Molecular Microbiology

Cover image for Vol. 97 Issue 5

Early View (Online Version of Record published before inclusion in an issue)

Edited By: John D. Helmann

Impact Factor: 4.419

ISI Journal Citation Reports © Ranking: 2014: 20/119 (Microbiology); 66/289 (Biochemistry & Molecular Biology)

Online ISSN: 1365-2958

Associated Title(s): Cellular Microbiology


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  1. Research Articles

    1. Investigation into FlhFG reveals distinct features of FlhF in regulating flagellum polarity in Shewanella oneidensis

      Tong Gao, Miaomiao Shi, Lili Ju and Haichun Gao

      Article first published online: 22 AUG 2015 | DOI: 10.1111/mmi.13141

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      Flagella are bacterial organelles of locomotion but their location and number are controlled by yet-unclear mechanisms. In polarly flagellated bacteria, SRP-like GTPase FlhF is proposed to be a key factor for flagellar terminal localization. We show that GTPase activity of S. oneidensis FlhF is essential to motility but dispensable to polar targeting. While the G domain of FlhF dictates the localization, the B and N domains play an opposite role in the process.

    2. Live cell imaging of SOS and prophage dynamics in isogenic bacterial populations

      Stefan Helfrich, Eugen Pfeifer, Christina Krämer, Christian Carsten Sachs, Wolfgang Wiechert, Dietrich Kohlheyer, Katharina Nöh and Julia Frunzke

      Article first published online: 22 AUG 2015 | DOI: 10.1111/mmi.13147

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      The spontaneous activation of prophage elements in single cells (SPI) is a frequent but often unnoted phenomenon of lysogenic bacterial populations. Here, we have analyzed SPI of the cryptic prophage CGP3 of Corynebacterium glutamicum using time-lapse fluorescence microscopy of reporter strains. These data highlight the impact of sporadic DNA damage on the activity of prophage elements and provide a time-resolved, quantitative description of SPI as general phenomenon of bacterial populations.

    3. ArsP: a methylarsenite efflux permease

      Jian Chen, Mahendra Madegowda, Hiranmoy Bhattacharjee and Barry P. Rosen

      Article first published online: 22 AUG 2015 | DOI: 10.1111/mmi.13145

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      Some microbes generate toxic methylarsenite that acts like an antibiotic to kill other microbes. In response, members of microbial communities have evolved resistance to this environmental toxin. ArsP is a bacterial efflux permease that confers resistance to the methylarsenite by extruding it from cells. In addition, ArsP confers resistance to synthetic organoarsenicals antimicrobial growth promoters used in animal husbandry.

    4. Ribosomal protein S6 phosphorylation is controlled by TOR and modulated by PKA in Candida albicans

      Tahmeena Chowdhury and Julia R. Köhler

      Article first published online: 22 AUG 2015 | DOI: 10.1111/mmi.13130

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      Phosphorylated ribosomal protein S6 (P-S6) levels respond to pharmacological, genetic, and physiological manipulation of the TOR pathway in Candida albicans. The P-S6 signal directly correlates with translation of a heterologous GFP reporter system, suggesting its utility as a readout for TOR-regulated anabolic processes. Epistasis experiments indicate that PKA components modulate P-S6 by acting upstream of, or in parallel to, the TOR pathway.

    5. Against the mainstream: the membrane-associated type I toxin BsrG from Bacillus subtilis interferes with cell envelope biosynthesis without increasing membrane permeability

      Natalie Jahn, Sabine Brantl and Henrik Strahl

      Article first published online: 22 AUG 2015 | DOI: 10.1111/mmi.13146

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      The analysis of the cellular toxicity caused by the Bacillus subtilis chromosomally encoded type I toxin BsrG revealed that it neither dissipates membrane potential nor affects cellular ATP-levels. Instead, BsrG induces membrane invaginations which delocalize the cell wall synthesis machinery, and ultimately trigger autolysis. These findings question the assumption that membrane associated type I toxins generally act by permeabilizing the membrane, and result in cell death by energy starvation.

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      Protein kinase C is essential for viability of the rice blast fungus Magnaporthe oryzae

      Tina J. Penn, Mark E. Wood, Darren M. Soanes, Michael Csukai, Andrew John Corran and Nicholas J. Talbot

      Article first published online: 18 AUG 2015 | DOI: 10.1111/mmi.13132

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      Magnaporthe oryzae is the causal agent of rice blast disease and a continuing threat to global food security. Identifying novel targets for disease intervention is therefore vital. Protein kinase C (PKC) is shown by three independent lines of evidence to be essential for cellular viability of M.oryzae. The transcriptional response to PKC inhibition in an analogue-sensitive kinase mutant of M.oryzae involves major changes in calcium signalling, secondary metabolism, autophagy and a wide range of cellular functions, in addition to the cell integrity pathway.

