Antimicrobial Activity and Morphological Changes of Streptomyces Ascendable and Streptomyces Eighty-three's as Affected by Environmental Conditions and Gamma Radiation

Fourteen actinomycetes out of thirty isolates were recovered from different Egyptian soils and exhibited antimicrobial activities. Streptomyces ascendable and Streptomyces eighty-three's used in the present work showed the most active antimicrobial potentialities against bacteria, moulds and yeasts. The optimum temperature and acidity for their growth and production of microbial activity were 50 degree and ph 7.0, while the maximum biomass yield and the highest antimicrobial activity were attained 10 days of incubation. Among carbon sources starch at 30 gm/L highly supported the growth and antimicrobial activity by the two species, while sodium nitrate (3 gm/L) and dipotassium hydrogen phosphate (0.75 gm/L) were the most favorable for both isolates. The presence of microelements such as manganese chloride, zinc sulphate, ferrous sulphate and copper sulphate in the growth medium at a concentration of 1 mg/L for each had a good stimulatory effect on the growth and antimicrobial activity for both Streptomyces species. As different irradiation doses were used (up to 5.0 kGy), the high levels clearly affected the morphological characteristics of both tested isolates either in the first or second generation