John Cherwonogrodzky urges members of this discussion group to engage in
discussion of fundamental principles every now and then, and that's a good
idea. He poses as a suitable subject the question of what is the "true"
function of antibiotics, and raises the possibility that it "is primarily to
shut down or inhibit biochemical pathways in the producer so that it can mature
into a different form. It just so happens that this inhibition works on other
life-forms. If so, even in relatively simple life-forms, antibiotics are being
produced to regulate or change pathways." He notes that what the antibiotic
producers have most in common is a "complicated life style".
In reply, I would suggest first that while the bacterial antibiotic producers
may indeed have more "complicated" life styles (e.g., spores) than do many
other bacteria, it isn't a very tight correlation (not all spore-formers
produce known antibiotics) -- and besides, the same doesn't hold true of the
molds, which are very simple compared to their teleomorphic (sexually
reproducing) cousins. Antibiotic secretion seems more closely tied to
ecological role than to morphological complexity.
Second, while some self-regulatory function is always a theoretical possibility
until disproven (ah, to disprove the negative), the fact still remains that in
the case of penicillin, at least, it would be a surprise indeed if its
marvelously specific activity against murein synthesis (strictly prokaryotic)
should turn out to be only an accidental side-effect of some entirely different
and as yet undiscovered role in Penicillium's own development. Pending at
least *some* evidence of autoregulatory function, this aspect of the hypothesis
seems unpersuasive.
Cherwonogrodzky is right to keep us questioning our paradigms, but until
someone genetically blocks antibiotic production in a normally producing strain
and shows a correlated block in some stage of development, we should continue
to think of antibiotics as being primarily, if not solely, weapons of
interspecific competition.
Terry W. Hill
Dept. of Biology
Rhodes College
Memphis, TN 38112