    7. Outer membrane protein P1 is the CEACAM-binding adhesin of Haemophilus influenzae

      Arnaud Kengmo Tchoupa, Sabine Lichtenegger, Joachim Reidl and Christof R. Hauck

      Article first published online: 18 AUG 2015 | DOI: 10.1111/mmi.13134

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      Similar to several other bacterial inhabitants of the human nasopharynx, Haemophilus influenzae engages carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) on mucosal tissues. In our report, we identify the Haemophilus outer membrane protein (OMP) P1 as the CEACAM-binding adhesin present in diverse H. influenzae strains. OMP P1 selectively binds human, but not other mammalian CEACAM family members and OMP P1 is necessary and sufficent to trigger CEACAM-mediated internalisation of the bacteria.

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      PHO4 transcription factor regulates triacylglycerol metabolism under low-phosphate conditions in Saccharomyces cerevisiae

      Kamlesh Kumar Yadav, Neelima Singh and Ram Rajasekharan

      Article first published online: 18 AUG 2015 | DOI: 10.1111/mmi.13133

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      - Low-Pi conditions increase the levels of nonpolar lipids, which is due to the increased expression of PHM8 by Pho4p transcription factor.

      - Dga1p is capable of acylating monoacylglycerol to diacylglycerol.

    9. Non-equivalent roles of two periplasmic subunits in the function and assembly of triclosan pump TriABC from Pseudomonas aeruginosa

      Jon W. Weeks, Logan M. Nickels, Abigail T. Ntreh and Helen I. Zgurskaya

      Article first published online: 18 AUG 2015 | DOI: 10.1111/mmi.13124

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      We report that TriABC-OpmH efflux transporter from Pseudomonas aeruginosa possesses a surprising substrate specificity and structure. In addition to triclosan, this transporter protects against the detergent SDS, which interacts antagonistically with triclosan and negates its antibacterial properties. The two different periplasmic MFPs TriA and TriB function as a heterodimer, in which TriA is primarily responsible for stabilizing interactions with the outer membrane channel, while TriB is important for the stimulation of the transporter TriC.

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      Vibrio cholerae phosphatases required for the utilization of nucleotides and extracellular DNA as phosphate sources

      EmilyKate McDonough, Heather Kamp and Andrew Camilli

      Article first published online: 16 AUG 2015 | DOI: 10.1111/mmi.13128

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      V. cholerae was previously shown to use extracellular DNA as a source of phosphate. We have identified three phosphatases/nucleotidases that are essential for this phenotype: PhoX, UshA, and CpdB. We also show that UshA is a 5′nucleotidase and that CpdB is a low phosphate activated 3′nucleotidase.

    11. Molecular mechanisms of xylose utilization by Pseudomonas fluorescens: overlapping genetic responses to xylose, xylulose, ribose and mannitol

      Yunhao Liu, Paul B. Rainey and Xue-Xian Zhang

      Article first published online: 16 AUG 2015 | DOI: 10.1111/mmi.13142

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      We report unconventional regulatory mechanisms of xylose utilization in the plant growth-promoting bacterium Pseudomonas fluorescens SBW25, which involve two AraC-type regulators acting in the absence of DNA-looping. The isomerase gene (xutA) is regulated by XutR in a xylose-, xylulose- and ribose-dependent manner, whereas xylose-induced expression of the xylulokinase gene xutB1 is mediated by the mannitol-responsive regulator MtlR, using xylulose as the direct inducer. Our data reveal complex overlapping cellular responses to those plant-derived carbon substrates.

    12. G-protein coupled receptor-mediated nutrient sensing and developmental control in Aspergillus nidulans

      Neil Andrew Brown, Thaila Fernanda dos Reis, Laure Nicolas Annick Ries, Camila Caldana, Jae-Hyung Mah, Jae-Hyuk Yu, Jeffrey M. Macdonald and Gustavo Henrique Goldman

      Article first published online: 15 AUG 2015 | DOI: 10.1111/mmi.13135

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      GprH - A multi-functional GPCR-mediated nutrient sensing system that regulates primary metabolism, hyphal growth and represses sexual development, via influencing the cAMP-PKA and RosA pathways, in Aspergillus nidulans.

    13. A LysR-family transcriptional regulator required for virulence in Brucella abortus is highly conserved among the α-proteobacteria

      Lauren M. Sheehan, James A. Budnick, Catlyn Blanchard, Paul M. Dunman and Clayton C. Caswell

      Article first published online: 14 AUG 2015 | DOI: 10.1111/mmi.13123

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      In this work, we describe a LysR-family transcriptional regulator, VtlR that is critical for the full virulence of the pathogenic bacterium Brucella abortus. VtlR acts as a transcriptional activator of the small RNA abcR2, as well as three small hypothetical encoding proteins. Most importantly, the VtlR system is highly conserved among members of the α-proteobacteria, suggesting this regulatory system plays an important role in diverse host-bacterium interactions.

    14. Regulatory rewiring confers serotype-specific hyper-virulence in the human pathogen group A Streptococcus

      Eric W. Miller, Jessica L. Danger, Anupama B. Ramalinga, Nicola Horstmann, Samuel A. Shelburne and Paul Sumby

      Article first published online: 14 AUG 2015 | DOI: 10.1111/mmi.13136

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      Some serotypes of the group A Streptococcus (GAS) are non-randomly associated with particular disease manifestations. Here, we show that a contributing factor to the association of serotype M3 GAS isolates with severe invasive infections is the presence of a null mutant allele for the orphan kinase RocA. Our data are consistent with RocA enhancing the activity of the two-component system CovR/S, and that the absence of this activity in M3 GAS leads to enhanced expression of multiple immunomodulatory virulence factors by isolates of this serotype.

