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Stephen V Gordon, Tanya Parish
MΦ, Macrophage; DC, Dendritic cell; CORD, Cord factor; MDR, Multidrug resistance.Mycobacterium tuberculosis is an expert and deadly pathogen, causing the disease tuberculosis (TB) in humans. It has several notable features: the ability to enter non-replicating states for long periods and cause latent infection; metabolic remodelling during chronic infection; a thick, waxy cell wall; slow growth rate in culture; and intrinsic drug resistance and antibiotic tolerance. As a pathogen, M. tuberculosis has a complex relationship with its host, is able to replicate inside macrophages, and expresses diverse immunomodulatory molecules...
February 21, 2018: Microbiology
Sunhee Ha, Bora Shin, Woojun Park
The aceA and glcB genes, encoding isocitrate lyase (ICL) and malate synthase, respectively, are not in an operon in many bacteria, including Pseudomonas aeruginosa, unlike in Escherichia coli. Here, we show that expression of aceA in P. aeruginosa is specifically upregulated under H2O2-induced oxidative stress and under iron-limiting conditions. In contrast, the addition of exogenous redox active compounds or antibiotics increases the expression of glcB. The transcriptional start sites of aceA under iron-limiting conditions and in the presence of iron were found to be identical by 5' RACE...
February 21, 2018: Microbiology
Paul A Hoskisson
Diphtheria AB toxin mode of action. The diphtheria AB exotoxin consists of two polypeptide chains - A and B which are linked by a disulfide bridge. The B chain binds to the heparin-binding epidermal growth factor precursor on eukaryotic cells and is endocytosed. Acidification of the endosome results in a conformational change to the A and B chains and breaking of the disulphide bridge. The B chain remains in the endosome, but the A chain is translocated to the cytoplasm where it ADP-ribosylates host eEF-2, blocking protein synthesis which leads to cell death...
February 21, 2018: Microbiology
Hiraku Takada, Yuh Shiwa, Yuta Takino, Natsuki Osaka, Shuhei Ueda, Satoru Watanabe, Taku Chibazakura, Masayuki Su'etsugu, Ryutaro Utsumi, Hirofumi Yoshikawa
WalRK is an essential two-component signal transduction system that plays a central role in coordinating cell wall synthesis and cell growth in Bacillus subtilis. However, the physiological role of WalRK and its essentiality for growth have not been elucidated. We investigated the behaviour of WalRK during heat stress and its essentiality for cell proliferation. We determined that the inactivation of the walHI genes which encode the negative modulator of WalK, resulted in growth defects and eventual cell lysis at high temperatures...
February 20, 2018: Microbiology
Tania Selas Castiñeiras, Steven G Williams, Antony Hitchcock, Jeffrey A Cole, Daniel C Smith, Tim W Overton
As high-level recombinant protein production (RPP) exerts a massive stress on the production host, an extensive literature on RPP optimization focuses on separating the growth phase from RPP production once sufficient biomass has been obtained. The aim of the current investigation was to optimize the benefits of the relatively neglected alternative strategy to achieve high-level RPP during growth by minimizing stress on the host. High yields of the biopharmaceutical recombinant human tumour necrosis factor alpha (rhTNFα) were obtained by fed-batch fermentation relevant to industrial production based upon parameters that most severely affected RPP in preliminary laboratory scale batch cultures...
February 14, 2018: Microbiology
Kazuki Nosho, Hiroko Fukushima, Takehiro Asai, Masahiro Nishio, Reiko Takamaru, Koseki Joseph Kobayashi-Kirschvink, Tetsuhiro Ogawa, Makoto Hidaka, Haruhiko Masaki
A variety of bacteria, including Escherichia coli, are known to enter the viable but non-culturable (VBNC) state under various stress conditions. During this state, cells lose colony-forming activities on conventional agar plates while retaining signs of viability. Diverse environmental stresses including starvation induce the VBNC state. However, little is known about the genetic mechanism inducing this state. Here, we aimed to reveal the genetic determinants of the VBNC state of E. coli. We hypothesized that the VBNC state is a process wherein specific gene products important for colony formation are depleted during the extended period of stress conditions...
February 8, 2018: Microbiology
Paul R Norris, Ludovic Laigle, Susan Slade
The mineral sulfide-oxidising Acidithiobacillus ferrooxidans has been extensively studied over many years but some fundamental aspects of its metabolism remain uncertain, particularly with regard to its anaerobic oxidation of sulfur. This label-free, liquid chromatography-electron spray ionisation-mass spectrometry-based proteomic analysis estimated relative protein abundance during aerobic and anaerobic growth of At. ferrooxidans. One of its two bc1 complexes, that encoded by the petII operon, was strongly implicated in anaerobic ferric iron-coupled sulfur oxidation, probably in conjunction with two cytochromes...
