Effects of farnesol and the off-flavor derivative geosmin on Streptomyces tendae.

Effects of the sesquiterpene farnesol (3,7,11-trimethyl-2,6,10-dodecatrien-1-ol) and the sesquiterpene derivative geosmin (1,10-trans-dimethyl-trans-9-decalol) were investigated in a geosmin-producing actinomycete, Streptomyces tendae. Exposure to 300 microM farnesol reduced biomass (fresh matter) accumulation by 97% compared with biomass accumulation by controls, whereas an equal amount of geosmin did not affect biomass accumulation. Increasing exposure to farnesol corresponded with reduced optical density of the culture, reduced levels of geosmin, and reduced metabolic heat production compared with controls, while exogenous geosmin did not affect these parameters. Geosmin dissipated from unioculated medium more rapidly than farnesol, indicating that in addition to the lower toxicity of geosmin, the actual exposure to geosmin over time may be less than exposure to an equal amount of farnesol. Cultures grown on Actinomyces-B medium contained 99.5% less geosmin and were more sensitive to farnesol than those grown on Hickey-Tresner medium, indicating that geosmin synthesis was associated with reduced sensitivity to farnesol. Consumption of farnesyl moieties during geosmin synthesis may reduce the potential for farnesol-induced inhibition of growth and metabolism.

Aquaculture product quality issues: market position opportunities under mandatory seafood inspection regulations.

Impending legislation for a mandatory seafood inspection program will be important in shaping the consumer's perception and expectation of quality in seafood products. Because aquacultured species are produced in controlled environments, fed special diets, and processed under optimum conditions, they possess unique product characteristics. The perception by the consumer that these products could be safer, fresher, more wholesome, and better tasting may lead to a competitive marketing position relative to captured products.

Simplified method to quantify geosmin and 2-methylisoborneol concentrations in water and microbiological cultures.

A simple and rapid method for the extraction and quantification of geosmin and 2-methylisoborneol is described. Using methylene chloride extraction and gas chromatography, the procedure eliminates costly stripping devices. Recovery efficiency of the procedure is approximately 65% with a sensitivity equal to the human threshold for these two important off-flavor compounds.

Sex pheromones of the sea lamprey (Petromyzon marinus): Steroid studies.

Pheromone-containing and pheromone-devoid samples of male sea lamprey (Petromyzon marinus) urine were analyzed for the concentrations of nine steroids [dehydroepiandrosterone (DHEA), testosterone (T), dihydrotestosterone (DHT), progesterone (P), androstenedione (A), estrone (E1), estradiol (E2), corticosterone (B), and cortisol (F)] by radioimmunoassay (RIA). Samples analyzed included native urine that had been enzymatically hydrolyzed with mixed ß-glucuronidase/sulfatase. Values of the analyses were used to prepare solutions of the individual steroids for bioassay at concentrations which bracketed the urinary concentrations. Results show that only testosterone elicited a preference response in spawning-run female sea lampreys, and in concentrations three to four orders of magnitude greater than those found in active, unhydrolyzed male urine. The possibility that testosterone acts as a pheromone in this species is discussed.