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PubMed Journal Database | Microbiology (Reading, England) RSS

05:13 EDT 19th May 2019 | BioPortfolio

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Showing PubMed Articles 1–25 of 105 from Microbiology (Reading, England)

Staphylococcus aureus adaptation to aerobic low-redox-potential environments: implications for an intracellular lifestyle.

Methicillin-resistant Staphylococcus aureus is a 'superbug' that is responsible for extensive death and morbidity. Chronic S. aureus infections are associated with the presence of intracellular bacteria and the host cytosol is an aerobic low-redox-potential (Eh) environment. How S. aureus adapts to aerobic low-Eh environments is understudied. A low external Eh, imposed by the non-metabolizable reductant dithiothreitol, resulted in transcriptional reprogramming mediated by the redox-responsive transcription ...

Sharpea azabuensis: a ruminal bacterium that produces trans-11 intermediates from linoleic and linolenic acid.

To investigate the metabolism of 18:2n-6 and 18:3n-3 by pure cultures of Sharpea azabuensis, two different strains (RL 1 and ST18) were each incubated in the presence of 40 µg ml 18:2n-6 or 18:3n-3. Pure cultures of Butyrivibriofibrisolvens D1 and Butyrivibrio proteoclasticus P18 were included as control treatments. Similar to the metabolism of B. fibrisolvens, both S. azabuensis strains converted 18:2n-6 or 18:3n-3 to cis-9, trans-11 CLA or cis-9, trans-11, cis-15 CLnA, after which it was further reduced ...

Heterogeneity of ROS levels in antibiotic-exposed mycobacterial subpopulations confers differential susceptibility.

Phenotypically heterogeneous but genetically identical mycobacterial subpopulations exist in in vitro cultures, in vitro-infected macrophages, infected animal models and tuberculosis patients. In this regard, we recently reported the presence of two subpopulations of cells, which are phenotypically different in length and buoyant density, in mycobacterial cultures. These are the low-buoyant-density short-sized cells (SCs), which constitute ~10-20 % of the population, and the high-buoyant-density normal/lo...

A mycobacteriophage genomics approach to identify novel mycobacteriophage proteins with mycobactericidal properties.

Mycobacteriophages that are specific to mycobacteria are sources of various effector proteins that are capable of eliciting bactericidal responses. We describe a genomics approach in combination with bioinformatics to identify mycobacteriophage proteins that are toxic to mycobacteria upon expression. A genomic library comprising phage genome collections was screened for clones capable of killing Mycobacterium smegmatis strain mc155. We identified four unique clones: clones 45 and 12N (from the mycobacteriop...

High frequency of double crossover recombination facilitates genome engineering in Pseudomonas aeruginosa PA14 and clone C strains.

Pseudomonas aeruginosa is a key opportunistic human pathogen. An established procedure to replace a target gene is two-step allelic exchange, i.e. selection of single crossover at homologous sequences and subsequent counter selection to induce double crossover for excision of the suicide vector. In this study, we found that certain strains of P. aeruginosa display a high rate of instant double crossover upon introduction of a suicide vector containing an antibiotic resistance cassette flanked by adjacent se...

Rhizobium tropici CIAT 899 copA gene plays a fundamental role in copper tolerance in both free life and symbiosis with Phaseolus vulgaris.

Rhizobium tropici CIAT 899 is a facultative symbiotic diazotroph able to deal with stressful concentrations of metals. Nevertheless the molecular mechanisms involved in metal tolerance have not been elucidated. Copper (Cu) is a metal component essential for the heme-copper respiratory oxidases and enzymes that catalyse redox reactions, however, it is highly toxic when intracellular trace concentrations are surpassed. In this study, we report that R. tropici CIAT 899 is more tolerant to Cu than other Rhizobi...

The ridA gene of E. coli is indirectly regulated by BglG through the transcriptional regulator Lrp in stationary phase.

Regulators encoded by the beta-glucoside (bgl) operon of Escherichia coli are known to influence the expression of downstream target genes that confer a fitness advantage in stationary phase. We have examined the role of bglG in the regulation of ridA that encodes an enamine/imine deaminase essential for the elimination of reactive intermediates generated during the catabolism of amino acids such as serine. We report here that ridA is positively regulated by leucine responsive regulatory protein (Lrp) and l...

Building the GreenCut2 suite of proteins to unmask photosynthetic function and regulation.

The suite of GreenCut proteins, initially assembled in 2007 and updated in 2011 (GreenCut2), comprises 597 Chlamydomonas reinhardtii proteins; these proteins, identified as putative orthologues in all green lineage organisms examined, but not (or poorly conserved) in non-photosynthetic organisms, are potentially enriched for proteins affiliated with photosynthesis. The annotation of GreenCut2 proteins and the characterization of mutants with lesions in genes encoding those proteins identified catalytic comp...

Antibiotic export: transporters involved in the final step of natural product production.

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 case...

Use of the counter selectable marker PheS* for genome engineering in Staphylococcus aureus.

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 selec...

In praise of preprints.

ngrA-dependent natural products are required for interspecies competition and virulence in the insect pathogenic bacterium Xenorhabdus szentirmaii.

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 ...

The Type VI secretion system: a versatile bacterial weapon.

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 dist...

The relevance of persisters in tuberculosis drug discovery.

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 characteristic...

Transcription activation in bacteria: ancient and modern.

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 ...

