Genetics of zwittermicin a production by Bacillus cereus.
Zwittermicin A represents a new chemical class of antibiotic and has diverse biological activities, including suppression of oomycete diseases of plants and potentiation of the insecticidal activity of Bacillus thuringiensis. To identify genes involved in zwittermicin A production, we generated 4,800 transposon mutants of B. cereus UW101C and screened them for zwittermicin A accumulation. Nine mutants did not produce detectable zwittermicin A, and one mutant produced eightfold more than the parent strain. The DNA flanking the transposon insertions in six of the nine nonproducing mutants contains significant sequence similarity to genes involved in peptide and polyketide antibiotic biosynthesis. The mutant that overproduced zwittermicin A contained a transposon insertion immediately upstream from a gene that encodes a deduced protein that is a member of the MarR family of transcriptional regulators. Three genes identified by the mutant analysis mapped to a region that was previously shown to carry the zwittermicin A self-resistance gene, zmaR, and a biosynthetic gene (E. A. Stohl, J. L. Milner, and J. Handelsman, Gene 237:403-411, 1999). Further sequencing of this region revealed genes proposed to encode zwittermicin A precursor biosynthetic enzymes, in particular, those involved in the formation of the aminomalonyl- and hydroxymalonyl-acyl carrier protein intermediates. Additionally, nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) homologs are present, suggesting that zwittermicin A is synthesized by a mixed NRPS/PKS pathway.
Emmert
Elizabeth A B
EA
Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Klimowicz
Amy K
AK
Thomas
Michael G
MG
Handelsman
Jo
J
D001409:Bacillus cereus / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D016366:Open Reading Frames / Q000235:genetics; D010455:Peptides / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D014161:Transduction, Genetic
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D010455:Peptides; C088290:zwittermicin A