COMPARATIVE PHYSIOLOGY OF GEOSMIN PRODUCTION BY STREPTOMYCES-HALSTEDII AND ANABAENA SP

Geosmin and 2-methylisoborneol (MIB) are microbial metabolites that ca n cause earthy or musty off-flavors in aquatic food animals as well as seasonal taste and odor episodes in drinking water. This paper compar es effects of selected environmental factors on biomass and geosmin pr oduction by the actinomycete Streptomyces halstedii and the cyanobacte rium Anabaena sp., isolated from an aquaculture pond and from a source -water reservoir, respectively. For S. halstedii, optimal biomass prod uction occurred at pH 6-7 and 30 degrees C, and optimal geosmin synthe sis occurred at pH 9 and 35 degrees C. Low concentrations of both nitr ate- and ammonium-nitrogen favored geosmin production, with higher con centrations stimulating biomass production. For Anabaena sp., optimal biomass production at 20 days occurred at 15 degrees C and a light int ensity of 17 mu E/m(2)/s; optimal geosmin synthesis occurred at 20 deg rees C and 17 mu E/m(2)/s. Chlorophyll a (chl a)/biomass varied invers ely with light intensity. Maximal geosmin/biomass occurred at 20 degre es C (17 mu E/m(2)/s), and geosmin/chl a varied inversely with tempera ture. It was concluded that at 20 degrees C, increasing light intensit y favors lower chl a and greater geosmin synthesis by Anabaena sp.; at 17 mu E/m(2)/s, increasing temperature stimulates chl a production (t o 25 degrees C) but represses geosmin synthesis (above 20 degrees C).