Functional Characterization and Whole-Genome Analysis of an Aflatoxin-Degrading Rhodococcus pyridinivorans Strain.

Aflatoxin B 1 (AFB 1 ) is one of the most toxic, naturally occurring carcinogen compounds and is produced by specific strains of fungi. Crop contamination with AFB 1 can cause huge economic losses and serious health problems. Many studies have examined the microbiological degradation of AFB 1 , especially the use of efficient AFB 1 -degrading microorganisms, to control AFB 1 contamination. Here, we reported the identification of a new Rhodococcus pyridinivorans strain (4-4) that can efficiently degrade AFB 1 (degradation rate 84.9%). The extracellular component of this strain showed the strongest capacity to degrade AFB 1 (degradation rate 83.7%). The effects of proteinase K, SDS, temperature, pH, incubation time, and AFB 1 concentration on the AFB 1 degradation ability of the extracellular component were investigated. We sequenced the complete genome of this strain, encoding 5246 protein-coding genes and 169 RNA genes on a circular chromosome and two plasmids. Comparative genomic analysis revealed high homology with other Rhodococcus strains with high AFB 1 -degradation ability. Further proteomic analyses of this strain identified a total of 723 proteins in the extracellular component, including multiple potential AFB 1 -degrading enzymes, along with enzymes that are reported to response to AFB 1 treatment. Overall, the results demonstrate that R. pyridinivorans 4-4 would be an excellent candidate for the biodegradation and detoxification of AFB 1 contamination.