The growth phases of five cultures of antibiotic producing Streptomyces isolated from western region, Saudi Arabia were studied special al reference to their potentiality to excrete antibiotics. It was found that these organisms grew exponentially during the first 4 to 7 days of incubation. The highest specific growth "rate was observed in the case of Streptomyces MY18 being 0.48 day-l (1.44 days doubling time). This isolate also showed the highest inhibition zone against Staph. aureus as compared with the other four Streptomyces isolates. This antagonistic effect was more pronounced at the last five d~ys of incubation (stationary phase). Morphological, cultural and physiological properties of most active antibiotic producers revealed that Streptomyces MY18 and Streptomyces MR13 are strains of S. aureofaciens and S. reseviolaceus respectively.
ABSTRACf. The effect of n~ural falling and dipping of house flies on the degree of contamination of sterile water and milk was investigated. The study was made on sterile tap water and also on sterile water at pH 4, which represents the reaction of stOOlach fluids. It was found that the total microbial flora showed progressing drop in their counts after 60 minutes incubation. Dipping treatments of house flies gave lower microbial contamination of water at pH 4 than at neutral pH. This trend was also observed for non-haemolytic and haemolytic microflora determined on blood agar medium. Dipping the house flies three times generally resulted in lower microbial count than natural falling and dipping once treatments. It was also found that complete dipping of fly in milk reduced the initial microbial contamination and retarded their growth. This paradoxial result is quite interesting since the logical condition, if the microbial load is only a matter of contamination without the influence of any other factor. is that dipping treatment would give higher figures than natural falling. All these observations suggest the presence of antimicrobial factors on the house flies.
Microbiological and chemical studies have been carried on some widely consumed nuts stored in leddah markets. Results indicated that mould count was generally higher than bacterial count specially on shelled nuts. Walnuts showed the highest average of microbial contamination including mould, bacteria, proteolytic and lipolytic microorganisms comparing with other kinds of nuts. While the lowest counts were found to be on pistachio-nuts and cashewnuts even shelled or unshelled. Mould isolates occurring most frequently were Aspergillus, Penicellium, Rhizopus, Mucor and Cladosporium. Regarding bacterial flora, G + ve sporeforming bacilli, G + ve cocci and G -ve short rods were the most dominant isolates. The microbial contamination which plays an important role in the spoilage of various nuts was generally affected by the composition of nuts specially proteins, lipids and water content.
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