[Growth and spore formation in Bacillus thuringiensis at high substrate concentrations]. / Rost i sporoobrazovanie Bacillus thuringiensis pri vysokikh kontsentratsiiakh substratov.

The work was aimed at studying the effect exerted by elevated concentrations of glucose, yeast extract and acetate on the growth of Bacillus thuringiensis subsp. galleriae, strain 69-6, and on the formation of spores and crystals by it. Glucose concentrations from 30 to 100 g per litre did not prevent spore formation. Yeast extract inhibited spore formation to a greater extent and stopped it almost completely at a concentration of 20 g per litre. Acetate at a concentration of 1.0 to 10 g per litre delayed spore formation and produced a less action on crystal formation, so that those processes were uncoupled in time.

[Cultivation of the producer of alpha-amylase Bacillus subtilis under batch and continuous conditions]. / Kul'tivirovanie produtsenta alpha-amilazy Bacillus subtilis v periodicheskikh i nepreryvnykh usloviiakh.

The growth of Bacillus subtilis FU-79 and its production of alpha-amylase (EC 3.2.1.1) were studied under the conditions of batch and continuous cultivation in a semisynthetic medium. The enzyme activity fell down abruptly upon a pulse addition of either glucose or yeast extract to the chemostat culture, and remained at a low level for the following ten generations. Apparently, a double limitation of the culture growth (viz., with residual glucose and with yeast extract components) is required for the activity of alpha-amylase to be high.

[Morphological changes in a chemostat culture of Candida utilis undergoing cyclic changes of pH and pO2]. / Morfologicheskie izmeneniia khemostatnoi kul'tury Candida utilis pri tsiklicheskikh izmeneniiakh pH i pO2.

The effect of cyclic pH and pO2 changes on the morphology of Candida utilis was studied with time intervals measured in minutes. The pH was varied from 4.5 to 2.6, the pO2 from 70% of the saturation to 0%. The morphology was studied both visually and using the technique of optical-structural computer analysis. The regime with pH changes increased the biomass yield. However, the averaged morphological characteristics showed that the growth was slightly inhibited. Therefore, the yeast population was very heterogeneous, some cells were inhibited while other cells were stimulated, which made the economic coefficient rise. The cells were also inhibited when they were exposed in the conditions of oxygen deficiency for a short period of time. However, the cells could not be inhibited if, at the same time, the pH was extremely low. Changes in the morphology were detected earlier than either the inhibition or stimulation of growth was recorded by measuring the weight of biomass.

[Growth and development kinetics of Bacillus thuringiensis in batch culture]. / Kinetika rosta i razvitiia Bacillus thuringiensis pri periodicheskom kul'tivirovanii.

The kinetics of Bacillus thuringiensis growth and its assimilation of nutrient substances were studied under the conditions of batch cultivation in a complex medium containing yeast extract and in a chemically defined medium with amino acids. The growth of B. thuringiensis can be divided into five phases: exponential growth; decelerated growth; stationary phase when protein crystals are formed; stationary phase when spores are formed; lysis of sporangia releasing spores. The first phase may in turn be subdivided into three stages according to changes in the specific growth rate and substrate assimilation: a high specific growth rate and no glucose assimilation; an abrupt drop in mu and the beginning of intensive glucose assimilation from the medium; a new rise in the specific growth rate. As follows from the results of studying the kinetics of B. thuringiensis growth in a chemically defined medium, the above changes in the exponential growth phase are due to the fact that the culture assimilates yeast extract components in the complex medium or amino acids in the chemically defined medium during this phase, and then starts to assimilate glucose and ammonium in the following phases of growth.

[Biological characteristics of the variants of Bacillus thuringiensis subsp. galleriae formed during continuous culture]. / O nekotorykh biologicheskikh osobennostiakh variantov Bacillus thuringiensis subsp. galleriae, obrazuiushchikhsia pri nepreryvnom kul'tivirovanii.

Bacillus thuringiensis subsp. galleriae S. variants formed during continuous cultivation differ from the parent culture in certain properties. In contrast to the parent R form, their growth in the chemostat does not yield virulent mutants which can cause their lysis on solid media. The chemostat S forms are resistant against virulent phage mutants produced when the R variants are grown under the conditions of continuous cultivation and against a virulent phage obtained from the parent culture 69-6 under the action of vancomycin. The R forms are sensitive to these phages. When the S forms are grown under the chemostat conditions, they do not revert to the R forms. The R and S forms do not differ noticeably in the character of their growth, formation of spores and crystals, and biological activity.

[Variability of Bacillus thuringiensis under various growth conditions]. / Izmenchivost' Bacillus thuringiensis pri raznykh usloviiakh vyrashchivaniia.

