232 research outputs found
Rusland: En grå stormagts dilemmaer
Jens Worning Sørensen ser på Rusland og det frygtede såkaldte gasvåben, som han dog mener i dag er stærkt overvurderet. 
Staphylococcus saprophyticus causing infections in humans is associated with high resistance to heavy metals
Research Areas: Microbiology ; Pharmacology & PharmacyStaphylococcus saprophyticus is a common pathogen of the urinary tract, a
heavy metal-rich environment, but information regarding its heavy metal resistance is
unknown. We investigated 422 S. saprophyticus isolates from human infection and colonization/contamination, animals, and environmental sources for resistance to copper, zinc,
arsenic, and cadmium using the agar dilution method. To identify the genes associated
with metal resistance and assess possible links to pathogenicity, we accessed the wholegenome sequence of all isolates and used in silico and pangenome-wide association
approaches. The MIC values for copper and zinc were uniformly high (1,600mg/liter).
Genes encoding copper efflux pumps (copA, copB, copZ, mco, and csoR) and zinc transporters (zinT, czrAB, znuBC, and zur) were abundant in the population (20 to 100%).
Arsenic and cadmium showed various susceptibility levels. Genes encoding the ars operon
(arsRDABC), an ABC transporter and a two-component permease, were linked to resistance
to arsenic (MICs 200mg/liter; 20% [85/422]; P, 0.05). These resistance genes were frequently carried
by mobile genetic elements. Resistance to arsenic and cadmium were linked to human
infection and a clonal lineage originating in animals (P, 0.05). Altogether, S. saprophyticus
was highly resistant to heavy metals and accumulated multiple metal resistance determinants. The highest arsenic and cadmium resistance levels were associated with infection,
suggesting resistance to these metals is relevant for S. saprophyticus pathogenicityinfo:eu-repo/semantics/publishedVersio
Evidence for the evolutionary steps leading to mecA-mediated ß-lactam resistance in staphylococci
The epidemiologically most important mechanism of antibiotic resistance in Staphylococcus aureus is associated with mecA–an acquired gene encoding an extra penicillin-binding protein (PBP2a) with low affinity to virtually all β-lactams. The introduction of mecA into the S. aureus chromosome has led to the emergence of methicillin-resistant S. aureus (MRSA) pandemics, responsible for high rates of mortality worldwide. Nonetheless, little is known regarding the origin and evolution of mecA. Different mecA homologues have been identified in species belonging to the Staphylococcus sciuri group representing the most primitive staphylococci. In this study we aimed to identify evolutionary steps linking these mecA precursors to the β-lactam resistance gene mecA and the resistance phenotype. We sequenced genomes of 106 S. sciuri, S. vitulinus and S. fleurettii strains and determined their oxacillin susceptibility profiles. Single-nucleotide polymorphism (SNP) analysis of the core genome was performed to assess the genetic relatedness of the isolates. Phylogenetic analysis of the mecA gene homologues and promoters was achieved through nucleotide/amino acid sequence alignments and mutation rates were estimated using a Bayesian analysis. Furthermore, the predicted structure of mecA homologue-encoded PBPs of oxacillin-susceptible and -resistant strains were compared. We showed for the first time that oxacillin resistance in the S. sciuri group has emerged multiple times and by a variety of different mechanisms. Development of resistance occurred through several steps including structural diversification of the non-binding domain of native PBPs; changes in the promoters of mecA homologues; acquisition of SCCmec and adaptation of the bacterial genetic background. Moreover, our results suggest that it was exposure to β-lactams in human-created environments that has driven evolution of native PBPs towards a resistance determinant. The evolution of β-lactam resistance in staphylococci highlights the numerous resources available to bacteria to adapt to the selective pressure of antibiotics
Complete genome sequence of <em>Staphylococcus aureus</em> strain M1, a unique t024-ST8-IVa Danish methicillin-resistant <i>S.</i> <em>aureus</em> clone
We report the genome sequence, in five contigs, of a methicillin-resistant Staphylococcus aureus isolate designated M1. This clinical isolate was from the index patient of a methicillin-resistant Staphylococcus aureus (MRSA) outbreak in Copenhagen, Denmark, that started in 2003. This strain is sequence type 8 (ST8), spa type t024, and staphylococcal cassette chromosome mec element (SCCmec) type IVa
Coexistence of different base periodicities in prokaryotic genomes as related to DNA curvature, supercoiling, and transcription
We analyzed the periodic patterns in E. coli promoters and compared the
distributions of the corresponding patterns in promoters and in the complete
genome to elucidate their function. Except the three-base periodicity,
coincident with that in the coding regions and growing stronger in the region
downstream from the transcriptions start (TS), all other salient periodicities
are peaked upstream of TS. We found that helical periodicities with the lengths
about B-helix pitch ~10.2-10.5 bp and A-helix pitch ~10.8-11.1 bp coexist in
the genomic sequences. We mapped the distributions of stretches with A-, B-,
and Z- like DNA periodicities onto E.coli genome. All three periodicities tend
to concentrate within non-coding regions when their intensity becomes stronger
and prevail in the promoter sequences. The comparison with available
experimental data indicates that promoters with the most pronounced
periodicities may be related to the supercoiling-sensitive genes.Comment: 23 pages, 6 figures, 2 table
Ori-Finder: A web-based system for finding oriCs in unannotated bacterial genomes
<p>Abstract</p> <p>Background</p> <p>Chromosomal replication is the central event in the bacterial cell cycle. Identification of replication origins (<it>oriC</it>s) is necessary for almost all newly sequenced bacterial genomes. Given the increasing pace of genome sequencing, the current available software for predicting <it>oriC</it>s, however, still leaves much to be desired. Therefore, the increasing availability of genome sequences calls for improved software to identify <it>oriC</it>s in newly sequenced and unannotated bacterial genomes.</p> <p>Results</p> <p>We have developed Ori-Finder, an online system for finding <it>oriC</it>s in bacterial genomes based on an integrated method comprising the analysis of base composition asymmetry using the <it>Z</it>-curve method, distribution of DnaA boxes, and the occurrence of genes frequently close to <it>oriC</it>s. The program can also deal with unannotated genome sequences by integrating the gene-finding program ZCURVE 1.02. Output of the predicted results is exported to an HTML report, which offers convenient views on the results in both graphical and tabular formats.</p> <p>Conclusion</p> <p>A web-based system to predict replication origins of bacterial genomes has been presented here. Based on this system, <it>oriC </it>regions have been predicted for the bacterial genomes available in GenBank currently. It is hoped that Ori-Finder will become a useful tool for the identification and analysis of <it>oriC</it>s in both bacterial and archaeal genomes.</p
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