Of symbiotic marine microorganisms

Kobayashi, J. and Ishibashi, M., Bioactive metabolites of symbiotic marine microorganisms, Chem. Rev., 93, 1753, 1993. 

N- and O-Heterocycles bioactive metabolites of symbiotic marine microorganisms 93CRV1753. 

The structure of piimaic acid (24) from the bivalve P. muricata has been shown to be closely similar to that of halichlorine (26) from the marine sponge H. okadai. Each carbon atom has been tentatively numbered according to the supposed biogenetic formation of the N-C23 bond. Thus, these two bioactive metabolites may each be biosynthesized by symbiotic marine microorganisms. 

Finally, recent reviews indicate that marine microorganisms are potentially a greater source of bioactive compounds than marine macroorganisms,78 81 Marine microorganisms can be found in seawater or sediment, associated with macroorganisms either on the surface or symbiotically, and in extreme environments. Extremophiles, in particular, may have the greatest capacity for the production of unique bioactive metabolites.78... 

Isolation and culture of putative symbiotic microorganisms to obtain the bioactive metabolites isolated from the invertebrate-microbe assemblages has been particularly problematic. It has been estimated that only 1% of marine microbes can be isolated and fermented using techniques modified to approximate marine conditions. However, to address this problem, several groups have used differential fractionation or flow cytometric techniques to separate populations of extracellularly associated microorganisms from invertebrate host cells. Chromatographic and spectroscopic analyses of the enriched cell fractions have been used to determine which cell type is producing the compounds. The assumption is that the metabolites are produced in the cell types in which they are detected. 

Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms... 

Calycnlin A (38) is an extraordinary metabolite composed of C28 fatty acid and two y-amino acids isolated from the sponge Discodermia calyx. It is not only highly antifnngal and antitnmor bnt also a potent cancer promoter that was fonnd to be cansed by potent inhibition of protein phosphatases 1 and 2A (1). More than 15 calycnlin derivatives were isolated from several marine sponges, which indicates the involvement of symbiotic microorganisms in the prodnction of calycnhns (6). 

---