Shewanella algae is known for its ability to
alter the ionization state of toxic chemicals and is therefore important in
bioremediation, however it is also gradually emerging as a human pathogen. It
is frequently isolated from different infection sites and is capable of causing
a range of diseases from soft tissue infections to bacteremia. Members
belonging to the genus Shewanella are
genetically very diverse, which complicates molecular taxonomy but more
importantly suggests the likelihood of lateral gene transfer (LGT) playing a
major role in shaping the representative genomes. The role of LGT is perhaps
not surprising, given the ability of S.
algae to survive in diverse habitats including fresh and salt water, spoilt
food, sewage and different parts of the human body. The ability to survive in a
range of habitats also exposes S. algae
to a wider gene pool, contributed by multiple organisms, further increasing the
potential for LTG. Our group recently recovered a S. algae isolate, SA1, from Sydney on bacteriological growth media
formulated for the selection of Vibrio
cholerae. We characterized the genome of SA1, (the first S. algae genome to be sequenced) and carried
out a comparative genomic analysis with other members of the genus Shewanella. This analysis revealed a myriad
of ‘S. algae-specific’ genes encoding
putative virulence factors. Proteomic analysis of SA1 lysates grown on LB-agar,
horse blood-agar and TCSB-agar showed that many putative virulence factors were
expressed only when SA1 was grown in the presence of bile salts or blood -
suggesting that gene expression was regulated to suit a specific lifestyle
choice. A detailed analysis of our proteomic and genomic data of SA1 suggests that
this marine microorganism carries the requisite genetic repertoire important for
an emerging pathogen.