Ahn, T. I.

Park, M.

Yang, GS

The X-bacteria are obligate endocellular symbionts and induce irreversible genetic changes to the host nucleus. In molecular phylogeny we confirmed the bacteria as Candiatus ‘Legionella jeonii’. In order to detect genes related to intracellular survival and integration to the host we performed comparative genomic analysis. A total of 520 non-redundant clones from a genomic DNA library were tagged by nucleotide sequencing. Among 1087 genes tagged in 1,6 Mbp DNA insert to date, we identified 402 genes of assigned functions, 195 conserved hypothetical genes and 490 genes of low homology. Comparing with the genome of Legionella pneumophilla (3.4 Mbp), about half of the genome of L. jeonii has been tagged. The 58.2% of high and 31.4% of low homology genes had matches in L. pneumophila database. We predicted 29 genes of L. jeonii to be related with infection and endocellular life style including genes for stress proteins (dnaJK, dpsA, and mutT), virulence (dotA, icmKTS, and lvrABC), infection and pathogenecity (rcp, rhuM, rpfB, and sbpA), drug resistance (mdfA and norM), transporter proteins (ceaA, necA, and proP), type IV secretion system (virB3), a global response regulation sensor kinase (grrS), a GTP-binding protein (rabB) and ppGpp-regulated growth inhibitors (mazEF). We detected 24 putative transposases relevant to genetic interaction among genomes in the symbiotic system. These results suggest that L. jeonii still contains most genes for infectivity and endocellular life style of pathogenic bacteria and that the genome has potential for genetic interaction in symbiosis and evolution.

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