The antimicrobial properties of bacteria have been a focus of extensive research since the accidental discovery of penicillin in 1928. Research in the field has shown that bacteria produce antibiotics that eliminate a broad range of species. On the other hand, bacteria also produce antimicrobial compounds or toxins that eliminate a much narrower spectrum of species. An example of these antimicrobial compounds include bacteriocins, which mainly eliminate members of the same species or genus. The evolution of such a wide spectrum of antimicrobial compounds that target a large range of species and of compounds that target specific species, however, remains unknown. In a recent study, Jacob D. Palmer and Kevin R. Foster developed an evolutionary model to better understand the antimicrobial spectrum of bacteria.
The model studies the growth of a focal species that can evolve to use toxins; these toxins target either conspecific members that share the focal species’ ecological niche, or a wider bacterial community. The authors used a set of differential equations to model the growth of the focal species, the conspecific species and the larger range of bacteria fighting for limited resources. The system was assumed to be a patchy landscape, in which each patch had a different focal species, a different conspecific species and a different availability of nutrients; in each patch, the focal species had a different evolutionary strategy. In addition, each patch was modeled until one species emerges in that patch as a dominant species, following which an invasion analysis is carried out. The invasion analysis posits that one species with a certain evolutionary strategy invades another patch, and tries to use its own strategy in that environment. This was repeated until an evolutionarily stable strategy was reached such that a patch cannot be invaded by species with other strategies.
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