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D Noack

Publications and source records attributed to D Noack.

At least 37 records · Page 2Linked to original sources
PubMed1986

Directed selection of differentiation mutants of Streptomyces noursei using chemostat cultivation.

A nourseothricin-producing Streptomyces noursei strain was continuously cultivated in a chemostat equipped with a stirrer for mechanical fractionation of the mycelium. Different cultivation conditions allowed the selection of six types of differentiation mutants after the culture had reached a population genetically stationary state. The mutants showed an altered control pattern of sporulation as well as altered antibiotic biosynthesis and antibiotic resistance. In addition, the stability of the recombinant plasmid pIJ385 in several differentiation type mutants as host strains was tested. The results suggest that there exists a strong correlation between the cultivation conditions employed and the type of differentiation mutants selected.

Anti-Bacterial Agents↗
PubMed1986

Self-resistance of the nourseothricin-producing strain Streptomyces noursei.

The nourseothricin producer Streptomyces noursei is resistant to its own antibiotic in submerged as well as in surface culture. The strain shows no cross-resistance to miscoding inducing aminoglycoside antibiotics. Cell free extracts of Streptomyces noursei inactivate nourseothricin by enzymatic acetylation. The pattern of cross-resistance of Streptomyces noursei correlates well with the substrate specificity of the nourseothricin acetyltransferase. Furthermore, the acetyltransferase activity parallels the resistance level in nourseothricin-producing strains and nonproducing mutants. The results suggest that the nourseothricin acetyltransferase is important in the self-defence strategy of the nourseothricin-producing strain.

Acetyltransferases↗
PubMed1984

Gene expression after transformation of Streptomyces lividans protoplasts with plasmid pIJ2 DNA.

A new method has been developed for the selection of antibiotic-resistant clones after transformation of Streptomyces protoplasts with plasmid DNA. This method is based on establishing a spatial concentration gradient for the antibiotic, the resistance to which is encoded by the transforming plasmid. By this method, the resistance development of regenerating protoplasts can be followed. The results suggest that antibiotic resistance is inducible. In addition, we were able to show that resident plasmids incompatible with the incoming ones are eliminated when this direct selection principle is used. Moreover, this method, which may facilitate the application of gene technology in Streptomyces, works even though the transformation procedure gives variable results.

DNA, Bacterial↗
PubMed1983

Possible plasmid involvement in turimycin production in Streptomyces hygroscopicus.

Streptomyces hygroscopicus JA 6599 is the producer of the macrolide antibiotic turimycin. Mapping analysis by conventional matings and protoplast fusion techniques were carried out. The sequence of auxotrophic markers determined by using the method of minimizing the frequency of quadruple crossover recombinants, could be shown to be in accordance with the related marker sequence of Streptomyces coelicolor after both conjugation and protoplast fusion. However, the tur locus could localized between chromosomal markers only assuming quadruple crossover. Moreover, after conventional crosses the tur marker has to be localized at quite another site than after protoplast fusion. Regarding also our results on the evidence of extrachromosomal DNA in strains of S. hygroscopicus, the following hypothesis is proposed: the structural genes for turimycin biosynthesis are localized on the bacterial genome, but plasmid-borne genes might be involved in the control of the antibiotic production in a yet unknown way, possibly by inducing chromosomal rearrangements.

DNA, Bacterial↗
PubMed1982

beta-1.3.-1.4-Glucanase in spore-forming microorganisms. VI. Genetic instability of beta-glucanase production in a high-producer strain of Bacillus amyloliquefaciens grown in a chemostat.

A Bacillus amyloliquefaciens strain high-producing for beta-1.3-1.4-glucanase has gradually lost the ability to produce this enzyme during long-time continuous cultivation, independent of the culture conditions. Mutant strains isolated after long-term cultivation exhibited changed behaviour concerning extracellular enzyme formation and sporulation. By agarose gel electrophoresis of alkaline DNA extracts isolated form original and mutant strains we demonstrate that the observed pleiotropic phenomena are not caused by the loss of a complete plasmid present in the original strain. From extracts of both the original and mutant strains plasmid DNAs with approximately the same molecular weight of about 35 Mdal were isolated.

Bacillus↗
PubMed1982

Genetic segregation in a high-yielding streptomycin-producing strain of Streptomyces griseus.

The streptomycin-producing Streptomyces griseus HP spontaneously segregated non-reverting derivatives with altered phenotypes. Clones characterized by increased spore formation and decreased streptomycin production were found. Two other types of derivatives were defective in aerial mycelium and streptomycin formation as well, but differed in the capacity to synthesize a yellow pigment. These derivatives were examined with respect to further properties. The stability of S. griseus HP was investigated in relation to conditions of continuous culture. Both at 26 and 30 degrees C, under glycerol and NH4Cl limitation a rapid segregation and enrichment of streptomycin-non-producing derivatives occurred. At 34 degrees C and glycerol limitation segregation began only after about 35 generations of continuous culture. In NH4Cl-limited chemostats the original strain was stable during 80 generations. In the course of the continuous culture experiments it was shown that the onset of genetic segregation within mycelia can be detected before it becomes obvious in colonies grown from the mycelia. This was achieved by fractionation of the mycelia by protoplast formation and subsequent plating on regeneration medium allowing colony growth and differentiation.

