Mainstreams of Horizontal Gene Exchange in Enterobacteria: Consideration of the Outbreak of Enterohemorrhagic E. coli O104:H4 in Germany in 2011

Escherichia coli O104:H4 caused a severe outbreak in Europe in 2011. The strain TY-2482 sequenced from this outbreak allowed the discovery of its closest relatives but failed to resolve ways in which it originated and evolved. On account of the previous statement, may we expect similar upcoming outbreaks to occur recurrently or spontaneously in the future? The inability to answer these questions shows limitations of the current comparative and evolutionary genomics methods.status: publishe

Full Sequence and Comparative Analysis of the Plasmid pAPEC-1 of Avian Pathogenic E. coli χ7122 (O78∶K80∶H9)

(APEC), are very diverse. They cause a complex of diseases in Human, animals, and birds. Even though large plasmids are often associated with the virulence of ExPEC, their characterization is still in its infancy., are also present in the sequence of pAPEC-1. The comparison of the pAPEC-1 sequence with the two available plasmid sequences reveals more gene loss and reorganization than previously appreciated. The presence of pAPEC-1-associated genes is assessed in human ExPEC by PCR. Many patterns of association between genes are found.The pathotype typical of pAPEC-1 was present in some human strains, which indicates a horizontal transfer between strains and the zoonotic risk of APEC strains. ColV plasmids could have common virulence genes that could be acquired by transposition, without sharing genes of plasmid function

Genome Sequences and Phylogenetic Analysis of K88- and F18-Positive Porcine Enterotoxigenic Escherichia coli

Porcine enterotoxigenic Escherichia coli (ETEC) continues to result in major morbidity and mortality in the swine industry via postweaning diarrhea. The key virulence factors of ETEC strains, their serotypes, and their fimbrial components have been well studied. However, most studies to date have focused on plasmid-encoded traits related to colonization and toxin production, and the chromosomal backgrounds of these strains have been largely understudied. Here, we generated the genomic sequences of K88-positive and F18-positive porcine ETEC strains and examined the phylogenetic distribution of clinical porcine ETEC strains and their plasmid-associated genetic content. The genomes of porcine ETEC strains UMNK88 and UMNF18 were both found to contain remarkable plasmid complements containing known virulence factors, potential novel virulence factors, and antimicrobial resistance-associated elements. The chromosomes of these strains also possessed several unique genomic islands containing hypothetical genes with similarity to classical virulence factors, although phage-associated genomic islands dominated the accessory genomes of these strains. Phylogenetic analysis of 78 clinical isolates associated with neonatal and porcine diarrhea revealed that a limited subset of porcine ETEC lineages exist that generally contain common toxin and fimbrial profiles, with many of the isolates belonging to the ST10, ST23, and ST169 multilocus sequencing types. These lineages were generally distinct from existing human ETEC database isolates. Overall, most porcine ETEC strains appear to have emerged from a limited subset of E. coli lineages that either have an increased propensity to carry plasmid-encoded virulence factors or have the appropriate ETEC core genome required for virulence

Genome Plasticity in Pathogenic and Nonpathogenic Enterobacteria

The Enterobacteriaceae comprise a distinct phylogenetic cluster that share a common ancestor with other γ-Proteobacteria. This prokaryotic family comprises 40 genera with 200 species (Garrity 2001). Within this division many representatives live in intimate association with hosts either as pathogens, as commensals or as symbionts (Steinert et al. 2000). The best-studied examples are the entero-bacteria, which comprise the clinically relevant human and animal pathogenic species Escherichia coli, Salmonella enterica, and Shigella spp., as well as Yersinia pestis, Y. pseudotuberculosis and Y. enterocolitica. The entomopathogenic bacterium Photorhabdus luminescens also belongs to the Enterobacteriaceae. This bacterium is unusual in that it combines a symbiotic life style within the guts of nematodes with a pathogenic life style that results in the killing of insects. Among the γ-Proteobacteria there are many species establishing symbiotic interactions mostly with invertebrate hosts, for example with insects, with bioluminescent squid and other marine invertebrates, and with nematodes. The genomes of several pathogens and symbionts have been sequenced recently and work is still in progress. In spite of the diverse manifestations of bacteria-host interactions, there are similar fundamental mechanisms that mediate the interaction and communication between the bacterial and eukaryotic partners (Hentschel et al. 2000; Steinert et al. 2000)