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Bioluminescent Bacteria and Fish
Name: Dale
Status: Student
Age: 19
Location: N/A
Country: N/A
Date: N/A
Question:
I read that certain deep sea fishes have spots of
bioluminescence directly under their eye, this
made possible by a colony of luminescent bacteria living there.
How do the
bacteria manage to get into this spot in every fish? Or are there just
some fish with this spot
and some without, without actual regard as to which species it is but
rather just which fish was lucky enough to meet up
with some bacteria?
Replies:
Hi Dale,
You are right, 'always' and 'never' are very strong
concepts in biology, however host-specificity in
bacteria can be very definite. It is best described
for bacterial pathogens that colonize some hosts but
not others, and cause disease in some (or all) of the
hosts they colonize. Commensals and symbionts also
display host-specificity, dictated by adhesin-receptor
interactions, and less well-defined mechanisms. In the
case of luminous bacteria in fish light organs, my
guess is that this is a specific interaction, where
only certain fish species 'allow' the presence of only
certain types of bacteria. In this particular case it
even seems gender specific. I couldn't find literature
that described the mechanism behind it, but you can
guess this may be hormone-dependent (do male fishes
produce a light-organ all together?), or receptor
specific.
In conclusion, the interaction of these fish and their
bacteria is probably specific. The way these bacteria
find their right host may be by chance. It is likely
that both bacteria and host profit from the situation.
Trudy Wassenaar
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Update: June 2012
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