Impact of transgenic cotton varieties on activity of enzymes in their rhizosphere.

The impact of five Bacillus thuringiensis (Bt) cotton varieties and their respective isogenic non-Bt(NBt) isolines (ANKUR-2534, MECH-6304, RCH-317, ANKUR-651 and MECH-6301) was assessed on the key soil enzymes i.e., dehydrogenase, alkaline phosphatase and urease in their rhizosphere at four growth stages of the crop, namely vegetative, flowering, bolling and harvesting. These varieties were grown on farmer’s field in villages 22 miles and 24 miles of Ganganagar District of Rajasthan State in India. Results showed that dehydrogenase, alkaline phosphatase and urease activities were higher in rhizosphere of Bt isolines as compared to NBt isolines of all the varieties. Except phosphatase, differences in dehydrogenase and urease activities in rhizosphere of Bt and NBt isolines of all five varieties were significant (P<0.05). Maximum enhancement in the three enzymes activities was observed in MECH-6304 Bt isoline rhizosphere. Maximum and minimum activities of dehydrogenase and urease were observed in MECH-6304 and RCH-317 Bt isolines, respectively, whereas phosphatase activity was maximum and minimum in MECH-6304 and ANKUR-651 Bt isolines, respectively. Maximum dehydrogenase and urease activities were observed at boll formation and minimum at flowering and harvesting stage, respectively, while maximum phosphatase activity was observed at vegetative stage and minimum at harvesting stage. In conclusion, all the studied Bt isolines of cotton varieties showed no adverse effect on dehydrogenase, alkaline phosphatase and urease activities in the rhizosphere.

Characterization of extracellular cellulose-degrading enzymes from bacillus thuringiensis strains

The gram-positive spore-forming bacteria, Bacillus thuringiensis (Bt) strains produced novel cellulases which could liberate glucose from soluble cellulose, carboxymethyl cellulose (CMC), and insoluble crystalline cellulose. The maximal cellulase activities were obtained after 60 hrs incubation at 28ºC in a LB broth medium with 1 percent CMC. Maximum CMCase activities were got at 40ºC and pH 4.0, respectively, and more than 50 percent of its maximal activity was retained at 40-60ºC for 1 hr, while approximately 40 percent of its maximal activity was also retained after incubating at 70ºC for 1 hr. Most metal ions and reagents such as Ca2+, Mg2+, Cd2+, Pb2+, Zn2+, Cu2+, EDTA, and SDS inhibited the enzyme activities, but K+ and Mn2+ activated the activities. The enzymes from Bacillus thuringiensis strains could be applied in bioconversion of lignocellulosic biomass into fermentable sugars.

Methodology for fast evaluation of "Bacillus thuringiensis" crystal protein content

The development of the production and use of "Bacillus thuringiensis in Brazil at a commercial scale faces certain difficulties, among them the establishment of efficient methodologies for the quantification of toxic products to be commercialized. Presently, the amount of toxin is given in percentage by analyzing the samples total protein content. Such methodology however, does not measure the actual amount of active protein present in the product, since most strains express different endotoxin genes and might even produce b-toxin. Since the various types of toxins exhibit different antigenic characteritics, this work has objective the utilization of fast immunological techniques to quantify the level of crystal protein. Crystal protein produced by a subspecies of "Bacillus thuringiensis" var. "israelensis" was purified by ultracentrifugation and utilized to immunize rabbits and to produce hiperimmune sera. Such sera were latter used to evaluate the level of proteins on commercial bioinsecticide and on laboratory cultures of "B. thuringiensis" through the immunodot technique. The results were obtained by comparison of data obtained from reactions with known concentrations of crystal protein permitting to evaluate the level of such protein on various materials.

Activation of adenyl cyclase in insect midgut membrane vesicles by bacillus thuringiensis delta endotoxins and melittin

Addition of Bacillus thuringiensis aizawai ICI toxins to brush-border membrane vesicles, prepared from Pieris brassicae midgut, increased cyclic AMP which was paralleled by activation of adenylate cyclase in direct measurements. Bee venom toxin melittin, which is cytolytic, also increased cyclic AMP in these vesicles. It is proposed that activation of adenylate cyclase may be due to alteration of its lipid environment by these toxins

Extra cellular hydrolytic enzyme secretion in Bacillus thuringiensis H14 & B. sphaericus & their significance in media design.

Level of extracellular proteolytic and amylolytic enzyme production was determined to assess the ability of these strains in utilizing complex carbon and nitrogen sources. Protease secretion reached maximum at around 12th h of growth in case of all the three B. thuringiensis strains and declined sharply thereafter. In B. sphaericus strains the protease level gradually increased and reached maximum at around 24th h of growth. Amylase activity was not detectable in the culture supernatants of B. sphaericus strains whereas all the three B. thuringiensis strains tested showed significant amount of amylase activity.