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Naji Al Ibrahim, Jeffrey Green
The Escherichia coli K-12 ydhY-T operon, coding for a predicted oxidoreductase complex, is activated under anaerobic conditions and repressed in the presence of nitrate or nitrite. Anaerobic activation is mediated by the transcription factor FNR and nitrate/nitrite repression is mediated by NarXL and NarQP. In vitro transcription reactions revealed that the DNA upstream of ydhY-T contains sufficient information for RNA polymerase alone to initiate transcription from five locations. FNR severely inhibited synthesis of two of these transcripts (located upstream of, and within, the FNR binding site) and activated the FNR-dependent promoter previously identified in vivo...
February 3, 2017: Microbiology
Teal Furnholm, Medhat Rehan, Jessica Wishart, Louis S Tisa
Several Frankia strains have been shown to be lead-resistant. The mechanism of lead resistance was investigated for Frankia sp. strain EAN1pec. Analysis of the cultures by SEM, EDAX, and FTIR demonstrated that Frankia sp. strain EAN1pec undergoes surface modifications and binds high quantities of Pb2+. Both labeled and un-labeled shotgun proteomics approaches were used to determine changes in Frankia sp. strain EAN1pec protein expression in response to lead and zinc. Pb2+ specifically induced changes in exopolysaccharides, the stringent response, and the phosphate (pho) regulon...
January 28, 2017: Microbiology
Sintu Samanta, Albel Singh, Priyanka Biswas, Apoorva Bhatt, Sandhya Visweswariah
The mycobacterial cell envelope is unique in its chemical composition, and has an important role to play in pathogenesis. Phthiocerol dimycocerosates (PDIMs) and glycosylated phenolphthiocerol dimycocerosates, also known as phenolic glycolipids (PGLs), contribute significantly to the virulence of M. tuberculosis. FadD22 is essential for PGL biosynthesis. We have recently shown in vitro that FadD22 is a substrate for lysine acylation by a unique cAMP-dependent, protein lysine acyl transferase found only in mycobacteria...
January 28, 2017: Microbiology
Ann-Mette Meisner Hviid, Peter Rudahl Jensen, Mogens Kilstrup
Lactic acid bacteria currently used extensively by the dairy industry have a superior tolerance towards small chain alcohols, which makes them interesting targets for use in future bio-refineries. The mechanism underlying the alcohol tolerance of lactic acid bacteria has so far received little attention. In the present study the physiological alcohol stress response of Lactococcus lactis subsp. cremoris MG1363 towards the primary, even-chain alcohols; ethanol, butanol, and hexanol was characterized. The alcohol tolerance of L...
January 28, 2017: Microbiology
Richard N Besingi, Iwona B Wenderska, Dilani B Senadheera, Dennis G Cvitkovitch, Joanna R Long, Zezhang T Wen, L Jeannine Brady
Amyloids have been identified as functional components of the extracellular matrix of bacterial biofilms. Streptococcus mutans is an established etiologic agent of dental caries and biofilm dweller. In addition to the previously identified amyloidogenic adhesin P1 (aka AgI/II, PAc), we show that the naturally occurring Antigen A derivative of S. mutans wall-associated protein A (WapA), and the secreted protein SMU_63c, can also form amyloid fibrils. P1, WapA and SMU_63c were found to significantly influence biofilm development and architecture, and all three proteins were shown by immunogold electron microscopy to reside within fibrillar extracellular matrix of the biofilms...
January 28, 2017: Microbiology
Kathrin Baumgardt, Hendrik Melior, Ramakanth Madhugiri, Sebastian Thalmann, Adam Schikora, Matthew McIntosh, Anke Becker, Elena Evguenieva-Hackenberg
The ribonucleases (RNases) E and J play major roles in Escherichia coli and Bacillus subtilis, respectively, and co-exist in Sinorhizobium meliloti. We analyzed S. meliloti 2011 mutants with mini-Tn5 insertions in the corresponding genes rne and rnj and found many overlapping effects. We observed similar changes in mRNA levels including lower mRNA levels of the motility and chemotaxis related genes flaA, flgB, and cheR and higher levels of ndvA (important for glucan export). The acyl-homoserine lactone (AHL) levels were also higher during exponential growth in both RNase mutants, despite no increase in the expression of the sinI AHL synthase gene...
January 28, 2017: Microbiology
Fabien Labroussaa, Michael Ionescu, Adam Zeilinger, Steven Lindow, Rodrigo Almeida
Xylella fastidiosa colonizes the xylem network of host plant species as well as the foregut of required insect vectors to ensure its efficient propagation. Disease management strategies remain inefficient due to a limited comprehension of mechanisms governing both insect and plant colonization. It was previously shown that X. fastidiosa has a functional chitinase (ChiA), and that chitin likely serves as a carbon source for this bacterium. We expand on that research showing that a chiA mutant strain is unable to grow on chitin as the sole carbon source...
