Antibiotics: Conflict and Communication in Microbial Communities Antibiotics mediate species interactions in natural habitats, affecting the dynamics of microbial coevolution

The discovery that microbes produce antibiotic compounds that kill or inhibit other microbes revolutionized modern medicine by offering a means to treat microbial infections. Thus, the “golden age” of antibiotic discovery began when hundreds of antibiotics from diverse microbial genera were characterized for their effıcacy in controlling pathogens and the infections they cause. When used at subinhibitory concentrations, however, antibiotics can alter microbial gene expression, suggesting that they also act as signaling compounds. The threat of a postantibiotic era in human medicine is galvanizing another search for novel antibiotics, raising questions about what ecological conditions are likely to lead to novel or inhibitory phenotypes. Meanwhile, some experts are also seeking to identify environmental reservoirs of antibiotic resistance genes, while wondering what maintains antibiotic resistance in natural habitats. Similarly, agricultural scientists, who are interested in managing soil microbes as an alternative means to inhibit plant pathogens and reduce reliance on pesticides, do not know what selects for broadly antagonistic communities of soil microorganisms. Recent research in our lab and by others is shedding light on how antibioticsmediate species interactions in natural habitats and on how they affect the dynamics of microbial coevolution. Insights into the specifıc roles of antibiotics in naturally occurring communities can not only lead us to antibiotic discoveries, but may help explain how distinct phenotypic structures are generated and how to better manage microbial communities for specifıc functions.