February 6, 2018: Microbiology
Clarice de Azevedo Souza, Kristian L Richards, YoSon Park, Michael Schwartz, Julie Torruellas Garcia, Sara Schesser Bartra, Gregory V Plano
The needle structures of type III secretion (T3S) systems are formed by the secretion and polymerization of a needle subunit protein, YscF in Yersinia pestis. A subset of T3S systems employ unique heterodimeric chaperones, YscE and YscG in Y. pestis, to prevent the polymerization of needle subunits within the bacterial cell. We demonstrate that the YscE/YscG chaperone is also required for stable YscF expression and for secretion of YscF. Overexpression of a functional maltose-binding protein (MBP)-YscG hybrid protein stabilized cytoplasmic YscF but YscF was not secreted in the absence of YscE...
February 5, 2018: Microbiology
Luca Rossoni, Reuben Carr, Scott Baxter, Roxann Cortis, Thomas Thorpe, Graham Eastham, Gill Stephens
Bio-production of fuels and chemicals from lignocellulosic C5 sugars usually requires the use of the pentose phosphate pathway (PPP) to produce pyruvate. Unfortunately, the oxidation of pyruvate to acetyl-coenzyme A results in the loss of 33 % of the carbon as CO2, to the detriment of sustainability and process economics. To improve atom efficiency, we engineered Escherichia coli to utilize d-xylose constitutively using the Weimberg pathway, to allow direct production of 2-oxoglutarate without CO2 loss. After confirming enzyme expression in vitro, the pathway expression was optimized in vivo using a combinatorial approach, by screening a range of constitutive promoters whilst systematically varying the gene order...
February 5, 2018: Microbiology
Maylis Chapelais-Baron, Isabelle Goubet, Renaud Péteri, Maria de Fatima Pereira, Tâm Mignot, Apolline Jabveneau, Eric Rosenfeld
Iridescence is an original type of colouration that is relatively widespread in nature but has been either incompletely described or entirely neglected in prokaryotes. Recently, we reported a brilliant 'pointillistic' iridescence in agar-grown colony biofilms of Cellulophaga lytica and some other marine Flavobacteria that exhibit gliding motility. Bacterial iridescence is created by a unique self-organization of sub-communities of cells, but the mechanisms underlying such living photonic crystals are unknown...
February 5, 2018: Microbiology
Hazael Hernandez, Luis R Martinez
Fungi are critical organisms for the environment and offer many benefits to modern society through their application in the pharmaceutical, beverage and food industries. In contrast, fungal pathogens are emerging threats to humans, animals, plants and insects with potential to cause devastating mortality, morbidity and economic loss. Outbreaks associated with anthropogenic alterations of the environment, including climate change-related events such as natural disasters, are responsible for human, animal and plant disease...
February 5, 2018: Microbiology
Robert Howlett, Nicholas Read, Anpu Varghese, Charles Kershaw, Y Hancock, Margaret C M Smith
Polyprenol phosphate mannose (PPM) is a lipid-linked sugar donor used by extra-cytoplasmic glycosyl tranferases in bacteria. PPM is synthesiszed by polyprenol phosphate mannose synthase, Ppm1, and in most Actinobacteria is used as the sugar donor for protein O-mannosyl transferase, Pmt, in protein glycosylation. Ppm1 and Pmt have homologues in yeasts and humans, where they are required for protein O-mannosylation. Actinobacteria also use PPM for lipoglycan biosynthesis. Here we show that ppm1 mutants of Streptomyces coelicolor have increased susceptibility to a number of antibiotics that target cell wall biosynthesis...
February 1, 2018: Microbiology
Tatsuya Fukushima, Natsuki Uchida, Masatoshi Ide, Takeko Kodama, Junichi Sekiguchi
Biopolymers on the cell surface are very important for protecting microorganisms from environmental stresses, as well as storing nutrients and minerals. Synthesis of biopolymers is well studied, while studies on the modification and degradation processes of biopolymers are limited. One of these biopolymers, poly-γ-glutamic acid (γ-PGA), is produced by Bacillus species. Bacillus subtilis PgdS, possessing three NlpC/P60 domains, hydrolyses γ-PGA. Here, we have demonstrated that several dl-endopeptidases with an NlpC/P60 domain (LytE, LytF, CwlS, CwlO, and CwlT) in B...
