Some biological activities of Azotobacter chroococcum, strain Azcap 1, (spontaneous mutant, captan resistant up to 300 μg/ml) were assayed on RM medium with and without the presence of the fungicide. Comparisons were also carried out with Az. chroococcum sensitive strains Azwt, Azcan 10 and 14. The hydrolysis of captan, incorporated in agar plats of RM at 100 μg/ml, was rapid, since on 4-day plates, no effect was found on the strain Azwt, while on freshly prepared ones its growth was completely blocked. As for Azcap 1, grown on RM only, the behaviour was similar to that of sensitive strains, whereas when grown on captan the results of experiments showed: (i) a lag of ∼ 12 h to reach the maximum nitrogen-fixing activity; (ii) delay of 12–24 h in the full consumption of glucose present in the medium, although the invertase activity did not present differences; (iii) high ATP culture content during the 50 h of the experiment; (iv) ∼6–10-fold lower production of PHB poly-B-hydroxybutyrate); (v) lack of typical encystment phase, for the tested 96 h and reduced viability in developing colonies on agar RM medium. In contrast, when captan was added to cultural medium at sublethal concentration, 50 μg/ml for sensitive strain Azwt and 200 μg/ml for Azcap 1, the amount of glutathione produced (to remove the fungicide toxicity) was several times higher for the former.

Evidence of reduced poly-B-hydroxybutyrate biosyntesis in free-living nitrogen-fixing bacteria, Azotobacter chroococcum, following acquired resistance to the fungicide Captan

CELANO, Giuseppe;
1993

Abstract

Some biological activities of Azotobacter chroococcum, strain Azcap 1, (spontaneous mutant, captan resistant up to 300 μg/ml) were assayed on RM medium with and without the presence of the fungicide. Comparisons were also carried out with Az. chroococcum sensitive strains Azwt, Azcan 10 and 14. The hydrolysis of captan, incorporated in agar plats of RM at 100 μg/ml, was rapid, since on 4-day plates, no effect was found on the strain Azwt, while on freshly prepared ones its growth was completely blocked. As for Azcap 1, grown on RM only, the behaviour was similar to that of sensitive strains, whereas when grown on captan the results of experiments showed: (i) a lag of ∼ 12 h to reach the maximum nitrogen-fixing activity; (ii) delay of 12–24 h in the full consumption of glucose present in the medium, although the invertase activity did not present differences; (iii) high ATP culture content during the 50 h of the experiment; (iv) ∼6–10-fold lower production of PHB poly-B-hydroxybutyrate); (v) lack of typical encystment phase, for the tested 96 h and reduced viability in developing colonies on agar RM medium. In contrast, when captan was added to cultural medium at sublethal concentration, 50 μg/ml for sensitive strain Azwt and 200 μg/ml for Azcap 1, the amount of glutathione produced (to remove the fungicide toxicity) was several times higher for the former.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11563/6723
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