Living in harmony

Published: Sunday 15 December 1996

Two strains of bacteria competing for basic neccessities in the human gut evidently have a stable coexistence. Researchers say it is because the slow-growing strain feeds off the excreta of the fast-growing counterpart. Paul Turner of the Michigan State University, US, and his team found this when they were experimenting on bacterial evolution using two strains of Escherichia coli.

When the two strains were transferred to a growth medium of broth rich in glucose, the fast-growing strain multiplied quickly but stopped growing once it had consumed all the glucose. But the other strain continued to grow slowly. Further experiments showed that the slow-growing strain could grow only when the fast-growing strain was also present in the medium. This indicated that the sluggish strain was feeding off the by-products of its companion's metabolism (New Scientist, Vol 151, No 2051).

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