Zeitschrift fur allgemeine Mikrobiologie最新文献

We describe optimized conditions for isolation of relaxed mutants of bacteria with 4-thiouridine-containing tRNAs. The results presented here imply that besides the knowledge of the action spectra for near UV-induced growth inhibition of stringent and relaxed cells the fluence--fluence rate dependence of growth inhibition is an essential factor for optimizing the enrichment of relaxed mutants. We investigated systematically the dependence of growth inhibition of both stringent and relaxed strains of E. coli on the wavelength lambda, on the fluence F and on the fluence rate I within the ranges lambda = 301-365 nm, F = 0-48 kJ X m-2 and I = 0-60 W X m-2. The optimized conditions for selection of relaxed mutants of E. coli are lambda = 334 nm, F = 48 kJ X m-2 and I = 60 W X m-2. These optimized parameters determined for E. coli may be used in general to select relaxed mutants of other bacterial species by combining the turbidostat technique with near UV irradiation (Riesenberg et al. 1983).

The results present evidence for the important role of phosphate-mediated regulation of the nourseothricin biosynthesis by the processes of phosphate limitation and release of phosphate. Also, higher initial concentrations of phosphate were found to have a strong inhibitory effect on the biosynthesis of nourseothricin. It is concluded that the initial phosphate concentration was the primary target for the biometrical optimization of the fermentation medium. The presence of zinc ions neutralized the negative effect of high initial concentrations of phosphate which was also strongly influenced by the regime of sterilization.

Various blocked mutants were isolated from three leukaemomycin-(daunomycin-)producing strains IMET JA 3933, IMET JA 5142 and IMET JA 5570 of Streptomyces griseus by NTG and UV treatments. Among them, one class of four mutants ZIMET 43707/1P, IMET JA 5570/3P, IMET JA 5570/10P and IMET JA 5142/01P1 produced new blue and red pigments. Two red compounds designated 1PI and 1PII are the main components of the pigment complex produced by culture of the blocked mutant ZIMET 43707/1P. This paper describes the isolation of 1PI and IPII; furthermore, the spectral and physicochemical properties of these anthracyclinones and the elucidation of their structures are reported.

The mixed culture kinetics of stringent and relaxed Escherichia coli cells were investigated in a glucose-limited chemostat at different dilution rates. Independent of the dilution rate the stringent cells competed out the relaxed cells. But the number of generations necessary for displaying the relaxed cells by the stringent ones increased with increasing dilution rate. The results are discussed as a consequence of the regulatory role of guanosine-5'-diphosphate-3'-diphosphate (ppGpp) which is known to be present at different concentrations in stringent and relaxed cells under conditions of nutrient limitation. In addition, it is postulated that the coefficient of the maintenance metabolism according to PIRT (1965) is slower in stringent cells than in relaxed cells of E. coli.

Escherichia coli K12 strains containing the plasmid pBR322 often show varying contents of plasmid oligomers, in which the monomer units are arranged in tandem. When the concentration of the plasmid-selective antibiotic tetracycline in the medium becomes increased selection of cells containing largely higher oligomers occurs. The number of monomer units organized in the oligomers increases with tetracycline concentration. recA- mutants are unable to generate oligomers under the same conditions and show lower tetracycline resistance. This observations suggest a selective advantage of oligomer containing cells in the presence of tetracycline as a result of higher gene dosage. But E. coli cells transformed with monomers, dimers, trimers, as well as tetramers of pBR322 are characterized by roughly the same plasmid DNA content as well as plasmid coded beta-lactamase and resistance to tetracycline.

Two series of aerial-mycelium-negative (Amy-), anthracycline-nonproducing (Ant-) mutants were obtained from ancestral Amy+Ant+ strains of S. griseus: a) derivatives represented by the met- strain 39 which could not differentiate although they were still producing both the butyrolactone-type autoregulator 1 and NADP-glycohydrolase, and b) mutants whose incapability to form spores and anthracycline pigments was apparently caused by the loss of autoregulator production. These latter mutants responded to the addition of 1 or the naturally occurring dihydro derivative 2 with complete or at least partial reconstitution of differentiation-associated functions. All of the b)-type mutant strains exhibited similar biochemical alterations in the presence of 1 or 2 regardless of the presence of additional genetic changes in the primary metabolism. Two mutants, however, displayed an altered pattern of secondary product formation. In submerged cultures the major biochemical changes observed in presence of 1 (or 2) were an increase of the lipid level in the mycelium, an alteration of the lipid composition, and a stimulation of neutral proteinase production. All of the blocked autoregulator-negative mutants were discernible from the ancestral strains and strain 39 by their lack of NADP-glycohydrolase production. This suggested the existance of a common genetic locus or a common pleiotropic regulator gene controling both gene functions. Present ideas concerning the role of butyrolactone-type autoregulator 1 as a pleiotropic effector molecule interacting with development of S. griseus are summarized in a hypothetical scheme.

A Streptomyces griseus strain deficient in the formation of aerial mycelium and arthrospore development (Amy-) was studied by electron microscopy and compared with the sporulating parental strain (Amy+). The investigations were performed with colonies grown on solid medium. The substructural characteristics of the essential events of sporogenesis could clearly been demonstrated in the aerial mycelium of the Amy+ colonies. The mycelium of the surface region of the Amy- colonies showed altered features. The most pronounced alteration was the absence of the surface sheath, normally present on the aerial hyphae of the parental strain. The cross wall type II, characteristic of sporogeneous hyphae, was not discernible in the Amy- hyphae. Some substructural features resembling the essential events of normal sporogenesis were evident in the Amy- strain, albeit diminished and interfered with by abnormalities. The resulting propagative cells were of different size and feature.

The virulence of Pasteurella multocida strains in experimental infections of mice has been shown to depend on the iron contents of the cultivation media. Frequent passages of bacteria on iron-deficient growth media result in drastic decrease of virulence. In the case of one strain also immunogenicity was lowered. The results with nutritional media differing in their iron contents show that iron probably exhibits a regulatory effect on the production of a not yet identified virulence.

The significance of the sequential processes of phosphate limitation and of phosphate release from medium constituents is demonstrated in technical streptomycin fermentations. The phosphate limitation initiated the streptomycin synthesis as well as the formation of phosphatases and protease. In later periods of the process the phosphate release influences especially the enzyme formation.

Results furnish evidence for a partial uncoupling of respiration at conditions of phosphate limitation in turimycin fermentations. The uncoupling was primarily caused by the high intracellular ATP hydrolase activity and probably also by the CN-resistant respiration. The results support the idea that high dephoshorylating enzyme activities may have a regulatory effect on the secondary product biosynthesis.