Effect of amino acids on anaerobic microbial communities

The mutualistic cooperation among members of microbial communities based on the exchange of public goods such as amino acids (AAs) has attracted widespread attention. How the availability of AAs in the environment affects the interactions among members and the structure and function of a community is a core issue. This issue has only been studied in artificially constructed flora and has not yet been explored in natural complex microbial communities. To further validate the effect of AA accessibility on complex microbial communities and its mechanism of action, trace amounts of AAs combinations with different synthetic costs (low cost, medium cost, high cost, and all 20 AAs) were supplemented separately to acetate-degrading thermophilic methanogenic reactors, and the differences in microbial community structure and co-occurring networks of main members were compared to a control reactor without AA supplementation. The results showed that the supplementation of AAs significantly affected the bacterial community as well as the biogas production and biogas composition. Increased accessibility of AAs significantly reduced the number of interactions between members, and increased accessibility of AAs with high synthetic costs significantly reduced the proportion of positive interactions between members in community. This study provides meaningful references to the effects of public goods accessibility on the interactions between members of complex microbial communities, as well as on community function.