Effects on growth and sporulation of inactivation of a Bacillus subtilis gene (ctc) transcribed in vitro by minor vegetative cell RNA polymerases (E-sigma 37, E-sigma 32)

Summary The E-³⁷ gene ctc was inactivated by a site-specific insertion into the Bacillus subtilis chromosome. The resulting mutation inhibited sporulation by 95% at elevated temperatures (48° C). If the ctc ^- mutation is placed in a strain that carries a mutation in the closely linked but distinct spoVC gene, ctc now affects both growth and sporulation at elevated temperatures. Growth of the ctc ^- spoVC285 strain was transiently inhibited when exponentially growing cultures were shifted from 37° C to 48° C. A similar, but less pronounced growth lag, was also seen in a B. subtilis strain carrying only the spoVC-285 mutation. This finding suggests that both the ctc and spoVC products function in vegetatively growing B. subtilis.     

Ferricrocin functions as the main intracellular iron-storage compound in mycelia ofNeurospora crassa

Summary Neurospora crassa produces several structurally distinct siderophores: coprogen, ferricrocin, ferrichrome C and some minor unknown compounds. Under conditions of iron starvation, desferricoprogen is the major extracellular siderophore whereas desferriferricrocin and desferriferrichrome C are predominantly found intracellularly. Mössbauer spectroscopic analyses revealed that coprogen-bound iron is rapidly released after uptake in mycelia of the wild-typeN.crassa 74A. The major intracellular target of iron distribution is desferriferricrocin. No ferritin-like iron pools could be detected. Ferricrocin functions as the main intracellular iron-storage peptide in mycelia ofN. crassa. After uptake of ferricrocin in both the wild-typeN. crassa 74A and the siderophore-free mutantN. crassa arg-5 ota aga, surprisingly little metabolization (11%) could be observed. Since ferricrocin is the main iron-storage compound in spores ofN. crassa, we suggest that ferricrocin is stored in mycelia for inclusion into conidiospores.     

Amino acid pool and protein turnover during differentiation (spherulation) ofPhysarum polycephalum

The composition of the amino acid pool during spherulation was determined. It changes in size and in composition, the concentration of each amino acid behaving individually. The first response to the onset of spherulation either by starvation or osmotic shock (0.5 M mannitol) always is a decrease of the pool's size, which during further starvation expands for a short period and then decreases again. During development induces by mannitol in the presence of external amino acids, the pool size increases continuously after the initial depletion.As shown by radioactive labeling, amino acids were actively released from the plasmodium into a medium containing amino acids, but retained by the microplasmodia in an amino acid-free medium. The kinetics of the uptake of radioactive amino acids from the medium is biphasic, indicating the existence of multiple pools. Even after a labeling period of 8 h the amino acid pool is not yet in equilibrium with the medium. The possibility of a compartimentation of the pool was confirmed by density labeling of two different enzymes.Whereas the turnover of total protein is only very low during growth, it is rather high in spherulating microplasmodia. At least 70% of the originally existing protein is degraded during this development, while, simultaneously, at least 50% of the protein present after 24 h starvation is newly synthesized during that period.     

Isolation and characterization of a unique protease from sporulating cells of Bacillus subtilis

Two proteases, designated I and II, have been isolated from sporulating cells of Bacillus subtilis. They were partially purified by ammonium sulfate fractionation, Sephadex chromatography and affinity columns. Protease I was found to be similar to an already characterized B. subtilis protease. Protease II is trypsin-like in its substrate specificity and is distinct from protease I in its pH optimum, pH stability, molecular weight, substrate specificity, heat stability and sensitivity to various inhibitors. While both enzymes were produced primarily during sporulation, they attained maximum levels of activity at different times. Distinct functions for these proteases in post exponential B. subtilis are likely.     

Nutritional Requirements of the Nematophagous Fungus Hirsutella rhossiliensis

Six natural media were examined for growth and sporulation of six isolates of the nematophagous fungus Hirsutella rhossiliensis , using solid and/or liquid culture. Twenty carbohydrates, 19 nitrogen (N) compounds, and nine vitamins were also tested for their effects on growth, sporulation, and spore germination of a further three isolates (ATCC46487, OWVT-1 and JA16-1). Variations in nutritional requirements existed among the fungal isolates. In general, V-8 juice agar (VA), cornmeal agar and potato dextrose agar were good media for growth, and malt extract agar, VA and yeast dextrose agar were good for sporulation of all six isolates. Glycogen was the best and sucrose, inulin, D- ( + ) - trehalose and soluble starch were also good carbon (C) sources for growth and spore germination of the three isolates ATCC46487, OWVT-1 and JA16-1 in both liquid and solid culture. None of the isolates utilized D- ( + )xylose as a C source. L- sorbose, D- ribose, citric acid and D- fructose were poor for growth of all isolates. The best C source for sporulation was D- ( + )-trehalose for ATCC46487, D- sorbitol for OWVT-1 and D- ( + )-cellobiose for JA16-1. Casein was the best N source for growth of ATCC46487 and OWVT-1, while peptone was best for JA16-1. L- asparagine, L- proline, and peptone were also good for growth of all three isolates. L - cystine was not utilized by H. rhossiliensis and DL- methionine inhibited growth of all isolates. Spore germination of all isolates was well supported by most N compounds examined but was inhibited by L- cystine. No significant difference in sporulation of ATCC46487 was observed among the N sources. DL- threonine was the best N source for spore production by OWVT-1 and L- phenylalanine was best for JA16-1. Vitamins generally enhanced fungal growth and sporulation, with thiamine having the greatest influence. Excluding some vitamins individually from the medium containing all other test vitamins sometimes increased growth and/or sporulation of certain isolates.     

枯草芽孢杆菌微生态制剂发酵研究进展

微生态制剂是饲用抗生素的绿色有效替代品。枯草芽孢杆菌在逆境中可形成抗逆性强的芽孢,在生产和应用过程中保持高活性,是一种高效的微生态制剂菌种。提高枯草芽孢杆菌活菌数及芽孢率是保证微生态制剂产品质量的关键。本文综述了枯草芽孢杆菌芽孢形成的分子生物学机制及影响芽孢形成的重要因素,进一步比较枯草芽孢杆菌微生态制剂不同发酵方式的特点,重点阐述了提高枯草芽孢杆菌有效生物量的工艺优化,最后介绍了枯草芽孢杆菌微生态制剂的应用,并对将来研究思路进行了讨论。