A tellurite resistance determinant, believed to have been cloned from the IncHII plasmid pHH1508a (E. G. Walter, J. H. Weiner, and D. E. Taylor, Gene 101:1-7, 1991), was shown instead to have originated from the chromosome of Escherichia coli K-12. The two genes, tehA and tehB, constitute an operon located in the terminus at approximately 32.3 min.