  2. MicroReview

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      Molecular biology research to benefit patients with Entamoeba histolytica infection

      Koji Watanabe and William A. Petri Jr.

      Article first published online: 14 AUG 2015 | DOI: 10.1111/mmi.13131

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      It is still difficult to apply findings from laboratory research to the care of individual patients or at a public health level, although molecular microbiology has deepened our understanding of the pathogenesis of amebiasis. We have to promote collaboration between the clinic and laboratory more tightly, as well as improve experimental models so that they more closely replicate human infection. It will provide us a key to a comprehensive understanding of this parasitic disease.

  3. Research Articles

    1. Analysis of conserved NCS2 motifs in the Escherichia coli xanthine permease XanQ

      Ekaterini Karena, Ekaterini Tatsaki, George Lambrinidis, Emmanuel Mikros and Stathis Frillingos

      Article first published online: 14 AUG 2015 | DOI: 10.1111/mmi.13138

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      The xanthine permease XanQ of Escherichia coli, a paradigm for the evolutionarily broad family nucleobase-cation symporter-2 (NCS2), was subjected to Cys-scanning and site-directed mutagenesis at conserved sequence motifs distant from the homology-modeled binding site. We identified several key amino acid residues, including six essential Gly residues in the gate domain and Gln-75 which appears to be involved in crucial hydrogen bonding interactions in the core domain.

    2. Dynamic interplay of membrane-proximal POTRA domain and conserved loop L6 in Omp85 transporter FhaC

      Jeremy Guérin, Nathalie Saint, Catherine Baud, Albano C. Meli, Emilien Etienne, Camille Locht, Hervé Vezin and Françoise Jacob-Dubuisson

      Article first published online: 14 AUG 2015 | DOI: 10.1111/mmi.13137

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      The ubiquitous Omp85 proteins mediate transport of other proteins across or into biological membranes, notably the outer membrane of Gram-negative bacteria. They are composed of a transmembrane beta barrel, which is preceded by soluble ‘POTRA’ domains. Here using the bacterial FhaC transporter as a model, we show that conserved elements in the Omp85 family, i.e., the POTRA domains and the loop L6, communicate with each other and thus function together in the transport process.

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      The Clostridium difficile cell wall protein CwpV confers phase-variable phage resistance

      Ognjen Sekulovic, Maicol Ospina Bedoya, Amanda S. Fivian-Hughes, Neil F. Fairweather and Louis-Charles Fortier

      Article first published online: 8 AUG 2015 | DOI: 10.1111/mmi.13121

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      CwpV is a cell wall-associated protein conserved across the Clostridium difficile species. An epigenetic switch controls the expression of the cwpV gene in a phase-variable manner. Bacterial cells that are in the « ON » state express cwpV and become resistant to phage infection through blocking of phage DNA injection, in a manner reminiscent of superinfection exclusion systems. CwpV thus represents a novel antiphage system conserved in C. difficile.

    4. You have full text access to this OnlineOpen article
      Structural and molecular basis for the novel catalytic mechanism and evolution of DddP, an abundant peptidase-like bacterial Dimethylsulfoniopropionate lyase: a new enzyme from an old fold

      Peng Wang, Xiu-Lan Chen, Chun-Yang Li, Xiang Gao, De-yu Zhu, Bin-Bin Xie, Qi-Long Qin, Xi-Ying Zhang, Hai-Nan Su, Bai-Cheng Zhou, Lu-ying Xun and Yu-Zhong Zhang

      Article first published online: 3 AUG 2015 | DOI: 10.1111/mmi.13119

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      The microbial cleavage of dimethylsulfoniopropionate (DMSP) generates volatile dimethyl sulfide (DMS) and is an important step in global sulfur and carbon cycles. DddP is an abundant metallopeptidase-like Dimethylsulfoniopropionate (DMSP) lyase belonging to the M24 family. However, DddP cleavages C-S bond other than hydrolyzing C-N bond. This study sheds light on the novel catalytic mechanism and the divergent evolution of DddP, leading to a better understanding of marine bacterial DMSP catabolism and global DMS production.

    5. SuhB is a novel ribosome associated protein that regulates expression of MexXY by modulating ribosome stalling in Pseudomonas aeruginosa

      Jing Shi, Yongxin Jin, Ting Bian, Kewei Li, Ziyu Sun, Zhihui Cheng, Shouguang Jin and Weihui Wu

      Article first published online: 3 AUG 2015 | DOI: 10.1111/mmi.13126

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      We found that mutation of a suhB gene leads to decreased antibiotic susceptibility of Pseudomonas aeruginosa, which is caused by up regulation of a multiple drug efflux system MexX-MexY. SuhB is found to associate with ribosome. Mutation of suhB increases the stalling of ribosome at the leader peptide mRNA of PA5471, causing the transcription of PA5471 mRNA, which subsequently activates the expression of MexX-MexY.

