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Molecular Microbiology

Yuri Nedialkov, Dmitri Svetlov, Georgiy A Belogurov, Irina Artsimovitch
Universally conserved NusG/Spt5 factors reduce RNA polymerase pausing and arrest. In a widely accepted model, these proteins bridge the RNA polymerase clamp and lobe domains across the DNA channel, inhibiting the clamp opening to promote pause-free RNA synthesis. However, recent structures of paused transcription elongation complexes show that the clamp does not open and suggest alternative mechanisms of antipausing. Among these mechanisms, direct contacts of NusG/Spt5 proteins with the nontemplate DNA in the transcription bubble have been proposed to prevent unproductive DNA conformations and thus inhibit arrest...
May 14, 2018: Molecular Microbiology
Vladimir Svetlov, Evgeny Nudler
Unlike transcription initiation and termination, which have easily discernable signals such as promoters and terminators, elongation is regulated through a dynamic network involving RNA/DNA pause signals and states- rather than sequence-specific protein interactions. A report by Nedialkov et al. (in press) provides experimental evidence for sequence-specific recruitment of elongation factor RfaH to transcribing RNA polymerase (RNAP) and outlines the mechanism of gene expression regulation by restraint ("locking") of the DNA non-template strand...
May 14, 2018: Molecular Microbiology
Patrick T McLaughlin, Vidhi Bhardwaj, Brooke E Feeley, Penelope I Higgs
MrpC, a member of the CRP/Fnr superfamily of transcriptional regulators, plays a key role in coordination of the multicellular developmental program in Myxococcus xanthus. Previous reports suggest MrpC is subject to complex regulation including activation by an unusual LonD-dependent proteolytic processing event that removes its unique N-terminal peptide, producing the isoform MrpC2. MrpC2 is proposed to positively autoregulate and regulate transcription of hundreds of genes necessary for both the aggregation and sporulation phases of the developmental program...
May 10, 2018: Molecular Microbiology
Pierre-Mehdi Hammoudi, Bohumil Maco, Sunil Kumar Dogga, Karine Frénal, Dominique Soldati-Favre
Invasion and egress are two key steps in the lytic cycle of Apicomplexa that are governed by the sequential discharge of proteins from two apical secretory organelles called micronemes and rhoptries. In Toxoplasma gondii, the biogenesis of these specialized organelles depends on the post Golgi trafficking machinery, forming an endosomal-like compartment (ELC) resembling endomembrane systems found in eukaryotes. In this study, we have characterized four phylogenetically related Transporter Facilitator Proteins (TFPs) conserved among the apicomplexans...
May 8, 2018: Molecular Microbiology
Andreas Schmitt, Kai Jiang, Martha I Camacho, Venkateswara Rao Jonna, Anders Hofer, Fredrik Westerlund, Peter J Christie, Ronnie P-A Berntsson
Gram-positive bacteria deploy type IV secretion systems (T4SSs) to facilitate horizontal gene transfer. The T4SSs of Gram-positive bacteria rely on surface adhesins as opposed to conjugative pili to facilitate mating. Enterococcus faecalis PrgB is a surface adhesin that promotes mating pair formation and robust biofilm development in an extracellular DNA (eDNA) dependent manner. Here we report the structure of the adhesin domain of PrgB. The adhesin domain binds and compacts DNA in vitro. In vivo PrgB deleted of its adhesin domain does not support cellular aggregation, biofilm development and conjugative DNA transfer...
May 3, 2018: Molecular Microbiology
Shao-Yu Lin, Yit-Heng Chooi, Peter S Solomon
To investigate effector gene regulation in the wheat pathogenic fungus Parastagonospora nodorum, the promoter and expression of Tox3 was characterised through a series of complementary approaches. Promoter deletion and DNase I footprinting experiments identified a 25 bp region in the Tox3 promoter as being required for transcription. Subsequent yeast one-hybrid analysis using the DNA sequence as bait identified that interacting partner as the C2H2 zinc finger transcription factor PnCon7, a putative master regulator of pathogenesis...
May 3, 2018: Molecular Microbiology
Suzanne E Greer-Phillips, Nattakan Sukomon, Teck Khiang Chua, Mark S Johnson, Brian R Crane, Kylie J Watts
The diarrheal pathogen Vibrio cholerae navigates complex environments using three chemosensory systems and 44-45 chemoreceptors. Chemosensory cluster II modulates chemotaxis, whereas clusters I and III have unknown functions. Ligands have been identified for only five V. cholerae chemoreceptors. Here we report that the cluster III receptor, VcAer2, binds and responds to O2 . VcAer2 is an ortholog of Pseudomonas aeruginosa Aer2 (PaAer2), but differs in that VcAer2 has two, rather than one, N-terminal PAS domain...
