RESUMO
Mutation of a novel cry-like gene (cry256) from Bacillus thuringiensis resulted in a protein crystal, normally located within the spore's exosporium, being found predominately outside the exosporium. The cry256 gene codes for a 3-domain Cry-like protein that does not correspond to any of the known Cry protein holotypes.
Assuntos
Bacillus thuringiensis/metabolismo , Proteínas de Bactérias/metabolismo , Endotoxinas/metabolismo , Proteínas Hemolisinas/metabolismo , Esporos Bacterianos/metabolismo , Bacillus thuringiensis/genética , Toxinas de Bacillus thuringiensis , Proteínas de Bactérias/genética , DNA Bacteriano/química , DNA Bacteriano/genética , Endotoxinas/genética , Proteínas Hemolisinas/genética , Dados de Sequência Molecular , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Esporos Bacterianos/genéticaRESUMO
In order to better understand the range and role of Bacillus thuringiensis (Bt) and its toxins in nature, we have undertaken a study of Bt taken directly from the rectum of 117 cows from 37 farms on the Caribbean island of Trinidad. Thirty-seven fecal samples (32%) were found to contain at least one Bt. Generally only one or two isolates with a particular crystal morphology were isolated from any one sample, however, a few samples contained more, up to 11 isolates, suggesting post-ingestion amplification. Bioassays using larvae of Musca domestica, Caenorhabditis elegans and Tetrahymena pyriformis showed no observable toxicity in gross bioassays. Very small dot-like parasporal bodies, not generally characteristic of Bt, were isolated from 44% of the samples, which in many instances appeared unstable and whose relation to Bt Cry protein-containing parasporal bodies is unknown. In conclusion, we find little evidence for a host adapted strain of Bt in the cows examined, nor toxicity to organisms that might logically be associated with either the cow or its feces. The presence of a large number of isolates containing small dot-like parasporal bodies, possibly either poly-beta-hydroxybutyrate storage bodies or Cry proteins, was unexpected and merits further investigation.