January 28, 2017: Microbiology
Junho Cho, Anita Carr, Lisa Whitworth, Brent Johnson, Kevin Scott Wilson
When exposed to antibiotics, many bacteria respond by activating intracellular "toxin" proteins, which arrest cell growth and induce formation of persister cells that survive antibiotics. After antibiotics are removed, persisters can regrow by synthesizing "antitoxin" proteins that sequester toxin proteins. In E. coli, MazE antitoxin sequesters the activity of MazF toxin, which extensively cleaves cellular RNAs. Although the functions of MazEF proteins are well characterized, there is surprisingly little known about their effects on cell structure...
January 22, 2017: Microbiology
Rodney Honrada Perez, Haruki Sugino, Naoki Ishibashi, Takeshi Zendo, Pongtep Wilaipun, Vichien Leelawatcharamas, Jiro Nakayama, Kenji Sonomoto
Enterocin NKR-5-3B is a 64-residue novel circular bacteriocin synthesized from an 87-residue prepeptide. Albeit through a still unknown mechanism, the EnkB1234 biosynthetic enzyme complex processes the prepeptide to yield its mature active, circular form. To gain insights into the key region/residue that plays a role in Ent53 maturation, several mutations near the cleavage site on the precursor peptide were generated. The interaction of the precursor peptide and EnkB1234 appeared to be hydrophobic in nature...
January 22, 2017: Microbiology
Rajendra Kc, Shakti D Shukla, Eugene H Walters, Ronan F O'Toole
Host surface receptors provide bacteria with a foothold from which to attach, colonize and in some cases, invade tissue and elicit human disease. In this review, we discuss several key host receptors and cognate adhesins that function in bacterial pathogenesis. In particular, we examine the elevated expression of host surface receptors such as CEACAM-1, CEACAM-6, ICAM-1 and PAFR in response to specific stimuli. We explore how upregulated receptors, in turn, expose the host to a range of bacterial infections in the respiratory tract...
January 22, 2017: Microbiology
Marina Stanić, Strahinja Križak, Mirna Jovanović, Tanja Pajić, Ana Ćirić, Milan Žižić, Joanna Zakrzewska, Tijana Cvetić Antić, Nataša Todorović, Miroslav Živić
Increasing resistance of fungal strains to known fungicides has prompted identification of new candidates for fungicides among substances previously used for other purposes. We have tested the effects of known anion channel inhibitors anthracene-9-carboxylic (A9C) and niflumic acid (NFA) on growth, energy metabolism and anionic current of mycelium of fungus Phycomyces blakesleeanus. Both inhibitors significantly decreased growth and respiration of mycelium, but complete inhibition was only achieved by 100 or 500 µM NFA, for growth and respiration, respectively...
January 18, 2017: Microbiology
Liliana Soto-Castro, Laura Yuliana Plata-Guzman, Elisa Elvira Figueroa-Angulo, Jaeson Calla-Choque, Magda Reyes-Lopez, Mireya DE LA Garza, Nidia Leon-Sicairos, Jose Antonio Garzon-Tiznado, Rossana Arroyo, Claudia Leon-Sicairos
In Entamoeba histolytica, iron modulates virulence and gene expression via unknown regulatory mechanisms. The existence of a posttranscriptional iron regulatory system parallel to the IRE/IRP (Iron-Responsive Element/Iron Regulatory Protein) system in the protozoan Trichomonas vaginalis has recently been reported. Due to their evolutionary closeness and the importance of iron for growth and virulence in these protozoa, we hypothesized the existence of an IRE/IRP-like mechanism in E. histolytica. To determine the presence of IRE-like elements in some mRNAs from this parasite, we performed in silico analyses of the 5'- and 3'-UTRs of mRNAs encoding virulence factors and cytoskeleton, ribosomal, and metabolism proteins...
January 18, 2017: Microbiology
Nadin Pade, Stefan Mikkat, Martin Hagemann
Cyanobacteria are photoautotrophic microorganisms, which are increasingly being used as microbial cell factories to produce for example ethanol directly from solar energy and CO2. Here we analyzed the effects of different salt concentrations on an ethanol-producing strain of Synechocystis sp. PCC 6803 that over-expresses the pyruvate decarboxylase (pdc) from Zymomonas mobilis and the native alcohol dehydrogenase (adhA). Moderate salinities of 2% NaCl had no negative impact on ethanol production, whereas the addition of 4% NaCl resulted in significantly decreased ethanol yields compared to low salt conditions...
