No abstract

A unique selective enrichment procedure has resulted in the isolation and identification of two new genera of marine-derived actinobacteria. Approximately 90% of the microorganisms cultured by using the presented method were from the prospective new genera, a result indicative of its high selectivity. In this study, 102 actinomycetes were isolated from subtidal marine sediments collected from the Bismarck Sea and the Solomon Sea off the coast of Papua New Guinea. A combination of physiological parameters, chemotaxonomic characteristics, distinguishing 16S rRNA gene sequences, and phylogenetic analysis based on 16S rRNA genes provided strong evidence for the two new genera (represented by strains of the PNG1 clade and strain UMM518) within the family Micromonosporaceae. Biological activity testing of fermentation products from the new marine-derived actinomycetes revealed that several had activities against multidrug-resistant grampositive pathogens, malignant cells, and vaccinia virus replication.The order Actinomycetales is composed of approximately 80 genera, nearly all from terrestrial soils, where they live primarily as saprophytes (30,36). All members of the order are characterized in part by their high GϩC DNA content, and most exhibit a highly differentiated developmental life cycle (30). Several recent systematic reevaluations of the order reflected more closely the integration of molecular data (16S rRNA gene sequences). This reorganization resulted in the placement of the two most prolific producers of secondary metabolites, Streptomyces and Micromonospora, in the families Streptomycetaceae and Micromonosporaceae, respectively (30).The diversity of actinomycete secondary metabolites is unrivaled and unmatched in medical significance. Structurally and functionally diverse bioactive compounds have also been isolated from other prokaryotes, including members of the myxobacteria (e.g., Sorangium) and cyanobacteria (e.g., Nostoc), as antibiotics with antimicrobial, antiviral, and antitumor activities (16,21,24,25). Recently, the rate of discovery of new compounds from existing genera obtained from terrestrial sources has decreased, while the rate of reisolation of known compounds has increased. Moreover, the rise in the number of drug-resistant pathogens and the limited success of strategies such as combinatorial chemistry in providing new agents indicate an uncertain forecast for future antimicrobial therapy (17, 18). Thus, it is critical that new groups of microbes from unexplored habitats be pursued as sources of novel antibiotics and other small-molecule therapeutic agents (3).The oceans cover more than 70% of the earth's surface, and little is known about the microbial diversity of marine sediments. As with terrestrial soils, marine sediments contain limited amounts of readily available organic matter, with most sources of carbon being present in complex forms (i.e., cellulose and chitin). However, culture-independent methods have demonstrated that marine sediments contain a wide range of unique microo...

The structure of a new dibenzodiazepine alkaloid, diazepinomicin (1), isolated from the culture of a marine actinomycete of the genus Micromonospora was characterized using spectroscopic methods. Diazepinomicin represents a unique molecular class composed of a dibenzodiazepine core linked to a farnesyl side chain.

No abstract

Fermentation of a marine fungal species obtained from a tissue sample of a marine sponge collected in Indonesia in October 1996, yielded the novel hexaketide compounds iso-cladospolide B (1); seco-patulolide C (2); the 12-membered macrolides, pandangolide 1 (3) and pandangolide 2 (4); and the known terrestrial fungal metabolite, cladospolide B (5).