  4. MicroReview

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      Bacterial microcompartments: widespread prokaryotic organelles for isolation and optimization of metabolic pathways

      Thomas A. Bobik, Brent P. Lehman and Todd O. Yeates

      Article first published online: 3 AUG 2015 | DOI: 10.1111/mmi.13117

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      Bacterial microcompartments (MCPs) are widespread organelles that play important roles in processes ranging from CO2 fixation to enteric pathogenesis. Their function is to optimize metabolic pathways by confining toxic or volatile intermediates. Because their outer boundary is a protein shell rather than a lipid membrane, distinctive operational and assembly principles apply.

  5. Research Articles

    1. A coiled coil switch mediates cold sensing by the thermosensory protein DesK

      Emilio Saita, Luciano A. Abriata, Yi Ting Tsai, Felipe Trajtenberg, Thomas Lemmin, Alejandro Buschiazzo, Matteo Dal Peraro, Diego de Mendoza and Daniela Albanesi

      Article first published online: 3 AUG 2015 | DOI: 10.1111/mmi.13118

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      The thermosensor histidine kinase DesK from Bacillus subtilis senses changes in membrane fluidity initiating an adaptative response. In vivo, in vitro and in silico analyses of structure-based mutants show that stabilization/destabilization of a 2-helix coiled coil connecting the transmembrane sensory domain of DesK with its cytosolic catalytic region is crucial to control its function. A mechanism emerges where helical rotations induced by changes in membrane thickness propagate the signal through stabilization/disruption of the coiled coil.

    2. Bacillithiol has a role in Fe–S cluster biogenesis in Staphylococcus aureus

      Zuelay Rosario-Cruz, Harsimranjit K. Chahal, Laura A. Mike, Eric P. Skaar and Jeffrey M. Boyd

      Article first published online: 30 JUL 2015 | DOI: 10.1111/mmi.13115

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      The maturation of iron-sulfur (Fe-S) proteins in Staphylococcus aureus requires Fe-S cluster synthesis, trafficking and insertion into apo-proteins. S. aureus cells unable to produce bacillithiol display growth abnormalities, which are, in part, the result of decreased activities of Fe-S cluster requiring enzymes. Overexpression of an Fe-S cluster carrier (Nfu or SufA) alleviates the phenotypic abnormalities of a bacillithiol-deficient strain suggesting that bacillithiol has a role in the carriage of Fe-S clusters in S. aureus.

  6. MicroReview

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      Mycolic acids: deciphering and targeting the Achilles' heel of the tubercle bacillus

      Vijayashankar Nataraj, Cristian Varela, Asma Javid, Albel Singh, Gurdyal S. Besra and Apoorva Bhatt

      Article first published online: 30 JUL 2015 | DOI: 10.1111/mmi.13101

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      Mycolic acids are unique long chain fatty acids found in the lipid-rich cell walls of mycobacteria, including the tubercle bacillus Mycobacterium tuberculosis. Essential for viability and virulence, enzymes involved in the biosynthesis of mycolic acids represent novel targets for drug development. We discuss recent advances including the potential role of specialised fatty acid synthase complexes, a recently described mycolic acid transporter MmpL3, mycolic acids in the context of the bacterial cytoskeleton, and their role beyond maintaining cell envelope integrity.

  7. Research Articles

    1. The chromosomal SezAT toxin–antitoxin system promotes the maintenance of the SsPI-1 pathogenicity island in epidemic Streptococcus suis

      Xinyue Yao, Tian Chen, Xiaodong Shen, Yan Zhao, Min Wang, Xiancai Rao, Supeng Yin, Jing Wang, Yali Gong, Shuguang Lu, Shuai Le, Yinling Tan, Jiaqi Tang, Hu Fuquan and Ming Li

      Article first published online: 30 JUL 2015 | DOI: 10.1111/mmi.13116

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      Streptococcus suis is a re-emerging pathogen capable of causing human meningitis and streptococcal toxic shock syndrome, which may be due to a laterally acquired pathogenicity island (renamed SsPI-1). SsPI-1 can spontaneously excise to form an extrachromosomal circular product, however, attempts to cure SsPI-1 have been unsuccessful. Here, we report that a functional Epsilon/Zeta toxin-antitoxin system promotes SsPI-1 stability in bacterial populations, which may explain the persistence of epidemic S. suis.

    2. Type-II NADH:quinone oxidoreductase from Staphylococcus aureus has two distinct binding sites and is rate limited by quinone reduction

      Filipa V. Sena, Ana P. Batista, Teresa Catarino, José A. Brito, Margarida Archer, Martin Viertler, Tobias Madl, Eurico J. Cabrita and Manuela M. Pereira

      Article first published online: 30 JUL 2015 | DOI: 10.1111/mmi.13120

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      We explored protein-substrate interaction in Type-II NADH:quinone oxidoreductase (NDH-2) from Staphylococcus aureus, a worldwide problem in clinical medicine due to its multiple drug resistant forms. We demonstrated the presence of distinct binding sites for the two substrates. We also showed the establishment of a ternary complex upon turnover and identify quinone reduction as the rate limiting step. Our work aims to provide the basis of a possible approach to rational drug design.