January 30, 2018: Microbiology
Masayuki Hashimoto, Hiroaki Matsushima, I Putu Suparthana, Hiroshi Ogasawara, Hiroki Yamamoto, ChingHao Teng, Junichi Sekiguchi
Bacterial cells are covered with peptidoglycan (PG) layer(s), serving as the cellular exoskeleton. The PG sacculus changes its shape during cell growth, and thus both the synthesis and disassembly of PG are important for cell proliferation. In Bacillus subtilis, four dl-endopeptidases (DLEPases; LytE, LytF, CwlO and CwlS) are involved in the maintenance of cell morphology. The lytE cwlO double mutant exhibits synthetic lethality and defective cell elongation, while the lytE lytF cwlS triple mutant exhibits defective cell separation, albeit with septum formation...
January 25, 2018: Microbiology
Sushovan Dam, Jean-Marie Pagès, Muriel Masi
Bacteria have evolved several strategies to survive a myriad of harmful conditions in the environment and in hosts. In Gram-negative bacteria, responses to nutrient limitation, oxidative or nitrosative stress, envelope stress, exposure to antimicrobials and other growth-limiting stresses have been linked to the development of antimicrobial resistance. This results from the activation of protective changes to cell physiology (decreased outer membrane permeability), resistance transporters (drug efflux pumps), resistant lifestyles (biofilms, persistence) and/or resistance mutations (target mutations, production of antibiotic modification/degradation enzymes)...
January 25, 2018: Microbiology
Alex Remmington, Claire E Turner
DNases are abundant among the pathogenic streptococci, with most species harbouring genes for at least one. Despite their prevalence, however, the role for these extracellular enzymes is still relatively unclear. The DNases of the Lancefield group A Streptococcus, S. pyogenes are the best characterized, with a total of eight DNase genes identified so far. Six are known to be associated with integrated prophages. Two are chromosomally encoded, and one of these is cell-wall anchored. Homologues of both prophage-associated and chromosomally encoded S...
January 25, 2018: Microbiology
Shanmugasundaram Karuppusamy, Lucy Mutharia, David Kelton, Niel Karrow, Gordon Kirby
Johne's disease (JD) is a contagious, chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). The aim of this study was to identify antigenic proteins from the MAP cell envelope (i.e. cell wall and cytoplasmic membranes) by comparing MAP, M. avium subsp. hominissuis (MAH) and M. smegmatis (MS) cell envelope protein profiles using a proteomic approach. Composite two-dimensional (2D) difference gel electrophoresis images revealed 13 spots present only in the image of the MAP cell envelope proteins...
January 24, 2018: Microbiology
Carolina M A Santos, Maria Cecília V Pires, Thiago L Leão, Anna Karolina S Silva, Lilian S Miranda, Flaviano S Martins, Aristóbolo M Silva, Jacques R Nicoli
Lactobacilli are the dominant bacteria of the vaginal tract of healthy women and they play a major role in the maintenance of mucosal homeostasis, preventing genital infections, such as bacterial vaginosis (BV) and vulvovaginal candidiasis (VVC). It is now known that one mechanism of this protection is the influence that lactobacilli can exert on host immune responses. In this context, we evaluated two Lactobacillus strains (L. plantarum 59 and L. fermentum 137) for their immunomodulatory properties in response to Gardnerella vaginalis (BV) or Candida albicans (VVC) infections in a HeLa cell infection model...
January 23, 2018: Microbiology
Livia C Barbosa, Carolina L Goulart, Marcela M Avellar, Paulo M Bisch, Wanda M A von Kruger
Ornithine lipids (OLs) are phosphorus-free lipids found in many bacteria grown under phosphate deprivation, a condition that activates the PhoBR system and leads to phosphate uptake and metabolism. Two OL synthesis pathways have already been described. One depends on OlsB and OlsA acyltransferases to add, respectively, the first and second acyl chains to an ornithine molecule. The other pathway is carried out by OlsF, a bifunctional enzyme responsible for both acylation steps. Although Vibrio cholerae lacks olsBA genes, an olsF homologue (vc0489) was identified in its genome...
January 22, 2018: Microbiology
Stephen K Dolan, Andre Wijaya, Stephen M Geddis, David R Spring, Rafael Silva-Rocha, Martin Welch
Propionate is an abundant catabolite in nature and represents a rich potential source of carbon for the organisms that can utilize it. However, propionate and propionate-derived catabolites are also toxic to cells, so propionate catabolism can alternatively be viewed as a detoxification mechanism. In this review, we summarize recent progress made in understanding how prokaryotes catabolize propionic acid, how these pathways are regulated and how they might be exploited to develop novel antibacterial interventions...
January 22, 2018: Microbiology
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