, making it unclear whether hyphal inducers must stimulate cAMP, or if normal basal levels of cAMP are required to maintain cellular health needed for hyphal growth...
November 26, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27888605/natural-antisense-transcripts-are-linked-to-the-modulation-of-mitochondrial-function-and-teliospore-dormancy-in-ustilago-maydis
#6
Lauren A Ostrowski, Barry J Saville
The basidiomycete smut fungus Ustilago maydis causes common smut of corn. This disease is spread through the production of teliospores, which are thick-walled dormant structures characterized by low rates of respiration and metabolism. Teliospores are formed when the fungus grows within the plant, and the morphological steps involved in their formation have been described, but the molecular events leading to dormancy are not known. In U. maydis, natural antisense transcripts (NATs) can function to alter gene expression and many NATs have increased levels in the teliospore...
November 26, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27882646/symb-and-symc-two-membrane-associated-proteins-are-required-for-epichlo%C3%A3-festucae-hyphal-cell-cell-fusion-and-maintenance-of-a-mutualistic-interaction-with-lolium-perenne
#7
Kimberly A Green, Yvonne Becker, Aiko Tanaka, Daigo Takemoto, Helen L Fitzsimons, Stephan Seiler, Hervé Lalucque, Philippe Silar, Barry Scott
Cell-cell fusion in fungi is required for colony formation, nutrient transfer and signal transduction. Disruption of genes required for hyphal fusion in Epichloë festucae, a mutualistic symbiont of Lolium grasses, severely disrupts the host interaction phenotype. We examined whether symB and symC, the E. festucae homologs of Podospora anserina self-signaling genes IDC2 and IDC3, are required for E. festucae hyphal fusion and host symbiosis. Deletion mutants of these genes were defective in hyphal cell fusion, formed intra-hyphal hyphae, and had enhanced conidiation...
November 23, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27879020/membrane-protein-insertase-yidc-in-bacteria-and-archaea
#8
REVIEW
Andreas Kuhn, Dorothee Kiefer
The insertion of proteins into the prokaryotic plasma membrane is catalyzed by translocases and insertases. On one hand, the Sec translocase operates as a transmembrane channel that can open laterally to first bind and then release the hydrophobic segments of a protein into the lipid bilayer. On the other hand, YidC insertases interact with their substrates in a groove-like structure at an amphiphilic protein-lipid interface thus allowing the transmembrane segments of the substrate to slide into the lipid bilayer...
November 23, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27875634/the-stringent-response-plays-a-key-role-in-bacillus-subtilis-survival-of-fatty-acid-starvation
#9
A A Pulschen, D E Sastre, F Machinandiarena, A Crotta Asis, D Albanesi, D de Mendoza, F J Gueiros-Filho
The stringent response is a universal adaptive mechanism to protect bacteria from nutritional and environmental stresses. The role of the stringent response during lipid starvation has been studied only in Gram-negative bacteria. Here we report that the stringent response also plays a crucial role in the adaptation of the model Gram-positive Bacillus subtilis to fatty acid starvation. B. subtilis lacking all three (p)ppGpp-synthetases (RelBs , RelP and RelQ) or bearing a RelBs variant that no longer synthesizes (p)ppGpp suffer extreme loss of viability upon lipid starvation...
November 22, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27874229/exopolysaccharides-promote-myxococcus-xanthus-social-motility-by-inhibiting-cellular-reversals
#10
Tianyi Zhou, Beiyan Nan
The biofilm-forming bacterium Myxococcus xanthus moves on surfaces as structured swarms utilizing type IV pili-dependent social (S-) motility. In contrast to isolated cells that reverse their moving direction frequently, individual cells within swarms rarely reverse. The regulatory mechanisms that inhibit cellular reversal and promote the formation of swarms are not well understood. Here we show that exopolysaccharides (EPS), the major extracellular components of M. xanthus swarms, inhibit cellular reversal in a concentration-dependent manner...
