Microbial control of growth, differentiation, metamorphosis and settlement of marine organisms.

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In this study we attempted to make clear a mechanism of metamorphosis and settlement, and to search and isolate microalgae and bacteria participating in these phenomena, and to identify' their bioactive substances. The results obtained are as follows ;1. The endocine system ii of fundamental importance in controlling development and growth of fishes. Thyroid and pituitary glands differentiate during the final phase of yolk absorption in pelagic -egg species. Interrenal tissues appear later than both glands, around 2 weeks after hatching in Japanese flounder. Immumehistochemical techniques revealed production of GH and PRL prior to the time when the pituitary is histologically detectable. Tissue TH concentrations were at higher levels at fertilization, thereafter markedly reduced with embryonic development. They gradually increased with postlawal growth and development, and appreciably increased during metamorphosis in flatfishes. In some flatfishes, tissue concentration of cortisol als … More o exhibited a prominent surge, but the timing was significantly earlier than that of TH. These hormone level dynamics appeared to be intimately related to body structual, behavioral and ecological changes.2. Many marine microorganisms which stimulate settlement of flounder (Paralichthys obivaceus) larvae were surveyed. Marine Acinetobacter SS6-2 and Raphidophyta Chattonella antiqua a86 were effective on the settlement. The active substances were found in acetone or ethanol insoluble fraction.3. Dimethylsulfoniopropionate (DMSP) is the precursor of dimethylsulfide (DMS) which is the most abundant volatile sulfur compound in seawater. Various species of marine macroalgae (especially Rhodopohyta) and microalgae (especially Dinophyta and Haptophyta) contain DMSP. ' DMSP has promoting effect on growth, feeding and thrust power of several fishes. The biosynthetic pathway of DMSP from methionine in Crypthecodinium cohnii (Dinophyta). Methionine is first decarboxylated by methionine decarboxylase which requires pyridoxyal phsphate. We are now trying to purify this enzyme.4. Polyethyleneglycol method was applied to tranformation of the linearized plasmid pBI121 which contains the neomycin phosophotransferease II (NPTII) gene and beta-gluconidase (GUS) gene into the cell wall-less mutant of Chiamydomonas reinhardtii. This transformation procedure is very simple. Cells tranformed to kanamycin resistance were obtained. Southem blots of DNA from the transformant demonstrate the integration of the PNT II gene but GUS gene. We are now trying to make transgenic thalli of Ulva pertusa which can produce the growth hormone of tuna. Less