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Eugenio Alcalde, Paul David Fraser
The filamentous fungus Phycomyces blakesleeanus provides a renewable biosource of industrial high value compounds such as carotenes, other isoprenoids (ubiquinone and sterols), organic acids and fatty acids. Several Phycomyces mutants involved in the formation of β-carotene are available. For example the carA mutants have a leaky mutation in the phytoene synthase and produce significantly lower amount of carotenes, while the carB and carR mutants produce phytoene and lycopene respectively, due to a null mutation in the genes encoding the phytoene dehydrogenase and lycopene cyclase respectively...
October 4, 2016: Microbiology
Saeed Banawas, Daniel Paredes-Sabja, Peter Setlow, Mahfuzur R Sarker
Clostridium perfringens type A can cause both food poisoning (FP) and non-food-borne (NFB) gastrointestinal diseases. Our previous study reported that a mixture of L-asparagine and KCl (AK) germinated spores of FP and NFB isolates well, but KCl and, to a lesser extent, L-asparagine induced spore germination only in FP isolates. We now report that the germination response of FP and NFB spores differs significantly in several defined germinants and rich media. Spores of NFB strain F4969 gerAA, gerKA-KC or gerKC mutants lacking specific germinant receptor proteins germinated slower than wild-type spores with rich media, did not germinate with AK, and germinated poorly compared to wild-type spores with L-cysteine...
September 29, 2016: Microbiology
Masaki Serata, Mayumi Kiwaki, Tohru Iino
Lactic acid bacteria have a variety of mechanisms for tolerance to oxygen and reactive oxygen species, and these mechanisms differ among species. Lactobacillus casei strain Shirota grows well under aerobic conditions, indicating that the various systems involved in oxidative stress resistance function in this strain. To elucidate the mechanism of oxidative stress resistance in L. casei strain Shirota, we examined the transcriptome response to oxygen or hydrogen peroxide exposure. We then focused on an uncharacterized gene that was found to be up-regulated by both oxygen and hydrogen peroxide stress; we named the gene hprA1 (hydrogen peroxide resistance gene)...
September 29, 2016: Microbiology
Belinda Vangchhia, Sam Abraham, Jan M Bell, Peter Collignon, Justine S Gibson, Paul R Ingram, James R Johnson, Karina Kennedy, Darren J Trott, John D Turnidge, David M Gordon
Unlike Escherichia coli strains belonging to phylogroup B2, the clinical significance of strains belonging to phylogroup F is not well understood. Here we report on a collection of phylogroup F strains recovered in Australia from faeces and extra-intestinal sites from humans, companion animals, and native animals, as well as from poultry meat and water samples. The distribution of sequence types was clearly non-random with respect to isolate source. The antimicrobial resistance and virulence trait profiles also varied with the sequence type of the isolate...
September 22, 2016: Microbiology
Carolina Lage Goulart, Livia Carvalho Barbosa, Paulo Mascarello Bisch, Wanda Maria Almeida von Krüger
All cells are subjected to oxidative stress, a condition in which reactive oxygen species (ROS) production exceeds elimination. Bacterial defenses against ROS include synthesis of antioxidant enzymes like peroxidases and catalases. Vibrio cholerae can produce two distinct catalases, KatB and KatG, which contribute to ROS homeostasis. In this study, we analyzed the mechanism behind katG and katB expression in two V. cholerae O1 pandemic strains, O395 and N16961, respectively of Classical and El Tor biotypes...
September 22, 2016: Microbiology
Almudena Ortiz-Urquiza, Yanhua Fan, Timothy Garrett, Nemat O Keyhani
The entomopathogenic fungus, Beauveria bassiana, is a microbial biological control agent capable of infecting a wide range of insect hosts. Conidia (spores) initiate infection via adhesion, growth, and penetration of the insect cuticle, whose outmost layer is rich in lipids. Conidial virulence was investigated in B. bassiana wild type and caleosin mutants (ΔBbcal1), the latter a protein involved in lipid storage and turnover. Topical insect bioassays revealed that conidia of the wild type strain showed up to 40-fold differences in mean lethal dose (LD₅₀) values depending upon the growth substrate...
September 21, 2016: Microbiology
Jacob Mensah-Attipoe, Tiina Reponen, Anna-Maria Veijalainen, Helena Rintala, Martin Täubel, Panu Rantakokko, Jun Ying, Anne Hyvärinen, Pertti Pasanen
Fungal growth on indoor surfaces can decay building materials and release hazardous substances that affect indoor air quality. Despite the numerous methods available for growth determination, there is no commonly accepted standard. The goal of this study was to compare five different assay methods for the measurement of fungal growth: cultivation, mass spectrometry-based determination of ergosterol, beta-N-acetylhexosaminidase (NAHA) activity, quantitative polymerase chain reaction (qPCR) and microscopic spore counting...
