Abstract
Experiments were designed to isolate, characterize and study the interaction between external microbiota (bacteria and fungi) carried by adult M. domestica after dipping, then removal of the flies from distilled water, sugar solution and saline solution. M. domestica was collected from Sakaka city, Northwestern Saudi Arabia. Three groups of adult M. domestica were completely dipped in and then removed from each of the above-mentioned solutions separately. Bacteria and fungi were isolated using corresponding media, characterized using macro and microscopic examinations, and then tested for antagonistic activity. Three bacterial species; Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa and three fungi; Candida albicans, Rhizopus stolonifer and Aspergillus niger have been isolated, characterized and tested for antagonism. Biochemical tests of bacterial strains confirmed the ability to secrete economically important materials. Different efficiencies to ferment sugars and produce gases have been confirmed, too. Antagonistic tests between microorganisms have revealed that both E. coli and P. aeruginosa bacteria are antagonists to both A. niger and C. albicans fungi. However, R. stolonifer fungus is antagonist to both E. coli and P. aeruginosa bacteria. B. subtilis bacterium is antagonist to the 3 fungi and to the other 2 bacteria. The antagonistic activity of our bacterial strains could be attributed to the secretion of antimicrobial materials. Further study on the mechanism of antimicrobial activity of B. subtilis strain is recommended. It was concluded that this strain could be useful in controlling some bacterial and fungal infections.