End Of Logarithmic Growth Research Articles

Sporulation properties of cytochrome a-deficient mutants of Bacillus subtilis.

Three classes of cytochrome a-deficient mutants of Bacillus subtilis have been found to be asporogenic or oligosporogenic. All three classes showed declines in adenosine 5'-triphosphate (ATP) concentrations during early sporulation, at a time when ATP levels in wild-type strains are constant. Class III mutants were found to be deficient in aconitase and isocitric dehydrogenase, and showed reduced maximum growth in nutrient sporulation medium. These mutants also suffered the most rapid decline in ATP concentration in early sporulation, and exhibited neither the biphasic oxygen consumption curve nor the increase in pH normally observed at the end of logarithmic growth in nutrient sporulation medium. Nicotinamide adenine dinucleotide oxidase activities of purified membrane preparations were approximately normal for mutants in all classes, except for two of the class II mutants and one class III mutant. Neither cytochrome a nor cytochrome c appears to be an obligatory intermediate in cyanide-sensitive nicotinamide adenine dinucleotide oxidation in B. subtilis.

Ribosomal RNA synthesis is turned off during sporulation of Bacillus subtilis

In Bacillus subtilis the percentage of the incorporation of radioactive uracil that enters into ribosomal subunits and ribosomal RNA decreases drastically, early during spore formation. This finding suggests that ribosomal RNA genes are turned off in sporulating cells. The RNA polymerase of B. subtilis loses a template specificity characteristic of the vegetative enzyme early during spore formation (Losick & Sonenshein, 1969). However, a rifampicin-resistant mutant known as rfr-10 (Sonenshein & Losick, 1970) alters the RNA polymerase in such a way that it retains vegetative template specificity during stationary phase. We now report that rfr-10 continues synthesizing ribosomal subunits and ribosomal RNA after the end of logarithmic growth. On the other hand, rfr-10 ceases to synthesize ribosomal RNA under conditions of amino-acid starvation, indicating that the mechanism responsible for turning off ribosomal RNA genes during sporulation is different from the mechanism of stringent control of ribosomal RNA synthesis.

Further study on the activation of collagen proline hydroxylase in cultures of L-929 fibroblasts

Collagen proline hydroxylase was measured throughout the growth cycle of L-929 fibroblasts grown in suspension culture. Enzyme activity increased near the end of logarithmic growth as was found previously for monolayer cultures. Direct cell contact was not necessary for the increase in enzyme activity but occurred when cells at a saturation density ceased dividing. When log phase cells from monolayers or suspension cultures were concentrated to high cell densities, the hydroxylase activity rapidly increased. This increase in enzyme activity was shown to be an activation process and not to require new protein synthesis. Some stimulation of hydroxylase activity occurred on preincubation of cell sonicates at pH 6.0 suggesting that the cellular acidosis which occurs in high density cultures may contribute to the increase in enzyme activity.

The course of phage ∅e infection in sporulating cells of Bacillus subtilis strain 3610

Infection of Bacillus subtilis strain 3610 by the virulent phage ∅e at a critical stage during sporulation results in failure to produce phage and in incorporation of the phage genome within the developing spore. This phage “trapping” is maximal if infection occurs 5–6 hours after the end of logarithmic growth and is correlated with the failure of three phage-induced enzyme activities to appear at measurable levels. A nonsporulating mutant has been isolated which allows phage production in cells infected at a time when cells of the wild-type bacterium produce no phage. This mutant is blocked before the prespore stage but produces an antibiotic factor and a protease characteristically formed in the early steps of the sporulation process.

The induction of multinuclearity in agitated and in aging cultures of Acanthamoeba sp. Neff.

AbstractUnagitated cultures of Acanthamoeba in the logarithmic growth phase have been observed to consist of over 99% mononucleates and less than 1% multinucleates. A small increase in the relative numbers of multinucleates occurs as the culture age and conditions for growth become limiting. A large increase in the proportion of multinucleates occurs during logarithmic growth, if the cultures are agitated by shaking or by the bubbling from a stream of air. After an initial increase and until the end of logarithmic growth, the numbers of multinucleates in the agitated cultures are maintained at a constant fraction of the total population. Proportions of multinucleates as high as 25% are observed during this period. A second increase in the relative numbers occurs as conditions for growth become limiting. Under these conditions, the multinucleates may exceed 50% of the total population. The factors inducing multinuclearity as well as the kinetics of the mononucleate and multinucleate accumulation curves are discussed.

THIAMINE AND TETRAHYMENA

1. Tetrahymena geleii will grow in serial transplants in completely dethiaminized filtered and diluted casein solution plus salts and riboflavin. Added thiamine has no effect upon the population.2. Growth rate, population at the end of exponential growth and maximum yield are greatly increased when dethiaminized alfalfa extract is added.3. No growth occurs in completely hydrolysed casein even with added thiamine.4. Good growth occurs in casein hydrolysate plus dethiaminized alfalfa extract. Heat and alkali treatment of the hydrolysate or the addition of thiamine have no significant effect.5. Whole gelatin and dethiaminized whole gelatin support transplantable growth. The addition of thiamine has no effect during logarithmic growth but causes an increase in maximum yield.6. The addition of dethiaminized alfalfa extract to gelatin and to dethiaminized gelatin increases significantly the reproductive rate, population at the end of logarithmic growth and the maximum yield.7. Gelatin hydrolysate and dethiaminized gelatin hydrolysate support growth only when alfalfa extract is added. The addition of thiamine has no significant effect.8. Ciliates growing in gelatin or heated gelatin alone become extremely small and sluggish after about the eighth day. They remain viable up to 30 days, however. The addition of thiamine causes the ciliates to become very large in old cultures. The addition of alfalfa extract produces ciliates intermediate in size.9. The conclusion is reached that casein and gelatin possesses small amounts of "factor S" which makes it possible for Tetrahymena geleii to synthesize thiamine. "Factor S" from alfalfa extract, together with "factors I and II" (Dewey, 1944) added to casein or gelatin, produce rapid and heavy growth. Thiamine is not a "growth factor" for T. geleii (strain W).