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Zachary N Phillips, Asma-Ul Husna, Michael P Jennings, Kate L Seib, John M Atack
Phase-variable DNA methyltransferases control the expression of multiple genes via epigenetic mechanisms in a wide variety of bacterial species. These systems are called phasevarions, for phase-variable regulons. Phasevarions regulate genes involved in pathogenesis, host adaptation and antibiotic resistance. Many human-adapted bacterial pathogens contain phasevarions. These include leading causes of morbidity and mortality worldwide, such as non-typeable Haemophilus influenzae, Streptococcus pneumoniae and Neisseria spp...
April 17, 2019: Microbiology
Jaime Carrasco, Maria Luisa Tello, Maria de Toro, Andrzej Tkacz, Philip Poole, Margarita Pérez-Clavijo, Gail Preston
The casing material required in mushroom cultivation presents a very rich ecological niche, which is inhabited by a diverse population of bacteria and fungi. In this work three different casing materials, blonde peat, black peat and a 50 : 50 mixture of both, were compared for their capacity to show a natural suppressive response against dry bubble, Lecanicillium fungicola (Preuss) Zare and Gams, and wet bubble, Mycogone perniciosa (Magnus) Delacroix. The highest mushroom production was collected from crops cultivated using the mixed casing and black peat, which were not significantly different in yield...
April 17, 2019: Microbiology
Natsumi Ogawa, Hiromi Kato, Kouhei Kishida, Eikichi Ichihashi, Taichiro Ishige, Hirofumi Yoshikawa, Yuji Nagata, Yoshiyuki Ohtsubo, Masataka Tsuda
In natural environments contaminated by recalcitrant organic pollutants, efficient biodegradation of such pollutants has been suggested to occur through the cooperation of different bacterial species. A phenanthrene-degrading bacterial consortium, MixEPa4, from polluted soil was previously shown to include a phenanthrene-degrading strain, Mycobacterium sp. EPa45, and a non-polycyclic aromatic hydrocarbon (PAH)-degrading strain, Burkholderia sp. Bcrs1W. In this study, we show that addition of phenanthrene to rich liquid medium resulted in the transient growth arrest of EPa45 during its degradation of phenanthrene...
April 17, 2019: Microbiology
Emmanuele Severi, Gavin H Thomas
In the fight against antimicrobial resistance (AMR), antibiotic biosynthetic gene clusters are constantly being discovered. These clusters often include genes for membrane transporters that are involved in the export of the produced natural product during biosynthesis and/or subsequent resistance through active efflux. Despite transporter genes being integral parts of these clusters, study of the function of antibiotic export in natural producers such as Streptomyces spp. remains underexplored, in many cases lagging far behind our understanding of the biosynthetic enzymes...
April 9, 2019: Microbiology
Peter C Fineran
Bacteria are under a constant pressure from their viruses (phages) and other mobile genetic elements. They protect themselves through a range of defence strategies, which can be broadly classified as 'innate' and 'adaptive'. The bacterial innate immune systems include defences provided by restriction modification and abortive infection, among others. Bacterial adaptive immunity is elicited by a diverse range of CRISPR-Cas systems. Here, I discuss our research on both innate and adaptive phage resistance mechanisms and some of the evasion strategies employed by phages...
April 8, 2019: Microbiology
Masaki Osawa, Harold P Erickson
L form bacteria do not have a cell wall and are thought to require medium of high osmolality for survival and growth. In this study we tested whether L forms can adapt to growth in lower osmolality medium. We first tested the Escherichia coli L form NC-7, generated in 1987 by Onoda following heavy mutagenesis. We started with growth in osmoprotective medium (~ 764 mOsm kg-1 ) and diluted it stepwise into medium of lower osmolality. At each step the cells were given up to 10 days to adapt and begin growing, during which they apparently acquired multiple new mutations...
April 8, 2019: Microbiology
Christopher F Schuster, Sophie A Howard, Angelika Gründling
The gold standard method for the creation of gene deletions in Staphylococcus aureus is homologous recombination using allelic exchange plasmids with a temperature-sensitive origin of replication. A knockout vector that contains regions of homology is first integrated into the chromosome of S. aureus by a single crossover event selected for at high temperatures (non-permissive for plasmid replication) and antibiotic selection. Next, the second crossover event is encouraged by growth without antibiotic selection at low temperature, leading at a certain frequency to the excision of the plasmid and the deletion of the gene of interest...