September 20, 2016: Microbiology
Silvia Cardarelli, Sirio D'Amici, Paola Tassone, Angela Tramonti, Daniela Uccelletti, Patrizia Mancini, Michele Saliola
In Saccharomyces cerevisiae Adr1 is a zinc-finger transcription factor involved in the transcriptional activation of ADH2. Deletion of KlADR1, its putative ortholog in Kluyveromyces lactis, led to reduced growth in glycerol, oleate and yeast extract-peptone medium suggesting, as in S. cerevisiae, its requirement for glycerol, fatty acids and nitrogen utilization. Moreover, growth comparison on yeast extract and peptone plates showed in K. lactis a KlAdr1-dependent growth trait not present in S. cerevisiae indicating different metabolic roles of the two factors in their environmental niches...
September 15, 2016: Microbiology
Kyoung Lee, Gwang Su Ha, Yaligara Veeranagouda, Young-Su Seo, Ingyu Hwang
Pseudomonas alkylphenolica is an important strain for biodegradation of toxic alkylphenols and mass production of bioactive polymannuronate polymers. This strain forms a diverse, three dimensional biofilm architecture, including mushroom-like aerial structures, circular pellicles and surface spreading, depending on culture conditions. A mutagenesis and complementation study showed that a predicted transmembrane kinase, PSAKL28_21690 (1,164 aa), harboring a periplasmic CHASE3 domain flanked by two transmembrane helices in addition to its cytoplasmic GAF, histidine kinase and three CheY-like response regulator domains, plays a positive role in the formation of the special biofilm architecture and a negative role in swimming activity...
September 15, 2016: Microbiology
Ramses Gallegos-Monterrosa, Eisha Mhatre, Akos T Kovacs
Bacillus subtilis is an intensively studied Gram-positive bacterium that has become one of the models for biofilm development. B. subtilis 168 is a well-known domesticated strain that has been suggested to be deficient in robust biofilm formation. Moreover, the diversity of available B. subtilis laboratory strains and their derivatives has made it difficult to compare independent studies related to biofilm formation. Here, we have analyzed numerous 168 stocks from multiple laboratories for their ability to develop biofilms in different setups and media...
September 13, 2016: Microbiology
Stéphanie Borland, Claire Prigent-Combaret, Florence Wisniewski-Dye
Two-component signal transduction systems (TCS) are essential for many bacteria to maintain homeostasis and adapt to environmental changes. TCS typically involve a membrane-bound histidine kinase (HK) that senses stimuli, autophosphorylates in the transmitter region and then transfers the phosphoryl group to the receiver domain of a cytoplasmic response regulator (RR) that mediates appropriate changes in bacterial physiology. Although usually found on distinct proteins, the transmitter and receiver modules are sometimes fused into a so-called hybrid HK (HyHK)...
September 8, 2016: Microbiology
Thao L Masters, Jenny Wachter, Stuart Hill
Regulation of the Neisseria gonorrhoeae pilE gene is ill-defined. In this study, post-transcriptional effects on expression were assessed. In silico analysis predicts the formation of three putative stable stem-loop structures with favorable free energies within the 5 untranslated region (UTR) of the pilE message. Using quantitative reverse transcriptase PCR (qRT-PCR) analyses, we show that each loop structure forms, with introduced destabilizing stem loop mutations diminishing loop stability. Utilizing a series of pilE translational fusions, deletion of either loop 1 or loop 2 caused a significant reduction of pilE mRNA resulting in reduced expression of the reporter gene...
September 1, 2016: Microbiology
Katherine M Mann, Aaron Pride, Kelly Flentie, Jacqueline Kimmey, Leslie Weiss, Christina Stallings
Mycobacterium tuberculosis (Mtb) is one of the world's most successful pathogens. Millions of new cases of tuberculosis (TB) occur each year, emphasizing the need for better methods of treatment. The design of novel therapeutics is dependent on our understanding of factors that are essential for pathogenesis. Many bacterial pathogens use pili and other adhesins to mediate pathogenesis. The recently identified Mycobacterium tuberculosis pilus (MTP) and the hypothetical, widely conserved Flp pilus have been speculated to be important for Mtb virulence based on in vitro studies and homology to other pili, respectively...
August 31, 2016: Microbiology
Lillian G Acuña, M José Barros, Diego Martínez, Paula I Rodas, Daniel Paredes-Sabja, Juan A Fuentes, Fernando Gil, Iván L Calderón
Base-pairing small RNAs (sRNAs) regulate gene expression commonly by direct interaction with cognate mRNAs. Nevertheless, recent studies have expanded this knowledge with the discovery of the RNA "sponges" which are able to interact and repress the functions of classical base-pairing sRNAs. In this work we present evidence indicating that the sponge RNA SroC from Salmonella Typhimurium base pairs with the MgrR sRNA, thereby antagonizing its regulatory effects on both gene expression and resistance to the antimicrobial peptide polymyxin B (PMB)...