Ammonium Chloride↗
PubMed1982

Transformation of Streptococcus sanguis (Challis) by linear plasmid molecules.

The streptococcal erythromycin resistance plasmid pSM9 was used to study the problem of how the transforming activity of mixtures of two unique linear products of restriction enzyme digestion depends on the distance between the cleavage sites. In transformation of the Challis strain of S. sanguis, the transforming activity of mixed digests increased with increasing relative distances (x) between the restriction sites, where 0 less than or equal to X less than or equal to 0.5. To explain the experimental results, a mathematical model was proposed according to which the overall probability (p) of transformation resulting in a functional replicon is the product of the partial probabilities of initial single-strand pairing, circularization, and stability of the paired intermediate, all of which were assumed to depend on x. A linear relationship found between transformation frequency and p was taken to support the model. Transformation of Challis by mixtures of two linearized plasmid molecules with regions of internal nonhomology resulting in paired intermediates with insertion or substitution loops allowed either donor molecule to contribute to the transformation yield.

DNA Restriction Enzymes↗
PubMed1982

Genetic stability of differentiated functions in Streptomyces hygroscopicus in relation to conditions of continuous culture.

The genetic stability of the capacity of an improved strain of Streptomyces hygroscopicus to produce the macrolide antibiotic turimycin was investigated during long-term continuous culture. Dilution rate, growth-limiting substrate and culture temperature were varied. Certain culture conditions resulted in the stable propagation of the inoculated turimycin-producing population. Other conditions led to segregation of the initial population. Turimycin non-producing phenotypes appeared, and in each case the simultaneous loss of ability to form aerial mycelium was observed. The non-differentiating clones were found to be stable, without any reversion to the parental phenotype, indicating that a loss of genetic information probably took place.

Ammonium Chloride↗
PubMed1981

Maintenance and genetic stability of vector plasmids pBR322 and pBR325 in Escherichia coli K12 strains grown in a chemostat.

The maintenance and genetic stability of the vector plasmids pBR322 and pBR325 in two genetically different Escherichia coli hosts were studied during chemostat cultivation with glucose and ammonium chloride limitation and at two different dilution rates. The plasmid pBR322 was stably maintained under all growth conditions tested. However pBR325 segregated from both hosts preferentially during glucose limitation and at low dilution rate. In addition to this general segregation process a separate loss of tetracycline resistance was observed. The remaining plasmid conferred resistance to ampicillin and chloramphenicol only, without any remarkable alteration of its molecular weight. Cultivation conditions in the chemostat were found that allowed the stable genetic inheritance of both plasmids in the hosts studied.

Ammonium Chloride↗
PubMed1980

[Hematopoietic stimulation for enhanced bone marrow regeneration after chemotherapy (author's transl)].

The aggressivity of cancer chemotherapy is limited by hematologic side effects or makes expensive supportive therapy necessary. This article summarizes known and clinically usable methods of stimulating hematopoiesis to enhance bone marrow recovery after therapy. Longest known is the stimulatory effect of anabolic steroids, which may accelerate the regeneration of granulopoiesis and erythropoiesis. Lithium increases CSA-levels and enhances the regeneration of granulopoiesis and questionably thrombopoiesis according to several publications. The stem cell shift by hypertransfusion promotes granulopoiesis. As malnutrition limits hematopoietic recovery, optimal nutrition after chemotherapy should favor maximal hematopoiesis. Further studies are necessary before the application of the above mentioned methods to stimulate bone marrow - singly or in combination - can be recommended.

Anabolic Agents↗
PubMed1980

Transfection of protoplasts from Streptomyces lividans 66 with actinophage SH10 DNA.

The slightly modified procedure for the transformation of protoplasts of S. coelicolor A3 (2) with SCP2 plasmid DNA and polyethylenglycol (PEG) (Bibb et al., 1978) was extended to infection of protoplasts of S. lividans 66 with actinophage SH10 DNA (Klaus et al., 1979). Maximal yield of transfected protoplasts was obtained at 20% PEG, 3 MM sodium-citrate and 150 mM NaCl final concentrations. The efficiency of transfection was determined to be about 2 x 10(-8) to 2 x 10(-7). The average value of competent protoplasts was about 1-2 x 10(-4) of regenerating protoplasts. In comparison with outgrowing spores infected with phage particles the average burst size of transfected protoplasts was reduced from 100 to 10 pfu/infected cell, the latent period prolonged from 45 min to 120 min and the rise period was not affected.

Bacteriophages↗