Genomic Insights into a New Citrobacter koseri Strain Revealed Gene Exchanges with the Virulence-Associated Yersinia pestis pPCP1 Plasmid.

The history of infectious diseases raised the plague as one of the most devastating for human beings. Far too often considered an ancient disease, the frequent resurgence of the plague has led to consider it as a reemerging disease in Madagascar, Algeria, Libya, and Congo. The genetic factors associated with the pathogenicity of Yersinia pestis, the causative agent of the plague, involve the acquisition of the pPCP1 plasmid that promotes host invasion through the expression of the virulence factor Pla. The surveillance of plague foci after the 2003 outbreak in Algeria resulted in a positive detection of the specific pla gene of Y. pestis in rodents. However, the phenotypic characterization of the isolate identified a Citrobacter koseri. The comparative genomics of our sequenced C. koseri URMITE genome revealed a mosaic gene structure resulting from the lifestyle of our isolate and provided evidence for gene exchanges with different enteric bacteria. The most striking was the acquisition of a continuous 2 kb genomic fragment containing the virulence factor Pla of the Y. pestis pPCP1 plasmid; however, the subcutaneous injection of the CKU strain in mice did not produce any pathogenic effect. Our findings demonstrate that fast molecular detection of plague using solely the pla gene is unsuitable and should rather require Y. pestis gene marker combinations. We also suggest that the evolutionary force that might govern the expression of pathogenicity can occur through the acquisition of virulence genes but could also require the loss or the inactivation of resident genes such as antivirulence genes.

Non contiguous-finished genome sequence and description of Bacillus jeddahensis sp. nov.

Strain JCE(T) was isolated from the fecal sample of a 24-year-old obese man living in Jeddah, Saudi Arabia. It is an aerobic, Gram-positive, rod-shaped bacterium. This strain exhibits a 16S rRNA nucleotide sequence similarity of 97.5 % with Bacillus niacini, the phylogenetically closest species with standing nomenclature. Moreover, the strain JCE(T) presents many phenotypic differences, when it is compared to other Bacillus species, and shows a low MALDI-TOF Mass Spectrometry score that does not allow any identification. Thus, it is likely that this strain represents a new species. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 4,762,944 bp long genome (1 chromosome but no plasmid) contains 4,654 protein-coding and 98 RNAs genes, including 92 tRNA genes. The strain JCE(T) differs from most of the other closely Bacillus species by more than 1 % in G + C content. In addition, digital DNA-DNA hybridization values for the genome of the strain JCE(T) against the closest Bacillus genomes range between 19.5 to 28.1, that confirming again its new species status. On the basis of these polyphasic data made of phenotypic and genomic analyses, we propose the creation of Bacillus jeddahensis sp. nov. that contains the strain JCE(T).

Staphylococcus aureus subsp. anaerobius strain ST1464 genome sequence.

Staphylococcus aureus subsp. anaerobius is responsible for Morel's disease in animals and a cause of abscess in humans. It is characterized by a microaerophilic growth, contrary to the other strains of S. aureus. The 2,604,446-bp genome (32.7% GC content) of S. anaerobius ST1464 comprises one chromosome and no plasmids. The chromosome contains 2,660 open reading frames (ORFs), 49 tRNAs and three complete rRNAs, forming one complete operon. The size of ORFs ranges between 100 to 4,600 bp except for two ORFs of 6,417 and 7,173 bp encoding segregation ATPase and non-ribosomal peptide synthase, respectively. The chromosome harbors Staphylococcus phage 2638A genome and incomplete Staphylococcus phage genome PT1028, but no detectable CRISPRS. The antibiotic resistance gene for tetracycline was found although Staphylococcus aureus subsp. anaerobius is susceptible to tetracycline in-vitro. Intact oxygen detoxification genes encode superoxide dismutase and cytochrome quinol oxidase whereas the catalase gene is impaired by a stop codon. Based on the genome, in-silico multilocus sequence typing indicates that S. aureus subsp. anaerobius emerged as a clone separated from all other S. aureus strains, illustrating host-adaptation linked to missing functions. Availability of S. aureus subsp. anaerobius genome could prompt the development of post-genomic tools for its rapid discrimination from S. aureus.