Triclocarban (TCC), an emerging organic contaminant (EOC), has become a severe threat to soil microbial communities and ecological security. Here, the TCC-degrading strain Rhodococcus rhodochrous BX2 and DCA-degrading strain Pseudomonas sp. LY-1 (together referred to as TC1) were immobilized on biochar to remove TCC and its intermediates in TCC-contaminated soil. High-throughput sequencing was used to investigate the microbial community structure in TCC-contaminated soil. Analysis of co-occurrence networks was used to explore the mutual relationships among soil microbiome members. The results showed that the immobilized TC1 significantly increased the removal efficiency of TCC from 84.7 to 92.7% compared to CK (no TC1 cells on biochar) in 10 mg/L TCC liquid medium. The utilization of immobilized TC1 also significantly accelerated the removal of TCC from contaminated soil. Microbial community analysis revealed the crucial microorganisms and their functional enzymes participating in TCC degradation in soil. Moreover, the internal labor division patterns and connections of TCC-degrading microbes, with a focus on strains BX2 and LY-1, were unraveled by co-occurrence networks analysis. This work provides a promising strategy to facilitate the bioremediation of TCC in soil, which has potential application value for sustainable biobased economies.
Shumei Fang,Xuejiao An,Hongyuan Liu,Yi Cheng,Ning Hou,Lu Feng,Xinning Huang,Chunyan Li
Nitriles are common environmental pollutants, and their removal has attracted increasing attention. Microbial degradation is considered to be the most acceptable method for removal. In this work, we investigated the biodegradation of three aliphatic nitriles (acetonitrile, acrylonitrile and crotononitrile) by Rhodococcus rhodochrous BX2 and the expression of their corresponding metabolic enzymes. This organism can utilize all three aliphatic nitriles as sole carbon and nitrogen sources, resulting in the complete degradation of these compounds. The degradation kinetics were described using a first-order model. The degradation efficiency was ranked according to t 1/2 as follows: acetonitrile > trans-crotononitrile > acrylonitrile > cis-crotononitrile. Only ammonia accumulated following the three nitriles degradation, while amides and carboxylic acids were transient and disappeared by the end of the assay. mRNA expression and enzyme activity indicated that the tested aliphatic nitriles were degraded via both the inducible NHase/amidase and the constitutive nitrilase pathways, with the former most likely preferred.
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