Candicidin Biosynthesis Gene Cluster Is Widely Distributed among Streptomyces spp. Isolated from the Sediments and the Neuston Layer of the Trondheim Fjord, Norway

Abstract

A large number of Streptomyces bacteria with antifungal activity isolated from samples collected in the Trondheim fjord (Norway) were found to produce polyene compounds. Investigation of polyene-containing extracts revealed that most of the isolates produced the same compound, which had an atomic mass and UV spectrum corresponding to those of candicidin D. The morphological diversity of these isolates prompted us to speculate about the involvement of a mobile genetic element in dissemination of the candicidin biosynthesis gene cluster (can). Eight candicidin-producing isolates were analyzed by performing a 16S rRNA gene-based taxonomic analysis, pulsed-field gel electrophoresis, PCR, and Southern blot hybridization with can-specific probes. These analyses revealed that most of the isolates were related, although they were morphologically diverse, and that all of them contained can genes. The majority of the isolates studied contained large plasmids, and two can-specific probes hybridized to a 250-kb plasmid in one isolate. Incubation of the latter isolate at a high temperature resulted in loss of the can genes and candicidin production, while mating of the "cured" strain with a plasmid-containing donor restored candicidin production. The latter result suggested that the 250-kb plasmid contains the complete can gene cluster and could be responsible for conjugative transfer of this cluster to other streptomycetes.

Chemical basis of the synergism and antagonism in microbial communities in the nests of leaf-cutting ants

“…Phylogenetic analysis is widely used to classify microorganisms and more recently, to study evolutionary relationships among secondary metabolite producers (19)(20)(21). Here, we show that 16S rDNA data combined with database search and LC-MS profiling can be highly valuable for quickly identifying secondary metabolite profiles from new microbial isolates.…”

“…Instead of using the 16S rDNA sequences for evolutionary studies (19)(20)(21), we used phylogenetic data as a guideline to rapidly identify secondary metabolites that might play a crucial role in the interactions of the complex microbial community of leaf-cutting ants. We identified the closest well-studied relatives to Streptomyces symbionts from leaf-cutting ants based on their 16S rDNA sequence similarity to sequences from the Greengenes and National Center for Biotechnology Information (NCBI) databases using the blast algorithm.…”

“…Extending phylogenetic comparisons of secondary metabolite producers (19)(20)(21), we used a combination of phylogenetic analysis, database screening, and electrospray ionisation high resolution mass spectrometry (ESI-HR-MS) analysis to rapidly identify ecologically relevant secondary metabolites from microbial symbionts. In this way, we identified several antibiotics and investigated their role in shaping the complex interactions in the leaf-cutting ants' ecosystem.…”

Insights into the Evolution of Macrolactam Biosynthesis through Cloning and Comparative Analysis of the Biosynthetic Gene Cluster for a Novel Macrocyclic Lactam, ML-449

“…Dimethyl sulfoxide (DMSO) extracts of Streptomyces sp. MP39-85 were used in a robotic bioassay procedure with Candida albicans CCUG3943 and Candida glabrata CCUG3942 as indicator organisms as described by Jørgensen et al (18). The latter strain has a high level of resistance against polyene antibiotics, while the C. albicans strain is sensitive to polyenes.…”

“…Growth in the presence of ML-449 at different concentrations was compared to growth in reference wells where only a solvent (DMSO) was added, and the concentration resulting in 50% or more reduction in growth was determined. The assay conditions were otherwise as described by Jørgensen et al (18).…”