Microbial symbionts

Sudek S, LopanikNB, Waggoner LE, Hildebrand M, Anderson C, Liu HB, Patel A, Sherman DH, Haygood MG (2007) Identification of the putative bryostatin polyketide synthase gene cluster from Candidatus endobugula sertula , the uncultivated microbial symbiont of the marine bryozoan Bugula neritina. J Nat Prod 70 67-74... 

Marine animals, such as sponges and soft-bodied invertebrates, are well known to synthesize a large number of organohalogens or to harbor microbial symbionts that synthesize these compounds. Many have physiological activities that made them useful as marine natural products. Examples of these are provided in Chapter 28, namely furanone (S5), oroidin (S9), Tyrian purple (S20), spisulosine (S25), and salinosporamide A (S39). 

We should also learn which organisms and allelochemicals adversely affect the microbial symbionts. Some have already been shown to suppress growth of bacterial nitrogen fixers and nitrifiers as well as mycorrhizal fungi. Compounds that inhibit nitrification could prove to be important agriculturally. 

Under this situation of stress, natural products unique to endangered areas are the most threatened, while those of wide distribution are subjected to a lessened pressure. The analysis of natural product losses is made difficult also by the presence of microbial symbionts that may be responsible for the presence of unusual metabolites in macroorganisms. 

Webster, N. S. and Taylor, M. W. (2011). Marine sponges and their microbial symbionts Love and other relationships. Environ. Microbiol, doi 10.1111/j.l462-2920.2011.02460.x. 

Seeto, G.S., Veivers, P.C., Clements, K.D., and Slaytor, M., Carbohydrate utilisation by microbial symbionts in the marine herbivorous fishes Odax cyanomelas and Crinodous lophodon, J. Comp. Physiol. B, 165, 571, 1996. 

The biosynthetic origin of marine natural products is a complex topic that has gained more clarity through application of molecular biological study microbial symbionts may represent the true source in many sponges, ascidians, and bryozoans, even in cases in which localization studies have suggested an invertebrate source for... 

Usher, K. M., Sutton, D. C., ei al. (2005). Inter-generational transmission of microbial symbionts in the marine sponge Chondrilla australiensis (Demospongiae). Mar. Freshwater Res. 56, 125—131. 

Sung SJ, Lin PS, Schmidt-Ullrich R, Hall CE, Walters JA, Mc-Crady C, Grant S. Effects of the protein kinase C stimulant bryostatin 1 on the proliferation and colony formation of irradiated human T-lymphocytes. Int. 1. Radial. Biol. 1994 66 775-783. Kortmansky J, Schwartz GK. Bryostatin-1 a novel PKC inhibitor in clinical development. Cancer Invest. 2003 21 924-936. Lopanik N, Lindquist N, Targett N. Potent cytotoxins produced by a microbial symbiont protect host larvae from predation. Oecologia 2004 139 131-139. 

The discovery that several major anticancer drugs, originally isolated from plants, are produced by associated endophytic fungi (Section III.B.3.) opens up further avenues for exploring the large-scale production of plant-derived pharmaceuticals. Likewise, the probable role of microbial symbionts in the production of bioactive agents from marine macroorganisms (Section III.B.4.) offers... 

Misakinolide A (35) also binds simultaneously to two actin subunits with virtually the same affinity as swinholide A (34), but it does not sever actin filaments like swinholide A (34) rather it caps the barbed end of F-actin [78]. The presence of microbial symbionts in T. swinhoei was reported and the production of these natural products such as swinholide A (34) was believed to be responsible for symbiotic cyanobacteria. Studies by transmission electron microscopy, however, suggested that production of these macrolides was attributable to heterotrophic unicellular bacteria rather than cyanobacteria [79]. 

Other labs are joining the search for deep-sea organisms in a quest for new bioactive secondary metabolites. A few of these labs are studying the microbial symbionts of macroorganisms or microbes from deep-sea sediments. In 2003, Jongheon Shin s lab at the Natural Products Research Institute, Seoul National University, reported the... 

Cyanobacteria known to produce hepatotoxins include species of Microcystis (32-36), Anabaena (37-40), Nostoc (41,42), Oscillatoria (43,44) and the brackish water Nodularia spumigena (45,46). These cyanobacteria produce a wide range of toxins including neurotoxic alkaloids, lipopolysaccharides, phenolic compounds and most importantly, the cyclic hepatotoxic peptides microcystins and nodularins. Since both microcystins and nodularins were recently discovered even in shellfish (47) and tropical fish species (48), and a nodularin variant was isolated in Papua New Guinea also from the tropical marine sponge Theonella swinhoei (49), marine prokaryotes are apparently producing identical toxins as the cyanobacteria. However, since this nodularin variant was isolated from a marine sponge it may well be produced by a microbial symbiont. 

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