Identification and characterization of a germination operon from Bacillus thuringiensis.

Spore cortex-lytic enzymes are essential for germination in Bacillus. A homologue of the cwlJ gene involved in spore germination was isolated from Bacillus thuringiensis. The deduced product of this gene exhibits striking sequence similarity to CwlJ of Bacillus subtilis. Another open reading frame (ORF) was found 27 bp downstream of cwlJ and its deduced product shows high similarity to YwdL of B. subtilis. Reverse transcription polymerase chain reaction analysis indicated that cwlJ and ywdL formed a bicistronic operon in B. thuringiensis. Disruption of this operon did not affect sporulation and the spores of corresponding mutant showed the same refractility as the wild-type strain. In contrast, the fall of optical density at 600 nm in the mutant culture was slower than that of the wild-type strain during the spore germination response to different germinants such as L: -alanine, inosine or CaDPA. The spore germination of the cwlJ mutant was restored by introducing this operon into the disruption mutant. These results suggest this operon is essential for normal spore germination in B. thuringiensis. The expression of cwlJ was observed in the sporulating cells through Western blot experiments.