STUDIES ON STRAIN-PRESERVATION AND FUNCTION-DEVELOPMENT OF AQUATIC PLANTS

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Cryopreservation of the conchocelis of Porphyra yezoensis by the two-step cooling method was attempted. A solution composed of 10% DMSO and 0.5 M sorbitol in 50% seawater had the most favorable cryoprotective effect on the conchocelis. The appropriate cryopreservation procedure was as follows: DMSO was added gradually over a period of 15 min followed by an equilibration period of several minutes. Conchocelis cells were then cooled slowly to -40ﾟC prior to immersion in liquid nitrogen. After storage in liquid nitrogen, the conchocelis suspension was thawed quickly by agitation of the vial in a water bath at 40ﾟC, and cryoprotectants were washed off by gradual dilution with seawater. The survival was independent of the period of storage at least for 300 d. The survival evaluated by staining with neutral red was approx. 60%. The conchocelis cells stored in liquid nitrogen were able to form colonies, and retained the ability to form conchospores which grew to gametophytic thalli. This two- … More step cooling method is applicable to other macroalgae (e.g. Enteromorpha intestinalis, Macrocystis pyrifera).Hydrogen photoproduction capability in 39 strains of newly isolated marine and brackish nonsulfur phototrophic bacteria was surveyed. Among these, TU-PSB 105-1, which was isolated from a mud sample collected at brackish environment, exhibited highest hydrogen production capability (80 mulH_2・(mg prot)^<-1>・hr^<-1>). Using this strain TU-PSB 105-1, effects of nitrogen sources, substrates, pH and sodium chloride concentration to the hydrogen production capability were examined. Higher rates of hydrogen production were observed in glutamate-grown cells than in ammonia-grown cells. Organic acids such as fumarate, malate and succinate were more effective as a substrate for hydrogen production than sugars such as fructose and glucose. However, utilization of glucose was enhanced by preculturing the cells with glucose. Optimum hydrogen production was observed at low concentration of added sodium chloride (approx. 0.5%). At 0.5% of added sodium chloride, the rate of 160 mulH_2・(mg prot)^<-1>・hr^<-1> observed. Less