  8. Research Article

    1. SUMOylation of Wor1 by a novel SUMO E3 ligase controls cell fate in Candida albicans

      Minghui Yan, Xinyi Nie, Huafeng Wang, Ning Gao, Haoping Liu and Jiangye Chen

      Article first published online: 30 JUL 2015 | DOI: 10.1111/mmi.13108

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      A novel SUMO E3 ligase Wos1 was identified to interact with Wor1 and regulate Wor1 sumoylation at lysine 385. Wos1 acts downstream of Flo8 under high levels of CO2 and mediates Wor1 sumoylation to control white-to-opaque switching and opaque maintenance in Candida albicans.

  9. Research Articles

    1. CdiA promotes receptor-independent intercellular adhesion

      Zachary C. Ruhe, Loni Townsley, Adam B. Wallace, Andrew King, Marjan W. Van der Woude, David A. Low, Fitnat H. Yildiz and Christopher S. Hayes

      Article first published online: 30 JUL 2015 | DOI: 10.1111/mmi.13114

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      CdiB/CdiA two-partner secretion systems mediate inter-bacterial competition in a process termed contact-dependent growth inhibition (CDI). CDI+ cells use CdiA proteins to bind specific receptors on target bacteria and deliver inhibitory toxins. Here, we show that CdiA from E. coli EC93 also mediates receptor-independent cell-cell adhesion through a putative homotypic interaction domain. CdiA-CdiA binding interactions promote auto-aggregation and biofilm formation, demonstrating a role in collective behavior that is independent of growth-inhibition activity.

  10. MicroReview

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      RNA degradosomes in bacteria and chloroplasts: classification, distribution and evolution of RNase E homologs

      Soraya Aït-Bara and Agamemnon J. Carpousis

      Article first published online: 22 JUL 2015 | DOI: 10.1111/mmi.13095

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      The RNase E of E. coli, an essential ribonuclease involved in stable RNA maturation and mRNA degradation, has a large intrinsically disordered noncatalytic region that is the scaffold for assembly of the multienzyme RNA degradosome. Homologs of RNase E are found throughout bacteria and in chloroplasts. Here we have classified the homologs into four types based on primary structure of the protein and we have reviewed RNA degradosome composition, which is species-specific due to rapid evolution of the noncatalytic region.

  11. Research Articles

    1. The CrdRS two-component system in Helicobacter pylori responds to nitrosative stress

      Chiu-Lien Hung, Hsin-Hung Cheng, Wan-Chen Hsieh, Zing Tsung-Yeh Tsai, Huai-Kuang Tsai, Chia-Han Chu, Wen-Ping Hsieh, Yi-Fan Chen, Yu Tsou, Chih-Ho Lai and Wen-Ching Wang

      Article first published online: 22 JUL 2015 | DOI: 10.1111/mmi.13089

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      Helicobacter pylori successfully responds and adapts to various stresses from gastric environment via its three-pair two-component systems (TCSs). This report shows that a unique TCS, CrdRS, functions as a sensor for nitrosative stress. Nitrosative challenge differentially upregulates the expression of resistance determinant A (crdA). Further, CrdR binds to the proximal promoter region of crdA that consists of a two AC-rich region. These findings demonstrate that CrdR-crdA interaction enables H. pylori to survive under nitrosative stress.

  12. Microcommentary

    1. The art of destruction: revealing the proteolytic capacity of bacterial caspase homologs

      Johannes Asplund-Samuelsson

      Article first published online: 22 JUL 2015 | DOI: 10.1111/mmi.13111

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      Bacterial caspase homologs are putative proteases with evolutionary connections to eukaryotic genetically controlled cell death programs. Klemenčič et al. have, for the first time, exposed the biochemical properties of one of these proteins, specifically the cyanobacterial caspase homolog MaOC1. The demonstrated proteolytic capability and activation mechanism of this caspase-like protein carries important implications for further studies in this relatively uncharted field.

  13. Research Articles

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      The TatC component of the twin-arginine protein translocase functions as an obligate oligomer

      François Cléon, Johann Habersetzer, Felicity Alcock, Holger Kneuper, Phillip J. Stansfeld, Hajra Basit, Mark I. Wallace, Ben C. Berks and Tracy Palmer

      Article first published online: 22 JUL 2015 | DOI: 10.1111/mmi.13106

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      We have identified amino acid substitutions in the Escherichia coli TatC protein that block the function of the wild type TatC when the two proteins are co-produced. We show that in the presence of a substrate protein two TatC wild type protomers come into close proximity, allowing a disulphide bond to form across position M205C. The amino acid variants abolish this substrate-induced disulphide crosslink. Our findings show that TatC functions as an obligate multimer.

