The effect of sporulation temperature on sporal characteristics ofBacillus subtilis A

Spores ofBacillus subtilis A were produced at different temperatures (23°–49°C) and examined for a number of sporal characteristics. Spore heat resistance increased with sporulation temperature to 45°C, with spores grown at 49°C showing a dramatic reduction in resistance. Spore crops showed biphasic thermal death curves whether enumerated on germination medium with or without calcium dipicolinate. This strain produces both rough and smooth variants. Of the spores produced at 23°C, 99% were rough, had a density of 1.305, and an average core/core + cortex volume ratio of 0.1838. At 49°C, 99% were smooth, had a density of 1.275, and an average volume ratio of 0.3098. Between these temperatures both spore types were produced. There appeared to be no direct correlation with sporulation temperature, heat resistance, and dipicolinate content. There was an increase in both the magnesium and calcium contents to 45°C with a dramatic reduction at 49°C. The 1.305 density spores had higher calcium and dipicolinate contents than the 1.275 spores, although both spore types showed biphasic thermal death curves. The mechanisms involved in determining which spore type (rough/smooth) is produced at a specific growth temperature is unknown.Florida Agricultural Experiment Station Journal Series Number R-00312.     

The program of protein synthesis during sporulation in Bacillus subtilis

The program of protein synthesis was examined during sporulation in Bacillus subtilis as an index of the control of gene expression. At various stages of growth and spore formation, cells of B. subtilis were pulse-labeled with ³⁵S-methionine. Protein was extracted from the radioactively labeled bacteria and then subjected to high resolution one-dimensional and two-dimensional slab gel electrophoresis. We report that sporulating cells restricted or “turned off” the synthesis of certain polypeptides characteristic of the vegetative phase of growth. In certain cases, this “turn off” was prevented in a mutant (SpoOa-5NA) blocked at the first stage of spore formation. Sporulating bacteria also elaborated new polypeptide species that could not be detected in vegetatively growing cells or in cells of the asporogenous mutant SpoOa-5NA in sporulation medium. The synthesis of these sporulation-specific proteins was “turned on” in a temporally defined sequence throughout the period of spore formation. Spore coat protein, for example, was first synthesized at 4 hr after the onset of sporulation, the time at which refractile prespores appeared. Certain sporulation-specific polypeptides including the coat protein were among the most actively produced polypeptides in sporulating cells.     

Effect of temperature and aeration on Bacillus thuringiensis growth and sporulation

The growth of Bacillus thuringiensis was studied as a function of temperature and aeration. The vegetative growth, the yield of viable spores and their thermoresistance did not depend, for all practical purposes, on the rate of aeration within the range of 25 to 60 mg O2 per litre per minute. A rise of temperature from 20 to 35 degrees C doubled the titre of spores and increased their thermoresistance. When the temperature of cultivation was increased to 40 degrees C, the process of spore formation was inhibited.     

Metabolic rates during sporulation of Saccharomyces cerevisiae on acetate

We have quantified yeast carbon and oxygen consumption fluxes and estimated anabolic fluxes through glyoxylate and gluconeogenic pathways under various conditions of sporulation on acetate. The percentage of sporulation reached a maximum of 55% to 60% after 48 h in sporulation medium, for cells harvested from logarithmic growth in acetate minimal medium. When cells were harvested in the stationary phase of growth before transfer to sporulation medium, the maximum percentage of sporulation decreased to 40% along with the occurrence of meiosis as could be judged by counting of bi- and tetra-nucleated cells. In both experiments, the rates of acetate and oxygen consumption decreased as a function of time when exposed to sporulation medium. Apparently, the decrease of metabolic rates was not due to alkalinization. By systematically varying the cell concentration in sporulation medium from 1.4×10⁷ to 20×10⁷ cell ml^-1, the percentage of sporulating cells was found to decrease in parallel with the rate of acetate consumption. When the sporulation efficiency attained under the different experimental conditions was plotted as a function of the rate of acetate consumption, a linear correlation was found. Anabolic fluxes estimation revealed a decrease of the rate through gluconeogenic and glyoxylate pathways occurring during sporulation progression. The pattern of metabolic fluxes progressively evolved toward a predominance of more oxidative catabolic fluxes than those exhibited under growth conditions. The results obtained are discussed in terms of a characteristic pattern of metabolic fluxes and energetics, associated to the development of yeast sporulation.Abbreviations DAPI 4,6-diamidino-2-phenylindole - dw dry weight - OD₅₄₀ optical density at 540 nm - SEM standard error of the mean - RQ respiratory quotient     

Influence of the sporulation temperature upon the heat resistance of Bacillus subtilis

