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Molecular Microbiology

Alexander J F Egan
The outer membrane of Gram-negative bacteria is a crucial permeability barrier allowing the cells to survive a myriad of toxic compounds, including many antibiotics. This innate form of antibiotic resistance is compounded by the evolution of more active mechanisms of resistance such as efflux pumps, reducing the already limited number of clinically relevant treatments for Gram-negative pathogens. During cell division Gram-negative bacteria must coordinate constriction of the outer membrane in conjunction with other crucial layers of the cell envelope, the peptidoglycan cell wall and the inner membrane...
January 8, 2018: Molecular Microbiology
Nao Yokoyama, Chihiro Nonaka, Yukari Ohashi, Masaharu Shioda, Takuya Terahata, Wen Chen, Kotomi Sakamoto, Chihiro Maruyama, Takuya Saito, Eiki Yuda, Naoyuki Tanaka, Takashi Fujishiro, Tomohisa Kuzuyama, Kei Asai, Yasuhiro Takahashi
The biosynthesis of iron-sulfur (Fe-S) clusters in Bacillus subtilis is mediated by the SUF-like system composed of the sufCDSUB gene products. This system is unique in that it is a chimeric machinery comprising homologs of E. coli SUF components (SufS, SufB, SufC, and SufD) and an ISC component (IscU). B. subtilis SufS cysteine desulfurase transfers persulfide sulfur to SufU (the IscU homolog); however, it has remained controversial whether SufU serves as a scaffold for Fe-S cluster assembly, like IscU, or acts as a sulfur shuttle protein, like E...
January 2, 2018: Molecular Microbiology
Joseph Conti, Marissa G Viola, Jodi L Camberg
Cell division in prokaryotes initiates with assembly of the Z-ring at midcell, which, in Escherichia coli, is tethered to the inner leaflet of the cytoplasmic membrane through a direct interaction with FtsA, a widely conserved actin homolog. The Z-ring is comprised of polymers of tubulin-like FtsZ and has been suggested to provide the force for constriction. Here, we demonstrate that FtsA exerts force on membranes causing redistribution of membrane architecture, robustly hydrolyzes ATP and directly engages FtsZ polymers in a reconstituted system...
December 27, 2017: Molecular Microbiology
Tatyana Romantsov, Karen Gonzalez, Naheda Sahtout, Doreen E Culham, Chelsea Coumoundouros, Jennifer Garner, Craig H Kerr, Limei Chang, Raymond J Turner, Janet M Wood
Osmosensing by transporter ProP is modulated by its cardiolipin (CL)-dependent concentration at the poles of Escherichia coli cells. Other contributors to this phenomenon were sought with the BACterial Two-Hybrid System (BACTH). The BACTH-tagged variants T18-ProP and T25-ProP retained ProP function and localization. Their interaction confirmed the ProP homo-dimerization previously established by protein crosslinking. YdhP, YjbJ and ClsA were prominent among the putative ProP interactors identified by the BACTH system...
December 27, 2017: Molecular Microbiology
Lotte Lambertsen, Anna Rubio-Cosials, Kiran Raosaheb Patil, Orsolya Barabas
Rapid spread of resistance to vancomycin has generated difficult to treat bacterial pathogens worldwide. Though vancomycin resistance is often conferred by the conjugative transposon Tn1549, it is yet unclear whether Tn1549 moves actively between bacteria. Here we demonstrate, through development of an in vivo assay system, that a mini-Tn1549 can transpose in E. coli away from its natural Gram-positive host. We find the transposon-encoded INT enzyme and its catalytic tyrosine Y380 to be essential for transposition...
December 22, 2017: Molecular Microbiology
Daniel F Rojas-Tapias, John D Helmann
The transcription factor Spx is the master regulator of the disulfide stress response in Bacillus subtilis. Intriguingly, the activation of Spx by diamide relies entirely on posttranslational regulatory events in spite of the complex transcriptional control of the spx gene. Here, we show that cell wall stress, but not membrane stress, also results in induction of the Spx regulon. Remarkably, two major differences were found regarding the mechanism of induction of Spx under cell wall stress in comparison to disulfide stress...
December 22, 2017: Molecular Microbiology
Anne Buddeweg, Kundan Sharma, Henning Urlaub, Ruth A Schmitz
Several non-coding RNAs potentially involved in nitrogen (N)-regulation have been detected in Methanosarcina mazei, however, targets have been identified only for one of them. Here, we report on the function of sRNA41 , highly expressed under N-sufficiency. Comprising 120 nucleotides, sRNA41 shows high sequence and structural conservation within draft genomes of numerous Methanosarcina species. In silico target prediction revealed several potential targets, including genes of two homologous operons encoding for acetyl-CoA-decarbonylase/synthase complexes (ACDS) representing highly probable target candidates...
