Isolation and biological properties of arsenate‐resistant strains of Streptomyces noursei

Abstract

Eingegangen arn 27. 5. 1983) Arsenate-resistant (AsR) clones were obtained with high frequency from colony populations of streptothricin-producing strains of Streptomyces noursei by the paper strip method. Whereas in the AsR-strains obtained from both wild type and mutant NG 13 the antibiotic production was reduced to approx. 60% of the parental level, the AsR clones isolated from colony populations of mutant UV 12 displayed increased productivity (5150%).However, their improved capacity to produce streptothricins was lost rapidly after repeated cell propagation in submerged cultures, suggesting that unstable genetic elements were involved in enabling S. noursei to grow in the presence of toxic concentrations of arsenate.Many reports on antibiotic fermentations attest that excessive supply with inorganic phosphate suppresses the production of secondary metabolites of streptomycetes and PeniciZZium species (DEMAIN 1982). Therefore, most fermentations of antibiotics require the addition of inorganic phosphate in growth-limiting amounts, if high yields are to be obtained (MARTIN 1978, INOUE et al. 1982, OMURA et al. 1981).The molecular mechanism of the so-called 'phosphate effect' appears to be complex and may also depend on the particular microorganism (MARTIN 1977). Among the possible mechanisms are the inhibition and repression of the antibiotic-specific pathway as well as interference with the energy metabolism and the system of precursor generation (MARTLN and DEMAIN 1976).In order to release antibiotic fermentations from the regulation by inorganic phosphate, efforts have been mainly directed to the control of the phosphate pool in the medium. Recent results show that mutants deregulated in their response to inorganic phosphate can be obtained from the candicidine-producing Streptomyces griseus by either the conventional screening techniques or selection of arsenateresistant (AsR) strains (MARTIN etal. 1979, NAHARRO et aZ. 1981). Because corresponding data for other antibiotic-producing streptomycetes are missing, the general value of the latter methods for the isolation of superior producers of antibiotics cannot he assessed.I n the present work, we report on the isolation and some properties of arsenateresistant strains of Streptomyces noursei, a microorganism producing streptothricintype antibiotics (BRADLER and THRUM 1963). Materials and methodsStrains: Streptomyces ltoursei J A 3890b (BRADLER and THRUM 1963) was received from the culture collection of the Central Institute of Microbiology and Experimental Therapy, Jena.Mutant strains UV 12 and NG 13 were obtained by random selection for high antibiotic activity after using UV light and nitrosomethyl guanidine, respectively, as mutagens. The latter strains showed a 2-3 fold higher capacity to produce streptothricins (nourseothricin) than the parental strain.

Arsenical Resistance of Growth and Phosphate Control of Antibiotic Biosynthesis in Streptomyces

“…Culture conditions. Culture media for Streptomyces strains were AL53 agar (Friedrich et al, 1984), M79 medium (Kriigel et al, 1988, and minimal agar medium (Hopwood et al, 1985). E. coli strains were grown on Luria agar (LA) or Luria broth (LB) (Maniatis et al, 1982).…”

“…Selection of Streptomyces mutants resistant to the toxic phosphate analogue arsenate is an efficient way of overcoming the sensitivity of many antibiotic biosynthetic pathways to repression by inorganic phosphate in the medium (Naharro et a/., Friedrich et al, 1984). Most of these arsenate-resistant mutants show an uptake of [32P]phosphate identical to that of the wild-type.…”

Directed selection of differentiation mutants of Streptomyces noursei using chemostat cultivation

“…Bacterial strain and plasmid: 8treptomyces noursei JA3890b NG13 was received from the culture collection of this institute (FRIEDRICH et al 1984). Plasmid pB385 conferring resistance to neomycin and thiostrepton was provided by D. A.…”

“…For these experiments we used the strain Streptomyces noursei IMET 3890b NG13 (for reference FRIEDRICH et al 1984) which is the producer of the streptothricin antibiotic nourseothricin. Six types of differentiation mutants were selected after t h echemostat culture has reached a stationary state with respect to their genetic composition.…”

ATP levels in phosphate‐deregulated and arsenate‐resistant mutants of Streptomyces noursei

“…12 also proved less sensitive than the wild-type strain (FRIEDRICH et al 1984), and selection of the arsenateresistant strain U\' 12-13-AsR7 froin rillitant U\-12 further led to declining sensitivity towards PO:ions. Strain Ncl 13 already exhibited naturally high resistance to toxic nrsenate ions which, noticeably, cxcaeeded that of strain 13-13-AsR7.…”