November 22, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27874224/multiple-transporters-are-involved-in-natamycin-efflux-in-streptomyces-chattanoogensis-l10
#11
Tan-Jun Wang, Yi-Ming Shan, Han Li, Wei-Wang Dou, Xin-Hang Jiang, Xu-Ming Mao, Shui-Ping Liu, Wen-Jun Guan, Yong-Quan Li
Antibiotic-producing microorganisms have evolved several self-resistance mechanisms to prevent auto-toxicity. Overexpression of specific transporters to improve the efflux of toxic antibiotics has been found one of the most important and intrinsic resistance strategies employed by many Streptomyces strains. In this work, two ATP-binding cassette (ABC) transporter-encoding genes located in the natamycin biosynthetic gene cluster, scnA and scnB, were identified as the primary exporter genes for natamycin efflux in Streptomyces chattanoogensis L10...
November 22, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27870221/inductors-and-regulatory-properties-of-the-genomic-island-associated-fru2-metabolic-operon-of-streptococcus-agalactiae
#12
Kévin Patron, Philippe Gilot, Vanessa Rong, Aurélia Hiron, Laurent Mereghetti, Emilie Camiade
The fru2 metabolic operon of Streptococcus agalactiae encodes the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) enzyme II complex Fru2 (EIIB(Fru2) , EIIA(Fru2) , and EIIC(Fru2) ); Fru2 R, a transcriptional activator with PTS regulatory domains (PRDs); a D-allulose-6-phosphate 3-epimerase; a transaldolase; and a transketolase. We showed that the transcription of fru2 is induced during the stationary phase of growth in complex media and during incubation in human cerebrospinal or amniotic fluids...
November 21, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27868255/regulatory-gene-mutation-a-driving-force-behind-group-a-streptococcus-strain-and-serotype-specific-variation
#13
Poulomee Sarkar, Paul Sumby
Data from multiple bacterial pathogens are consistent with regulator-encoding genes having higher mutation frequencies than the genome average. Such mutations drive both strain- and type- (e.g. serotype, haplotype) specific phenotypic heterogeneity, and may challenge public health due to the potential of variants to circumvent established treatment and/or preventative regimes. Here, using the human bacterial pathogen the group A Streptococcus (GAS; S. pyogenes) as a model organism, we review the types and regulatory-, phenotypic-, and disease-specific consequences of naturally occurring regulatory gene mutations...
November 21, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27868254/extensive-functional-redundancy-in-the-regulation-of-candida-albicans-drug-resistance-and-morphogenesis-by-lysine-deacetylases-hos2-hda1-rpd3-and-rpd31
#14
Xinliu Li, Nicole Robbins, Teresa R O'Meara, Leah E Cowen
Current treatment efforts for fungal infections are hampered by the limited availability of antifungal drugs and by the emergence of drug resistance. A powerful strategy to enhance the efficacy of antifungal drugs is to inhibit the molecular chaperone Hsp90. Hsp90 governs drug resistance, morphogenesis, and virulence in a leading fungal pathogen of humans, Candida albicans. Our previous work with Saccharomyces cerevisiae established acetylation as a novel mechanism of posttranslational control of Hsp90 function in fungi...
November 21, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27859784/membrane-skeletal-association-and-post-translational-allosteric-regulation-of-toxoplasma-gondii-gapdh1
#15
Rashmi Dubey, Bart L Staker, Ian T Foe, Matthew Bogyo, Peter J Myler, Huân M Ngô, Marc-Jan Gubbels
When Toxoplasma gondii egresses from the host cell, glyceraldehyde-3-phosphate dehydrogenase 1 (GAPDH1), which is primary a glycolysis enzyme but actually a quintessential multifunctional protein, translocates to the unique cortical membrane skeleton. Here we report the 2.25Å resolution crystal structure of the GAPDH1 holoenzyme in a quaternary complex providing the basis for the molecular dissection of GAPDH1 structure-function relationships Knockdown of GAPDH1 expression and catalytic site disruption validate the essentiality of GAPDH1 in intracellular replication but we confirmed that glycolysis is not strictly essential...
