by Roberto
There is no need to go into great length to describe the current interest in the human microbiome, particularly the intestinal microbiome. It's a topic in microbial ecology that has recently attracted scientists and laypeople from across the world. But from reading about it in both the scientific literature and the popular press, the field could be thought to be relatively new. Some say it's a field in its infancy. Not true. Fact is, investigators have been interested in gut microbial ecology for pretty much as long as microbiology has been a discipline, as was nicely described in a recent perspective by Walker and Hoyles. My personal experience with the topic does not go quite that far back but still...
It was in the mid-1970s, during graduate school, when I was struck by the originality of a paper, from a group of Spanish microbiologists led by Fernando Baquero, that described the discovery of antibiotics from enterobacteria. The authors termed this family of low-molecular-weight compounds the microcins. The microcins were the reason I first traveled to Spain in 1983 and why I made such wonderful long-lasting friendships with numerous Spanish scientists, prime among them Felipe Moreno, Fernando Baquero, and Victor de Lorenzo. There is no doubt in my mind that they as well as others in Spain greatly helped get my career off the ground.
Fig. 1. Antibiotic assay for 6 enterobacteria isolated from infant feces on the growth of E. coli K-12. The picture shows the same plate, before and after laying aside the Cellophane film (lower part) on which the isolates had grown. The inhibitory effect of 3 of them can be seen. Source
What strikes me most about the discovery of the microcins is the ecological mindset of the investigators, who set out to study the chemical basis for species successions in the human intestine. Though written in 1976, their introductory words have a remarkable present-day ring to them: "Present knowledge on the chemical communication between the cells of microbial ecosystems is scarce. It is even the case for the bacterial population of the human intestinal tract where there is a rather well-defined community of microorganisms that show, however, a dynamic succession in both species composition and relative abundance of each type, under either normal or pathological conditions. Successions in these systems are not infrequently rapid and very specific in regard to the main invaders, which are able somehow to effectively displace other closely related bacterial species by mechanisms poorly understood." Their search for compounds that could mediate such successions was experimentally simple: identify compounds that could pass through cellophane (molecular weight cut-off ~1000 Daltons) and kill a lawn of E. coli. Their findings provided a solid foundation for present-day studies on the chemical ecology of the intestine and gave birth to the burgeoning field of the genetics of ribosomally synthesized and post-translationally modified peptides (RiPPs). Their thinking was many decades ahead!
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