Volatiles production and attractiveness to the Mexican fruit fly of Enterobacter agglomerans isolated from apple maggot and Mexican fruit flies.

We investigated two strains of uricase (+) Enterobacter agglomerans, one isolated from the apple maggot fly (AMF) and one from the Mexican fruit fly (MFF), for 1) attractiveness to MFF, and 2) production of attractive chemicals. Regarding chemicals demonstrated attractive to the MFF, the MFF bacterial strain produced more 2,5-dimethylpyrazine, 2-phenylethanol, and indole than the AMF strain, whereas the AMF, but not the MFF strain, produced 3-hydroxybutanone. Cell types that predominated in plated subcultures varied from batch to batch resulting in variation in volatiles production, especially by the AMF strain where indole was sometimes a major component of the odor and at other times not detectable. Despite the greater production of attractive chemicals by the MFF strain, the AMF strain was consistently more attractive and the MFF strain was not different from uninoculated control plates. Statistical analyses indicated negative correlations of attractiveness with production of indole, 2,5-dimethylpyrazine, and 2-phenylethanol, and positive correlation with 3-hydroxybutanone. Results support previous findings with the Mexican fruit fly that showed combinations of attractive chemicals sometimes are not attractive.

A continuous spectrophotometric assay for the determination of diamondback moth esterase activity.

Conventional methods to determine esterase activity from insects are composed of a three-step process where the enzyme is allowed to hydrolyze a 1-naphthyl acetate substrate, that reaction is quenched by a SDS detergent, and then a Fast Blue B dye complex is formed with 1-naphthol, the product of 1-naphthyl acetate hydrolysis. These methods measure dye-product complex rather than the product, 1-naphthol. A new assay is presented that continuously monitors the formation of 1-naphthol with the hydrolysis of an esterase substrate. The esterase activity was determined as the slope of the linear regression change in absorbance over time at 320 nm. The continuous assay provides a simple, rapid, and sensitive method for measuring esterases extracted from a single diamondback moth in 1-10 min. The detection limit of the assay is approximately 0.6 microM 1-naphthol. The 1-naphthol product from the esterase reaction was confirmed by HPLC analysis. According to the assay, the K(m) and V(max) values of the esterase were 28 +/- 2 microM and 6.0 +/- 0.1 microM/min, respectively, at 37 degrees C for 1-naphthyl acetate. The K(i) value was 9 +/- 2 microM using azadirachtin, an insecticide from neem tree, Azadirachta indica (A.Juss). Azadirachtin was a reversible competitive inhibitor of the esterase activity.