Effect of malathion on certain beneficial microbial activities in Egyptian soils

Malathion was incorporated into Azotobacter chrococcum growth medium with different concentrations up to 600 ppm. The increase in the insecticide concentrations gradually inhibited microbial growth and nitrogen fixation. Meanwhile, the fixed nitrogen continued to increase, for each concentration throughout the experimental period [30 days]. On the other hand, low doses of malathion [100 and 200 ppm] increased both viable count of Bacillus megaterium and its capability of dissolving rock phosphate all over the incubation periods [30 days]. Meanwhile, high doses [800 and 100 ppm] were deleterious to growth and mineralization activity of B. megaterium. The applied malathion up to 400 ppm completely disappeared at the end of the incubation period

Effect of malathion on the metabolism of certain Egyptian soil microflora

The dry masses of Corynebacterium pseudotuberculosis, Streptomyces chibaensis and Aspergillus candidus grown in media containing [10, 50, 200 and 500 ppm] of malathion were analyzed. The presence of 50 ppm malathion increased the total nitrogen and protein-N contents for all isolates followed by a decrease with increasing insecticide concentrations. The content of soluble protein fractions varied with the malathion concentrations and the microbial isolate. The increase in malathion concentrations were accompanied with a gradual decrease in total carbohydrates contents for all isolates under test. The increase in malathion concentration caused an increase in both RNA and DNA content, while suppressed the DNA content of Streptomyces chibaensis. Streptomyces chibaensis was the most efficient isolate in the mineralization of rock phosphate in the presence or absence of the insecticide. Malathion suppressed phosphate solubilization processes for the first ten days. Thereafter, the amounts of soluble phosphate were significantly increased

Effect of gamma irradiation, water activity, relative humidity and their combination treatments on the growth and aflatoxin production by two toxigenic aspergillus flavus isolates

All combination treatments of gamma irradiation and water activity induced a clear drop in both growth and aflatoxin production by the two isolates if compared with control value. Both isolates of toxigenic A. Flavus [8 and 22] were able to produce aflatoxins B1 and B2 respectively on peanut seeds under controlled conditions or in seeds inoculated with 1.0 or 2.0 KGy irradiated inocula. However, aflatoxins were not produced by the two isolates on peanut seeds adjusted to water activity values of 0.995 and 0.960, either alone or in combination with any of the two irradiation doses [1.0 and 2.0 KGy] after all storage periods