FUMIHIKO TAKEUCHI & KEIICHI HIRAMATSU (Juntendo University, Tokyo, Japan)</br>

Comparative genomics among <I>Staphylococcus</I> species and strains
for the identification of genomic islands (Gislands) involved in
pathogenesis and drug resistance</br></br>

<B>Introduction. </B><I>Staphylococcus aureus</I> is one of the most
important hospital pathogens. We previously identified its
pathogenesis and drug resistance capability on several genomic islands
(Gislands) of its chromosome. However, we also learned that the
repertoire of Gislands and their deployment on the chromosome differ
from strain to strain. In this study, we developed a new approach to
identify the realm of diversity of the Gisland families in
<I>S.aureus</I>. A total of ten staphylococcal chromosomes were
analyzed in this study; they were seven <I>S.aureus</I>, two
<I>S.epidermidis</I>, and one <I>S.haemolyticus</I>
strains.<BR><B>Methods. </B>Two independent programs were used for
analysis: (1) Pattern of homologue set distribution across the
chromosome: "homologue sets" among the 10 strains were identified, and
were classified according to their distribution pattern. (2) Whole
genome multiple alignment: for the detection of dissimilar regions
among the chromosomes. <BR><B>Results. </B>Combined use of the above
two methods clearly demonstrated the Gislands' distribution across the
<I>S.aureus</I> chromosome where candidate <I>orfs</I> of foreign
origin were accumulated. A total of 188 Gislands and Gislets (smaller
Gislands) were identified among seven <I>S.aureus</I>
chromosomes. Method 1 clearly demonstrated the first sextant of
<I>S.aureus</I> chromosome as the locale of accumulation of foreign
genes. <BR><B>Conclusion. </B>The program turned out to be a powerful
visual identification tool of bacterial Gisland and Gislet families.