[Microbes and cancer].

Recently, due to the use of germ-free animals in cancer research, many facts have been accumulated indicating that bacteria may produce different effects (enhancing or inhibiting) on carcinogenesis, depending on the features of the carcinogenic substance metabolism. At the same time, epidemiological investigations have shown that in human populations with a high or a low risk of cancer development (mostly cancer of the colon and mammary gland) the composition of the intestinal bacterial flora and its metabolic properties have peculiar features. In both instances, certain bacterial species are presumed to take part in the formation of final carcinogenic metabolites or in the synthesis of endogenic carcinogens (and/or cocarcinogens).