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Genetics of zwittermicin a production by Bacillus cereus.

ABSTRACT: 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.

SUBMITTER: Emmert EA

PROVIDER: S-EPMC321298 | biostudies-literature | 2004 Jan

REPOSITORIES: biostudies-literature

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Genetics of zwittermicin a production by Bacillus cereus.

Emmert Elizabeth A B EA Klimowicz Amy K AK Thomas Michael G MG Handelsman Jo J

Applied and environmental microbiology 20040101 1

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 pare ...[more]

PMID: 14711631

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Project description:Lactoferrin is an iron-binding glycoprotein exhibiting antibacterial, antiviral, antifungal, antiparasitic, antiinflammatory, antianaemic and anticarcinogenic properties. While its inhibitory effects against bacterial pathogens are well investigated, little is known about its influence on the production and/or mode of action of bacterial toxins. Thus, the present study aimed to determine the impact of food supplements based on bovine lactoferrin on Bacillus cereus enterotoxin production. First, strain-specific growth inhibition of three representative isolates was observed in minimal medium with 1 or 10 mg/mL of a lactoferrin-based food supplement, designated as product no. 1. Growth inhibition did not result from iron deficiency. In contrast to that, all three strains showed increased amounts of enterotoxin component NheB in the supernatant, which corresponded with cytotoxicity. Moreover, lactoferrin product no. 1 enhanced NheB production of further 20 out of 28 B. cereus and Bacillus thuringiensis strains. These findings again suggested a strain-specific response toward lactoferrin. Product-specific differences also became apparent comparing the influence of further six products on highly responsive strain INRA C3. Highest toxin titres were detected after exposure to products no. 7, 1 and 2, containing no ingredients except pure bovine lactoferrin. INRA C3 was also used to determine the transcriptional response toward lactoferrin exposure via RNA sequencing. As control, iron-free medium was also included, which resulted in down-regulation of eight genes, mainly involved in amino acid metabolism, and in up-regulation of 52 genes, mainly involved in iron transport, uptake and utilization. In contrast to that, 153 genes were down-regulated in the presence of lactoferrin, including genes involved in flagellar assembly, motility, chemotaxis and sporulation as well as genes encoding regulatory proteins, transporters, heat and cold shock proteins and virulence factors. Furthermore, 125 genes were up-regulated in the presence of lactoferrin, comprising genes involved in sporulation and germination, nutrient uptake, iron transport and utilization, and resistance. In summary, lactoferrin exposure of B. cereus strain-specifically triggers an extensive transcriptional response that considerably exceeds the response toward iron deficiency and, despite down-regulation of various genes belonging to the PlcR-regulon, ultimately leads to an increased level of secreted enterotoxin by a mechanism, which has yet to be elucidated.

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Genetics of zwittermicin a production by Bacillus cereus.

Publications

Genetics of zwittermicin a production by Bacillus cereus.

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