SUMMARY: Pyrimethamine (PY), an inhibitor of folate reductase, blocks mitochondrial protein synthesis in yeast, presumably by creating a shortage of formylmethionyl-tRNA. This has been established by measuring in intact cells the effect of the drug on the formation of cytochromes a-a 3 and b, and on the incorporation of labelled leucine when cytoplasmic protein synthesis is suppressed by cycloheximide. As a result, growth of the organism in non-fermentable (glycerol) medium is arrested by relatively low concentrations of PY, which have little effect in fermentable (dextrose) medium where respiratory activity is not essential. However, higher drug concentrations do inhibit growth in dextrose medium, probably by preventing thymine synthesis. Under some conditions the budding process is modified, giving rise to abnormal elongated cells. The inhibitory effect of PY is prevented by exogenous tetrahydrofolate.
Prolonged exposure to low concentrations of the drug, or shorter exposure to higher concentrations, leads to an induction of mitochondrial petite mutants and cell death, presumably as a consequence of thymine starvation. Petite mutants are particularly susceptible to killing by PY. Those induced by the drug are of the suppressible type, and hence would appear to result from a modification to (rather than a loss of) the mitochondrial DNA.
SUMMARY: Membrane vesicles of Thiobacillus neapolitanus take up amino acids at 25 °C in the presence of the nonphysiological electron donor, ascorbate-N, N, N′,N ′-tetramethyl-p-phenylenediamine. The amino acids accumulate inside the membrane vesicles against a concentration gradient. Inhibitors of the electron transport chain inhibit the accumulation; therefore active transport of amino acids in T. neapolitanus is coupled to the electron transport chain. The Km values for the transport of glycine and L-serine in this organism are 2.5 and 5 μM respectively.
SUMMARY: Mannans isolated from Kluyveromyces species, from their imperfect forms Candida pseudotropicalis and Torulopsis sphaerica, and from Saccharomyces species were examined for their reactivities with Kluyveromyces fragilis and Saccharomyces cerevisiae antisera. It was found that Kluyveromyces fragilis, K. marxianus, K. lactis, Candida pseudotropicalis and Saccharomyces chevalieri possessed a specific antigenic mannan which after acetolysis yielded fragments up to pentasaccharide. Moreover these mannans showed high cross-reactivity with S. cerevisiae antiserum that could have been caused by the presence of a determinant group common to Kluyveromyces and Saccharomyces species. Polysaccharides obtained from K. polysporus and K. drosophilarum showed different immunological properties from the former mannans.
SUMMARY: The most abundant fatty acids of Caulobacter crescentus, as determined by gas-liquid chromatography, were 18:1,16:1,16:0, 12:0, 15:0, 17:0 and cyclopropane acid 17 Δ. The composition of the two morphological forms of this bacterium differed, in that the stalked bacteria and isolated stalk fragments contained more 16:0 and 17Δ, and less 16:1 than the swarmers.