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Molecular Microbiology

Luis Felipe Muriel-Millán, Soledad Moreno, Ramsés Gallegos-Monterrosa, Guadalupe Espín
The nitrogen-related phosphotransferase system (PTS(Ntr) ) is composed of the EI(Ntr) , NPr and EIIA(Ntr) proteins that form a phosphorylation cascade from phosphoenolpyruvate. PTS(Ntr) is a global regulatory system present in most Gram-negative bacteria that controls some pivotal processes such as potassium and phosphate homeostasis, virulence, nitrogen fixation and ABC transport activation. In the soil bacterium Azotobacter vinelandii, unphosphorylated EIIA(Ntr) negatively regulates the expression of genes related to the synthesis of the bioplastic polyester poly-β-hydroxybutyrate (PHB) and cyst-specific lipids alkylresorcinols (ARs)...
January 18, 2017: Molecular Microbiology
Aaron T Whiteley, Nicholas E Garelis, Bret N Peterson, Philip H Choi, Liang Tong, Joshua J Woodward, Daniel A Portnoy
Cyclic di-adenosine monophosphate (c-di-AMP) is a conserved nucleotide second messenger critical for bacterial growth and resistance to cell wall-active antibiotics. In Listeria monocytogenes, the sole diadenylate cyclase, DacA, is essential in rich, but not synthetic media and ΔdacA mutants are highly sensitive to the β-lactam antibiotic cefuroxime. In this study, loss of function mutations in the oligopeptide importer (oppABCDF) and glycine betaine importer (gbuABC) allowed ΔdacA mutants to grow in rich medium...
January 18, 2017: Molecular Microbiology
Yasmine Fathy Mohamed, Mohamad Hamad, Ximena P Ortega, Miguel A Valvano
Lipid A anchors the lipopolysaccharide (LPS) to the outer membrane and is usually composed of a hexa-acylated diglucosamine backbone. Burkholderia cenocepacia, an opportunistic pathogen, produces a mixture of tetra- and penta-acylated lipid A. "Late" acyltransferases add secondary acyl chains to lipid A after the incorporation of four primary acyl chains to the diglucosamine backbone. Here, we report that B. cenocepacia has only one late acyltransferase, LpxL (BCAL0508), which adds a myristoyl chain to the 2' position of lipid A resulting in penta-acylated lipid A...
January 13, 2017: Molecular Microbiology
Frederique Ness, Brian S Cox, Jintana Wongwigkarn, Wesley R Naeimi, Mick F Tuite
The ability of a yeast cell to propagate [PSI(+) ], the prion form of the Sup35 protein, is dependent on the molecular chaperone Hsp104. Inhibition of Hsp104 function in yeast cells leads to a failure to generate new propagons, the molecular entities necessary for [PSI(+) ] propagation in dividing cells and they get diluted out as cells multiply. Over-expression of Hsp104 also leads to [PSI(+) ] prion loss and this has been assumed to arise from the complete disaggregation of the Sup35 prion polymers. However, in conditions of Hsp104 over-expression in [PSI(+) ] cells we find no release of monomers from Sup35 polymers, no monomerisation of aggregated Sup35 which is not accounted for by the proportion of prion-free [psi(-) ] cells present, no change in the molecular weight of Sup35-containing SDS-resistant polymers and no significant decrease in average propagon numbers in the population as a whole...
January 10, 2017: Molecular Microbiology
Zhiqiang Du, Dustin Kenneth Goncharoff, Xudong Cheng, Liming Li
The budding yeast, Saccharomyces cerevisiae, harbors several prions that are transmitted as altered, heritable protein conformations. [SWI(+) ] is one such prion whose determinant is Swi1, a subunit of the evolutionarily conserved chromatin-remodeling complex SWI/SNF. Despite the importance of Swi1, the molecular events that lead to [SWI(+) ] prionogenesis remain poorly understood. In this study, we have constructed floccullin-promoter-based URA3 reporters for [SWI(+) ] identification. Using these reporters, we show that the spontaneous formation frequency of [SWI(+) ] is significantly higher than that of [PSI(+) ] (prion form of Sup35)...
December 30, 2016: Molecular Microbiology
Dan M Park, K Wesley Overton, Megan J Liou, Yongqin Jiao
Despite the well-known toxicity of uranium (U) to bacteria, little is known about how cells sense and respond to U. The recent finding of a U-specific stress response in Caulobacter crescentus has provided a foundation for studying the mechanisms of U- perception in bacteria. To gain insight into this process, we used a forward genetic screen to identify the regulatory components governing expression of the urcA promoter (PurcA ) that is strongly induced by U. This approach unearthed a previously uncharacterized two-component system, named UzcRS, which is responsible for U-dependent activation of PurcA ...
