Adelaido J. Martinez

Coprecipitation with lactose as a means of recovering the spore-crystal complex of Bacillus thuringiensis

Abstract Although the spore-crystal complex of Bacillus thuringiensis can be precipitated from concentrated aqueous suspensions derived from fermentation beers by the addition of acetone, the spores and crystals in the resulting products have a strong tendency to clump, and they are difficult to resuspend in water. Clumping can be reduced by suspending the concentrated complex in 4–6% lactose solutions and precipitating the lactose along with the complex by the addition of 4 vol of acetone. The precipitate is then easily recovered as a dry, stable preparation that is not difficult to resuspend in water. Yields of over 70% were obtained, and the ratios of spores to crystals did not change during the process. A new term, the diet dilution unit, was defined and used to express potencies and calculate yields.

VOLATILES ATTRACTIVE TO THE MEXICAN FRUIT FLY (DIPTERA: TEPHRITIDAE) FROM ELEVEN BACTERIA TAXA

Filtrates of 11 bacteria representing 4 higher taxonomic categories were attractive to Mexican fruit flies, Anastrepha ludens (Loew) (Diptera: Tephritidae) in laboratory bioassays. All bacterial filtrates were more attractive at pH 9 than at pH 5 although filtrates at pH 5 were more attractive than water controls. The effects of pH on attractiveness of filtrates were consistent with an hypothesis that attractive principals of bacterial filtrates were various nitrogen-containing compounds and carboxylic acids that became more volatile at specific pHs resulting in increased attractiveness. Volatiles produced by the bacteria were sampled by solid-phase microextraction and identified by GC and GC-MS. Attractive principals identified were ammonia, aliphatic amines, pyrazines, imines, and acetic acid. Relative amounts of most of the chemicals were not closely tied to bacteria taxonomy.

Research Reports: Laboratory and Field Olfactory Attraction of the Mexican Fruit Fly (Diptera: Tephritidae) to Metabolites of Bacterial Species

Bacteria isolated from the Mexican fruit fly, Anastrepha ludens Loew, were identified and found to be similar to bacteria isolated from other fruit fly species. Bacteria of the same species as those identified from A. ludens were obtained from the American Type Culture Collection (ATCC). These bacteria were cultured and attractiveness to A. ludens adults was determined for the whole beer, and for filtered and autoclaved supernatants in laboratory bioassays. All bacterial cultures were attractive to A. ludens, and some were significantly more attractive than others. Autoclaved supernatants were significantly more attractive than the whole beer or filtered supernatants. Two strains of Bacillus thuringiensis (serovars finitimus and kurstaki), not previously reported to attract fruit flies, were attractive to A. ludens. In field studies, metabolites from bacterial fermentation of two cultures (ATCC #8090 and #13883) captured as many A. ludens adults as Torula yeast/borate pellets. Metabolites from these two cultures caught nearly twice as many females as males compared to about equal numbers of males and females captured by Torula yeast/borate pellets and Nulure@^R. Consistent with laboratory bioassays, metabolites from RGM-1 caught significantly fewer A. ludens adults than the metabolites from #8090 and #13883.

Interaction of larval age and antibiotic on the susceptibility of three insect species to Bacillus thuringiensis

Abstract The addition of chlortetracycline hydrochloride to bioassay diets increased the LC50S of the HD-1 isolate of Bacillus thuringiensis 2.4–67.1 times when bioassayed against 4-day-old larvae of Trichoplusia ni, Heliothis virescens, and Ostrinia nubilalis. There were no significant differences in LC50 s when bioassays were conducted with neonate larvae in the presence or absence of antibiotic, nor were there any highly significant differences between the LC50 s for HD-1 when neonate larvae were used in the presence or absence of antibiotic or when 4-day-old larvae were used in the absence of antibiotic. Viable counts of B. thuringiensis did not increase over time in any of three bioassay diets. There were no differences in activity of pure chlortetracycline hydrochloride and veterinary grade Aureomycin. There was a direct correlation between amount of antibiotic and elevation of HD-1 LC50 s when 4-day-old larvae were used. LC50 elevation in presence of antibiotic first appeared in 2-day-old larvae.

Recovery of the nuclear polyhedrosis virus of the cabbage looper, Trichoplusia ni, by coprecipitation with lactose

Abstract Polyhedral inclusion bodies of the nuclear polyhedrosis virus of the cabbage looper, Trichoplusia ni, were precipitated from concentrated suspensions in 4–6% solutions of lactose by adding acetone. In this procedure, the lactose precipitates along with the polyhedra and helps to obtain a dry product with minimum clumping that is easily resuspended in water. The polyhedra may be precipitated directly from crude suspensions of larvae that have been macerated in water and coarse-filtered to remove body parts. In this case, lactose is dissolved in the suspension to the desired concentration. Greater purity can be obtained by first centrifuging the polyhedra and then resuspending them in the lactose solution. Yields of 80% were obtained. The product has proved to be a useful replacement for the usual lyophilized preparation.