Copper-Containing Aquatic Herbicides Increase Geosmin Biosynthesis byStreptomyces tendaeandPenicillium expansum

Abstract

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 bacteriumStreptomyces tendaeand the fungusPenicillium expansum.Cultures ofS. tendaetreated 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. expansumcultures 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 ofP. expansumandS. 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.tendaeof untreated control cultures indicated that cellular copper concentrations were below 0.5 mg Cu kg−1. However,S. tendaecells grown on a medium containing 5 mg Cu L−1copper 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.