Commensalism I. C.'s
Many years ago, our group studied the commensalism of Saccharomyces
cerevisiae and Proteus vulgaris where the yeast could grow alone
but the bacterium could not because of its requirement for the vitamin
niacin. Together the mixed culture showed the yeast essentially unaffected
by the bacterium, but the bacterium could thrive on niacin excreted by
the yeast. Adding niacin broke the commensalism and let the fast-growing
bacteria outcompete the yeast (A. Shindala, H.R. Bungay, N.R. Kreig, and
K. Culbert, "Mixed culture interactions: 1. Commensalism of Proteus
vulgaris with Saccharomyces cerevisiae", Jour. Bacteriol, 89
693 1964).
Theory
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while on sabbatical leave at ESB, Porto, Portugal,
1996