The influence of different sporulation temperatures (30, 37, 44 and 52°C) upon heat resistance of Bacillus subtilis was investigated.
Heat resistance was greater after higher sporulation temperatures. Relation of heat resistance and temperature of sporulation was not linear over all the range of temperatures tested. Heat resistance increased about tenfold in the range of 30–44°C. Sporulation at 52°C did not show any further increase in heat resistance.
This effect was constant over all the range of heating temperatures tested (100–120°C). z value remained constant ( z = 9°C).
Greater heat resistances at higher temperatures of sporulation were not due to selection of more heat resistant cells by a higher sporulation temperature. Spores obtained from cells incubated at 32 or 52°C always possessed heat resistances that corresponded to the sporulation temperature regardless of the incubation temperature of their vegetative cells.     

Effects of temperature and light on growth and sporulation of aquatic hyphomycetes

Nine isolates of the aquatic hyphomycetes Dactylella aquatica, Flagellospora penicillioides, Flagellospora saccata, Helicomyces sp., Lunulospora curvula, Phalangispora constricta, Tetracladium setigerum, Vermispora cauveriana and Wiesneriomyces laurinus were incubated at different temperatures (5–35 °C) to study their growth on MEA medium. Maximum growth was observed between 20 and 30 °C. Growth rate was highest in Vermispora cauveriana and lowest in Tetracladium setigerum. Colonies on submerged leaves showed maximum spore production at 25 °C. Light was confirmed as a stimulus to sporulation.     

Stability and synthesis of the penicillin-binding proteins during sporulation

The penicillin-binding proteins (PBPs) of Bacillus subtilis were examined after incubation of vegetative and sporulating cultures with chloramphenicol, an inhibitor of protein synthesis. The results indicate that the sporulation-specific increases in vegetative PBPs 2B and 3 and the appearance of two new PBPs, 4* and 5*, depend on concurrent protein synthesis, which is most likely to be de novo synthesis of the PBPs rather than synthesis of an activator or processing enzyme. It was also learned that in vivo the PBPs differ in their individual stabilities, which helps to explain some of the quantitative changes that occur in the PBP profile during sporulation. All the membrane-bound PBPs, except possibly PBP 1, were found to be stable in the presence of crude extracts of sporulating cells that contained proteolytic activity.     

Studies on the pycnidial formation by macrophomina phaseoli (Maubl.) ashby size of pycnidia,ostiole and pycnidiospores and its significance

Summary Studies on the size of pycnidia, ostiole, length and width of pycnidiospores and ratio between length and width of pycnidiospores ofM. phaseoli isolates from cotton, castor, sesame and groundnut, the pycnidia of which were obtained by artificial inoculation on the hosts and also in culture medium of one cotton isolate, revealed that all the isolates were true to the type species and that the isolates had significant differences among them for these characters. The measurements of pycnidia and spores were dependant on the substratum for their production, and as such should preferably be made when these structures are obtained on the host of the isolate. Delimitation ofM. phaseoli on basis of these measurements from other hosts of the isolates is considered unwarranted or invalid.     

Autolysins during sporulation of Bacillus subtilis 168

Conditions for zymographic detection of a 41-kDa spore cortex hydrolysis-specific autolysin, A6, from Bacillus subtilis 168 were optimised. A6 was present during sporulation from stages II–IV and remained active in the dormant spore. Its expression was controlled by the mother cell-specific early-sporulation sigma factor σ^E. The characteristic muramic acid δ-lactam of spore cortical peptidoglycan was not necessary for cortex hydrolysis by A6, but it may be important in the inability of the major vegetative autolysin LytC to digest wild-type cortex. Two other minor autolysins were also observed during sporulation. The possible physiological significance of these observations is discussed.     

Effects of temperature and different food matrices on Cyclospora cayetanensis oocyst sporulation

Effects of temperature on the sporulation of the parasite Cyclospora cayetanensis were studied in 2 food substrates, dairy and basil. Unsporulated Cyclospora oocysts were subjected to freezing and heating conditions for time periods ranging from 15 min to 1 wk. Oocysts were then removed from the food substrates and placed in 2.5% potassium dichromate for 2 wk to allow viable unsporulated oocysts to differentiate and fully sporulate, and to determine the percentage sporulation as an indicator of viability. Sporulation occurred when oocysts resuspended in dairy substrates were stored within 24 hr at -15 C. When oocysts were placed in water or basil, sporulation occurred after incubation for up to 2 days at -20 C, and up to 4 days at 37 C. Few oocysts sporulated when incubated for 1 hr at 50 C. Sporulation was not observed in basil leaves or water at -70 C, 70 C, and 100 C. Sporulation was not affected when incubated at 4 C and 23 C for up to 1 wk, which was the duration of the experiment in both of the tested substrates.