Zobrazení zdroje stránky Pittsrubin2213

The healthy human epidermis provides physical protection and is impenetrable for pathogenic microbes. Nevertheless, commensal and pathogen bacteria such as Staphylococcus aureus are able to colonize the skin surface, which may subsequently lead to infection. To identify and characterize regulatory elements facilitating adaptation of S. aureus to the human skin environment we used ex vivo tissue explants and quantified S. aureus gene transcription during co-culture. This analysis provided evidence for a significant downregulation of the global virulence regulator agr upon initial contact with skin, regardless of the growth phase of S. aureus prior to co-culture. In contrast, the alternative sigma factor B (sigB) and the antimicrobial peptide-sensing system (graRS) were expressed during early colonization. Consistently, sigB target genes such as the clumping factor A (clfA) and fibrinogen and fibronectin binding protein A (fnbA) were strongly upregulated upon skin contact. At later timepoints of the adhesion process, wall teichoic acid (WTA) synthesis was induced. Besides the expression of adhesive molecules, transcription of molecules involved in immune evasion were increased during late colonization (staphylococcal complement inhibitor and staphylokinase). Similar to nasal colonization, enzymes involved in cell wall metabolism (sceD and atlA) were highly transcribed. Finally, we detected a strong expression of proteases from all three catalytic classes during the entire colonization process. Taken together, we here present an ex vivo skin colonization model that allows the detailed characterization of the bacterial adaptation to the skin environment.Conjugative mega-plasmids play a special role in adaptation since they carry a huge number of accessory genes, often allowing the host to develop in new niches. In addition, due to conjugation they are able to effectively spread themselves and participate in the transfer of small mobilizable plasmids. In this work, we present a detailed characterization of a recently discovered family of multiple-drug resistance mega-plasmids of Acinetobacter species, termed group III-4a. We describe the structure of the plasmid backbone region, identify the rep gene and the origin of plasmid replication, and show that plasmids from this group are able not only to move between different Acinetobacter species but also to efficiently mobilize small plasmids containing different mob genes. Furthermore, we show that the population of natural Acinetobacter strains contains a significant number of mega-plasmids and reveal a clear correlation between the living conditions of Acinetobacter strains and the structure of their mega-plasmids. In particular, comparison of the plasmids from environmental and clinical strains shows that the genes for resistance to heavy metals were eliminated in the latter, with the simultaneous accumulation of antibiotic resistance genes by incorporation of transposons and integrons carrying these genes. The results demonstrate that this group of mega-plasmids plays a key role in the dissemination of multi-drug resistance among Acinetobacter species.L-2-halocid dehalogenases (L-2-HADs) have been mainly characterized from terrestrial polluted environments. [https://www.selleckchem.com/products/taurocholic-acid-sodium-salt-hydrate.html Taurocholic acid chemical] By contrast, knowledge is still scarce about their role in detoxification of predominant halocarbons in marine environments. Here, phylogenetic analyses showed a wide diversity of homologous L-2-HADs, especially among those belonging to marine bacteria. Previously characterized terrestrial L-2-HADs were part of a monophyletic group (named group A) including proteins of terrestrial and marine origin. Another branch (named group B) contained mostly marine L-2-HADs, with two distinct clades of Bacteroidetes homologs, closely linked to Proteobacteria ones. This study further focused on the characterization of the only L-2-HAD from the flavobacterium Zobellia galactanivorans DsijT (ZgHAD), belonging to one of these Group B clades. The recombinant ZgHAD was shown to dehalogenate bromo- and iodoacetic acids, and gene knockout in Z. galactanivorans revealed a direct role of ZgHAD in tolerance against both haloacetic acids. Analyses of metagenomic and metatranscriptomic datasets confirmed that L-2-HADs from group A were well-represented in terrestrial and marine bacteria, whereas ZgHAD homologs (group B L-2-HADs) were mainly present in marine bacteria, and particularly in host-associated species. Our results suggest that ZgHAD homologs could be key enzymes for marine Bacteroidetes, by conferring selective advantage for the recycling of toxic halogen compounds produced in particular marine habitats, and especially during interactions with macroalgae.Phage therapy, the therapeutic usage of viruses to treat bacterial infections, has many theoretical benefits in the 'post antibiotic era.' Nevertheless, there are currently no approved mainstream phage therapies. One reason for this is a lack of understanding of the complex interactions between bacteriophage, bacteria and eukaryotic hosts. These three-component interactions are complex, with non-linear or synergistic relationships, anatomical barriers and genetic or phenotypic heterogeneity all leading to disparity between performance and efficacy in in vivo versus in vitro environments. Realistic computer or mathematical models of these complex environments are a potential route to improve the predictive power of in vitro studies for the in vivo environment, and to streamline lab work. Here, we introduce and review the current status of mathematical modeling and highlight that data on genetic heterogeneity and mutational stochasticity, time delays and population densities could be critical in the development of realistic phage therapy models in the future. With this in mind, we aim to inform and encourage the collaboration and sharing of knowledge and expertise between