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Molecular Microbiology

Bethan A Wallbank, Caia S Dominicus, Malgorzata Broncel, Nathalie Legrave, James I MacRae, Henry M Staines, Moritz Treeck
Toxoplasma gondii parasites rapidly exit their host cell when exposed to calcium ionophores. Calcium-dependent protein kinase 3 (TgCDPK3) was previously identified as a key mediator in this process, as TgCDPK3 knockout (∆cdpk3) parasites fail to egress in a timely manner. Phosphoproteomic analysis comparing WT with ∆cdpk3 parasites revealed changes in the TgCDPK3-dependent phosphoproteome that included proteins important for regulating motility, but also metabolic enzymes, indicating that TgCDPK3 controls processes beyond egress...
November 6, 2018: Molecular Microbiology
Peter E Burby, Lyle A Simmons
All organisms possess DNA repair pathways that are used to maintain the integrity of their genetic material. Although many DNA repair pathways are well understood, new pathways continue to be discovered. Here, we report an antibiotic specific DNA repair pathway in Bacillus subtilis that is composed of a previously uncharacterized helicase (mrfA) and exonuclease (mrfB). Deletion of mrfA and mrfB results in sensitivity to the DNA damaging agent mitomycin C, but not to any other type of DNA damage tested. We show that MrfAB function independent of canonical nucleotide excision repair, forming a novel excision repair pathway...
October 31, 2018: Molecular Microbiology
Aaron Mychack, R N Amrutha, Charlie Chung, Karla Cardenas Arevalo, Manjula Reddy, Anuradha Janakiraman
The bacterial cytoplasmic membrane is a principal site of protein translocation, lipid and peptidoglycan biogenesis, signal transduction, transporters, and energy generating components of the respiratory chain. Although 25-30% of bacterial proteomes consist of membrane proteins, a comprehensive understanding of their influence on fundamental cellular processes is incomplete. Here, we show that YciB and DcrB, two small cytoplasmic membrane proteins of previously unknown functions, play an essential synergistic role in maintaining cell envelope integrity of Escherichia coli...
October 27, 2018: Molecular Microbiology
Irene Heredero-Bermejo, Joseph M Varberg, Robert Charvat, Kylie Jacobs, Tamila Garbuz, William J Sullivan, Gustavo Arrizabalaga
Dynamin-related proteins (Drps) are involved in diverse processes such as organelle division and vesicle trafficking. The intracellular parasite Toxoplasma gondii possesses three distinct Drps. TgDrpC, whose function remains unresolved, is unusual in that it lacks a conserved GTPase Effector Domain, which is typically required for function. Here, we show that TgDrpC localizes to cytoplasmic puncta; however, in dividing parasites, TgDrpC redistributes to the growing edge of the daughter cells. By conditional knockdown, we determined that loss of TgDrpC stalls division and leads to rapid deterioration of multiple organelles and the IMC...
October 26, 2018: Molecular Microbiology
Maike K Groenewold, Stefanie Hebecker, Christiane Fritz, Simon Czolkoss, Milan Wiesselmann, Dirk W Heinz, Dieter Jahn, Franz Narberhaus, Meriyem Aktas, Jürgen Moser
Agrobacterium tumefaciens transfers oncogenic T-DNA via the type IV secretion system (T4SS) into plants causing tumor formation. The acvB gene encodes a virulence factor of unknown function required for plant transformation. Here we specify AcvB as a periplasmic lysyl-phosphatidylglycerol (L-PG) hydrolase, which modulates L-PG homeostasis. Via functional characterization of recombinant AcvB variants, we showed that the C-terminal domain of AcvB (residues 232-456) is sufficient for full enzymatic activity and defined key residues for catalysis...
October 24, 2018: Molecular Microbiology
Mary O'Connell Motherway, Aileen Houston, Grace O'Callaghan, Justus Reunanen, Frances O'Brien, Tara O'Driscoll, Patrick G Casey, Willem M de Vos, Douwe van Sinderen, Fergus Shanahan
Development of the human gut microbiota commences at birth, with certain bifidobacterial species representing dominant and early colonizers of the newborn gastrointestinal tract. The molecular basis of Bifidobacterium colonization, persistence and presumed communication with the host has remained obscure. We previously identified tight adherence (Tad) pili from Bifidobacterium breve UCC2003 as an essential colonization factor. Here, we demonstrate that bifidobacterial Tad pili also promote in vivo colonic epithelial proliferation...
October 23, 2018: Molecular Microbiology
Guihong Cha, Zimin Chen, Ran Mo, Guangwen Lu, Beile Gao
Campylobacter jejuni is the leading cause of foodborne gastrointestinal illness worldwide, and chemotaxis plays an important role in its host colonization and pathogenesis. Although many studies on chemotaxis have focused on the physical organization and signaling mechanism of the system's protein complex, much less is known about the transcriptional regulation of its components. Here, we describe two novel regulators, CJJ81176_0275 and CJJ81176_0276 (designated as CheP and CheQ), which specifically activate the transcription of the chemotaxis core genes cheV, cheA and cheW in C...
