Ecological factors affecting toluene biosynthesis from bacterial communities.

As a highly emitted volatile organic compound, toluene significantly contributes to atmospheric pollution and poses high risks to human health. Its anthropogenic source is well understood, while its biosynthesis remains poorly understood, especially by bacterial communities. This research attempted to reveal the temporal changes of bacterial community structure during toluene biosynthesis and identify key bacterial factors using 16S rRNA sequencing gene and machine learning methods. The results showed that toluene biosynthesis by the bacterial consortium nonlinearly increased with phenylacetic acid concentration with the optimal temperature of 25-30 °C and pH of 7-7.5. Diversity and richness of the bacterial communities increased over time, as well as the abundance and composition of phyla (e.g. Bacteroidota and Synergistota), families (e.g. Acidaminococcaceae and Oscillospiraceae), species (e.g. Bacteroides and Parabacteroides), and functional genes (e.g. phenylalanine, tyrosine, and tryptophan biosynthesis and fatty acid metabolism). They were significantly related to toluene biosynthesis, of which the Shannon and Simpson indices and the abundances of Synergistaceae, Bacteroidaceae, and Spirochaetaceae species and functional genes related to metabolic pathways, biosynthesis of secondary metabolites, and alanine aspartate and glutamate metabolism were identified as key factors. Findings of this study contributed to new understandings of the underlying mechanisms of toluene biosynthesis by the bacterial community.