May 2, 2018: Molecular Microbiology
Alyson M Hockenberry, Deborah M B Post, Katherine A Rhodes, Michael Apicella, Magdalene So
Post-translational acetylation is a common protein modification in bacteria. It was recently reported that Neisseria gonorrhoeae acetylates the Type IV pilus retraction motor, PilT. Here, we show recombinant PilT can be acetylated in vitro and acetylation does not affect PilT ultrastructure. To investigate the function of PilT acetylation, we mutated an acetylated lysine, K117, to mimic its acetylated or unacetylated forms. These mutations were not tolerated by wild-type Neisseria gonorrhoeae, but they were tolerated by Neisseria gonorrhoeae carrying an inducible pilE when grown without inducer...
May 2, 2018: Molecular Microbiology
Kaisei Maeda, Jyunya Tamura, Yukiko Okuda, Rei Narikawa, Takafumi Midorikawa, Masahiko Ikeuchi
Cells of the thermophilic cyanobacterium Thermosynechococcus vulcanus strain RKN (NIES-2134) aggregate and produce extracellular cellulose under induced conditions of blue light and low temperature, and both aggregation and cellulose production require the cellulose synthase Tll0007 (XcsA) and photosensory diguanylate cyclases. However, overexpression of both the cellulose synthase and a constitutively active diguanylate cyclase was not sufficient to induce cellulose-mediated cell aggregation under normal growth conditions...
April 24, 2018: Molecular Microbiology
R G Sawers
Phthalic acid esters (phthalates) are anthropogenic compounds that are used as plasticizers. Unfortunately, because phthalates are non-covalently intercalated into plastic polymers they leach into the environment, accumulating in anoxic sediments. This has negative consequences for animal and human health. Denitrifying Betaproteobacteria, such as Aromatoleum aromaticum, can use ortho-phthalate, derived by ester hydrolysis, as a carbon and energy source. Mergelsberg et al. (in press) deconstruct the pathway whereby ortho-phthalic acid is converted, via the highly unstable phthaloyl-CoA, to the central intermediate of anaerobic aromatic degradation, benzoyl-CoA...
April 21, 2018: Molecular Microbiology
Jingjing Cao, Qian Wang, Tao Liu, Nan Peng, Li Huang
Nucleic acid-binding proteins of the Sac10b family, also referred to as Alba (for acetylation lowers binding affinity), are highly conserved in Archaea. It was reported that Sso10b, a Sac10b homologue from Sulfolobus solfataricus, was acetylated at the ε-amino group of K16 and the α-amino group of the N-terminal residue. Notably, acetylation of K16 reduced the affinity of Sso10b for DNA and de-repressed transcription in vitro. Here we show that Sis10b, a Sac10b homologue from Sulfolobus islandicus, underwent a range of post-translational modifications (PTMs)...
April 21, 2018: Molecular Microbiology
Ladan Dawoody Nejad, Mauro Serricchio, Jennifer Jelk, Andrew Hemphill, Peter Bütikofer
Mammalian phosphatidic acid phosphatases, also called lipins, show high amino acid sequence identity to Saccharomyces cerevisiae Pah1p and catalyze the dephosphorylation of phosphatidic acid (PA) to diacylglycerol. Both the substrate and product of the reaction are key precursors for the synthesis of phospholipids and triacylglycerol (TAG). We now show that expression of the Trypanosoma brucei lipin homolog TbLpn is essential for parasite survival in culture. Inducible down-regulation of TbLpn in T. brucei procyclic forms increased cellular PA content, decreased the numbers of lipid droplets, reduced TAG steady-state levels and inhibited in vivo [3 H]TAG formation after labeling trypanosomes with [3 H]glycerol...
April 21, 2018: Molecular Microbiology
Patrick Videau, Orion S Rivers, Sasa K Tom, Reid T Oshiro, Blake Ushijima, Vaille A Swenson, Benjamin Philmus, Michael O Gaylor, Loralyn M Cozy
Multicellular development requires the careful orchestration of gene expression to correctly create and position specialized cells. In the filamentous cyanobacterium Anabaena sp. strain PCC 7120, nitrogen-fixing heterocysts are differentiated from vegetative cells in a reproducibly periodic, and physiologically relevant pattern. While many genetic factors required for heterocyst development have been identified, the role of HetZ has remained unclear. Here we present evidence to clarify the requirement of hetZ for heterocyst production and support a model where HetZ functions in the patterning stage of differentiation...
April 20, 2018: Molecular Microbiology
Todd A Gray, Keith M Derbyshire
This review discusses a novel form of horizontal gene transfer (HGT) found in mycobacteria called Distributive Conjugal Transfer (DCT). While satisfying the criteria for conjugation, DCT occurs by a mechanism so distinct from oriT-mediated conjugation that it could be considered a fourth category of HGT. DCT involves the transfer of chromosomal DNA between mycobacteria and, most significantly, generates transconjugants with mosaic genomes of the parental strains. Multiple segments of donor chromosomal DNA can be co-transferred regardless of their location or the genetic selection and, as a result, the transconjugant genome contains many donor-derived segments; hence the name DCT...
