Isolation and application of new microorganisms from soil Samples

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To increase the possibility of discovering useful new bioactive compounds from microorganisms, we have attempted to isolate new microbial strains by adding various substances to the isolation agar media. In the course of searching for factors necessary for bacterial colony growth, we have found that the predominant bacterial strains release proteins into the culture broths that increase the number of bacterial colonies from a soil sample. Surprisingly, the common protein isolated from the active culture troths was superoxide dismutase (SOD). Moreover, commercial SODs increased the number of colonies, a response further enhanced by the addition of catalase. Superoxide (O_2) was quantitatively detected in the isolation agar medium and the level was suppressed by adding SOD or SOD plus catalase. Our results strongly suggest that some of the bacterial cells may be recovered by suppressing oxidative stress on the agar-based medium.