April 3, 2019: Microbiology
Kristin Ciezki, Shane Wesener, Danny Jaber, Shama Mirza, Steven Forst
Xenorhabdus species are symbionts of entomopathogenic nematodes and pathogens of susceptible insects. Nematodes enter insect hosts and perforate the midgut to invade the haemocoel where Xenorhabdus bacteria are released transitioning to their pathogenic stage. During nematode invasion microbes from the insect gut translocate into the haemocoel. Different species of nematodes carrying specific strains of Xenorhabdus can also invade the same insect. Xenorhabdus species thereby compete for nutrients and space with both related strains and non-related gut microbes...
April 2, 2019: Microbiology
Norman K Fry, Helina Marshall, Tasha Mellins-Cohen
No abstract text is available yet for this article.
April 2, 2019: Microbiology
Elena A Ianutsevich, Vera M Tereshina
The combinatorial action of osmotic (OS) and heat (HS) shocks on the composition of soluble cytosol carbohydrates and membrane lipids was studied. For the first time it was demonstrated that the combinatorial effect of these shocks led to the non-additive response - an increase in the trehalose level, characteristic for HS, but at the same time suppression of glycerol production, uncharacteristic of the OS response. In addition, combinatorial action resulted in a new effect - increase in the mannitol level, which was not typical for the individual HS or OS responses...
April 1, 2019: Microbiology
Sarah Coulthurst
The Type VI secretion system (T6SS) is a protein nanomachine that is widespread in Gram-negative bacteria and is used to translocate effector proteins directly into neighbouring cells. It represents a versatile bacterial weapon that can deliver effectors into distinct classes of target cells, playing key roles in inter-bacterial competition and bacterial interactions with eukaryotic cells. This versatility is underpinned by the ability of the T6SS to deliver a vast array of effector proteins, with many distinct activities and modes of interaction with the secretion machinery...
March 20, 2019: Microbiology
Ting L Luo, Michael Hayashi, Marianne Zsiska, Benjamin Circello, Marisa Eisenberg, Carlos Gonzalez-Cabezas, Betsy Foxman, Carl F Marrs, Alexander H Rickard
Biofilm model systems are used to study biofilm growth and predict the effects of anti-biofilm interventions within the human oral cavity. Many in vitro biofilm model systems use a confocal laser scanning microscope (CLSM) in conjunction with image analysis tools to study biofilms. The aim of this study was to evaluate an in-house developed image analysis software program that we call BAIT (Biofilm Architecture Inference Tool) to quantify the architecture of oral multi-species biofilms following anti-biofilm interventions using a microfluidic biofilm system...
March 18, 2019: Microbiology
Alexia Hapeshi, Jonatan Mimon Benarroch, David James Clarke, Nicholas Robin Waterfield
Members of the Gram-negative bacterial genus Photorhabdus are all highly insect pathogenic and exist in an obligate symbiosis with the entomopathogenic nematode worm Heterorhabditis. All members of the genus produce the small-molecule 3,5-dihydroxy-4-isopropyl-trans-stilbene (IPS) as part of their secondary metabolism. IPS is a multi-potent compound that has antimicrobial, antifungal, immunomodulatory and anti-cancer activities and also plays an important role in symbiosis with the nematode. In this study we have examined the response of Photorhabdus itself to exogenous ectopic addition of IPS at physiologically relevant concentrations...
March 18, 2019: Microbiology
Shravanthi S Kumar, Asit Ranjan Ghosh
Representation of various methods for the determination of bacterial viability.Assessing bacterial contamination in environmental samples is critical in determining threats to public health. The classical methods are time-consuming and only recognize species that grow easily on culture media. Viable but non-culturable (VBNC) bacteria are a possible threat that may resuscitate and cause infections. Recent dye-based screening techniques employ nucleic acid dyes such as ethidium monoazide (EMA) and propidium monoazide (PMA), along with many fluorescent dyes, which are an effective alternative for viability assessment...
