[ODP-005] 大腸菌における亜テルル酸耐性オペロンの多様性
Tellurite is highly toxic to most bacteria owing to its strong oxidative ability. However, some Escherichia coli strains, including Shiga toxin-producing E. coli O157:H7, are known to be resistant to tellurite. This resistance is involved in ter operon. To clarify the characteristics of the ter operon, we examined 106 E. coli strains carrying the ter operon from various animals. The genomes of representative strains revealed that ter operons were clearly classified into four subtypes, ter-type 1-4, at the nucleotide sequence level and that operons belonging to three ter-types (1, 3, and 4) were located on the prophage-like elements on the chromosome, whereas the ter-type 2 operon was on the IncHI2 plasmid. 106 strains were classified as type 1 (n = 66), 2 (n = 13), 3 (n = 8), and 4 (n = 17), and two strains carried both types 1 and 2. Furthermore, significant differences in the MIC of tellurite were observed between strains carrying ter-type 4 and the others (p > 0.05). The ter-type was also closely related to the isolation source, with types 2 and 4 associated with chickens and deer, respectively. This study provided new insights related not only to genetic characteristics of the ter operons, but also to phenotypic and ecological characteristics that may be related to the diversity of the operon.