biostudies-literaturePiccardi PEuropean Research Council828-840https://www.ebi.ac.uk/biostudies/studies/S-EPMC11637553biostudies-literatureUnknown8(6)Microbial evolution is typically studied in monocultures or in communities of competing species. But microbes do not always compete and how positive inter-species interactions drive evolution is less clear: Initially facilitative communities may either evolve increased mutualism, increased reliance on certain species according to the Black Queen Hypothesis (BQH), or weaker interactions and resource specialization. To distinguish between these outcomes, we evolved four species for 44 weeks either alone or together in a toxic pollutant. These species initially facilitated each other, promoting each other's survival and pollutant degradation. After evolution, two species (<i>Microbacterium liquefaciens</i> and <i>Ochrobactrum anthropi</i>) that initially relied fully on others to survive contEvolution lettersThe evolution of reduced facilitation in a four-species bacterial community.PMC11637553715097Garcia-Garcera MPiccardi PMartino RDMitri SUlrich ETesta SEAfalseThe evolution of reduced facilitation in a four-species bacterial community.Microbial evolution is typically studied in monocultures or in communities of competing species. But microbes do not always compete and how positive inter-species interactions drive evolution is less clear: Initially facilitative communities may either evolve increased mutualism, increased reliance on certain species according to the Black Queen Hypothesis (BQH), or weaker interactions and resource specialization. To distinguish between these outcomes, we evolved four species for 44 weeks either alone or together in a toxic pollutant. These species initially facilitated each other, promoting each other's survival and pollutant degradation. After evolution, two species (<i>Microbacterium liquefaciens</i> and <i>Ochrobactrum anthropi</i>) that initially relied fully on others to survive cont2024-01-01T00:00:00Z2024 Dec2026-06-03T03:07:32.367Z2025-04-04T02:32:52.628ZS-EPMC116375533967757810.1093/evlett/qrae036