January 18, 2017: Microbiology
Johanna J Kenyon, Anastasiya A Kasimova, Mikhail Shneider, Alexander S Shashkov, Nikolay P Arbatsky, Anastasiya V Popova, Konstantin A Miroshnikov, Ruth M Hall, Yuriy A Knirel
The whole genome sequence of the multiply antibiotic resistant Acinetobacter baumannii isolate RCH51 belonging to sequence type ST103 (Institut Pasteur scheme) revealed that the set of genes at the capsule locus, KL24, includes four genes predicted to direct the synthesis of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc) and this sugar was found in the capsular polysaccharide (CPS). One of these genes, fdtE, encodes a novel bifunctional protein with an N-terminal FdtA 3,4-ketoisomerase domain and a C-terminal acetyltransferase domain...
January 17, 2017: Microbiology
Zhongge Zhang, Chika Kukita, Mir Zafri Humayun, Milton H Saier
The flagellar system in E. coli K12 is expressed under the control of the flhDC-encoded master regulator, FlhDC. Transposition of insertion sequence (IS) elements to the upstream flhDC promoter region up-regulates transcription of this operon, resulting in more rapid motility. Wang and Wood (2011) provided evidence that insertion of IS5 into upstream activating sites occurs at higher rates in semisolid agar media in which swarming behavior is allowed as compared with liquid or solid media where swarming cannot occur...
January 17, 2017: Microbiology
Su San Toh, Zehua Chen, David J Schultz, Christina A Cuomo, Michael H Perlin
Microbotryum lychnidis-dioicae is an obligate biotrophic parasite of the wildflower species, Silene latifolia. This dikaryotic fungus, commonly known as an anther smut, requires that haploid, yeast-like sporidia of opposite mating types fuse and differentiate into dikaryotic hyphae that penetrate host tissue as part of the fungal lifecycle. Mating occurs under conditions of cool temperatures and limited nutrients. Further development requires host cues or chemical mimics, including a variety of lipids, e.g...
January 17, 2017: Microbiology
Melissa Jamerson, Jacqueline A Schmoyer, Jay Park, Francine Marciano-Cabral, Guy Cabral
Naegleria fowleri (N. fowleri) causes Primary Amebic Meningoencephalitis (PAM), a rapidly fatal disease of the central nervous system (CNS). This opportunistic pathogen can exist in cyst, flagellate, or amebic forms, depending on environmental conditions. The amebic form can invade the brain following introduction into the nasal passages. When applied intranasally to a mouse model, cultured N. fowleri amebae exhibit low virulence. However, upon serial passage in mouse brain the amebae acquire a highly virulent state...
January 12, 2017: Microbiology
Ping Jiang, Wen-Fan Wei, Guo-Wei Zhong, Xiao-Gang Zhou, Wei-Ran Qiao, Ling Lu
Phosphoribosyl pyrophosphate synthetase, which is encoded by the Prs gene, catalyzes the reaction of ribose-5-phosphate and adenine ribonucleotide triphosphate (ATP) and has central importance in cellular metabolism. However, knowledge about how Prs family members function and contribute to total PRPP synthetase activity is limited. In this study, we identified that the filamentous fungus Aspergillus nidulans genome contains three 5-phosphoribosyl-α-1-pyrophosphate (PRPP) synthase-homologous genes (AnprsA, B, and C), among which AnprsB and AnprsC but not AnprsA are auxotrophic genes...
January 12, 2017: Microbiology
David Smith, Manuela da Silva, Julian Jackson, Christopher Lyal
Working with genetic resources and associated data requires greater attention since the Nagoya Protocol on Access and Benefit Sharing came into force in October 2014. Biologists must ensure that they have legal clarity in how they can and cannot use the genetic resources on which they carry out research. Not only must they work within the spirit in the Convention for Biological Diversity (CBD) but may also have regulatory requirements to meet. Access legislation is in place in many countries and information on this can be found at the ABS Clearing House (https://absch...
January 12, 2017: Microbiology
José S Dávila Costa, Roxana A Silva, Lars Leichert, Héctor M Alvarez
Rhodococcus jostii RHA1 is able to degrade toxic compounds and accumulate high amount of triacylglycerols (TAG) upon nitrogen starvation. These NADPH-dependent processes are essential for the adaptation of rhodococci to fluctuating environmental conditions. In this study, we used a mass spectrometry (MS)-based, label-free, and quantitative proteomic approach to better understand the integral response of R. jostii RHA1 to the presence of methyl viologen (MV) in relation with the synthesis and accumulation of TAG...
January 10, 2017: Microbiology
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