RESUMEN
Entomopathogenic bacilli B. thuringiensis israelensis (Bti) and B. sphaericus (Bf) exhibit low survival on field application. It was previously shown that their spores are very sensitive to different stress effectors (heat, UV light) and especially to osmotic variations. Since SASP (Small, Acid-Soluble Spore Proteins), alpha/beta and gamma type, are involved in spore tolerance to heat, UV light, peroxide, and salt, they were analyzed in Bti and Bf. The molecular weight, migration pattern and amino acid composition of different SASP were determined and compared with other bacilli, in particular to B. subtilis. A relation between spore osmotolerance, SASP content, and amino acid composition was shown. In addition, the absence of gamma SASP in Bti and Bf is discussed.
Asunto(s)
Bacillus thuringiensis/metabolismo , Bacillus/metabolismo , Proteínas Bacterianas/metabolismo , Esporas Bacterianas/metabolismo , Bacillus/efectos de los fármacos , Bacillus/efectos de la radiación , Bacillus thuringiensis/efectos de los fármacos , Bacillus thuringiensis/efectos de la radiación , Proteínas Bacterianas/efectos de los fármacos , Proteínas Bacterianas/efectos de la radiación , Presión Osmótica/efectos de los fármacos , Peróxidos/farmacología , Cloruro de Sodio/farmacología , Esporas Bacterianas/efectos de los fármacos , Esporas Bacterianas/efectos de la radiación , Temperatura , Rayos UltravioletaRESUMEN
It was shown previously that spores and vegetative cells of Bacillus sphaericus (Bf) and Bacillus thuringiensis israelensis (Bti) are very sensitive to osmotic variations. Since spore osmotolerance has been associated with their SASP (small acid soluble spore proteins) content coded by ssp genes, hybridization assays were performed with sspE and sspA genes from B. subtilis as probes and showed that Bti and Bf strains could lack an sspE-like gene. The B. subtilis sspE gene was then introduced into Bti 4Q2 strain; spores were obtained and showed a 65 to 650 times higher level of osmotolerance to NaCl, without affecting other important properties: hypoosmotic resistance in vegetative cells, spore UV resistance, and larvicidal activity against diptera larvae.
Asunto(s)
Bacillus thuringiensis/genética , Proteínas Bacterianas/genética , Genes Bacterianos/fisiología , Factor sigma , Esporas Bacterianas/fisiología , Factores de Transcripción , Equilibrio Hidroelectrolítico/genética , Animales , Dípteros , Larva , Control Biológico de Vectores , Especificidad de la Especie , Transfección , Rayos UltravioletaRESUMEN
The transformation efficiency of competent Bacillus subtilis degU32(Hy) strains was found to depend on the marker that was selected. Prototrophic transformants were obtained at frequencies similar to those in the wild type control, but Spo- transformants were rare also when a spoOA::erm insertion that produces a selectable marker (ErmR) was used. The ErmR transformants obtained within the degU32(Hy) background were Spo+ and had lost the characteristics of the DegU(Hy) parental recipient strain i.e., secretion of exo-enzymes and sporulation resistance to catabolites. The spoOA::erm insertion was mapped to a location near degU. The similarities between the spoOA and degU sequences and the metabolic interferences between the mutated products which result in this unexpected recombination, are discussed.