microbiologists and theoretical modelers, synergising skills and smoothing the road to regulatory approval and widespread use of phage therapy.Class A β-lactamases are known for being able to rapidly gain broad spectrum catalytic efficiency against most β-lactamase inhibitor combinations as a result of elusively minor point mutations. The evolution in class A β-lactamases occurs through optimisation of their dynamic phenotypes at different timescales. At long-timescales, certain conformations are more catalytically permissive than others while at the short timescales, fine-grained optimisation of free energy barriers can improve efficiency in ligand processing by the active site. Free energy barriers, which define all coordinated movements, depend on the flexibility of the secondary structural elements. The most highly conserved residues in class A β-lactamases are hydrophobic nodes that stabilize the core. To assess how the stable hydrophobic core is linked to the structural dynamics of the active site, we carried out adaptively sampled molecular dynamics (MD) simulations in four representative class A β-lactamases (KPC-2, SME-1, TEM-1, and SHV-1). Using Markov State Models (MSM) and unsupervised deep learning, we show that the dynamics of the hydrophobic nodes is used as a metastable relay of kinetic information within the core and is coupled with the catalytically permissive conformation of the active site environment. Our results collectively demonstrate that the class A enzymes described here, share several important dynamic similarities and the hydrophobic nodes comprise of an informative set of dynamic variables in representative class A β-lactamases.Since the discovery of Mimivirus, viruses with large genomes encoding components of the translation machinery and other cellular processes have been described as belonging to the nucleocytoplasmic large DNA viruses. Recently, genome-resolved metagenomics led to the discovery of more than 40 viruses that have been grouped together in a proposed viral subfamily named Klosneuvirinae. Members of this group had genomes of up to 2.4Mb in size and featured an expanded array of translation system genes. Yet, despite the large diversity of the Klosneuvirinae in metagenomic data, there are currently only two isolates available. Here, we report the isolation of a novel giant virus known as Fadolivirus from an Algerian sewage site and provide morphological data throughout its replication cycle in amoeba and a detailed genomic characterization. The Fadolivirus genome, which is more than 1.5Mb in size, encodes 1,452 predicted proteins and phylogenetic analyses place this viral isolate as a near relative of the metagenome assembled Klosneuvirus and Indivirus. The genome encodes for 66 tRNAs, 23 aminoacyl-tRNA synthetases and a wide range of transcription factors, surpassing Klosneuvirus and other giant viruses. The Fadolivirus genome also encodes putative vacuolar-type proton pumps with the domains D and A, potentially constituting a virus-derived system for energy generation. The successful isolation of Fadolivirus will enable future hypothesis-driven experimental studies providing deeper insights into the biology of the Klosneuvirinae.Streptococcus pyogenes (group A Streptococcus-GAS) is an important pathogen for humans. GAS has been associated with severe and invasive diseases. Despite the fact that these bacteria remain universally susceptible to penicillin, therapeutic failures have been reported in some GAS infections. Many hypotheses have been proposed to explain these antibiotic-unresponsive infections; however, none of them have fully elucidated this phenomenon. In this study, we show that GAS strains have the ability to form antimicrobial persisters when inoculated on abiotic surfaces to form a film of bacterial agglomerates (biofilm-like environment). Our data suggest that efflux pumps were possibly involved in this phenomenon. In fact, gene expression assays by real-time qRT-PCR showed upregulation of some genes associated with efflux pumps in persisters arising in the presence of penicillin. Phenotypic reversion assay and whole-genome sequencing indicated that this event was due to non-inherited resistance mechanisms. The persister cells showed downregulation of genes associated with protein biosynthesis and cell growth, as demonstrated by gene expression assays. Moreover, the proteomic analysis revealed that susceptible cells express higher levels of ribosome proteins. It is remarkable that previous studies have reported the recovery of S. pyogenes viable cells from tissue biopsies of patients presented with GAS invasive infections and submitted to therapy with antibiotics. The persistence phenomenon described herein brings new insights into the origin of therapeutic failures in S. pyogenes infections. Multifactorial mechanisms involving protein synthesis inhibition, cell growth impairment and efflux pumps seem to play roles in the formation of antimicrobial persisters in S. pyogenes.Members of the genus Paradileptus are apex predators in microbial food webs. They are often encountered in freshwater biotopes and have been used in research on water quality monitoring and ecology. Nevertheless, our understanding of the biodiversity of Paradileptus, especially its ecological and genetic diversities, is very poor which hinders our ability to understand the ecosystem services it provides. The present study gives a detailed account of two Chinese populations of Paradileptus elephantinus and P. conicus including their living morphology, infraciliature, and molecular phylogenies based on 18S, 5.8S, and ITS ribosomal DNA sequences. The phylogenetic relationships between these two species and other rhynchostomatians are investigated. We also explore the potential contribution of differentiation of the proboscis (e.g., extrusomes, dorsal brush, and differentiated kineties) to niche partitioning and speciation in Paradileptus. The global distribution of Paradileptus is summarized based on published data.