Physiology and genetics of production of off-flavor compounds by aquatic microorganisms.

摘要

Geosmin production by Anabaena sp. was optimal at a light intensity of 17 ;Biomass production was similar at equal ammonium and nitrate-nitrogen (N) concentration; however, either nitrogen source promoted chl a synthesis with preference for nitrate-N. Lower nitrate-N concentration favored maximal geosmin synthesis. Geosmin synthesis and geosmin/biomass (G/B) values were directly related to ammonium-N concentration, with the G-value inversely related to either nitrogen source. Geosmin, biomass, chl a, G/B, geosmin/chl a values, and G-value were correlated with increasing phosphorus level. Anabaena sp. was unable to grow at high N:P ratios; however, a decrease in N:P ratio enhanced growth and favoured maximal geosmin, biomass, and chl a synthesis. Cellular release of geosmin increased by 37% at a rate of 0.375 ;No small circular plasmid DNA was detected in the different aquatic Streptomyces and cyanobacterial isolates. However, two large linear plasmids designated pIS1 (180 kbp) and pIS2 (115 kbp) were detected in Streptomyces halstedii and Streptomyces violaceusniger, respectively. Results indicated that off-flavor production is likely chromosomally-encoded.;Geosmin was degraded at a mean concentration of 4.3