This is a photograph of colonies of Brettanomyces growing on YM agar which contains calcium carbonate. This photo illustrates the "zone of clearing" which occurs due to the acid production by the yeast. The acetic acid which these yeasts prodcue dissolve the calcium carbonate and thus one gets the clear area on the agar. The metabolic pathway responsible for acdi prodcution is enhanced under aerobic conditions. When one maintains cultures of brettanomyces yeasts it is always a good idea to put caclium carbonate in the nutrient agar to help neutralize the acid. This helps increase the length of time the slants can be stored before replating has to be done.

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