The optimal growth pH and conditions necessary to give a full manifestation of the effect of reductants upon the growth of Campylobacter ,fetus were investigated using static cultivation. The multiplication of cells was limited to a narrow range of added reductants. Thioglycollate supplemented without heating produced heavy growth in combinations of 0.05% at pH 6.80 or 0.1% at pH 6.60, and 0.2% at pH 7.00 or 7.20. Although the stimulating effect depended upon the time between the addition of the supplement and inoculation, two prominent peaks in the growth curve always appeared with both alkaline and acidic pH ranges of the medium. Autoclaving the medium with some SH compounds brought about this growth only at around pH 6.50. Consequently there was a uniform decrease in the initial pH. L-Cysteine and ascorbic acid also gave similar effects. Glucose remarkably prevented the growth promotion due to SH compounds. Optimal initial reduction potential for growth in a semisolid medium was considered to be-0.05 to-0.08 volt at an initial pH of 6.60. SH compounds supplemented without heating brought about a marked longevity of the culture in comparison with a culture in an autoclaved medium of the same composition. For the growth of C. fetus in semisolid medium, it was important to avoid decreasing the growth-promoting activity of some of the supplemented SH compounds by not heating but adding the supplement aseptically. Also a rigid regulation of the pH, the concentration of the added reductants, and the time of inoculation into the fresh medium were important.
The distribution of kainic acid among various red algae was investigated. Analysis of free amino acids from different populations of Palmaria palmata showed that some were unable to accumulate kainic acid to detectable concentrations, whereas in two dwarf mutants it was a major component of the free amino acid composition. The amino acid profiles were also examined for unknown amino acids in the search for possible intermediates in kainic acid biosynthesis. The only unknown amino acid present in P. palmata extracts was isolated and identified by NMR spectroscopy as 1'-hydroxykainic acid. This compound was found in all samples that contained kainic acid. To investigate the effect of growth conditions on kainic acid production different strains of P. palmata were grown at 5, 10, and 15 degrees C with or without added nitrate. No effect on production was observed, suggesting that the growth conditions in these experiments do not affect the level of gene expression in the pathway of kainic acid biosynthesis. Furthermore, changing the growth conditions did not induce synthesis of kainic acid in the non-producing strains of Palmariales.
The ratio of the concentrations of κ- to λ-carrageenan is shown to be related to the nuclear phase in Chondrus crispus both in culture and in nature. This ratio is low in tetrasporic plants and relatively high in the gametophytes. It was found to vary somewhat amongst samples analysed, but was always less than unity in tetrasporophytes and greater than unity in gametophytic plants. The κ/λ ratio in Gigartina stellata was high in gametophytes as in C. crispus; the tetrasporophytic phase of this species is unknown. It is suggested that the commercial quality of carrageenan can be correlated with the biological status of the harvested plants.
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