Copper-Containing Aquatic Herbicides Increase Geosmin Biosynthesis byStreptomyces tendaeandPenicillium expansum

Copper-containing herbicides are often applied to control photoautotrophic populations to reduce biosynthesis of the earthy odorant geosmin. The objective of this investigation was to determine the effects of copper-containing herbicides on geosmin and biomass biosynthesis by heterotrophic cultures of the bacterium Streptomyces tendae and the fungus Penicillium expansum. Cultures of S. tendae treated with 12.7 mg Cu L −1 (copper sulfate) accumulated 44.6% more biomass and the mycelium contained five-fold greater concentrations of geosmin than controls. Additionally, P. expansum cultures exposed to 12.7 mg Cu L −1 (copper sulfate) accumulated 9.2% more biomass and 18-fold greater concentrations of geosmin than controls. Cultures of P. expansum and S. tendae , treated with copper chloride, copper-ethylenediamine complex, and copper chelate also accumulated more geosmin and biomass than controls. Inductively coupled plasma atomic emission spectrometry of S. tendae of untreated control cultures indicated that cellular copper concentrations were below 0.5 mg Cu kg −1 . However, S. tendae cells grown on a medium containing 5 mg Cu L −1 copper sulfate contained 12.88 ± 0.54 mg Cu kg −1 , suggesting that cellular accumulation of copper may be associated with increased geosmin biosynthesis. If field microbial populations exhibit similar responses to copper, copper-algicide application may contribute to geosmin-induced “off-flavors” under certain circumstances.