    2. Identification of critical residues for transport activity of Acr3p, the Saccharomyces cerevisiae As(III)/H+ antiporter

      Katarzyna Markowska, Ewa Maciaszczyk-Dziubinska, Magdalena Migocka, Donata Wawrzycka and Robert Wysocki

      Article first published online: 22 JUL 2015 | DOI: 10.1111/mmi.13113

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      The proton-driven antiporter Acr3p from budding yeast mediates extrusion of the toxic metalloids arsenic and antimony out of yeast cells. We identified several key amino acid residues that are important for proper folding, trafficking and/or transport activity of Acr3 protein. We propose that Acr3p exhibits a fold and transport mechanism similar to that commonly found in secondary active transporters.

    3. Cysteine scanning reveals minor local rearrangements of the horizontal helix of respiratory complex I

      Stefan Steimle, Christian Schnick, Eva-Maria Burger, Franziska Nuber, Dorothée Krämer, Hannah Dawitz, Sofia Brander, Bartlomiej Matlosz, Jacob Schäfer, Katharina Maurer, Udo Glessner and Thorsten Friedrich

      Article first published online: 22 JUL 2015 | DOI: 10.1111/mmi.13112

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      The proposed movement of the horizontal helix of respiratory complex I was directly investigated by labeling distinct positions of the helix. There was not significant change in TMR-labeling upon reduction of the oxidized complex. The mobility of an EPR spin-label attached to these positions was very similar in the oxidized and the reduced state of the complex indicating small local conformational changes within the helix in both redox states.

    4. Regulation of DNA phosphorothioate modifications by the transcriptional regulator DptB in Salmonella

      Qiuxiang Cheng, Bo Cao, Fen Yao, Jinli Li, Zixin Deng and Delin You

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13096

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      DNA phosphorothioate (PT) modification is a novel epigenetic modification recently discovered in many prokaryotic genomes. PT modifiable sites are only fractionally modified. The fraction of susceptible sites modified is increased when expression of the modifying enzymes is increased, but remains subsaturating. A widely conserved DNA-binding protein, DptB, is one negative regulator of this system.

    5. Acyl acceptor recognition by Enterococcus faecium l,d-transpeptidase Ldtfm

      Sébastien Triboulet, Catherine M. Bougault, Cédric Laguri, Jean-Emmanuel Hugonnet, Michel Arthur and Jean-Pierre Simorre

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13104

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      NMR studies of the Enterococcus faecium L,D-transpeptidase have identified the binding sites for the acyl donor and the acyl acceptor of the peptidoglycan cross-linking reaction. Amino acid substitutions in the acceptor binding pocket revealed three residues essential for stabilization of the acceptor and orientation of its nucleophilic nitrogen. These results raise the possibility to design inhibitors that would bind to the acceptor site and could act alone or in synergy with β-lactam antibiotics.

    6. Srr2, a multifaceted adhesin expressed by ST-17 hypervirulent Group B Streptococcus involved in binding to both fibrinogen and plasminogen

      Anne Six, Samuel Bellais, Abdelouhab Bouaboud, Agnès Fouet, Christelle Gabriel, Asmaa Tazi, Shaynoor Dramsi, Patrick Trieu-Cuot and Claire Poyart

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13097

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      Srr2 is a highly surfaceߚexpressed glycoprotein of S. agalactiae ST-17 hypervirulent strains (A). Here, we show that this multi-faceted adhesin (i) promotes bacterial aggregation through interaction with fibrinogen (B), (ii) binds plasminogen, (iii) increases bacterial uptake and survival in several immune cell lines (D, E), (iv) induces protective immunity in mice (F). These results illustrate the role of Srr2 during the different steps of ST-17 infections and its potential as a vaccine target.

    7. Bacillus subtilis SalA is a phosphorylation-dependent transcription regulator that represses scoC and activates the production of the exoprotease AprE

      Abderahmane Derouiche, Lei Shi, Vladimir Bidnenko, Magali Ventroux, Nathalie Pigonneau, Mirita Franz-Wachtel, Aida Kalantari, Sylvie Nessler, Marie-Françoise Noirot-Gros and Ivan Mijakovic

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13098

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      B. subtilis protein-tyrosine kinase PtkA phosphorylates the Mrp protein SalA. Phosphorylated SalA binds the promoter region of scoC and represses it. ScoC is a repressor of the exoprotease AprE, therefore SalA phosphorylation leads to increased exoprotease activity. SalA and PtkA contain the same ATP-binding Walker domain, and have thus presumably arisen from the common ancestral protein.

    8. FliL associates with the stator to support torque generation of the sodium-driven polar flagellar motor of Vibrio

      Shiwei Zhu, Ananthanarayanan Kumar, Seiji Kojima and Michio Homma

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13103

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      We investigated the role of FliL in the sodium-driven polar flagellar motor of Vibrio alginolyticus. We revealed that FliL is a cytoplasmic membrane protein and is its localization to the base of the flagellum depends on the stator. FliL seems to interact with the stator in order to support the motor functioning for swimming at high load conditions by maintaining the stator assembly.