October 19, 2018: Molecular Microbiology
Yih-Ling Tzeng, Zachary Berman, Evelyn Toh, Jose A Bazan, Abigail Norris Turner, Adam C Retchless, Xin Wang, David E Nelson, David S Stephens
Clusters of Neisseria meningitidis (Nm) urethritis among primarily heterosexual males in multiple United States cities have been attributed to a unique non-encapsulated meningococcal clade (the U.S. Nm urethritis clade, US_NmUC) within the hypervirulent clonal complex 11. Resistance to antimicrobial peptides (AMPs) is a key feature of urogenital pathogenesis of the closely related species, N. gonorrhoeae. The US_NmUC isolates were found to be highly resistant to the model AMP, polymyxin B (PmB, MICs 64-256 μg/ml)...
October 18, 2018: Molecular Microbiology
Lisa Demtröder, Franz Narberhaus, Bernd Masepohl
Biological nitrogen fixation, the reduction of chemically inert dinitrogen to bioavailable ammonia, is a central process in the global nitrogen cycle highly relevant for life on earth. N2 reduction to NH3 is catalyzed by nitrogenases exclusively synthesized by diazotrophic prokaryotes. All diazotrophs have a molybdenum nitrogenase containing the unique iron-molybdenum cofactor FeMoco. In addition, some diazotrophs encode one or two alternative Mo-free nitrogenases that are less efficient at reducing N2 than Mo-nitrogenase...
October 16, 2018: Molecular Microbiology
Monika Pióro, Tomasz Małecki, Magda Portas, Izabela Magierowska, Damian Trojanowski, David Sherratt, Jolanta Zakrzewska-Czerwińska, Katarzyna Ginda, Dagmara Jakimowicz
Although mycobacteria are rod shaped and divide by simple binary fission, their cell cycle exhibits unusual features: unequal cell division producing daughter cells that elongate with different velocities, as well as asymmetric chromosome segregation and positioning throughout the cell cycle. As in other bacteria, mycobacterial chromosomes are segregated by pair of proteins, ParA and ParB. ParA is an ATPase that interacts with nucleoprotein ParB complexes - segrosomes and non-specifically binds the nucleoid...
October 14, 2018: Molecular Microbiology
Peter E Burby, Zackary W Simmons, Lyle A Simmons
Bacteria coordinate DNA replication and cell division, ensuring a complete set of genetic material is passed onto the next generation. When bacteria encounter DNA damage, a cell cycle checkpoint is activated by expressing a cell division inhibitor. The prevailing model is that activation of the DNA damage response and protease mediated degradation of the inhibitor is sufficient to regulate the checkpoint process. Our recent genome-wide screens identified the gene ddcA as critical for surviving exposure to DNA damage...
October 13, 2018: Molecular Microbiology
Ragnhild Bager Skjerning, Meriem Senissar, Kristoffer Winther, Kenn Gerdes, Ditlev E Brodersen
Type II toxin-antitoxin (TA) modules, which are important cellular regulators in prokaryotes, usually encode two proteins, a toxin that inhibits cell growth and a non-toxic and labile inhibitor (antitoxin) that binds to and neutralizes the toxin. Here, we demonstrate that the res-xre locus from Photorhabdus luminescens and other bacterial species function as bona fide TA modules in E. coli. The 2.2 Å crystal structure of the intact Pseudomonas putida RES-Xre TA complex reveals an unusual 2:4 stoichiometry in which a central RES toxin dimer binds two Xre antitoxin dimers...
October 13, 2018: Molecular Microbiology
Ya Xu, Yu-Xin Li, Bang-Ce Ye
Phosphate concentration extensively modulates the central physiological processes mediated by the two-component system PhoR-PhoP in actinobacteria. The system serves a role beyond phosphate metabolism, mediating crucial functions in nitrogen and carbon metabolism, and secondary metabolism in response to the nutritional states. Here, we found that the phosphate-sensing regulator PhoP was propionylated, and thus lost its DNA-binding activity in vivo and in vitro in Saccharopolyspora erythraea. Two key conserved lysine residues 198 and 203 (K198 and K203) in winged HTH motif at the C-terminal domain of PhoP are propionylated by protein acyltransferase AcuA (encoding by sace_5148)...
