Adding to Yersinia enterocolitica Gene Pool Diversity : Two Cryptic Plasmids from a Biotype 1A Isolate

Abstract EN

We report the nucleotide sequence of two novel cryptic plasmids (4357 and 14 662 base pairs) carried by a Yersinia enterocolitica biotype 1A strain isolated from pork.

As distinguished from most biotype 1A strains, this isolate, designated 07-04449, exhibited adherence to eukaryotic cells.

The smaller plasmid pYe4449-1 carries five attributable open reading frames (ORFs) encoding the first CcdA/CcdB-like antitoxin/toxin system described for a Yersinia plasmid, a RepA-like replication initiation protein, and mobilizing factors MobA and MobC.

The deduced amino acid sequences showed highest similarity to proteins described in Salmonella (CcdA/B), Klebsiella (RepA), and Plesiomonas (MobA/C) indicating genomic fluidity among members of the Enterobacteriaceae.

One additional ORF with unknown function, termed ORF5, was identified with an ancestry distinct from the rest of the plasmid.

While the C+G content of ORF5 is 38.3%, the rest of pYe4449-1 shows a C+G content of 55.7%.

The C+G content of the larger plasmid pYe4449-2 (54.9%) was similar to that of pYe4449-1 (53.7%) and differed from that of the Y.

enterocolitica genome (47.3%).

Of the 14 ORFs identified on pYe4449-2, only six ORFs showed significant similarity to database entries.

For three of these ORFs likely functions could be ascribed: a TnpR-like resolvase and a phage replication protein, localized each on a low C+G island, and DNA primase TraC.

Two ORFs of pYe4449-2, ORF3 and ORF7, seem to encode secretable proteins.

Epitope-tagging of ORF3 revealed protein expression at 4°C but not at or above 27°C suggesting adaptation to a habitat outside swine.

The hypothetical protein encoded by ORF7 is the member of a novel repeat protein family sharing the DxxGN(x)nDxxGN motif.

Our findings illustrate the exceptional gene pool diversity within the species Y.

enterocolitica driven by horizontal gene transfer events.