RESUMEN
Culture supernatant of Bacillus thuringiensis 9816C had high toxicity against Helicoverpa armigera and Spodoptera exigua. However, it lost insecticidal activities after being bathed in boiling water for 5 min. Acrystalliferous mutants of Bt9816C (Bt9816C-NP1 and Bt9816C-NP2) cured of its endogenous plasmids no longer possessed vip3A gene and toxicity. The 89 kD protein which existed in Bt9816C supernatant disappeared in the two mutants' supernatant; nevertheless, the two mutants still exhibited hemolytic and phospholipase C activity as Bt9816C did. The vip3A gene of Bt9816C, vip3Aa18, was cloned and expressed in Escherichia coli BL21. Bioassay demonstrated that the recombinant E. coli had high toxicity against S. exigua. Taken together, it suggested that Vip3A protein was responsible for the toxicity of Bt9816C culture supernatants.
Asunto(s)
Bacillus thuringiensis/metabolismo , Proteínas Bacterianas/fisiología , Insectos/microbiología , Animales , Bacillus thuringiensis/genética , Proteínas Bacterianas/biosíntesis , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Spodoptera/microbiologíaRESUMEN
Bt L-7601 is a UV resistant wild-type strain, which belongs to Bacillus thuringiensis subsp. dendrolimus serotype H4a4b. It was isolated from nature, and produced a dark brown pigment during the exponential phase of growth. Bt L-7601 had the ability to produce pigment in a general nutrition-abundant medium, which had no L-tyrosine. The pigment was identified as melanin based on chemical testing, its light absorbance, and FT-IR analysis. Bt L-7601 has a strong resistance to UV light. After 30 min irradiation its survival rate was 17 times higher than that of the strain B. thuringiensis subsp. colmeri 15A3, which had no pigment. Results of the bioassays of residual insecticidal activity of Bt formulation with and without pigment produced by Bt L-7601 against larvae of Helicoverpa armigera and Spodoptera exigua after exposure to UV irradiation showed that the pigment is an excellent UV protective agent for the insecticidal proteins.
Asunto(s)
Bacillus thuringiensis/efectos de la radiación , Melaninas/biosíntesis , Melaninas/farmacología , Rayos Ultravioleta , Animales , Bacillus thuringiensis/crecimiento & desarrollo , Bacillus thuringiensis/metabolismo , Toxinas de Bacillus thuringiensis , Proteínas Bacterianas/farmacología , Toxinas Bacterianas/farmacología , Endotoxinas/farmacología , Proteínas Hemolisinas , Larva/crecimiento & desarrollo , Melaninas/química , Mariposas Nocturnas/crecimiento & desarrollo , Control Biológico de Vectores , Spodoptera/crecimiento & desarrolloRESUMEN
Bacillus thuringiensis isolates from different ecological regions and sources of China were analyzed to study the distribution and diversity of cry genes and to detect the presence of novel cry genes. Strains containing cry1-type genes were the most abundant and represent 237 of the 310 B. thuringiensis isolates (76.5%). About 70 and 15.5% of the isolates contained a cry2 gene or cry9 gene, respectively, while 10.0% of the strains did not contain a cry1, cry2, or cry9 gene. Among the cry1 containing isolates, cry1A (67.7%), cry1I (60.6%), cry1C (43.9%), and cry1D (39.4%) genes were the most abundant. Forty-three different cry1 gene profiles were detected in this collection. Several cry1 genes were associated at a high frequency, such as the cry1C-cry1D and cry1A-cry1I gene combination. The cry1A and cry2 amplicons were digested with selected restriction enzymes to examine sequence diversity. Based on this RFLP analysis, one novel cry1A-type gene was observed.
Asunto(s)
Bacillus thuringiensis/genética , Proteínas Bacterianas/genética , Toxinas Bacterianas , Proteínas de Drosophila , Endotoxinas/genética , Proteínas del Ojo , Flavoproteínas/genética , Células Fotorreceptoras de Invertebrados , Toxinas de Bacillus thuringiensis , China , Criptocromos , Perfilación de la Expresión Génica , Proteínas Hemolisinas , Receptores Acoplados a Proteínas GRESUMEN
Bacillus thuringiensis wild type strain 15A3 belongs to subspecies colmeri serotype H-21. RFLP and PCR analysis show that it contains six types of ICP genes: cry1Aa, cry1Ac, cry1Ca, cry1D, cry1I and cry. The sequence of the 1.45 kb N-terminal fragment of cry1Aa differed from that of published. SDS-PAGE showed that the crystal consists of proteins with molecular weight about 130, 79, 70, 65, 51 and 45 kD. Strain 15A3 didn't sysnthesize heat-stable beta-exotoxins according to test of house fly aberration. The 1.2 tons fermentative production exhibited high toxicity against three lepidopteran pests: H. armigera, S. exigua and H. cunea. It was proved that wild type strain can produce a broad specturm of ICP.