November 17, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27859892/discovery-of-the-type-vii-esx-1-secretion-needle
#16
Louis Ates, And Roland Brosch
Mycobacterium tuberculosis, the etiological agent of human tuberculosis harbours five ESAT-6/type VII secretion (ESX/T7S) systems. The first esx gene clusters were identified during the genome-sequencing project of M. tuberculosis H37Rv. Follow-up studies revealed additional genes playing important roles in ESX/T7S systems. Among the latter genes, one can find those that encode Pro-Glu (PE) and Pro-Pro-Glu (PPE) proteins as well as a gene cluster that is encoded > 260 kb upstream of the esx-1 locus and encodes ESX-1 secretion-associated proteins EspA (Rv3616c), EspC (Rv3615c) and EspD (Rv3614c)...
November 16, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27862467/combinatorial-control-of-adhesion-of-brucella-abortus-2308-to-host-cells-by-transcriptional-rewiring-of-the-trimeric-autotransporter-btae-gene
#17
Rodrigo Sieira, Magalí G Bialer, Mara S Roset, Verónica Ruiz-Ranwez, Tomás Langer, Gastón M Arocena, Estefanía Mancini, Angeles Zorreguieta
Regulatory network plasticity is a key attribute underlying changes in bacterial gene expression and a source of phenotypic diversity to interact with the surrounding environment. Here, we sought to study the transcriptional circuit of HutC, a regulator of both metabolic and virulence genes of the facultative intracellular pathogen Brucella. Using in silico and biochemical approaches, we identified a novel functional HutC-binding site upstream of btaE, a trimeric-autotransporter adhesin involved in the attachment of Brucella to host extracellular matrix components...
November 12, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27862445/identification-of-the-camp-phosphodiesterase-cpda-as-novel-key-player-in-camp-dependent-regulation-in-corynebacterium-glutamicum
#18
Julia Schulte, Meike Baumgart, Michael Bott
The second messenger cyclic AMP (cAMP) plays an important role in the metabolism of Corynebacterium glutamicum, as the global transcriptional regulator GlxR requires complex formation with cAMP to become active. Whereas a membrane-bound adenylate cyclase, CyaB, was shown to be involved in cAMP synthesis, enzymes catalyzing cAMP degradation have not been described yet. In this study we identified a class II cAMP phosphodiesterase named CpdA (Cg2761), homologs of which are present in many Actinobacteria. The purified enzyme has a Km(app) value of 2...
November 12, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27859904/espc-forms-a-filamentous-structure-in-the-cell-envelope-of-mycobacterium-tuberculosis-and-impacts-esx-1-secretion
#19
Ye Lou, Jan Rybniker, Claudia Sala, Stewart T Cole
Pathogenicity of Mycobacterium tuberculosis (M. tb) is mediated by the ESX-1 secretion system, which exports EsxA and EsxB, the major virulence factors that are co-secreted with EspA and EspC. Functional information about ESX-1 components is scarce. Here, we show that EspC associates with EspA in the cytoplasm and membrane, then polymerizes during secretion from M. tb. EspC was localized by immuno-gold electron microscopy in whole cells or cryo-sections as a surface-exposed filamentous structure that seems to span the cell envelope...
November 10, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27862457/a-pts-eii-mutant-library-in-group-a-streptococcus-identifies-a-promiscuous-man-family-pts-transporter-influencing-sls-mediated-hemolysis
#20
Ganesh S Sundar, Emrul Islam, Kanika Gera, Yoann Le Breton, Kevin S McIver
The Group A Streptococcus (GAS, Streptococcus pyogenes) is a Gram-positive human pathogen that must adapt to unique host environments in order to survive. Links between sugar metabolism and virulence have been demonstrated in GAS, where mutants in the phosphoenolpyruvate-dependent phosphotransferase system (PTS) exhibited Streptolysin S (SLS)-mediated hemolysis during exponential growth. This early onset hemolysis correlated with an increased lesion size and severity in a murine soft tissue infection model when compared with parental M1T1 MGAS5005...
November 8, 2016: Molecular Microbiology
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