December 22, 2017: Molecular Microbiology
Andrew D Blake, Nina R Beri, Hadassa S Guttman, Raymond Cheng, Jeffrey G Gardner
Lignocellulose degradation by microbes plays a central role in global carbon cycling, human gut metabolism, and renewable energy technologies. While considerable effort has been put into understanding the biochemical aspects of lignocellulose degradation, much less work has been done to understand how these enzymes work in an in vivo context. Here, we report a systems level study of xylan degradation in the saprophytic bacterium Cellvibrio japonicus. Transcriptome analysis indicated seven genes that encode carbohydrate active enzymes were up-regulated during growth with xylan containing media...
December 21, 2017: Molecular Microbiology
Chelsey M VanDrisse, Jorge C Escalante-Semerena
Protein acetylation is a rapid mechanism for control of protein function. Acetyl-CoA synthetase (AMP-forming, Acs) is the paradigm for the control of metabolic enzymes by lysine acetylation. In many bacteria, type I or II protein acetyltransferases acetylate Acs, however, in actinomycetes type III protein acetyltransferases control the activity of Acs. We measured changes in the activity of the Streptomyces lividans Acs (SlAcs) enzyme upon acetylation by PatB using in vitro and in vivo analyses. In addition to the acetylation of residue K610, residue S608 within the acetylation motif of SlAcs was also acetylated (PKTRSGK610 )...
December 20, 2017: Molecular Microbiology
René Uebe, Noa Keren-Khadmy, Natalie Zeytuni, Emanuel Katzmann, Yotam Navon, Geula Davidov, Ronit Bitton, Jürgen M Plitzko, Dirk Schüler, Raz Zarivach
Magnetospirillum gryphiswaldense MSR-1 synthesizes membrane-enclosed magnetite (Fe3 O4 ) nanoparticles, magnetosomes, for magnetotaxis. Formation of these organelles involves a complex process comprising key steps which are governed by specific magnetosome-associated proteins. MamB, a cation diffusion facilitator (CDF) family member has been implicated in magnetosome-directed iron transport. However, deletion mutagenesis studies revealed that MamB is essential for the formation of magnetosome membrane vesicles, but its precise role remains elusive...
December 15, 2017: Molecular Microbiology
Vinaya Sampath, William D McCaig, David G Thanassi
Francisella tularensis is a highly virulent Gram-negative bacterial pathogen that causes the zoonotic disease tularemia. F. novicida, a model tularemia strain, produces spherical outer membrane vesicles (OMV), as well as novel tubular vesicles and extensions of the cell surface. These OMV and tubes (OMV/T) are produced in a regulated manner and contain known virulence factors. Mechanisms by which bacterial vesicles are produced and regulated are not well understood. We performed a genetic screen in F. novicida to decipher the molecular basis for regulated OMV/T formation, and identified both hypo- and hyper-vesiculating mutants...
December 14, 2017: Molecular Microbiology
Pranav Chettri, Pierre-Yves Dupont, Rosie E Bradshaw
Genes required for fungal secondary metabolite production are usually clustered, co-regulated and expressed in stationary growth phase. Chromatin modification has an important role in co-regulation of secondary metabolite genes. The virulence factor dothistromin, a relative of aflatoxin, provided a unique opportunity to study chromatin level regulation in a highly fragmented gene cluster that is switched on during early exponential growth phase. We analysed three histone modification marks by ChIP-qPCR and gene deletion in the pine pathogen Dothistroma septosporum to determine their effects on dothistromin gene expression across a time course and at different loci of the dispersed gene cluster...
December 14, 2017: Molecular Microbiology
Michelle R Gibbs, Kurt Fredrick
Protein synthesis relies on several translational GTPases (trGTPases), related proteins that couple the hydrolysis of GTP to specific molecular events on the ribosome. Most bacterial trGTPases, including IF2, EF-Tu, EF-G, and RF3, play well-known roles in translation. The cellular functions of LepA (also termed EF4) and BipA (also termed TypA), on the other hand, have remained enigmatic. Recent studies provide compelling in vivo evidence that LepA and BipA function in biogenesis of the 30S and 50S subunit, respectively...
