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 de rivatives geosmin (1alpha,10beta-dimethyl-9alpha-decalol) and 2-methyl isoborneol )-1,2,7,7-tetramethyl-bicyclo-(2,2,1)-heptan-2-ol] (MIB), i mpart earthy/muddy ''off-flavors'' to many water and food resources. T he 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 con structed Salmonella typhimurium tester strains, and is a widely used i ndex of mutagenicity. This investigation indicated that neither MIB no r geosmin, when tested up to cytotoxic levels in both the presence and absence of exogenous metabolic activation, induced a mutagenic respon se in either strain TA98 or TA100 compared to controls. Doses of MIB a nd geosmin above 45.2 and 18.1 ppm, respectively, inhibited tester str ain growth, indicating that high concentrations of these metabolites m ay exhibit an antimicrobial activity, possibly by a mechanism similar to that reported for certain other terpene derived alcohols. Food or w ater resources containing similar concentrations of geosmin or MIB wou ld be extremely unpalatable and would probably not be consumed.