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

Abstract

Aflatoxin B1 (AFB1) is one of the most toxic, naturally occurring carcinogen compounds and is produced by specific strains of fungi. Crop contamination with AFB1 can cause huge economic losses and serious health problems. Many studies have examined the microbiological degradation of AFB1, especially the use of efficient AFB1-degrading microorganisms, to control AFB1 contamination. Here, we reported the identification of a new Rhodococcus pyridinivorans strain (4-4) that can efficiently degrade AFB1 (degradation rate 84.9%). The extracellular component of this strain showed the strongest capacity to degrade AFB1 (degradation rate 83.7%). The effects of proteinase K, SDS, temperature, pH, incubation time, and AFB1 concentration on the AFB1 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 AFB1-degradation ability. Further proteomic analyses of this strain identified a total of 723 proteins in the extracellular component, including multiple potential AFB1-degrading enzymes, along with enzymes that are reported to response to AFB1 treatment. Overall, the results demonstrate that R. pyridinivorans 4-4 would be an excellent candidate for the biodegradation and detoxification of AFB1 contamination.