December 13, 2017: Molecular Microbiology
Matthias Kretschmer, Scott Lambie, Daniel Croll, James W Kronstad
The fungal pathogen Ustilago maydis causes disease on maize by mating to establish an infectious filamentous cell type that invades the host and induces tumours. We previously found that β-oxidation mutants were defective in virulence and did not grow on acetate. Here we demonstrate that acetate inhibits filamentation during mating and in response to oleic acid. We therefore examined the influence of different carbon sources by comparing the transcriptomes of cells grown on acetate, oleic acid or glucose, with expression changes for the fungus during tumour formation in planta...
December 13, 2017: Molecular Microbiology
Elisabeth Grohmann, Peter J Christie, Gabriel Waksman, Steffen Backert
Type IV secretion systems (T4SSs) are versatile multiprotein nanomachines spanning the entire bacterial cell envelope in Gram-negative and Gram-positive bacteria. They play important roles through the contact-dependent secretion of effector molecules into eukaryotic hosts and conjugative transfer of mobile DNA elements as well as contact-independent exchange of DNA with the extracellular milieu. In the last few years, many details on the molecular mechanisms of T4SSs have been elucidated. Exciting structures of T4SS complexes from Escherichia coli plasmids R388 and pKM101, Helicobacter pylori and Legionella pneumophila have been solved...
December 13, 2017: Molecular Microbiology
Yutaro Yamaguchi, Yuka Katsuki, Seiya Tanaka, Ryotaro Kawaguchi, Hiroto Denda, Takuma Ikeda, Kouichi Funato, Motohiro Tani
Complex sphingolipids play critical roles in various cellular events in the yeast Saccharomyces cerevisiae. To identify genes that are related to the growth defect caused by disruption of complex sphingolipid biosynthesis, we screened for suppressor mutations and multicopy suppressor genes that confer resistance against repression of AUR1 encoding inositol phosphorylceramide synthase. From the results of this screening, we found that the activation of high-osmolarity glycerol (HOG) pathway is involved in suppression of growth defect caused by impaired biosynthesis of complex sphingolipids...
December 7, 2017: Molecular Microbiology
Jeanine Rismondo, Sabrina Wamp, Christine Aldridge, Waldemar Vollmer, Sven Halbedel
Listeria monocytogenes and other pathogenic bacteria modify their peptidoglycan to protect it against enzymatic attack through the host innate immune system, such as the cell wall hydrolase lysozyme. During our studies on GpsB, a late cell division protein that controls activity of the bi-functional penicillin binding protein PBP A1, we discovered that GpsB influences lysozyme resistance of L. monocytogenes. Mutant strains lacking gpsB were prone to spontaneous autolysis but showed an increased lysozyme resistance...
December 7, 2017: Molecular Microbiology
Lindsay M Wright, Emily M Carpinone, Terry L Bennett, Mary K Hondalus, Vincent J Starai
Rhodococcus equi is a multi-host, facultative intracellular bacterial pathogen that primarily causes pneumonia in foals less than six months in age and immunocompromised people. Previous studies determined that the major virulence determinant of R. equi is the surface bound virulence associated protein A (VapA). The presence of VapA inhibits the maturation of R. equi-containing phagosomes and promotes intracellular bacterial survival, as determined by the inability of vapA deletion mutants to replicate in host macrophages...
December 4, 2017: Molecular Microbiology
Cécile Muller, Sébastien Massier, Yoann Le Breton, Alain Rincé
Enterococcus faecalis is an opportunistic multidrug-resistant human pathogen causing severe nosocomial infections. Previous investigations revealed that the CroRS two-component regulatory pathway likely displays a pleiotropic role in E. faecalis, involved in virulence, macrophage survival, oxidative stress response as well as antibiotic resistance. Therefore, CroRS represents an attractive potential new target for antibiotherapy. In this report, we further explored CroRS cellular functions by characterizing the CroR regulon: the "domain swapping" method was applied and a CroR chimera protein was generated by fusing the receiver domain from NisR to the output domain from CroR...
December 4, 2017: Molecular Microbiology
Ján Burian, Charles J Thompson
Diseases caused by various Mycobacterium sp., especially Mycobacterium tuberculosis, are a major burden on global health care. Due to high intrinsic antibiotic resistance, treatment options are severely limited. In mycobacteria, WhiB7 coordinates intrinsic resistance to a broad range of antibiotics. While WhiB7 has been established as an auto-regulatory transcriptional activator, the signals and genes needed to induce its expression are poorly understood. Using Mycobacterium smegmatis as a model, we coupled transposon mutagenesis and next generation sequencing with WhiB7-specific antibiotic selection to identify genes that contribute to WhiB7 regulation and function...
December 4, 2017: Molecular Microbiology
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