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

Masanobu Kawanishi; Chiaki Shimohara; Yoshimitsu Oda; Yuuta Hisatomi; Yuta Tsunematsu; Michio Sato; Yuichiro Hirayama; Noriyuki Miyoshi; Yuji Iwashita; Yuko Yoshikawa; Haruhiko Sugimura; Michihiro Mutoh; Hideki Ishikawa; Keiji Wakabayashi; Takashi Yagi; Kenji Watanabe

doi:10.1186/s41021-020-00149-z

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

Genes Environ. 2020 Mar 11:42:12. doi: 10.1186/s41021-020-00149-z. eCollection 2020.

Authors

Masanobu Kawanishi¹, Chiaki Shimohara¹, Yoshimitsu Oda¹, Yuuta Hisatomi¹, Yuta Tsunematsu², Michio Sato², Yuichiro Hirayama², Noriyuki Miyoshi³, Yuji Iwashita⁴, Yuko Yoshikawa^{3

5}, Haruhiko Sugimura⁴, Michihiro Mutoh⁶, Hideki Ishikawa⁷, Keiji Wakabayashi³, Takashi Yagi¹, Kenji Watanabe²

Affiliations

¹ 1Graduate School of Science and Radiation Research Center, Osaka Prefecture University, 1-2 Gakuen-cho, Naka-ku, Sakai-shi, Osaka, 599-8570 Japan.
² 2Department of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
³ 3Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, Japan.
⁴ 4Department of Tumor Pathology, Hamamatsu University School of Medicine, Shizuoka, Japan.
⁵ 5School of Veterinary Medicine, Faculty of Veterinary Science, Nippon Veterinary and Life Science University, Tokyo, Japan.
⁶ 6Division of Prevention, Center for Public Health Sciences, National Cancer Center, Tokyo, Japan.
⁷ 7Department of Molecular-Targeting Cancer Prevention, Kyoto Prefectural University of Medicine, Kyoto, Japan.

Abstract

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

Findings: The analysis revealed that two of six strains possessed a clb gene cluster. These clb ⁺ 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 umu test was carried out with a cell extract of the strain, revealing that the extract had SOS-inducing potency in the umu tester bacterium.

Conclusion: These results support the observations that the clb gene cluster is widely distributed in nature and clb ⁺ E. coli having genotoxic potencies is not rare among microorganisms.

Keywords: Colibactin; Genotoxicity; Genotyping.