When a lysogenic culture of Bacillus thuringiensis subsp. galleriae 69-6 was grown under the batch conditions, 93-99% of cells in the population produced R-form colonies and ca. 1% yielded S-form colonies. The amount of spore-forming cells was 99% in R-variants and 8% in S-variants. The quantity of S-variants rose abruptly to 99% when the culture was grown under the chemostat conditions. The number of S-variants increased with the rate and the duration of growth. The process was influenced by growth-limiting factors. Temperate phage variants capable of host culture lysis on solid media (i.e. h-mutants) were not found under the conditions of batch cultivation. However, such phage particles (h-mutants) appeared under the conditions of chemostat. The titre of these phage particles reached 10(8), 10(7) and 10(4) particles per 1 ml at limitation with yeast extract, glucose and phosphorus, respectively. Under the conditions of chemostat, the particles behaved as temperate ones and their growth was not found. Irrespective of the limitation, the phage titre did not correlate with the ratio of R and S-forms in the population. When the growth was limited with phosphorus, the quantity of S-forms increased abruptly while the spontaneous induction of the phage was inhibited. The quantity of cells capable of spore formation decreased in the cultures isolated from the chemostat and grown on MPA: 69-80% of the cells in R-forms and merely 8% in S-forms.

[Sporulation and crystal formation in Bacillus thuringiensis during growth limitation via nutrient sources]. / Sporuliatsiia i kristalloobrazovanie u Bacillus thuringiensis pri limitatsii rosta istochnikami pitaniia.

The object of the work was to study the effect of limiting concentrations of glucose, yeast extract, phosphorus, magnesium and potassium on the growth, spore formation and crystal formation in Bacillus thuringiensis subsp. galleriae. The deficiency of the above components was shown to interfere in no way with the processes of spore and crystal formation. However, the type of limiting substrate influenced the character of spore formation, the duration of different phases in the culture growth, the yield of spores and crystals, and their quality.

[Chemical composition and morphological changes in the cells in a chemostat Candida utilis culture inhibited by zinc ions]. / Khimicheskii sostav i morfologicheskie izmeneniia kletok v khemostatnoi kul'ture Candida utilis, ingibirovannoi ionami tsinka.

The effect of zinc ions on the physiological state of Candida utilis VKM Y-1668 was studied during its chemostat cultivation. The concentration of zinc ions was maintained at a constant level. Zinc was found to inhibit the growth at a concentration of 300 mg/l. The cells were rapidly washed from the fermenter when zinc concentration was increased to 500 mg/l. Zinc uptake by the culture became greater when zinc concentration in the medium was gradually increased. If the yeast was cultivated in the presence of the inhibitor, the content of protein, RNA, DNA and polysaccharides fell while lipid content increased. Growth inhibition by zinc ions interfered with cell division; the cells could not separate from one another and formed catenae and conglomerates.

[Use of rifampicin for directed modification of the nucleotide composition of the cells of Bacillus megaterium and Candida utilis]. / Primenenie rifampitsina dlia napravlennogo izmeneniia nukleotidnogo sostava kletok Bacillus megaterium i Candida utilis.

The object of this work was to study the effect of rifampicin on the physiological state of Bacillus megaterium and Candida utilis in chemostat and batch cultures. When B. megaterium is cultivated in a medium containing 1 microgram of rifampicin per litre, its metabolism changes, the pool of free nucleotides rises, and the content of RNA drops in response to the specific action of the inhibitor. The modified state is observed throughout many generations. The action of the inhibitor is also non-specific: protein content falls and polyhydroxybutyric acid is accumulated. The morphology of B. megaterium cells changes: they become larger, their cell wall thickens, and the separation of cells from one another is complicated. At a high concentration (5 mg/l), rifampicin decelerates the growth of C. utilis and causes merely a minor non-specific inhibition.

[Transitional states in a chemostat culture of Candida utilis]. / Perekhodnye sostoianiia khemostatnoi kul'tury Candida utilis.

Transient states of the chemostat Candida utilis 1668-3-37 culture were studied when its growth was limited by ethanol and an abrupt acidification of the medium from pH 5.0 to 2.2 was done or when the dilution rate was rapidly changed from D = 0.1 to 0.3 h-1 and back to 0.07 h-1. The pH shock was found to cause stronger oscillations in a number of parameters (the weight of dry biomass, the content of residual ethanol, the content of RNA in the cells) than a change in the dilution rate. In the latter case the population density changed more smoothly than the content of RNA did. DNA content remained at one and the same level in all of the experiments. All of the oscillations were observed only in the first generation after a shock; there upon, the culture remained for a long time (7 to 10 generations) in a very stable state typical of chemostat cultures. The oscillations induced by the unfavourable pH of the medium were compared with those caused by an abrupt change in the dilution rate. The pH shock brought about multiple damping oscillations of the parameters whereas a change in the dilution rate resulted, most often, in a merely one oscillation.

