macrolactin-a and bacillaene

Macrolactins (MLNs) have unique structural patterns containing a 24-membered ring lactone and diverse bioactivities. The MLN skeleton is biosynthesized via a trans-acyl transferase (AT) type I polyketide synthase (PKS) pathway, but the tailoring steps are still unknown. Herein, we report the identification of a glycosyltransferase (GT) gene bmmGT1, which is located at different locus from the MLN gene cluster in the genome of marine-derived Bacillus marinus B-9987, and its functional characterization as an MLN GT, thus affording five novel MLNs analogues. Surprisingly, this GT is also capable of catalyzing the glycosylation of bacillaenes (BAEs), which are the prototypes of trans-AT polyketides, thus suggesting broad substrate flexibility. These results provide the first significant insights into the glycosylation step in MLN and BAE biosynthetic pathways.

Topics: Bacillus; Biosynthetic Pathways; Genes, Bacterial; Glycosylation; Glycosyltransferases; Macrolides; Multigene Family; Polyenes

Phytopathogenic fungi affecting crop and post-harvested vegetables are a major threat to food production and food storage. To face these drawbacks, producers have become increasingly dependent on agrochemicals. However, intensive use of these compounds has led to the emergence of pathogen resistance and severe negative environmental impacts. There are also a number of plant diseases for which chemical solutions are ineffective or non-existent as well as an increasing demand by consumers for pesticide-free food. Thus, biological control through the use of natural antagonistic microorganisms has emerged as a promising alternative to chemical pesticides for more rational and safe crop management.. The genome of the plant-associated B. amyloliquefaciens GA1 was sample sequenced. Several gene clusters involved in the synthesis of biocontrol agents were detected. Four gene clusters were shown to direct the synthesis of the cyclic lipopeptides surfactin, iturin A and fengycin as well as the iron-siderophore bacillibactin. Beside these non-ribosomaly synthetised peptides, three additional gene clusters directing the synthesis of the antibacterial polyketides macrolactin, bacillaene and difficidin were identified. Mass spectrometry analysis of culture supernatants led to the identification of these secondary metabolites, hence demonstrating that the corresponding biosynthetic gene clusters are functional in strain GA1. In addition, genes encoding enzymes involved in synthesis and export of the dipeptide antibiotic bacilysin were highlighted. However, only its chlorinated derivative, chlorotetaine, could be detected in culture supernatants. On the contrary, genes involved in ribosome-dependent synthesis of bacteriocin and other antibiotic peptides were not detected as compared to the reference strain B. amyloliquefaciens FZB42.. The production of all of these antibiotic compounds highlights B. amyloliquefaciens GA1 as a good candidate for the development of biocontrol agents.

Topics: Anti-Bacterial Agents; Bacillus; Lactones; Lipopeptides; Macrolides; Multigene Family; Oligopeptides; Peptides, Cyclic; Pest Control, Biological; Phylogeny; Polyenes