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Molecular Microbiology

Hendrik Szurmant
The genomic era along with major advances in high-throughput sequencing technology has led to a rapid expansion of the genomic and consequently the protein sequence space. Bacterial extracytoplasmic function sigma factors have emerged as an important group of signaling proteins in bacteria involved in many regulatory decisions, most notably the adaptation to cell envelope stress. Their wide prevalence and amplification among bacterial genomes has led to sub-group classification and the realization of diverse signaling mechanisms...
May 18, 2019: Molecular Microbiology
Ronan R McCarthy, Manda Yu, Kira Eilers, Yi-Chieh Wang, Erh-Min Lai, Alain Filloux
The Type VI secretion system (T6SS) is a bacterial nanomachine that delivers effector proteins into prokaryotic and eukaryotic preys. This secretion system has emerged as a key player in regulating the microbial diversity in a population. In the plant pathogen Agrobacterium tumefaciens the signalling cascades regulating the activity of this secretion system are poorly understood. Here we outline how the universal eubacterial second messenger cyclic di-GMP impacts the production of T6SS toxins and T6SS structural components...
May 18, 2019: Molecular Microbiology
Rachel M Burckhardt, Brandi A Buckner, Jorge C Escalante-Semerena
Lysine acylation is a posttranslational modification (PTM) used by cells of all domains of life to modulate cellular processes in response to metabolic stress. The paradigm for the role of lysine acylation in metabolism is the acetyl-coenzyme A synthetase (Acs) enzyme. In prokaryotic and eukaryotic cells alike, Acs activity is down regulated by acetylation, and reactivated by deacetylation. Proteins belonging to the bacterial GCN5-related N-acetyltransferase (bGNAT) superfamily acetylate the epsilon amino group of an active site lysine, inactivating Acs...
May 17, 2019: Molecular Microbiology
José A Vázquez-Boland, Wim G Meijer
Rhodococcus equi is the only animal pathogenic species within an extended genus of metabolically versatile Actinobacteria of considerable biotechnological interest. Best known as a horse pathogen, R. equi is commonly isolated from other animal species, particularly pigs and ruminants, and causes severe opportunistic infections in people. As typical in the rhodococci, R. equi niche specialization is extrachromosomally determined, via a virulence plasmid that promotes intramacrophage survival. Progress in the molecular understanding of R...
May 17, 2019: Molecular Microbiology
Neha Varshney, Kaustuv Sanyal
Candida albicans, an ascomycete, has an ability to switch to diverse morphological forms. While C. albicans is predominatly diploid, it can tolerate aneuploidy as a survival strategy under stress. Aurora kinase B homolog Ipl1 is a critical ploidy regulator that controls microtubule dynamics and chromosome segregation in Saccharomyces cerevisiae. In this study, we show that Ipl1 in C. albicans has a longer activation loop than that of the well-studied ascomycete S. cerevisiae. Ipl1 localizes to the kinetochores during the G1/S phase and associates with the spindle during mitosis...
May 16, 2019: Molecular Microbiology
Martina Stöckli, Brandon I Morinaka, Gerald Lackner, Anja Kombrink, Ramon Sieber, Céline Margot, Claire E Stanley, Andrew J deMello, Jörn Piel, Markus Künzler
Fungi defend their ecological niche against antagonists by producing antibiosis molecules. Some of these molecules are only produced upon confrontation with the antagonist. The basidiomycete Coprinopsis cinerea induces the expression of the sesquiterpene synthase-encoding gene cop6 and its two neighboring genes coding for cytochrome P450 monooxygenases in response to bacteria. We further investigated this regulation of cop6 and examined if the gene product is involved in the production of antibacterials. Cell-free supernatants of axenic cultures of the Gram-positive bacterium Bacillus subtilis were sufficient to induce cop6 transcription assessed using a fluorescent reporter strain...
May 14, 2019: Molecular Microbiology
Deborah Gore-Lloyd, Inés Sumann, Alexander O Brachmann, Kerstin Schneeberger, Raúl A Ortiz-Merino, Mauro Moreno-Beltrán, Michael Schläfli, Pascal Kirner, Amanda Santos Kron, Maria Paula Rueda-Mejia, Vincent Somerville, Kenneth H Wolfe, Jörn Piel, Christian H Ahrens, Daniel Henk, Florian M Freimoser
Metschnikowia pulcherrima synthesizes the pigment pulcherrimin, from cyclodileucine (cyclo(Leu-Leu)) as a precursor, and exhibits strong antifungal activity against notorious plant pathogenic fungi. This yeast therefore has great potential for biocontrol applications against fungal diseases; particularly in the phyllosphere where this species is frequently found. To elucidate the molecular basis of the antifungal activity of M. pulcherrima, we compared a wildtype strain with a spontaneously occurring, pigmentless, weakly antagonistic mutant derivative...
