Characterization of ribosomes of a strain ofStreptomyces aureofaciens producing chlortetracycline

These studies were designated to investigate the effect of chlortetracycline on sedimentation properties of polysomes and ribosomes present in the chlortetracycline producing strain ofStreptomyces aureofaciens. In presence of chlortetracycline polysomes and ribosomes are more stable than the bacterial ones. At lower chlortetracycline concentrations (1–5 μg/ml) dissociation of polysomes into 70 S monomers was not observed. Ribosomes in higher concentration of chlortetracycline (400 μg/ml) form aggregates. A decrease of Mg²⁺ to 0.1mm caused dissociation of ribosomes to two subunits and in this state none of indicated concentrations of chlortetracycline caused aggregation. The exact sedimentation values of ribosomes and ribosomal subunits were calculated from extrapolation to infinite dilution. S_20,w for monomer form was 68.8, and for ribosomal subunits 49.8 and 31.2 respectively. Ribosomal RNA sedimentates as two Schlieren peaks of 16 S and 22 S. It was found that 30 S subunits contain 15 structural proteins, while 21 proteins were resolved from 50 S subunits.     

Taxonomical study of the reference strain ofStreptomyces erythreus

The reference strainStreptomyces erythreus formed filamentous growth with Retinaculum-Apertum forms and narrow, long, extended spirals. Under defined conditions it produced abundant red and white mycelium; for its taxonomical characterization the production of red mycelium according to which the strain is classified in a certain series is conclusive. Chains of spiny spores were observed in the electron microscope. In its growth requirements (taxonomically important carbon sources) this strain differed from other strains of the genusStreptomyces. Components of the cell wall type IV were demonstrated in its mycelium.     

Physiology of a wild strain and high yielding mutants ofStreptomyces rimosus producing oxytetracycline

A wild-typeStreptomyces strain, yielding 1 g/L of oxytetracycline was compared with mutants giving up to 7 g/L, using complex media in stirred and shaken culture. Increased production of oxytetracycline was associated with high specific production rates and a longer production period. The superiority of the mutants was associated with changes in morphological behaviour during growth in submerged culture, and in their patterns of growth and respiration, coupled with increased resistance to the product. The productivity of the mutants was sensitive to the rate of stirring, the type of calcium carbonate used in the medium and the type of inoculum. Careful control of these factors was necessary to obtain high yields of oxytetracycline. With the exeption of acetyl-CoA carboxylase, the levels of enzymes measured and of amounts of adenylates in the mycelium did not appear to be related to the degree of antibiotic production.     

Isolation,characterization and biological activities of verotetrone from a mutant strain ofStreptomyces aureofaciens

A new metabolite denoted as verotetrone was isolated from the mycelium of the mutant strainStreptomyces aureofaciens NMG-2. Interpretations of physical data concerning verotetrone and its triacetate and, the determination of its degradation product indicate that verotetrone belongs to pretetramide-type metabolites. Verotetrone exhibits neither antibacterial nor antifungal activity.In vitro it inhibits the synthesis of nucleic acids as well as proteins in Ehrlich ascites carcinoma cells. Both verotetrone and its triacetate interferein vivo with the metabolism of tumour and lymphoid cells, exhibiting antitumour or immunosuppressive activity. This activity, which is more intense with verotetrone than with its triacetate, is detectable in a dose which is already toxic in some animals.     

Production of avermectin A2a and monoglycosides A2a and B2a by a strain ofStreptomyces avermitilis

A strain ofStreptomyces avermitilis producing almost predominantly avermectin A2a and monoglycosides A2a and B2a was described. Methods of analytical and preparative high performance liquid chromatography were used for comparison of chromatographic profiles and product isolation, respectively. Identification of isolated compounds was based on¹³C-NMR spectrometric results.     

Characteristics ofStreptomyces globisporus strain 0234A forming endospores in submerged cultures

Thermosensitive submerged endospores formed byStreptomyces globisporus 0234 and its natural variant A resembled those of thermoresistant actinomycetes not only in their morphology and ultrastructure, but also in the content of dipicolinic acid. The production of endospores containing this substance is unusual inStreptomyces while other features of the strain indicate relatedness to other streptomycetes. Chemotaxonomic analysis of variant A revealed the cell wall to be of chemotype I and fatty acid content typical ofStreptomyces. Most characteristics of surface cultures of variant A coincided with those of the original strain 0234 and its endosporeless variant B. Both the strain 0234 and its variants A and B produced identical antibiotics and pesticidal compounds.     

Control of the aspartokinase ofStreptomyces noursei and its AEC-resistant mutants

Summary Addition of L-lysine to cultures ofS. noursei enhanced the production of nourseothricin. The aspartokinase of the wild-type strain was under concerted feedback inhibition by lysine plus threonine but was stimulated by lysine alone. Threonine in the medium increased the synthesis of enzyme. 10% of the mutants resistant to AEC showed a higher specific production of the antibiotic.     

Influence of increased dissolved oxygen concentration on productivity and selectivity in cultures of a colabomycin-producing strain ofStreptomyces griseoflavus

The influence of enhanced O₂ concentration on growth and formation of secondary metabolites byStreptomyces griseoflavus (strain Tü 2880) was investigated in a stirred tank and in an air-lift fermentor. At a partial pressure of O₂ p_o2 = 1880 mbar the growth was lowered by 50% compared to p_o2 = 210 mbar, whilst substrate consumption and O₂ uptake rate increased markedly. Production of the colabomycin complex reached maximum values at p_o2 = 630 mbar. A similar increase of secondary metabolite formation was obtained when glycerol or acetate were fed at p_o2 = 220 mbar. The portion of the derivate colabomycin A in the product mixture rose from 43% at p_o2 = 210 mbar to 73% at p_o2 = 1260 mbar. Since dissolved O₂ concentration has a significant influence on productivity and selectivity it may be used to regulate aerobic fermentation processes.     

