BtI is active between about
T2andT6of sporulation and BtII is active from aboutT5on-wards (whereTnis nhours after the end of the exponential
phase). Two sigma factors,s ands, that specifically directtranscription of cry1Aa from BtI and BtII, respectively were
isolated. In vitro transcription experiments have also indi-cated that othercrygenes (e.g.cry1Ba) contain either BtI alone
or BtI with BtII.The genes encodings ands have been cloned and sequenced. Their deduced amino acid sequences
had showed 88 and 85% identity with E ands K of Bacillus subtilis respectively. The s Eands
K
factors of B. subtilisare
activated during the sporulation stage