EVALUATION OF GEOSMIN AND 2-METHYLISOBORNEOL ON THE HISTIDINE DEPENDENCE OF TA98 AND TA100 SALMONELLA-TYPHIMURIUM TESTER STRAINS

Low (ca 0.01 ppb) concentrations of the naturally occurring terpene derivatives geosmin (1alpha,10beta-dimethyl-9alpha-decalol) and 2-methylisoborneol [(1-R-exo)-1,2,7,7-tetramethyl-bicyclo-(2,2,1)-heptan-2-ol] (MIB), impart earthy/muddy ''off-flavors'' to many water and food resources. The presence of these ''off-flavors'' often elicits public concern over the safety of the affected resources. The ''Ames test'', assesses the induction of reverse mutation at the histidine locus in specially constructed Salmonella typhimurium tester strains, and is a widely used index of mutagenicity. This investigation indicated that neither MIB nor geosmin, when tested up to cytotoxic levels in both the presence and absence of exogenous metabolic activation, induced a mutagenic response in either strain TA98 or TA100 compared to controls. Doses of MIB and geosmin above 45.2 and 18.1 ppm, respectively, inhibited tester strain growth, indicating that high concentrations of these metabolites may exhibit an antimicrobial activity, possibly by a mechanism similar to that reported for certain other terpene derived alcohols. Food or water resources containing similar concentrations of geosmin or MIB would be extremely unpalatable and would probably not be consumed.