April 18, 2018: Molecular Microbiology
Prosenjit Pyne, Masrure Alam, Moidu Jameela Rameez, Subhrangshu Mandal, Abhijit Sar, Nibendu Mondal, Utsab Debnath, Boby Mathew, Anup Kumar Misra, Amit Kumar Mandal, Wriddhiman Ghosh
The SoxXAYZB(CD)2 -mediated pathway of bacterial sulfur-chemolithotrophy explains the oxidation of thiosulfate, sulfide, sulfur and sulfite, but not tetrathionate. Advenella kashmirensis, which oxidizes tetrathionate to sulfate, besides forming it as an intermediate during thiosulfate-oxidation, possesses a soxCDYZAXOB operon. Knock-out-mutations proved that only SoxBCD is involved in A. kashmirensis tetrathionate-oxidation, whereas thiosulfate-to-tetrathionate-conversion is Sox-independent. Expression of two glutathione-metabolism-related proteins increased under chemolithotrophic conditions, as compared to the chemoorganotrophic one...
April 18, 2018: Molecular Microbiology
Irina Laczkovich, Wei Ping Teoh, Sarah Flury, James P Grayczyk, Azul Zorzoli, Francis Alonzo
Lipoic acid is a cofactor required for intermediary metabolism that is either synthesized de novo or acquired from environmental sources. The bacterial pathogen Staphylococcus aureus encodes enzymes required for de novo biosynthesis, but also encodes two ligases, LplA1 and LplA2, that are sufficient for lipoic acid salvage during infection. S. aureus also encodes two H proteins, GcvH of the glycine cleavage system and the homologous GcvH-L encoded in an operon with LplA2. GcvH is a recognized conduit for lipoyl transfer to α-ketoacid dehydrogenase E2 subunits, while the function of GcvH-L remains unclear...
April 16, 2018: Molecular Microbiology
Mario Mergelsberg, Valentin Egle, Matthias Boll
Xenobiotic phthalates are industrially produced on the annual million ton scale. The oxygen-independent enzymatic reactions involved in anaerobic phthalate degradation have only recently been elucidated. In vitro assays suggested that phthalate is first activated to phthaloyl-CoA followed by decarboxylation to benzoyl-CoA. Here, we report the heterologous production and characterization of the enzyme initiating anaerobic phthalate degradation from 'Aromatoleum aromaticum': a highly specific succinyl-CoA:phthalate CoA transferase (SPT, class III CoA transferase)...
April 12, 2018: Molecular Microbiology
Michael P Prunty, David Noone, Kevin M Devine
The PhoPR-mediated response to phosphate limitation (PHO response) in Bacillus subtilis subsp subtilis is amplified and maintained by reducing the level of Lipid VG composed of poly(glycerol phosphate), a wall teichoic acid (WTA) biosynthetic intermediate that inhibits PhoR autokinase activity. However, the reduction in Lipid VG level is effected by activated PhoP∼P, raising the question of how the PHO response is first initiated. Furthermore, that WTA is composed of poly(ribitol phosphate) in Bacillus subtilis subsp spizizenii prompted an investigation of how the PHO response is regulated in that bacterium...
April 12, 2018: Molecular Microbiology
Daniel J Kosman
Most fungi express two transcription factors that regulate the expression of genes associated with copper uptake for nutritional needs, and with copper resistance when copper approaches a cytotoxic level. These factors are characterized by cysteine-rich motifs which are associated with copper-sensing, DNA-binding and release, and/or cytoplasmic retention. Cryptococcus neoformans differs from most in that it expresses a single such copper-sensing trans-factor, Cuf1, a protein that up-regulates copper uptake when copper is scarce, and up-regulates copper sequestration when cells become super-replete...
April 6, 2018: Molecular Microbiology
Jun-Jie Zhang, Wei-Lin Hu, Youyun Yang, Hongxia Li, Mathieu Picardeau, Jie Yan, X Frank Yang
Leptospira spp. comprise both pathogenic and free-living saprophytic species. Little is known about the environmental adaptation and survival mechanisms of Leptospira. Alternative sigma factor, σ54 (RpoN) is known to play an important role in environmental and host adaptation in many bacteria. In this study, we constructed an rpoN mutant by allele exchange, and the complemented strain in saprophytic L. biflexa. Transcriptome analysis revealed that expression of several genes involved in nitrogen uptake and metabolism, including amtB1, glnB-amtB2, ntrX, and narK, were controlled by σ54 ...
April 6, 2018: Molecular Microbiology
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