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

SIMPLE SUMMARY: The microbiological degradation of AFB(1) has been a promising approach to control AFB(1) contamination. Here, we characterize a Rhodococcus pyridinivorans strain that can efficiently degrade AFB(1). The AFB(1)-degrading capacity of this bacterial strain was characterized, and the completed genome was sequenced and analyzed. Further proteomic analyses of this strain identified a total of 723 proteins in an extracellular component that showed the strongest capacity to degrade AFB(1) (degradation rate 83.7%). Multiple potential AFB(1)-degrading enzymes, and enzymes that are reported to respond to AFB(1) treatment, have been identified accordingly. These findings provide a genomic, proteomic, and experimental approach for characterizing an efficient AFB(1)-degrading bacterial strain with great potential for use in the remediation of AFB(1) contamination. ABSTRACT: 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.