Project description:Considered a key taxon in soil and marine microbial communities, myxobacteria exist as coordinated swarms that utilize a combination of lytic enzymes and specialized metabolites to facilitate predation of microbes. This capacity to produce specialized metabolites and the associated abundance of biosynthetic pathways contained within their genomes have motivated continued drug discovery efforts from myxobacteria. Of all myxobacterial biosynthetic gene clusters deposited in the antiSMASH database, only one putative acylhomoserine lactone (AHL) synthase, agpI, was observed, in genome data from Archangium gephyra. Without an AHL receptor also apparent in the genome of A. gephyra, we sought to determine if AgpI was an uncommon example of an orphaned AHL synthase. Herein we report the bioinformatic assessment of AgpI and discovery of a second AHL synthase from Vitiosangium sp. During axenic cultivation conditions, no detectible AHL metabolites were observed in A. gephyra extracts. However, heterologous expression of each synthase in Escherichia coli provided detectible quantities of 3 AHL signals including 2 known AHLs, C8-AHL and C9-AHL. These results suggest that A. gephyra AHL production is dormant during axenic cultivation. The functional, orphaned AHL synthase, AgpI, is unique to A. gephyra, and its utility to the predatory myxobacterium remains unknown.
Project description:Family Cystobacteraceae is a group of eubacteria within order Myxococcales and class Deltaproteobacteria that includes more than 20 species belonging to 6 genera, that is, Angiococcus, Archangium, Cystobacter, Hyalangium, Melittangium, and Stigmatella. Earlier these members have been classified based on chitin degrading efficiency such as Cystobacter fuscus and Stigmatella aurantiaca, which are efficient chitin degraders, C. violaceus a partial chitin degrader and Archangium gephyra a chitin nondegrader. Here we report the 12.5 Mbp complete genome of A. gephyra DSM 2261T and compare it with four available genomes within the family Cystobacteraceae. Phylogeny and DNA-DNA hybridization studies reveal that A. gephyra is closest to Angiococcus disciformis, C. violaceus and C. ferrugineus, which are partial chitin degraders of the family Cystobacteraceae. Homology studies reveal the conservation of approximately half of the proteins in these genomes, with about 15% unique proteins in each genome. The total carbohydrate-active enzymes (CAZome) analysis reveals the presence of one GH18 chitinase in the A. gephyra genome whereas eight copies are present in C. fuscus and S. aurantiaca. Evolutionary studies of myxobacterial GH18 chitinases reveal that most of them are likely related to Terrabacteria and Proteobacteria whereas the Archangium GH18 homolog shares maximum similarity with those of chitin nondegrading Acidobacteria.