ZWITTERMICIN-A RESISTANCE GENE FROM BACILLUS-CEREUS

Zwittermicin A is a novel aminopolyol antibiotic produced by Bacillus cereus that is active against diverse bacteria and lower eukaryotes (L . A. Silo-Suh, B. J. Lethbridge, S. J. Raffel, H. He, J. Clardy, and J . Handelsman, Appl. Environ, Microbiol. 60:2023-2030, 1994), To identi fy a determinant for resistance to zwittermicin A, we constructed a ge nomic library from B. cereus UW85, which produces zwittermicin A, and screened transformants of Escherichia coli DH5 alpha, which is sensiti ve to zwittermicin A, for resistance to zwittermicin A, Subcloning and mutagenesis defined a genetic locus, designated zmaR, on a 1.2-kb fra gment of DNA that conferred zwittermicin A resistance on E, coli, A DN A fragment containing zmaR hybridized to a corresponding fragment of g enomic DNA from B. cereus UW85, Corresponding fragments were not detec ted in mutants of B. cereus UW85 that were sensitive to zwittermicin A , and the plasmids carrying zmaR restored resistance to the zwittermic in A-sensitive mutants, indicating that zmaR was deleted in the zwitte rmicin A-sensitive mutants and that zmaR is functional in B. cereus, S equencing of the 1.2-kb fragment of DNA defined an open reading frame, designated ZmaR, Neither the nucleotide sequence nor the predicted pr otein sequence had significant similarity to sequences in existing dat abases, Cell extracts from an E. call strain carrying zmaR contained a 43.5-kDa protein whose molecular mass and N-terminal sequence matched those of the protein predicted by the zmaR sequence, The results demo nstrate that we have isolated a gene, zmaR, that encodes a zwittermici n A resistance determinant that is functional in both B, cereus and E. coli.