Abstract
The marine environment represents a largely untapped source for isolation of new microorganisms with potential to produce biologically active secondary metabolites. Among such microorganisms, Gram-positive actinomycete bacteria are of special interest, since they are known to produce chemically diverse compounds with a wide range of biological activities. We have set out to isolate and characterize actinomycete bacteria from the sediments in one of the largest Norwegian fjords, the Trondheim fjord, with respect to diversity and antibiotic-producing potential. Approximately 3,200 actinomycete bacteria were isolated using four different agar media from the sediment samples collected at different locations and depths (4.5 to 450 m). Grouping of the isolates first according to the morphology followed by characterization of isolates chosen as group representatives by molecular taxonomy revealed that Micromonospora was the dominating actinomycete genus isolated from the sediments. The deep water sediments contained a higher relative amount of Micromonospora compared to the shallow water samples. Nine percent of the isolates clearly required sea water for normal growth, suggesting that these strains represent obligate marine organisms. Extensive screening of the extracts from all collected isolates for antibacterial and antifungal activities revealed strong antibiotic-producing potential among them. The latter implies that actinomycetes from marine sediments in Norwegian fjords can be potential sources for the discovery of novel anti-infective agents.
Highlights
The demand for new antibiotics continues to grow due to the rapid spread of antibiotic-resistant pathogens causing life-threatening infections
Some of the unusual structures and properties of compounds isolated from marine sources and the fact that 58 % of the isolated actinomycetes from sediments collected around Guam in the Pacific ocean required sea water for growth [5] implies that one may find microorganisms adapted to the marine environment and producing compounds not found among microorganisms adapted to the terrestrial sources
The second site (T-site) was located in the middle of the fjord and here samples were taken at 450 m depth, where the sediment was dominated by clay particles
Summary
The demand for new antibiotics continues to grow due to the rapid spread of antibiotic-resistant pathogens causing life-threatening infections. Bacteria belonging to the family Actinomycetaceae are well known for their ability to produce secondary metabolites, many of which are active against pathogenic microorganisms. These bacteria have been isolated from terrestrial sources the first report of mycelium-forming actinomycetes being recovered from marine sediments appeared several decades ago [4]. Some of the unusual structures and properties of compounds isolated from marine sources and the fact that 58 % of the isolated actinomycetes from sediments collected around Guam in the Pacific ocean required sea water for growth [5] implies that one may find microorganisms adapted to the marine environment and producing compounds not found among microorganisms adapted to the terrestrial sources
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