December 30, 2016: Molecular Microbiology
Eoin Scanlan, Laura Ardill, Matthew V X Whelan, Claire Shortt, Jarlath E Nally, Billy Bourke, Tadhg Ó Cróinín
Invasion of intestinal epithelial cells by Campylobacter jejuni is a critical step during infection of the intestine by this important human pathogen. In this study we investigated the role played by DNA supercoiling in the regulation of invasion of epithelial cells and the mechanism by which this could be mediated. A significant correlation between more relaxed DNA supercoiling and an increased ability of C. jejuni strains to penetrate human epithelial cells was demonstrated. Directly inducing relaxation of DNA supercoiling in C...
December 26, 2016: Molecular Microbiology
Katarzyna Leskinen, Maria I Pajunen, Markku Varjosalo, Helena Fernández-Carrasco, José A Bengoechea, Mikael Skurnik
In bacteria, the RNA chaperone Hfq enables pairing of small regulatory RNAs with their target mRNAs and therefore is a key player of post-transcriptional regulation network. As a global regulator, Hfq is engaged in the adaptation to external environment, regulation of metabolism and bacterial virulence. In this study we used RNA-sequencing and quantitative proteomics (LC-MS/MS) to elucidate the role of this chaperone in the physiology and virulence of Yersinia enterocolitica serotype O:3. This global approach revealed the profound impact of Hfq on gene and protein expression...
December 23, 2016: Molecular Microbiology
John M Farrow, Everett C Pesci
The ubiquitous bacterium Pseudomonas aeruginosa is an opportunistic pathogen that can cause serious infections in immunocompromised individuals. P. aeruginosa virulence is controlled partly by intercellular communication, and the transcription factor PqsR is a necessary component in the P. aeruginosa cell-to-cell signaling network. PqsR acts as the receptor for the Pseudomonas quinolone signal, and it controls the production of 2-alkyl-4-quinolone molecules which are important for pathogenicity. Previous studies showed that the expression of pqsR is positively controlled by the quorum-sensing regulator LasR, but it was unclear how LasR is able to induce pqsR transcription...
December 23, 2016: Molecular Microbiology
Richard J Lewis
Peptidoglycan (PG), an essential stress-bearing component of the bacterial cell wall, is synthesised by penicillin binding proteins (PBPs). PG synthesis at the cell division septum is necessary for constructing new poles of progeny cells, and cells cannot elongate without inserting new PG in the side-wall. The cell division regulator GpsB appears to co-ordinate PG synthesis at the septum during division and at the side-wall during elongation in rod-shaped and ovococcoid Gram-positive bacteria. How the control over PG synthesis is exerted is unknown...
December 23, 2016: Molecular Microbiology
Britta E Rued, Jiaqi J Zheng, Andrea Mura, Ho-Ching T Tsui, Michael J Boersma, Jeffrey L Mazny, Federico Corona, Amilcar J Perez, Daniela Fadda, Linda Doubravová, Karolína Buriánková, Pavel Branny, Orietta Massidda, Malcolm E Winkler
GpsB regulatory protein and StkP protein kinase have been proposed as molecular switches that balance septal and peripheral (side-wall like) peptidoglycan (PG) synthesis in Streptococcus pneumoniae (pneumococcus); yet, mechanisms of this switching remain unknown. We report that ΔdivIVA mutations are not epistatic to ΔgpsB division-protein mutations in progenitor D39 and related genetic backgrounds; nor is GpsB required for StkP localization or FDAA labeling at septal division rings. However, we confirm that reduction of GpsB amount leads to decreased protein phosphorylation by StkP and report that the essentiality of ΔgpsB mutations is suppressed by inactivation of PhpP protein phosphatase, which concomitantly restores protein phosphorylation levels...
December 23, 2016: Molecular Microbiology
Miguel Ángel Vences-Guzmán, M Paula Goetting-Minesky, Ziqiang Guan, Santiago Castillo-Ramirez, Luz América Córdoba-Castro, Isabel M López-Lara, Otto Geiger, Christian Sohlenkamp, J Christopher Fenno
Treponema denticola synthesizes phosphatidylcholine through a licCA-dependent CDP-choline pathway identified only in the genus Treponema. However, the mechanism of conversion of CDP-choline to phosphatidylcholine remained unclear. We report here characterization of TDE0021 (herein designated cpt) encoding a 1,2-diacylglycerol choline phosphotransferase homologous to choline phosphotransferases that catalyze the final step of the highly conserved Kennedy pathway for phosphatidylcholine synthesis in eukaryotes...
December 23, 2016: Molecular Microbiology
Vadim Molodtsov, Nathan T Scharf, Maxwell A Stefan, George A Garcia, Katsuhiko S Murakami
Since 1967, Rifamaycin (RIF) has been used as a first line antibiotic treatment for tuberculosis (TB), and it remains the cornerstone of current short-term TB treatment. Increased occurrence of RIF-resistant (RIF(R) ) TB, ∼41% of which results from the RpoB S531L mutation in RNA polymerase (RNAP), has become a growing problem worldwide. In this study, we determined the X-ray crystal structures of the Escherichia coli RNAPs containing the most clinically important S531L mutation and two other frequently observed RIF(R) mutants, RpoB D516V and RpoB H526Y...