    9. The MinD homolog FlhG regulates the synthesis of the single polar flagellum of Vibrio alginolyticus

      Hiroki Ono, Akari Takashima, Hikaru Hirata, Michio Homma and Seiji Kojima

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13109

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      This paper describes a molecular mechanism of how the MinD homolog FlhG regulates biogenesis of the single polar flagellum of marine bacterium Vibrio alginolyticus. Results reveal that polar localization of FlhF is critical for flagellation and that FlhG negatively regulates FlhF polar localization in an ATP-dependent manner. These findings provide insight into the spatial and numerical control of the flagellar assembly and reveal parallels between control of flagellar assembly and MinCDE-mediated control of septation. (74 words)

    10. Mycobacterium tuberculosis class II apurinic/apyrimidinic-endonuclease/3′-5′ exonuclease III exhibits DNA regulated modes of interaction with the sliding DNA β-clamp

      Taran Khanam, Niyati Rai and Ravishankar Ramachandran

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13102

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      The substrate-mediated modes of interactions between the mycobacterial class II AP endonuclease (XthA) and the sliding DNA β-clamp are reported for the first time. The clamp stimulates the activities of XthA by increasing its substrate affinity and processivity through direct protein-interactions. Also, we describe specific disruption of the bacterial clamp-XthA complex by synthetic peptides and bacterial clamp-specific inhibitor, which opens avenues for the development of anti-bacterials targeting the clamp mediated protein interactions.

    11. Regulation of Plasmodium falciparum Origin Recognition Complex subunit 1 (PfORC1) function through phosphorylation mediated by CDK-like kinase PK5

      Abhijit S. Deshmukh, Meetu Agarwal, Parul Mehra, Ashish Gupta, Nidhi Gupta, Christian D. Doerig and Suman Kumar Dhar

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13099

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      Origin recognition complex (ORC) plays important role in eukaryotic DNA replication. Here, we demonstrate that Plasmodium falciparum ORC1 is phosphorylated at the N-terminus by CDK like kinase, PfPK5. Phosphorylation of PfORC1 leads to its compromised association with subtelomeric regions followed by cytoplasmic translocation and degradation by proteosomal pathway during the late schizont stage. These results suggest phosphorylation mediated regulation of PfORC1 required for parasite DNA replication and var gene regulation.

    12. You have full text access to this OnlineOpen article
      Orthocaspases are proteolytically active prokaryotic caspase homologues: the case of Microcystis aeruginosa

      Marina Klemenčič, Marko Novinec and Marko Dolinar

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13110

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      Caspases are a family of proteases involved in the process of programmed cell death in metazoans. Here we present the first experimental characterisation of a prokaryotic caspase homologue. MaOC1, the caspase homologue from the toxic cyanobacterium Microcystis aeruginosa PCC 7806, is an arginine-directed protease and is activated by autocatalytic processing after residue Arg219. Due to structural and functional differences to other known caspase-like proteins we suggest to name these evolutionary primitive proteins orthocaspases.

    13. Turnover of mRNAs is one of the essential functions of RNase E

      Disa L. Hammarlöf, Jessica M. Bergman, Eva Garmendia and Diarmaid Hughes

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13100

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      RNase E is an essential bacterial enzyme responsible for initiating the processing of ribosomal and transfer RNAs and for the turnover of mRNAs. Here we show that the degradation of mRNA's is one of the essential functions of RNase E. The key evidence is that a conditional lethal defect in RNase E activity can be complemented by increased expression of RelE, a nuclease that specifically cuts mRNA.

    14. Growth on glucose decreases cAMP-CRP activity while paradoxically increasing intracellular cAMP in the light-organ symbiont Vibrio fischeri

      Deanna M. Colton, Julie L. Stoudenmire and Eric V. Stabb

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13087

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      CRP combines with the second messenger cAMP to activate the pheromone-signaling systems in Vibrio fischeri. We now show that cAMP-CRP is critical for V. fishceri colonization of its host squid, Euprymna scolopes. Moreover, the cAMP-CRP regulon is induced during growth on non-glucose carbon sources and in the host. Surprisingly however, we find cAMP levels can be higher in cells grown on glucose, and that cAMP-independent mechanisms can modulate cAMP-CRP activity in response to glucose availability.

    15. Induction of a quorum sensing pathway by environmental signals enhances group A streptococcal resistance to lysozyme

      Jennifer C. Chang, Juan Cristobal Jimenez and Michael J. Federle

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13088

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      The Rgg2/3 quorum sensing system in Streptococcus pyogenes (Group A Streptococcus, GAS) modulates gene expression in response to SHP pheromones. We identified metal limitation and the alternate carbon source mannose as two environmental indicators likely encountered by GAS in the host that induced the Rgg-SHP system. Significantly, induction led to enhanced resistance to the antimicrobial agent lysozyme, indicating the benefits for GAS to integrate environmental signals with intercellular communication pathways in protection from host defenses.

