Sporulation and delta-endotoxin synthesis by Bacillus thuringiensis.
Bacillus thuringiensis is distinguished from the very closely related Bacillus cereus and Bacillus anthracis by the presence of several plasmid-encoded delta-endotoxin genes. These delta-endotoxins, synthesized as protoxins, are produced in large quantities during sporulation and are packaged into intracellular inclusions. Ingestion of the inclusions by insect larvae leads to protoxin solubilization and conversion to toxins each specific for one of several orders of insects. The toxins form cation-selective channels in the membrane of cells lining the larval midgut with subsequent lethality. In most cases, delta-endotoxin synthesis and sporulation are closely coupled. The latter process in B. thuringiensis is probably virtually identical to that in Bacillus subtilis with the additional use of mother cell sporulation forms of RNA polymerase for the synthesis of the delta-endotoxins. There are other more subtle plasmid-encoded functions or plasmid interactions related to regulating protoxin synthesis. Consideration of both plasmid and chromosomal genes is thus critical for defining this organism.
Aronson
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Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA. aaronson@bilbo.bio.purdue.edu
D001413:Bacillus thuringiensis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D001427:Bacterial Toxins / Q000096:biosynthesis / Q000378:metabolism; D004731:Endotoxins / Q000096:biosynthesis* / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D006460:Hemolysin Proteins; D002479:Inclusion Bodies / Q000378:metabolism; D008854:Microscopy, Electron; D010572:Pest Control, Biological; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000096:biosynthesis / Q000378:metabolism; D013171:Spores, Bacterial / Q000378:metabolism*
D000083722:Bacillus thuringiensis Toxins; C029103:Bacillus thuringiensis protoxin; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D011498:Protein Precursors; C030956:insecticidal crystal protein, Bacillus Thuringiensis