Characterization of the Microbial Community and Activity of Nitrate-Reducing, Benzene-Degrading Enrichment Cultures

Benzene is a natural component of crude oil. It is highly toxic, carcinogenic, and persistent contaminant. This work studied anaerobic benzene-degrading, nitrate-reducing enrichment cultures that were previously cultivated for over twenty years. Amplicon sequencing of nitrate-reducing cultures amended with benzene and benzene degradation intermediates provided evidence for a process by which Peptococcaceae is responsible for initial substitution of the benzene ring, followed by further degradation by Azoarcus. A qPCR study found an increase in copy number of Peptococcaceae and the abcA subunit of a putative anaerobic benzene carboxylase (Abc) associated with Peptococcaceae was correlated with benzene degradation. Further study of an Azoarcus-enrichment culture found that it was capable of degrading the BTEX compounds, but only under limited conditions. Finally, a metagenome was assembled for the benzene-degrading, nitrate-reducing culture. Annotation of metatranscriptome data to this metagenome provided further evidence for carboxylation of the benzene ring by Peptococcaceae.M.A.S