Abstract
Forty four marine actinomycetes of the family Microccocaceae isolated from sponges collected primarily in Florida Keys (USA) were selected from our strain collection to be studied as new sources for the production of bioactive natural products. A 16S rRNA gene based phylogenetic analysis showed that the strains are members of the genera Kocuria and Micrococcus. To assess their biosynthetic potential, the strains were PCR screened for the presence of secondary metabolite genes encoding nonribosomal synthetase (NRPS) and polyketide synthases (PKS). A small extract collection of 528 crude extracts generated from nutritional microfermentation arrays was tested for the production of bioactive secondary metabolites against clinically relevant strains (Bacillus subtilis, methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter baumannii and Candida albicans). Three independent isolates were shown to produce a new anti-MRSA bioactive compound that was identified as kocurin, a new member of the thiazolyl peptide family of antibiotics emphasizing the role of this family as a prolific resource for novel drugs.
Highlights
Marine sponges are abundant multicellular invertebrates with a broad distribution in the oceans
Micrococcus strains were assigned to the same species M. yunnanensis whereas Kocuria strains were distributed among seven different species (K. flava, K. marina, K. palustris, K. rhizophila, K. rosea, K. sediminis and K. turfanensis)
Inhibition zones were measured in mm after 24 h incubation at 37 °C. This survey supports previous reports showing that marine environments, and especially sponges, are sources for novel bioactive metabolite producers with biotechnological use, and that geographic and environmental factors may affect the occurrence of these biochemical pathways and bioactivities
Summary
Marine sponges (phylum Porifera) are abundant multicellular invertebrates with a broad distribution in the oceans. The biosynthesis of large number of bioactive natural products is dependent on nonribosomal synthetase (NRPS) and type I and type II polyketide synthases (PKS-I, PKS-II) These biosynthetic systems are broadly distributed among actinomycetes, cyanobacteria, myxobacteria and fungi and molecular tools derived from conserved domain genes sequences have been useful for screening the biosynthetic potential of these microorganisms [13,14,15]. Natural products derived from these biosynthetic pathways have been extensively described for cultured and uncultured marine strains These marine metabolites include among others the polyketide synthase-derived bryostatin, a cytotoxic compound produced by a bryozoan bacterial symbiont [16]; abyssomicin C, a unique polycyclic polyketide from a marine Verrucosispora [6], salinisporamide A, a potent cytotoxic proteasome inhibitor from S. tropica, and promising new antitumor candidate in Phase I clinical trials [17,18], and the antitumor onnamides and theopederins, mixed polyketide-non ribosomal peptides produced by an uncultured Pseudomonas sp. We report a first insight into the occurrence of these biosynthetic systems and the production of new bioactive compounds by sponge-associated bacteria of the Micrococcaceae family
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