Genotyping of a gene cluster for production of colibactin and in vitro genotoxicity analysis of strains obtained from the Japan Collection of Microorganisms.

INTRODUCTION

Colibactin is a small genotoxic molecule produced by enteric bacteria, including certain () strains harbored in the human large intestine. This polyketide-peptide genotoxin is considered to contribute to the development of colorectal cancer. The colibactin-producing ( ) microorganisms possess a 54-kilobase genomic island ( gene cluster). In the present study, to assess the distribution of the gene cluster, genotyping analysis was carried out among strains randomly chosen from the Japan Collection of Microorganisms, RIKEN BRC, Japan.

FINDINGS

The analysis revealed that two of six strains possessed a gene cluster. These strains JCM5263 and JCM5491 induced genotoxicity in in vitro micronucleus (MN) tests using rodent CHO AA8 cells. Since the induction level of MN by JCM5263 was high, a bacterial test was carried out with a cell extract of the strain, revealing that the extract had SOS-inducing potency in the tester bacterium.

CONCLUSION

These results support the observations that the gene cluster is widely distributed in nature and having genotoxic potencies is not rare among microorganisms.