Enhanced functionalisation of major facilitator superfamily transporters via fusion of C-terminal protein domains is both extensive and varied in bacteria.

The evolution of gene fusions that result in covalently linked protein domains is widespread in bacteria, where spatially coupling domain functionalities can have functional advantages in vivo. Fusions to integral membrane proteins are less widely studied but could provide routes to enhance membrane function in synthetic biology. We studied the major facilitator superfamily (MFS), as the largest family of transporter proteins in bacteria, to examine the extent and nature of fusions to these proteins. A rema...

Staphylococcus aureus: setting its sights on the human innate immune system.

Staphylococcus aureus has colonized humans for at least 10 000 years, and today inhabits roughly a third of the population. In addition, S. aureus is a major pathogen that is responsible for a significant disease burden, ranging in severity from mild skin and soft-tissue infections to life-threatening endocarditis and necrotizing pneumonia, with treatment often hampered by resistance to commonly available antibiotics. Underpinning its versatility as a pathogen is its ability to evade the innate immune s...

Reciprocal control of motility and biofilm formation by the PdhS2 two-component sensor kinase of Agrobacterium tumefaciens.

A core regulatory pathway that directs developmental transitions and cellular asymmetries in Agrobacterium tumefaciens involves two overlapping, integrated phosphorelays. One of these phosphorelays putatively includes four histidine sensor kinase homologues, DivJ, PleC, PdhS1 and PdhS2, and two response regulators, DivK and PleD. In several different alphaproteobacteria, this pathway influences a conserved downstream phosphorelay that ultimately controls the phosphorylation state of the CtrA master response...

Thiamin transport in Helicobacter pylori lacking the de novo synthesis of thiamin.

Helicobacter pylori lacks the genes involved in the de novo synthesis of thiamin, and is therefore a thiamin auxotroph. The PnuT transporter, a member of the Pnu transporter family, mediates the uptake of thiamin across the membrane. In the genome of H. pylori, the pnuT gene is clustered with the thiamin pyrophosphokinase gene thi80. In this study, we found that [H]thiamin is incorporated into the H. pylori SS1 strain via facilitated diffusion with a Km value of 28 µM. The incorporation of radioactive th...

Comparative analysis of immunological properties of S-layer proteins isolated from Lactobacillus strains.

Previous studies have suggested that some Lactobacillus S-layer proteins could modulate immune responses. Primary structures of the S-layer proteins are variable, and their immunological differences are poorly understood. In this study, we evaluated the immunological properties of eight distinct S-layer proteins from different Lactobacillus species. We found that removal of the S-layer proteins from the cell surface reduced the immunological activities of Lactobacillus cells in THP-1 cells. Furthermore, the...

Inactivation of the exogenous fatty acid utilization pathway leads to increased resistance to unsaturated fatty acids in Staphylococcus aureus.

The human pathogen Staphylococcus aureus produces saturated fatty acids, but can incorporate both exogenous saturated and unsaturated fatty acids into its lipid membrane. S. aureus encounters unsaturated fatty acids in the host skin where they serve as an innate immune defence due to their toxicity. Previously, we identified a fatty acid kinase in S. aureus that is necessary for the utilization of exogenous fatty acids. The goal of this study was to determine the effects of fatty acids on mutants deficient ...

The quantity and distribution of biofilm growth of Escherichia coli strain ATCC 9723 depends on the carbon/energy source.

Escherichia coli strain 15 (ATCC 9723) formed robust biofilms of two distinct forms on glass tubes. In rich, low-osmolarity medium, the biofilms were restricted to the air/liquid interface, resulting in rings attached to the glass. As it was not evident that these biofilms extended across the liquid surface, we termed them 'ring' rather than 'pellicle' biofilms. In minimal medium supplemented with a non-fermentable substrate as the carbon/energy source, we observed either robust ring biofilms or little biof...

SrcA is a chaperone for the Salmonella SPI-2 type three secretion system effector SteD.

Effector proteins of type three secretion systems (T3SS) often require cytosolic chaperones for their stabilization, to interact with the secretion machinery and to enable effector delivery into host cells. We found that deletion of srcA, previously shown to encode a chaperone for the Salmonella pathogenicity island 2 (SPI-2) T3SS effectors SseL and PipB2, prevented the reduction of mature Major Histocompatibility Complex class II (mMHCII) from the surface of antigen-presenting cells during Salmonella infec...

Avoiding amino acid depletion in a complex medium results in improved Escherichia coli BW25113 growth.

We studied Escherichia coli BW25113 growth in a complex medium with emphasis on amino acid consumption. The aim was to profile amino acid utilization in acid-hydrolysed casein and a defined nutrient-rich medium and based on these measurements modify the medium for better growth performance. Amino acid depletions in both media caused apparent biomass growth stops that prolonged growth duration. Obtained amino acid consumption values enabled a new defined medium to be formulated, where no growth stops were ob...

Utilization of macrophage extracellular trap nucleotides by Mycoplasma hyopneumoniae.

Mycoplasma hyopneumoniae is the causative agent of enzootic pneumonia in swine, an important disease worldwide. It has finite biosynthetic capabilities, including a deficit in de novo nucleotide synthesis. The source(s) for nucleotides in vivo are unknown, but mycoplasmas are known to carry membrane-bound nucleases thought to participate in the acquisition of nucleotides from host genomic DNA. Recent research has demonstrated that neutrophils can produce extracellular traps (NETs), chromatin NETs decorated ...


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