August 26, 2016: Microbiology
Peng Zhou, Xiaoli Li, Fengxia Qi
Hemin/heme is one of the essential nutrients required by periodontopathogens like Porphyromonas gingivalis to grow in vitro. In the oral cavity, this nutrient is believed to be provided by the crevicular fluid, a serum-like exudate produced during gum inflammation. However, P. gingivalis is also present in the healthy dental biofilm where inflammation is absent. This study was designed to answer the question: what organism(s) in the healthy dental biofilm provides hemin/heme to those periodontal pathogens? We report here that veillonellae, a group of bridging species in dental biofilm development, harbor a complete gene cluster for heme biosynthesis...
August 26, 2016: Microbiology
Xiaowei Xue, Maria C Davis, Thomas Steeves, Adam Bishop, Jillian Breen, Allison MacEacheron, Christopher A Kesthely, FoSheng Hsu, Shawn R MacLellan
factors are single subunit general transcription factors that reversibly bind core RNA polymerase and mediate gene-specific transcription in bacteria. Previously, an atypical two-subunit factor was identified that activates transcription from a group of related promoters in Bacillus subtilis. Both of the subunits, named SigO and RsoA, share primary sequence similarity with the canonical 70 family of factors and interact with each other and with RNA polymerase subunits. Here we show that the 70 region 2.3-like segment of RsoA is unexpectedly sufficient for interaction with the amino-terminus of SigO and the ' subunit...
August 23, 2016: Microbiology
Sudhir Singh, Susheel Dwivedi, Vijay Shankar Singh, Anil Kumar Tripathi
OxyR proteins are LysR-type transcription regulators, which play an important role in responding to oxidative stress in bacteria. Azospirillum brasilense Sp7 harbours two copies of OxyR. Inactivation of the oxyR1, the gene organized divergently to ahpC in A. brasilense Sp7, led to an increased tolerance to alkyl hydroperoxides, which was corroborated by an increase in alkyl hydroperoxide reductase (AhpC) activity, enhanced expression of ahpC:lacZ fusion, and increased synthesis of AhpC protein in the oxyR1::km mutant...
August 23, 2016: Microbiology
Anne Breüner, Dorte Frees, Pekka Varmanen, Anna Monika Boguta, Karin Hammer, Jan Martinussen, Mogens Kilstrup
We analyzed the response of the model bacterium <italic>Lactococcus lactis</i> to abrupt depletion of glucose after several generations of exponential growth. Glucose depletion resulted in a drastic drop in the energy charge accompanied by an extremely low GTP level and almost total arrest of protein synthesis. Strikingly the cell prioritized the continued synthesis of a few proteins, of which the ribosome dimerization factor YfiA was the most highly expressed. Transcriptome analysis showed no immediate decrease in total mRNA levels despite the lowered nucleotide pools, and only marginally increased levels of the <italic>yfiA</i> transcript...
August 23, 2016: Microbiology
Daniel Buchvaldt Amby, Tom Manczak, Mikael Agerlin Petersen, Thomas Sundelin, Corinna Weitzel, Maciej Grajewski, Henrik Toft Simonsen, Birgit Jensen
Colletotrichum acutatum is a major fungal pathogen of fruit crops, which causes severe yield losses in strawberry productions. A potential key factor in plant-pathogen interactions is fungal sesquiterpenoids that have myco- and phytotoxic activities. The first committed step in sesquiterpenoids biosynthesised is performed by sesquiterpene synthases (TPS). Only a few TPS's have been functionally characterized from filamentous fungi and none from the Colletotrichum genus. Despite it as an important fungal pathogen to agriculture, it is poorly understood at the molecular and chemical level...
August 22, 2016: Microbiology
Yuri Ushijima, Osamu Yoshida, Montecillo Jake Adolf Villanueva, Ryosuke L Ohniwa, Kazuya Morikawa
Dps family proteins have the ferroxidase activity that contributes to oxidative stress resistance. In addition, a part of Dps family proteins including Escherichia coli Dps and Staphylococcus aureus MrgA (Metallo regulon gene A) bind DNA and induce the structural change of the nucleoid. We previously showed that a mutated MrgA with reduced ferroxidase activity was unable to contribute to the H2O2 and UV resistance in S. aureus, suggesting that the nucleoid clumping by MrgA is not sufficient for the resistance...
August 17, 2016: Microbiology
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