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.
AbstriictThe photosyiilhclic {•rowth of three species of Trebouxia was .so slow as to preclude the usual inorganic methods of algal cuUivalion. Heteiotrophic growth was much stronger --as many as 0.4 doublings per day were ohtained in Bold's solulion wilh glucose and amino acid hydrolysates. Ammoniimi salts of inorganic acids could not he used in llie culture medium because they caused excessive reductions in pH. Althouf^h the organisms showed variations in their giowth res|)onse to Minino acids, no specific ie([uirement was found. 7'. crici produced significantly lowei^ ({uantities of photosynthetic pigments in the dnik. Of the nineteen carl)ohydrates tested, onty gtuco.se, mannitol, and galactose stimulated growth of the algae. Preliminary studies showed that irebimxia incorporated '^CO^ more slowly than Chlorella pijrenoido.sa. However, the caihon fixed hy Trebouxia remained soluble in 80 "/o ethanol longer than Chlorella. Tlie carhon incorporated as CO^ in short term experiments was greater tlian would he expected from the growth rates of the organisms studied.
The lichenized fungus and alga of the fruticose lichen Ramalini ecklonii were isolated into pure cultures. The ascospores of the fungus failed to germinate in less than five weeks incubation in spite of the use of a variety of cultural conditions. The fungus showed a considerable increase in growth on malt extract agar. Both organisms showed a marked tolerance for high concentrations of glucose although growth was quantitatively reduced. The fungus was able to use a variety of carbon and nitrogen sources as well as an extract of algal cells. Cultivation in the absence of biotin and thiamine failed to yield significant amounts of growth. The alga yielded 27 mg of dry weight after three weeks in a synthetic medium under low light intensities. The alga could be grown in satisfactory amounts on CO2 and inorganic salts with moderate light intensities. Experiments using 14CO2 showed the fungus able to incorporate the extra‐cellular and intra‐cellular products of algal metabolism. The rate of incorporation of extra‐cellular products was inhibited by high concentrations of biotin and thiamine. The alga assimilated l4CO2 which was retained by the cells over a period of 14 days, at which time 78 per cent of the activity was insoluble in 80 per cent ethanol. An extract of the fungus labelled with 14C glucose was partially taken up by the alga and 50 per cent of the label was insoluble in 80 per cent after three days incubation in the light. No lichen acids were found in either the fungal cultures or the algal cultures although large amounts (e.g. 2 liters) of material were extracted and chromatographed. Usnic acid was produced by the intact lichen thallus.
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