October 10, 2018: Molecular Microbiology
Guanghua Huang, Qian Huang, Yujia Wei, Yue Wang, Han Du
Candida albicans is a major fungal pathogen of humans, causing both superficial and life-threatening systemic infections in immunocompromised people. The conserved Ras/cAMP/PKA pathway plays a key role in regulating multiple traits important for the virulence of C. albicans such as cell growth, yeast-hyphae transition, white-opaque switching, sexual reproduction, and biofilm development. Diverse external signals influence cell physiology by activating this signaling pathway. The key components of the Ras/cAMP/PKA pathway include two Ras GTPases (Ras1 and Ras2), an adenylyl cyclase (Cyr1, also known as Cdc35), two cyclic nucleotide phosphodiesterases (Pde1 and Pde2), and the catalytic (Tpk1 and Tpk2) and regulatory (Bcy1) subunits of PKA kinase...
October 9, 2018: Molecular Microbiology
Cecilia M Thompson, Alice H Tischler, Denise A Tarnowski, Mark J Mandel, Karen L Visick
Nitric oxide (NO) is an important defense molecule secreted by the squid Euprymna scolopes and sensed by the bacterial symbiont, Vibrio fischeri, via the NO-sensor HnoX. HnoX inhibits colonization through an unknown mechanism. The genomic location of hnoX adjacent to hahK, a recently identified positive regulator of biofilm formation, suggested that HnoX may inhibit colonization by controlling biofilm formation, a key early step in colonization. Indeed, deletion of hnoX resulted in early biofilm formation in vitro, an effect that was dependent on HahK and its putative phosphotransfer residues...
October 9, 2018: Molecular Microbiology
Jing Liu, Rilee Zeinert, Laura Francis, Peter Chien
DnaA initiates chromosome replication in bacteria. In Caulobacter crescentus, the Lon protease degrades DnaA to coordinate replication with nutrient availability and to halt the cell cycle during acute stress. Here we characterize the mechanism of DnaA recognition by Lon. We find that the folded state of DnaA appears crucial for its degradation, in contrast to the well-known role of Lon in degrading misfolded proteins. We fail to identify a single degradation motif (degron) sufficient for DnaA degradation, rather we show that both the ATPase domain and a species-specific N-terminal motif are important for productive Lon degradation of full length DnaA...
October 4, 2018: Molecular Microbiology
Lindsay A Matthews, Lyle A Simmons
DNA replication is a fundamental biological process that is tightly regulated in all cells. In bacteria, DnaA controls when and where replication begins by building a step-wise complex that loads the replicative helicase onto chromosomal DNA. In many low-GC Gram-positive species, DnaA recruits the DnaD and DnaB proteins to function as adaptors to assist in helicase loading. How DnaA, its adaptors, and the helicase form a complex at the origin is unclear. We addressed this question by using the bacterial two-hybrid assay to determine how the initiation proteins from Bacillus subtilis interact with each other...
October 4, 2018: Molecular Microbiology
Bin Li, Yukari Maezato, Sok Ho Kim, Shin Kurihara, Jue Liang, Anthony J Michael
Polyamines such as spermidine and spermine are primordial polycations that are ubiquitously present in the three domains of life. We have found that Gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis have lost either all or most polyamine biosynthetic genes, respectively, and are devoid of any polyamine when grown in polyamine-free media. In contrast to bacteria such as Pseudomonas aeruginosa, Campylobacter jejuni and Agrobacterium tumefaciens, which absolutely require polyamines for growth, S...
October 3, 2018: Molecular Microbiology
Xuefeng Yin, Mona Wu Orr, Hanbo Wang, Errett C Hobbs, Svetlana A Shabalina, Gisela Storz
In response to low levels of magnesium (Mg2+ ), the PhoQP two component system induces the transcription of two convergent genes, one encoding a 31-amino acid protein denoted MgtS and the second encoding a small, regulatory RNA (sRNA) denoted MgrR. Previous studies showed that the MgtS protein interacts with and stabilizes the MgtA Mg2+ importer to increase intracellular Mg2+ levels, while the MgrR sRNA base pairs with the eptB mRNA thus affecting lipopolysaccharide modification. Surprisingly, we found overexpression of the MgtS protein also leads to induction of the PhoRB regulon...
October 1, 2018: Molecular Microbiology
Christian González-Rivera, Pratick Khara, Dominik Awad, Roosheel Patel, Yang Grace Li, Maxim Bogisch, Peter J Christie
Mobile genetic elements (MGEs) encode type IV secretion systems (T4SSs) known as conjugation machines for their transmission between bacterial cells. Conjugation machines are composed of an envelope-spanning translocation channel, and those functioning in Gram-negative species additionally elaborate an extracellular pilus to initiate donor-recipient cell contacts. We report that pKM101, a self-transmissible MGE functioning in the Enterobacteriaceae, has evolved a second target cell attachment mechanism. Two pKM101-encoded proteins, the pilus-tip adhesin TraC and a protein termed Pep, are exported to the cell surface where they interact and also form higher order complexes appearing as distinct foci or patches around the cell envelope...
September 28, 2018: Molecular Microbiology
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