Comparative investigation on a hexane-degrading strain with different cell surface hydrophobicities mediated by starch and chitosan

Applied Microbiology and Biotechnology - Bioremediation usually exhibits low removal efficiency toward hexane because of poor water solubility, which limits the mass transfer rate between the...     

The mode of action of a nonpolyenic antifungal (desertomycin) produced by a strain of Streptomyces spectabilis

A metabolite with antifungal activity, of non polyenic macrolide structure, was extracted and purified from the culture supernatant of a soil-isolated Streptomyces spectabilis strain, BT 352. This product was found to be related to (or being) desertomycin. Six yeast and five filamentous fungus strains were used to determine minimum concentration of the metabolite that inhibits growth by 80% (IMC); it was established at 50 micrograms/mL for the fungi and at 100 micrograms/mL or more for the yeasts tested. Short-term genotoxicity tests showed no antifungal effect on the bacterial genome, and desertomycin at concentration levels of 100 micrograms/mL or more affected protein synthesis. The antifungal metabolite had no immediate inhibiting effect upon yeast respiration, even at high concentrations; however, the respiration activity of cells grown in the presence of subinhibiting doses and collected during their growth phase was reduced by as much as 40%. Saccharomyces uvarum spheroplast regeneration in a liquid medium containing desertomycin was inhibited at doses fivefold weaker than the IMC determined with intact cells. Contrary to amphotericin B, desertomycin subinhibiting doses do not modify, and if so lightly, the yeast latent phase or the spheroplast wall regeneration phase, thus indicating a fungicidal action. Moreover, following a 30-min contact with desertomycin subinhibiting and inhibiting doses, yeasts liberated potassium in large amounts, indicating that plasma membranes were affected.     

黑角直缘跳甲的生物学及其防治

黑角直缘跳甲是五倍子夏寄主盐肤木和红肤杨的重要食叶害虫,一年一代,以卵及卵块在寄主枝干上越冬,次年4月当寄主幼芽萌发达3cm,叶片尚未完全展开时孵化。幼虫期4—5月,蛹期5—6月,成虫期6—10月,卵期9至次年4月。幼虫始见期随不同年份和不同海拨而异,物候期明显。数量消长与天敌和降雨密切相关。本文首次报道了该虫的生物学特性,并提出人工灭虫和保护天敌的防治措施。     

Comparative analysis of a biofilm-forming Staphylococcus epidermidis strain and its adhesion-positive, accumulation-negative mutant M7

Abstract We have isolated a stable slime-negative mutant, M7, from the wild-type Staphylococcus epidermidis RP62A by mitomycin mutagenesis. Besides its inability to produce slime in the test tube this mutant differed also in two other properties from its parent strain: it lacked the ability to accumulate on a surface, and it did not produce a 115 kDa and a 18 kDa extracellular protein. In all other tested properties such as initial adherence, growth rate, cell-wall composition, surface characteristics, DNA restriction profile, the presence of a 29 kb antibiotic resistance plasmid, and antimicrobial susceptibility profile, M7 was indistinguishable from its wild-type. The mutant is an important basis for further study of the pathogenesis of polymer-associated S. epidermidis infections.     

Characterization ofStreptomyces sp. Strain DRS-1 and its ampicillin transformation product

Incubation of ampicillin with whole cells ofStreptomyces sp. DRS-1 resulted in accumulation of four compounds different from ampicillin. One of them was isolated, purified and partially characterized. On the basis of spectroscopic characteristics,R _F value and antibacterial activity the compound was identified as cephalexin. It could also be obtained from ampicillin by using crude protein extract of the strain.     

Protease activity and proteolytic modification of cellulases from a Trichoderma reesei QM 9414 selectant

Summary The secretion of multiple forms of cellulolytic enzymes by a Trichoderma reesei QM 9414 selectant exhibiting high protease activity (T. reesei QM 9414/A 30) was investigated using monoclonal, domain-specific antibodies against cellobiohydrolase (CBH) I, CBH II and -glucosidase, and a polyclonal antibody against endoglucanase I. The pattern of appearance of these proteins was followed during growth of the fungus on Avicel cellulose, using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE)/Western blotting/immunostaining. Evidence was obtained that, at late cultivation stages, CBH I and II became partially modified to lower molecular weight components, whereas -glucosidase and endoglucanase I appeared to remain largely intact. Modification of CBH I appeared to commence from the carboxy-terminal AB region, whereas CBH II appeared to become modified both from the amino- (ABB') and the carboxy-terminal. Evidence for a protease activity that modifies the already truncated cellobiohydrolases in the culture filtrate was obtained. These results show that proteolysis at late culture stages may contribute to the multiplicity of cellulases found in T. reesei culture fluids. Initial proteolytic cleavage of CBH I and II may, however, involve an unusual protease not detectable by the azocasein method.Offprint requests to: C. P. Kubicek     

Extracellular proteinase and chitinase produced by a culture ofStreptomyces kurssanovii

Extracellular enzymes—a chitinase and a proteinase with molecular weights 22 and 32 kDa, respectively—were isolated fromStreptomyces kurssanovii cells. After purification on modified regenerated chitin, the enzymes were virtually homogeneous according to denaturing PAGE. Both enzymes were found to degrade chitosan.