- Volume 21, Issue 3, 1959

SUMMARY: Seven analogues of vitamin B12 were examined for their influence upon the growth of Ochromonas malhamensis, Euglena gracilis, Lactobacillus leichmanniiATCC 4797 and Escherichia coli 113–3. The analogues were active in promoting the growth of E. gracilis and L. leichmannii, but were essentially inactive for O. malhamensis. For E. coli three of the analogues were active and four inactive. In O. malhamensis and in E. coli, the ‘inactive’ analogues antagonized the growth- promoting action of cyanocobalamin, apparently by satinrating the cells’ mechanism for ‘binding’ the vitamin and so preventing its uptake.

Tests were also carried out with Ochromonas malhamensis and Escherichia coli on twelve derivatives of benziminazole. None of these proved inhibitory towards E. coli, at least up to 100 µg./ml. culture medium. Eight of the compounds were inhibitory towards O. malhamensis; the effects were relatively small, however, and were possibly unrelated to the metabolism of vitamin B12.

SUMMARY: Several methods for growing animal cells in suspension culture were examined, to find the most efficient in terms of cells produced in a given time for the minimum of medium and attention. Continuous medium flow was more efficient than batch-culture, and the preferred system was to add medium to a culture vessel regularly in small doses via a time-switch-controlled solenoid closure at a rate similar to the growth rate; a turbidimetric safety device ensured that cell density did not drop below levels permitting growth. A mixture of galactose or fructose (6 g./l.) and glucose (2 g./l.) allowed better pH control than glucose alone (6 g./l.). Doubling times of 14–16 hr. were obtained on occasion; the gas-phase oxygen concentration for fastest growth depended on cell density and was frequently less than atmospheric, suggesting that these cells can behave as microaerophils.

SUMMARY: The fungus Blastocladiella emersonii possesses neither chlorophyll nor coloured carotenoids; yet, visible light induces increased nuclear multiplication, increased synthesis of DNA relative to total nucleic acid, and detectable changes in the soluble phosphorus pool of the fungus. The stimulatory effect is detectable through ontogeny, from the first few hours after germination to the end of the generation time of c. 15 to 25 hr. (depending on temperature). Light could be replaced by providing the plants with thymidine or thymine, but not with the corresponding RNA base, uracil. The DNA of B. emersonii contained the four principal bases usually associated with this nucleic acid. Finally, the interrelationships between DNA and RNA, and the effects thereon of nucleic acid analogues and inhibitors, were also studied. In particular, it was found that the DNA per cell doubled just before the first mitosis, while the total nucleic acid concentration did not change. The results of the latter experiments were interpreted in terms of the transformations which occur in the RNA-rich nuclear cap in the spores of the fungus during germination.

SUMMARY: Expanded descriptions of Mycobacterium phlei Lehmann & Neumann, M. smegmatis (Trevisan) Lehmann & Neumann, M. fortuitum Cruz, and the species tentatively designated as M. rhodochrous (Overbeck) Gordon & Mihm are presented. These characterizations are based on 40, 95, 80, and 79 strains respectively, upon which 39 different tests and observations were made.