76(P55) 野生陸生ラン藻Nostoc communeのジェリー層内微生物フローラ制御物質(ポスター発表の部)

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Recently blue-green algae (cyanobacteria) attract much attention because of their secondary metabolites with potent biological activities and unusual structures. Blue-green algae have also been checked for their metabolism influenced by symbiotic or parasitic microorganisms. For example, lichens, symbiotic organisms consisting of algae and fungi, produce peculiar secondary metabolites called lichen substances. Nostoc commune is a blue-green alga which often grows on wet ground surface in jelly clumps consisting of polysaccharides. Our preliminary experiment showed that many microorganisms including bacteria, fungi, and actinomycetes were residing in the jelly clumps of field grown Nostoc commune. On the other hand the methanol extract of this alga exhibited antifungal activity against 7 fungi (Aspergillus cardidus, Cladosporium herbarum, Botrytis fabae, Glomerella cingulata, Sclerotium rolfsii, Rhizoctoniasolani, Cercospora beticala) suggesting that the antimicrobial substance(s) may control microbial flora of the jelly clumps. As the first step to clarify the relationship between the alga and co-residing microorganisms, we isolated one of the antimicrobial principles-named nostofungicidine (1) from field-grown algal sample. The structure of nostofungicidine was elucidated mainly by chemical degradation and by extensive NMR measurements including DQF-COSY, HOHAHA, HMBC, and ROES Y techniques. Nostofungicidine was a novel lipopeptide containing a long chain beta amino acid, 3-amino-6-hydroxy stearic acid (Ahs) in its structure. Nostofungicidine was not found in the axenic culture of this alga and in the individual cultures of each tested microbial strain isolated from jelly clumps. On the other hand, one of the co-residing strain (tentatively identified as an actinomycete) produced a known antibiotic, echinomycin. Echinomycin had no antialgal effect toward axenic Nostoc commune at the concentration of 100 micro-g/ml. These results suggest that co-residing microorganisms may play an important role in the accumulation of microbial flora controlling substances not only through production of antimicrobial compound(s) but also through stimulation of the algal secondary metabolism.
天然有機化合物討論会の論文
1998-08-31

76(P55) 野生陸生ラン藻Nostoc communeのジェリー層内微生物フローラ制御物質(ポスター発表の部)

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