    16. You have full text access to this OnlineOpen article
      Deciphering the metabolic response of Mycobacterium tuberculosis to nitrogen stress

      Kerstin J. Williams, Victoria A. Jenkins, Geraint R. Barton, William A. Bryant, Nitya Krishnan and Brian D. Robertson

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13091

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      The ability to adapt to environments of fluctuating nutrient availability is vital for bacterial survival. In response to nitrogen limitation, Mycobacterium tuberculosis alters nitrate/nitrite metabolism, aspartate metabolism and cell wall biosynthesis. GlnR is a key regulator involved in this response, controlling the expression of genes involved in nitric oxide detoxification and intracellular survival, markedly different to the GlnR-mediated nitrogen scavenging response seen in non-pathogenic mycobacteria.

    17. Targeted mutagenesis of intergenic regions in the Neisseria gonorrhoeae gonococcal genetic island reveals multiple regulatory mechanisms controlling type IV secretion

      Meghan E. Ramsey, Tobias Bender, Amy K. Klimowicz, Kathleen T. Hackett, Ami Yamamoto, Adrienne Jolicoeur, Melanie M. Callaghan, Karen M. Wassarman, Chris van der Does and Joseph P. Dillard

      Article first published online: 17 JUL 2015 | DOI: 10.1111/mmi.13094

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      The gonococcal genetic island contains twenty-one genes that encode required components of a type IV secretion system (T4SS). The T4SS secretes chromosomal DNA into the environment. We show that T4SS gene and protein expression is subject to multiple layers of regulation. These include differential relative transcription of the four T4SS operons, post-transcriptional regulation via an RNA switch, and post-translation regulation by periplasmic proteases.

    18. Association of UBP1 to ribonucleoprotein complexes is regulated by interaction with the trypanosome ortholog of the human multifunctional P32 protein

      Alejandro Cassola, María Albertina Romaniuk, Debora Primrose, Gabriela Cervini, Iván D'Orso and Alberto Carlos Frasch

      Article first published online: 14 JUL 2015 | DOI: 10.1111/mmi.13090

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      Regulation of RBP function is yet poorly understood in trypanosomes. Here we analyzed the growth-dependent condensation of TcUBP1 RNP complexes, from a lax layout to condensed mRNA granules. We found that, besides growing conditions, TcP22 and phosphorylation can modulate the reassociation of TcUBP1 to RNP complexes, acting in conjunction in a consecutive manner over TcUBP1, respectively. TcP22 effect over TcUBP1 association to mRNA is probably mediated by interaction with the RNA-recognition motif β-sheet.

    19. Dual modes of membrane binding direct pore formation by Streptolysin O

      Cara C. Mozola and Michael G. Caparon

      Article first published online: 4 JUL 2015 | DOI: 10.1111/mmi.13085

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      This study describes two distinct pathways by which the cholesterol-dependent cytolysin Streptolysin O is able to induce membrane damage on host cells during S. pyogenes infection. One pathway is independent of the translocated toxin SPN and relies on a galactose-containing receptor and subsequent interaction with cholesterol, while an alternative pathway requires the co-dependent binding of SPN, resulting in both SPN translocation and pore formation by Streptolysin O.

    20. Helicobacter pylori CheZHP and ChePep form a novel chemotaxis-regulatory complex distinct from the core chemotaxis signaling proteins and the flagellar motor

      Paphavee Lertsethtakarn, Michael R. Howitt, Juan Castellon, Manuel R. Amieva and Karen M. Ottemann

      Article first published online: 4 JUL 2015 | DOI: 10.1111/mmi.13086

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      Chemotaxis phosphatases such as CheZ localize to specific cellular sites to provide optimal chemotaxis performance. We show here that phosphatases exploit unexpected locations beyond the flagellar and chemoreceptor complexes. Specifically, the CheZ phosphatase of Helicobacter pylori localizes independent of the motility and chemoreceptor proteins, and instead relies on interactions with the ChePep chemotaxis protein. Localizing some chemotaxis proteins separate from the canonical motility and chemotaxis complexes may be a mechanism to provide unique regulatory inputs to CheZ and ChePep.

    21. Revisiting the membrane interaction mechanism of a membrane-damaging β-barrel pore-forming toxin Vibrio cholerae cytolysin

      Anand Kumar Rai and Kausik Chattopadhyay

      Article first published online: 4 JUL 2015 | DOI: 10.1111/mmi.13084

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      Vibrio cholerae cytolysin (VCC) is a β-barrel pore-forming toxin with potent membrane-damaging cytotoxic activity. Present study explores the implications of the distinct structural signatures present in VCC for the functional interactions of the toxin with the membrane lipid components, a process that acts to drive the subsequent steps of the oligomeric β-barrel pore-formation mechanism and the cytotoxic responses.

    22. Transcriptional regulation of the Chlamydia heat shock stress response in an intracellular infection

      Brett R. Hanson and Ming Tan

      Article first published online: 4 JUL 2015 | DOI: 10.1111/mmi.13093

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      Bacteria encode heat shock proteins which aid in survival during stressful growth conditions. The transcription factor HrcA is responsible for regulating the expression of heat shock proteins and is responsive to stress conditions. We have shown for the first time that chlamydial HrcA regulates expression of heat shock genes in Chlamydia and that HrcA DNA-binding is lost after heat shock. We have also demonstrated that the unusual developmental cycle used by Chlamydia influences this regulation.


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