Sept. 27, 2006 — There was a discussion in our class about fungi producing antibiotics in our bodies. We reasoned that fungi and bacteria compete for available nutrients so random mutations and survival of the fittest comes into play. Do scientists perceive this phenomenon in this way? Is it possible that fungi know everything about the metabolic pathways of bacteria and specifically produce antibiotics that target those pathways?

—Submitted by Shrikant Mantri, Indian Institute of Information Technology Allahabad

Response by Robert Wheeler Postdoctoral researcher in Whitehead Member Gerald Fink's lab

It is certainly possible that our body is able to sense bactericidal antibiotics produced by fungi. It is also likely that fungi are able to perceive the presence of bacteria, by sensing bacteria-specific metabolites. However, it is unlikely that fungi “know” anything specific about the bacterial metabolic pathways. Over evolutionary time, they have developed weapons that work, but only through trial-and-error rather than through design.

Specifically, fungi undergo random mutations over time and the mutations that confer a selective growth advantage (for instance by production of antibiotics that kill bacteria) will allow the fungi with those mutations to reproduce more efficiently. In this way, beneficial mutations will accumulate and those fungi that create effective antibiotics will survive while those that do not will die. In this way, natural selection acts on random mutations to drive evolutionary change without any forethought or planning on the part of the organisms.

Last updated September 27, 2006