[Periodic changes in the morphophysiological properties of chemostat culture of Candida utilis yeasts under alternating temperatures]. / Periodicheskie izmeneniia morfofiziologicheskikh svoistv khemostatnoi kul'tury drozhzhei Candida utilis v usloviiakh peremennykh temperatur.

The object of this work was to find out whether it was possible to cultivate yeasts in chemostat in varying regime: at multiple changes to temperature from the optimal one (31 degrees C) to the supraoptimal one (37 degrees C) and back with a frequency comparable to the generation time; this regime was alternated during 32 generations. The cultures were compared with chemostat cultures grown in steady-state regimes at 31 or 37 degrees C. The value of Y, the composition of cells and morphometric characteristics were determined by the optical-structural computer analysis. The size and shape of cells and the optical properties of the protoplasm were found to be in the oscillatory regime correlating with changes in the growth temperature and periodically tending to the normal characteristics. The value of Y, the content of RNA and protein in the biomass gradually stabilized. A possibility, in principal, to continuously cultivate yeasts is discussed when the conditions of the environment are rhythmically changed and the process is controlled in the morpho-physiological characteristics of the cells.

[Method of calculating the specific growth rate of microorganisms by measurements of the substrate or product concentration]. / Metod vychisleniia udel'noi skorosti rosta mikroorganizmov po izmereniiam kontsentratsii substrata ili produkta.

A procedure and formulae are proposed for calculating the specific rate of microbial growth; these are based on measuring the concentration of either a limiting substrate or a product involved in the growth of a microorganism. Only the concentrations of a substrate (S) or a product (P) are determined periodically in the course of the cultural growth whereas the biomass yield (chi) in the medium is established only after long time intervals. The proposed equations may be used for controlling the specific growth rate in large-scale processes by the concentration of a product (or a substrate) using a computer, as well as in laboratory studies of mu as a function of the conditions for growth of slowly growing microorganisms.

[Effect of the protein synthesis inhibitor chloramphenicol on the basic growth indices of continuous and periodic Bacillus megaterium cultures]. / Vliianie ingibitora sinteza belka khloramfenikola na osnov nye pokazateli rosta nepreryvnoi periodicheskoi kul'tury Bacillus megaterium.

The action of chloramphenicol, a specific inhibitor of bacterial growth and an inhibitor of protein synthesis, was studied in the conditions of continuous and batch cultivation. Steady states of the population within the range of D from 0.2 to 0.7 hr-1 were obtained at a concentration of the antibiotic equal to 20 microgram per liter. The shape of the chemostat curve in the presence of chloramphenicol in the medium indicates that the antibiotic slightly decreases mu max and considerably diminished Y. A change of limiting factors occurs along the chemostat curve at different dilution rates (0.2, 0.4 and 0.7 hr-1): one-, two- and three-factor effects on the population were observed. Steady states of the population in the chemostat are possible by chloramphenicol concentrations of 10 to 100 microgram per litre; in this case, cellular metabolism changes in the following nonspecific way: less effective energy processes are activated, the Y decreases as well as protein content in the cells, but the content of poly-beta-hydroxybutyric acid in the biomass increases. If chloramphenicol is taken at a concentration of 1000 microgram per litre (a dose strongly inhibiting the growth rate), other changes specific for this inhibitor are found: the content of protein decreases while that of RNA increases, and substances of nucleotide nature are released into the medium. The changes remain for many generations. The data show that it is possible to change the ratio between cell polymers in growing population.

[Effect of Zn2+ on growth and the properties of Candida utilis in continuous cultivation]. / Vliianie Zn2+ na rost i nekotorye svoistva Candida utilis pri nepreryvnom kul'tivirovanii.

The purpose of this work was to study the effect of zinc ions on the growth and physiological properties of the chemostat culture of Candida utilis BKM Y-1668. Zinc at a concentration of 250-300 mg/l was found to inhibit the growth of the culture. The resistance of the culture to zinc ions can be increased within 40 generations if the yeast is grown in the regime of chemostat and the concentration of zinc ions is gradually increased. The growth of the resistant culture by zinc ions was inhibited at a concentration of 500 mg/l. If the yeast was cultivated with an addition of the inhibitor, the economic coefficient decreased, while the utilization of glycerol, nitrogen and phosphorus per 1 g of the biomass increased twofold and more; the rate of oxygen uptake by the cells and the rate of carbon dioxide evolution decreased, whereas the concentration of keto and amino acids in the medium increased.