March 7, 2019: Microbiology
Keith Poole, Thomas Hay, Christie Gilmour, Michael Fruci
Exposure of wild-type (WT) Pseudomonas aeruginosa PAO1 to ZnCl2 (Zn) yielded a concentration-dependent increase in depolarization of the cytoplasmic membrane (CM), an indication that this metal is membrane-damaging. Consistent with this, Zn activated the AmgRS envelope stress-responsive two-component system (TCS) that was previously shown to be activated by and to protect P. aeruginosa from the membrane-damaging effects of aminoglycoside (AG) antibiotics. A mutant lacking amgR showed enhanced Zn-promoted CM perturbation and was Zn-sensitive, an indication that the TCS protected cells from the CM-damaging effects of this metal...
March 5, 2019: Microbiology
Tejaswani Saragadam, Sunil Kumar, Narayan S Punekar
Arginase is the only fungal ureohydrolase that is well documented in the literature. More recently, a novel route for agmatine catabolism in Aspergillus niger involving another ureohydrolase, 4-guanidinobutyrase (GBase), was reported. We present here a detailed characterization of A. niger GBase - the first fungal (and eukaryotic) enzyme to be studied in detail. A. niger GBase is a homohexamer with a native molecular weight of 336 kDa and an optimal pH of 7.5. Unlike arginase, the Mn2+ enzyme from the same fungus, purified GBase protein is associated with Zn2+ ions...
February 26, 2019: Microbiology
Yiwei Meng, Peiwen Lv, Yanbing Cui, Lina Zhang, Yan Wang, Cuiqing Ma, Ping Xu, Chunyu Yang
In most halophiles, K+ generally acts as a major osmotic solute for osmotic adjustment and pH homeostasis. However, strains also need to extrude excessive intracellular K+ to avoid its toxicity. In the halotolerant and alkaliphilic Halomonas sp. Y2, an Na+ -induced K+ extrusion process was observed when the cells were confronted with high extracellular K+ pressure and supplementation by millimolar Na+ ions. Among three mechanosensitive channels (KefA) and two K+ /H+ antiporters founded in the genome of the strain, ke1 displayed around 3-5-fold upregulation to ion stress at pH 8...
February 19, 2019: Microbiology
Rachel L Darnell, Yoshio Nakatani, Melanie K Knottenbelt, Susanne Gebhard, Gregory M Cook
Bacitracin is a cell wall targeting antimicrobial with clinical and agricultural applications. With the growing mismatch between antimicrobial resistance and development, it is essential we understand the molecular mechanisms of resistance in order to prioritize and generate new effective antimicrobials. BcrR is a unique membrane-bound one-component system that regulates high-level bacitracin resistance in Enterococcus faecalis. In the presence of bacitracin, BcrR activates transcription of the bcrABD operon conferring resistance through a putative ATP-binding cassette (ABC) transporter (BcrAB)...
February 19, 2019: Microbiology
Stephen J W Busby
Regulatory interactions at the lac promoter.Activation of the transcription of genes is central to many processes of adaptation and differentiation in bacteria. Here, I review the molecular mechanisms by which transcription factors can activate the initiation of specific transcripts at bacterial promoters. The story is presented in the context of Marjory Stephenson's pioneering work on enzymatic adaptation in bacteria, and sets the different mechanisms in the greater context of how transcription regulatory mechanisms evolved...
February 18, 2019: Microbiology
Soma Mandal, Samuel Njikan, Anuradha Kumar, Julie V Early, Tanya Parish
Bacterial persisters are a subpopulation of cells that exhibit phenotypic resistance during exposure to a lethal dose of antibiotics. They are difficult to target and thought to contribute to the long treatment duration required for tuberculosis. Understanding the molecular and cellular biology of persisters is critical to finding new tuberculosis drugs that shorten treatment. This review focuses on mycobacterial persisters and describes the challenges they pose in tuberculosis therapy, their characteristics and formation, how persistence leads to resistance, and the current approaches being used to target persisters within mycobacterial drug discovery...
February 18, 2019: Microbiology
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