Antibiotics regulate bacterial diversification, niche expansion and evolution under primordial conditions

Antibiotics or bioactive small molecules and building blocks of life are simultaneously generated in the same chemical reaction networks that led to the origin of life. They play a pivotal yet unexplored role in maintaining the biosphere, particularly in the evolution of primordial microorganisms. We enriched bacterial communities (designated as #3 and #5) with earliest energetic metabolisms through monopolization effects from two groundwater samples using a "primordial soup" approach. These communities were exposed to tetracycline, penicillin, and chloramphenicol to investigate their impacts on bacterial evolution in a simulated primordial environment. Our findings indicate that antibiotics can counteract monopolization effects by stimulating the production of additional or enhanced energy sources such as sulfide, acetate, nitrate, and sulfate for earliest energetic metabolic bacteria. This leads to the expansion of bacterial niches and rapid adaptation of bacteria to new energy sources. Notably, tetracycline exposure may amplify the diversity disparity between autotrophs and heterotrophs in the #5 bacterial community, which is conducive to maintaining the stability of the micro-ecosystem in a primordial environment. Importantly, antibiotics accelerate bacterial phenotypic differentiation by increasing the abundance of Caulobacter and Piscinibacter. Together, antibiotics as by-products, along with building blocks of life are simultaneously generated in the same primordial chemical reaction network that led to the origin of life, serve as an evolutionary force that drives the diversification and niche expansion of primordial microorganisms, maintains micro-ecosystem stability, counteracts monopolization effects, and promotes the evolution of primordial microorganisms.