The time course of biotin-vitamer synthesis and the distribution of vitamers were studied in the growing culture of Phycomyces blakesleeanus. Over 92% of the synthesized vitamers accumulated in the culture medium during different stages of incubation period. The remaining part appeared as free and bound forms in the mycelia. The bound form contains only biotin. The vitamers were synthesized after the maximum growth had been attained. The highest growth coincided with the highest degree of assimilation of asparagine. Keto acids were the only detectable acids in the culture medium. P. blakesleeanus accumulated more than 50% dethiobiotin, 26% biotin d-sulphoxide, 15% biotin, and 3% 8-amino-7-ketopelargonic acid with biocytin sulphoxide and biocytin, of the total biotin-vitamers. The ratio of biotin to biotin sulphoxide depends on the culture condition.
Hexoses and maltose were suitable carbon sources in supporting the growth of Phycomyces blakesleeanus and synthesis of biotin. L-Asparagine and urea were the best nitrogen sources. Sulphur-containing amino acids inhibited the synthesis of biotin-vitamers. Some amino acids, organic acids, and Tweens stimulated the biosynthesis of biotin-vitamers. Lysine and pimelic acid were the most effective. It is assumed that some amino acids and organic acids play an important role in the biosynthesis of biotin- vitamers. Adenine increased the accumulation of true and total biotin- vitamers but other heterocyclic compounds repressed the synthesis of biotin- vitamers.
Dethiobiotin was the main portion of the conversion products of pimelic acid in Phycomyces blakesleeanus. It is suggested that pimelic acid participates in biotin biosynthesis. P. blakesleeanus has a high activity to convert pimelic acid to dethiobiotin rather than to convert dethiobiotin to biotin. A reason for this phenomenon is proposed. The presence of two sites of activity in the biotin pathway of P. blakesleeanus, which were controlled by repression with exogenous biotin, is suggested. It is found that the synthesis of dethiobiotin and biotin is notably controlled and that dethiobiotin is a normal intermediate in biotin biosynthesis.
DNA base composition (GC content) of 44 strains of yeasts and yeastlike fungi which represent 36 species belonging to 19 genera was calculated from the thermal denaturation temperature (Tm) of DNA. The GC content of these fungi ranged from 31.5 to 62.7%. Three species of Rhodosporidium showed GC values of 50.5%, 64.9-65.4%, and 67.1-67.3%, respectively, and were considered to be well-defined species. Seven species of Tremella showed a GC content of 47.6-58.5% which fell within the range of that reported in Cryptococcus. Three species of Protomyces and one species of Taphrina showed a GC content (52.0-52.4%) similar to one another, and the close relation assumed between these genera was supported. Endomycopsis javanensis and E. capsularis showed GC values of 31.5% and 43.4%, respectively, which were low and high extremes of this genus. Three species of Trichosporon showed the GC content in the range of 45.6 to 62.7%. Trichosporon lodderi, which is now regarded as a synonym for Candida tropicalis, showed a GC content of 45.6% which was about 10% higher than that of C. tropicalis. This species is considered to be different from C. tropicalis. Sterigmatomyces elviae showed a GC content of 51.5% and demonstrated strong urease activity, and is assumed to be related to heterobasidiomycetes.
The cells of Escherichia coli at the logarithmic phase of growth lost their colony-forming ability when the cells were suspended in 0.15M sodium chloride in Tris buffer. The presence of magnesium ion in Tris buffer containing 0.15M sodium chloride, in which the cells were suspended, protected the cells from the injurious effect of sodium chloride. A similar protection by calcium or manganese ion was also observed. When sodium chloride-treated cells were incubated immediately in Tris buffer containing magnesium, the colony-forming ability was recovered rapidly. An almost complete recovery by magnesium was observed. No such remarkable recovery was noted by incubation with calcium or manganese. A significant release of magnesium from the cells was observed during the incubation in sodium chloride. Therefore, the loss of viability is due, at least in part, to the release of magnesium ion from the cells.
Seventy-six strains of Candida krusei and allied species obtained from culture collections and newly isolated from various natural sources were studied taxonomically. The strains employed in this work were classified into 12 groups representing 14 species mainly on the basis of carbon assimilation pattern, vitamin requirement, maximum growth temperature, and guanine- cytosine content in DNA. Three new species, Candida citrea, Candidasorboxylosa, and Candida rugopelliculosa, were described.
The nutritional requirements for rapid utilization of allyl alcohol in shaken flask cultures were investigated for a strain of Trichoderma viride isolated from soil. Single variable and factorial experiments were used to determine the effects of various nitrogen sources and concentrations of phosphate, allyl alcohol, glucose, and yeast extract on utilization of allyl alcohol. Ammonia was a better nitrogen source than nitrate. Urea, also, was suitable provided the culture was kept below about pH 6.5. Phosphate as high as 0.1M did not inhibit and the improved pH control favoured allyl alcohol utilization. Glucose or yeast extract stimulated allyl alcohol utilization, the maximum effect being achieved at 1g of glucose/liter.
From the yeasts collected from various natural habitats in Japan from April 1962 to May 1965, six new species, Candida fibrae, Candida fragicola, Torulopsis auriculariae, Torulopsis fructus, Torulopsis musae, and Trichosporonbrassicae, were found. DNA base composition of these new species was calculated from the thermal denaturation temperature of DNA and used for confirmation of identification.
The conditions influencing the activity of polygalacturonase, produced by Clostridium felsineum, on flax pectin were studied. Three-quarters of the enzyme activity was achieved in the first 15min of the reaction at 30° and pH 4.0. At higher pH values, citrate-phosphate buffer was found to be less harmful than acetate buffer to the enzyme activity, probably due to the tying up of some calcium ions. On using dilute enzyme preparations, no chromatographically detectable galacturonic acids and no correlation between the reduction in viscosity and increase in reducing end groups of flax pectin were found. The contrary occurred when a concentrated enzyme preparation was used and no disappearance of the released oligogalacturonic acids to produce monogalacturonic acid was detected as the time of polygalacturonase action prolonged. This was taken as an indication that polygalacturonase had more affinity toward polymer flax pectin molecules than to lower oligogalacturonic acids. On the other hand, the acidity of the culture filtrate was found to be a limiting factor for detecting pectin- methylesterase by the hydroxamate method.