Research On Zwittermicin A Biosynthesis Cluster

Bacillus thuringiensis is an ubiquitous Gram-positive, spore-forming bacterium, which is well-known and widely used as biopesticide. Its insecticidal activity is largely attributed to the formation of parasporal crystals, which are formed during the stationary phase of the B. thuringiensis growth cycle. Many B. thuringiensis isolates also produce other virulent factors, such as helper protein, secreted vegetative insecticidal proteins (VIPs), and Zwittermicin A. Zwittermicin A, a novel, broad-spectrum, aminopolyol antibiotic, is produced by Bacillus cereus and B. thuringiensis strains. It has activity against Oomycetes and their relatives, algae, protists, and certain Gram-negative and Gram-positive bacteria, as well as many plant pathogenic fungi. Zwittermicin A can significantly enhance the insecticidal activity of B. thuringiensis toxins. The main contents of this study included: screening 196 B. thuringiensis by combination PCR analysis with inhibition assay; studing on the condition infected the production of Zwittermicin A and its activity to Erwinia hebicola; Cloning and analysis of the Zwittermicin A biosynthesis cluster.Among 196 B. thuringiensis isolates which were identified by combination PCR analysis with inhibition assay, 67 isoaltes inhibited the growth of Erwinia, and 21 of them were highly active to Erwinia hebicola.B. thuringiensis isolate G03 produces Zwittermicin A, and highly inhibited the growth of Erwinia. Combination cultures in different medium, spores obersevation with inhibition assay, we found that accumulation of Zwittermicin A was not relative to the formation of the spores. Supernatants after supersonic treated have higher activity to Erwinia hebicola than that before, suggesting there was a delay between production and secretion of Zwittermicin A. The results of the pH impact on activity of Zwittermicin A indicated that Zwittermicin A was more active against Erwinia herbicola at pH 7.0-9.0 than at pH 5.5-6.5.zmaR gene was cloned from the G03 isolate and sequenced later. Sequence analysis showed that this gene contained 1125bp, encoded 375 amino acids. Molecular weight of the peptide was 43.5 kDa, and the isoelectric point was pI4.945. This zmaR gene...