December 23, 2016: Molecular Microbiology
Nathan D Schwalm, Guy E Townsend, Eduardo A Groisman
Bacteroides thetaiotaomicron is a human gut symbiotic bacterium that utilizes a myriad of host dietary and mucosal polysaccharides. The proteins responsible for the uptake and break down of many of these polysaccharides are transcriptionally regulated by hybrid two-component systems (HTCSs). These systems consist of a single polypeptide harboring the domains of sensor kinases and response regulators, and thus, are thought to autophosphorylate in response to specific signals. We now report that the HTCS BT0366 is phosphorylated in vivo when B...
December 23, 2016: Molecular Microbiology
Hemant Kumar Prajapati, Syed Meraj Azhar Rizvi, Ishan Rathore, Santanu K Ghosh
The 2 μ plasmid of budding yeast shows high mitotic stability similar to that of chromosomes by using its self-encoded systems, namely partitioning and amplification. The partitioning system consists of the plasmid-borne proteins Rep1, Rep2 and a cis-acting locus STB that, along with several host factors, ensures efficient segregation of the plasmid. The plasmids show high stability as they presumably co-segregate with chromosomes through utilization of various host factors. To acquire these host factors, the plasmids are thought to localize to a certain sub-nuclear locale probably assisted by the motor protein, Kip1 and microtubules...
December 22, 2016: Molecular Microbiology
Alexandra E Paharik, Marta Kotasinska, Anna Both, Tra-My Hoang, Henning Büttner, Paroma Roy, Paul D Fey, Alexander R Horswill, Holger Rohde
The otherwise harmless skin inhabitant Staphylococcus epidermidis is a major cause of healthcare-associated medical device infections. The species' selective pathogenic potential depends on its production of surface adherent biofilms. Cell wall-anchored protein Aap promotes biofilm formation in S. epidermidis, independently from the polysaccharide intercellular adhesin PIA. Aap requires proteolytic cleavage to act as an intercellular adhesin. Whether and which staphylococcal proteases account for Aap processing is yet unknown...
December 20, 2016: Molecular Microbiology
Jessica A Klein, Biren M Dave, Amogelang R Raphenya, Andrew G McArthur, Leigh A Knodler
Type III Secretion Systems (T3SSs) are structurally conserved nanomachines that span the inner and outer bacterial membranes, and via a protruding needle complex contact host cell membranes and deliver type III effector proteins. T3SS are phylogenetically divided into several families based on structural basal body components. Here we have studied the evolutionary and functional conservation of four T3SS proteins from the Inv/Mxi-Spa family: a cytosolic chaperone, two hydrophobic translocators that form a plasma membrane-integral pore, and the hydrophilic "tip complex" translocator that connects the T3SS needle to the translocon pore...
December 20, 2016: Molecular Microbiology
Adrian Mehlitz, Eva Eylert, Claudia Huber, Buko Lindner, Nadine Vollmuth, Karthika Karunakaran, Werner Goebel, Wolfgang Eisenreich, Thomas Rudel
Metabolic adaptation is a key feature for the virulence of pathogenic intracellular bacteria. Nevertheless, little is known about the pathways in adapting the bacterial metabolism to multiple carbon sources available from the host cell. To analyze the metabolic adaptation of the obligate intracellular human pathogen Chlamydia trachomatis, we labeled infected HeLa or Caco-2 cells with (13) C-marked glucose, glutamine, malate or a mix of amino acids as tracers. Comparative GC-MS-based isotopologue analysis of protein-derived amino acids from the host cell and the bacterial fraction showed that C...
December 20, 2016: Molecular Microbiology
Chong Fang, Anna Nagy-Staroń, Martin Grafe, Ralf Heermann, Kirsten Jung, Susanne Gebhard, Thorsten Mascher
BceRS and PsdRS are paralogous two-component systems in Bacillus subtilis controlling the response to antimicrobial peptides. In the presence of extracellular bacitracin and nisin, respectively, the two response regulators (RRs) bind their target promoters, PbceA or PpsdA , resulting in a strong up-regulation of target gene expression and ultimately antibiotic resistance. Despite high sequence similarity between the RRs BceR and PsdR and their known binding sites, no cross-regulation has been observed between them...
December 20, 2016: Molecular Microbiology
Emöke Cserti, Sabine Rosskopf, Yi-Wei Chang, Sabrina Eisheuer, Lars Selter, Jian Shi, Christina Regh, Ulrich Koert, Grant J Jensen, Martin Thanbichler
Most commonly studied bacteria grow symmetrically and divide by binary fission, generating two siblings of equal morphology. An exception to this rule are budding bacteria, in which new offspring emerges de novo from a morphologically invariant mother cell. Although this mode of proliferation is widespread in diverse bacterial lineages, the underlying mechanisms are still incompletely understood. Here, we report the first molecular-level analysis of growth and morphogenesis in the stalked budding alphaproteobacterium Hyphomonas neptunium...
December 20, 2016: Molecular Microbiology
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