May 12, 2019: Molecular Microbiology
Niles P Donegan, Adhar C Manna, Ching Wen Tseng, George Y Liu, Ambrose L Cheung
Staphyloxanthin, a carotenoid in S. aureus, is a powerful antioxidant against oxidative stresses. The crtOPQMN operon driving pigment synthesis is under the control of σB . CspA, a cold-shock protein, is known to control σB activity. To ascertain genes that regulate cspA, we screened a transposon library that exhibited reduced cspA expression and pigmentation. We found that the adaptor protein YjbH activates cspA expression. Spx, the redox-sensitive transcriptional regulator and a proteolytic target for YjbH and ClpXP, complexes with αCTD of RNAP prior to binding the cspA promoter to repress cspA activity...
May 10, 2019: Molecular Microbiology
Xinhui Wang, Jun Cai, Nan Shang, Lin Zhu, Nana Shao, Xiuzhu Dong, Huichun Tong
Natural transformation increases the genetic diversity of bacteria, but is costly and must be strictly controlled. We previously found that deletion of ccpA, a key regulator of carbon catabolite repression (CCR), reduced transformation efficiency of Streptococcus oligofermentans, the current work further investigated the regulatory mechanisms of CcpA. The competence operon comCDE is subjected to basal and autoregulatory transcription. A luciferase reporter detected a transcriptional readthrough (TRT) from the upstream tRNAA rg into the comCDE operon, which was induced by L -arginine...
May 10, 2019: Molecular Microbiology
Emilisa Frirdich, Jacob Biboy, Mark Pryjma, Jooeun Lee, Steven Huynh, Craig T Parker, Stephen E Girardin, Waldemar Vollmer, Erin C Gaynor
Campylobacter jejuni is a prevalent enteric pathogen that changes morphology from helical to coccoid under unfavorable conditions. Bacterial peptidoglycan maintains cell shape. As C. jejuni transformed from helical to coccoid, peptidoglycan dipeptides increased and tri- and tetrapeptides decreased. The DL-carboxypeptidase Pgp1 important for C. jejuni helical morphology and putative N-acetylmuramoyl-L-alanyl amidase AmiA were both involved in the coccoid transition. Mutants in pgp1 and amiA showed reduced coccoid formation, with ∆pgp1∆amiA producing minimal coccoids...
May 9, 2019: Molecular Microbiology
Natalí B Rasetto, Antonela Lavatelli, Natalia Martin, María Cecilia Mansilla
Lipoate is an essential cofactor for key enzymes of oxidative and one-carbon metabolism. It is covalently attached to E2 subunits of dehydrogenase complexes and GcvH, the H subunit of the glycine cleavage system. Bacillus subtilis possess two protein lipoylation pathways: biosynthesis and scavenging. The former requires octanoylation of GcvH, insertion of sulfur atoms and amidotransfer of the lipoate to E2s, catalyzed by LipL. Lipoate scavenging is mediated by a lipoyl protein ligase (LplJ) that catalyzes a classical two-step ATP-dependent reaction...
May 7, 2019: Molecular Microbiology
Justin Clark, Austen Terwilliger, Chinh Nguyen, Christopher Nobles, Anthony Maresso
A challenge common to all bacterial pathogens is to acquire nutrients from hostile host environments. Iron is an important cofactor required for essential cellular processes such as DNA repair, energy production, and redox balance. Within a mammalian host, most iron is sequestered within heme, which in turn is predominantly bound by hemoglobin. While little is understood about the mechanisms by which bacterial hemophores attain heme from host-hemoglobin, even less is known about intracellular heme processing...
May 7, 2019: Molecular Microbiology
Soyoung Park, Jihee Yoon, Chang-Ro Lee, Ju Yeon Lee, Yeon-Ran Kim, Kyoung-Soon Jang, Kyu-Ho Lee, Yeong-Jae Seok
How motile bacteria recognize their environment and decide whether to stay or navigate toward a more favorable location is a fundamental issue in survival. The flagellum is an elaborate molecular device responsible for bacterial locomotion, and the flagellum-driven motility allows bacteria to move themselves to the appropriate location at the right time. Here, we identify the polar landmark protein HubP as a modulator of polar flagellation that recruits the flagellar assembly protein FapA to the old cell pole, thereby controlling its activity for the early events of flagellar assembly in Vibrio vulnificus...
