The
genotoxin colibactin produced by resident bacteria of the gut microbiota may have tumorigenic effect by inducing
DNA double-strand breaks in host cells. Yet, the effect of
colibactin on gut microbiota composition and functions remains unknown. To address this point, we designed an experiment in which pregnant mice were colonized with the following: (i) a commensal Escherichia coli strain, (ii) a commensal E. coli strain plus a genotoxic E. coli strain, (iii) a commensal E. coli strain plus a nongenotoxic E. coli mutant strain unable to produce mature
colibactin. Then, we analyzed the gut microbiota in pups at day 15 and day 35 after birth. At day 15, mice that were colonized at birth with the genotoxic strain showed lower levels of Proteobacteria and taxa belonging to the Proteobacteria, a modest effect on overall microbial diversity, and no effect on gut microbiome. At day 35, mice that received the genotoxic strain showed lower Firmicutes and taxa belonging to the Firmicutes, together with a strong effect on overall microbial diversity and higher microbial functions related to DNA repair. Moreover, the genotoxic strain strongly affected gut microbial diversity evolution of pups receiving the genotoxic strain between day 15 and day 35. Our data show that
colibactin, beyond targeting the host, may also exert its genotoxic effect on the gut microbiota.IMPORTANCE
Infections of genotoxic Escherichia coli spread concomitantly with urbanized progression. These bacteria may prompt cell senescence and affect
DNA stability, inducing
cancer via the production of
colibactin, a
genotoxin shown capable of affecting host
DNA in eukaryotic cells. In this study, we show that the action of
colibactin may also be directed against other bacteria of the gut microbiota in which genotoxic E. coli bacteria have been introduced. Indeed, the presence of genotoxic E. coli induced a change in both the structure and function of the gut microbiota. Our data indicate that genotoxic E. coli may use
colibactin to compete for gut niche utilization.