May 6, 2019: Molecular Microbiology
Matthew A Jorgenson, William J MacCain, Bernadette M Meberg, Suresh Kannan, Joseph C Bryant, Kevin D Young
Peptidoglycan (PG) is a highly cross-linked polysaccharide that encases bacteria, resists the effects of turgor and confers cell shape. PG precursors are translocated across the cytoplasmic membrane by the lipid carrier undecaprenyl phosphate (Und-P) where they are incorporated into the PG superstructure. Previously, we found that one of our Escherichia coli laboratory strains (CS109) harbors a missense mutation in uppS, which encodes an enzymatically defective Und-P(P) synthase. Here, we show that CS109 cells lacking the bifunctional aPBP PBP1B (penicillin binding protein 1B) lyse during exponential growth at elevated temperature...
April 25, 2019: Molecular Microbiology
Oksana Koshla, Oleksandr Yushchuk, Iryna Ostash, Yuriy Dacyuk, Maksym Myronovskyi, Gunilla Jäger, Roderich D Süssmuth, Andriy Luzhetskyy, Anders Byström, Leif A Kirsebom, Bohdan Ostash
Members of actinobacterial genus Streptomyces possess a sophisticated life cycle and are the deepest source of bioactive secondary metabolites. Although morphogenesis and secondary metabolism are subject to transcriptional co-regulation, streptomycetes employ an additional mechanism to initiate the aforementioned processes. This mechanism is based on delayed translation of rare leucyl codon UUA by the only cognate tRNAL eu UAA (encoded by bldA). The bldA-based genetic switch is an extensively documented example of translational regulation in Streptomyces...
April 24, 2019: Molecular Microbiology
Thomas Dubois, Christelle Lemy, Stéphane Perchat, Didier Lereclus
The infectious cycle of Bacillus thuringiensis in the insect host is regulated by quorum sensors of the RRNPP family. The activity of these regulators is modulated by their cognate signaling peptides translocated into the bacterial cells by oligopeptide permeases (Opp systems). In Bacillus thuringiensis, the quorum sensor NprR is a bi-functional regulator that connects sporulation to necrotrophism. The binding of the signaling peptide NprX switches NprR from a dimeric inhibitor of sporulation to a tetrameric transcriptional activator involved in the necrotrophic lifestyle of B...
April 24, 2019: Molecular Microbiology
Beer Chakra Sen, Sebastian Wasserstrom, Kim Findlay, Niklas Söderholm, Linda Sandblad, Claes von Wachenfeldt, Klas Flärdh
Bacterial cell division is orchestrated by the Z ring, which is formed by single-stranded treadmilling protofilaments of FtsZ. In Streptomyces, during sporulation, multiple Z rings are assembled and lead to formation of septa that divide a filamentous hyphal cell into tens of prespore compartments. We describe here mutant alleles of ftsZ in Streptomyces coelicolor and Streptomyces venezuelae that perturb cell division in such a way that constriction is initiated along irregular spiral-shaped paths rather than as regular septa perpendicular to the cell length axis...
April 19, 2019: Molecular Microbiology
Elena K Perry, Dianne K Newman
Bacteria in soils encounter redox-active compounds, such as phenazines, that can generate oxidative stress, but the mechanisms by which different species tolerate these compounds are not fully understood. Here, we identify two transcription factors, ActR and SoxR, that play contrasting yet complementary roles in the tolerance of the soil bacterium Agrobacterium tumefaciens to phenazines. We show that ActR promotes phenazine tolerance by proactively driving expression of a more energy-efficient terminal oxidase at the expense of a less-efficient alternative, which may affect the rate at which phenazines abstract electrons from the electron transport chain and thereby generate reactive oxygen species...
April 19, 2019: Molecular Microbiology
Hao Wu, Qiang Liu, Delia Casas-Pastor, Franziska Dürr, Thorsten Mascher, Georg Fritz
The activity of extracytoplasmic function σ factors (ECFs) is typically regulated by anti-σ factors. In a number of highly abundant ECF groups, including ECF41 and ECF42, σ-factors contain fused C-terminal protein domains, which provide the necessary regulatory function instead. Here, we identified the contact interface between the C-terminal extension and the core σ-factor regions required for controlling ECF activity. We applied direct-coupling analysis (DCA) to infer evolutionary co-variation between contacting amino acid residues for groups ECF41 and ECF42...
April 16, 2019: Molecular Microbiology
Seiya Watanabe, Fumiyasu Fukumori, Yasuo Watanabe
The gene context in microorganism genomes is of considerable help for identifying potential substrates. The C785_RS13685 gene in Herbaspirillum huttiense IAM 15032 is a member of the D-altronate dehydratase protein family, and which functions as a D-arabinonate dehydratase in vitro, is clustered with genes related to putative pentose metabolism. In the present study, further biochemical characterization and gene expression analyses revealed that L-xylonate is a physiological substrate that is ultimately converted to α-ketoglutarate via so-called Route II of a non-phosphorylative pathway...
April 15, 2019: Molecular Microbiology
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