The gerA operon is required for spore germination in Bacillus thuringiensis

Abstract:

Spore germination of Bacillus could be triggered by germinants like L-alanine which is thought to bind to and stimulate specific receptors. The GerA receptor responds to L-alanine in Bacillus subtilis. A homologous gerA operon of B. subtilis was isolated from Bacillus thuringiensis subsp. kurstaki. RT-PCR showed that the transcription of the gerA operon was switched on 3 hours after the initiation of sporulation and this operon was cotranscribed. Disruption of the gerA operon led to blockage of the L-alanine-initiated germination pathway and showed a delayed inosine-induced germination response. The germination rate of the gerA complementary strain spore deriving from introducing gerA operon into the disruption mutant was even faster than that of the wild type strain spore. This is caused by overdose GerA receptors which could enhance the sensibility of complementary spore to L-alanine. The overdose GerA receptors came from introducing multicopy plasmid- pKSV7 (about five copies) which could increase the amount of GerA receptors. After treatment of D-cycloserine which could inactivate alanine racemase irreversibly, L-alanine-induced spore could germinate faster than untreated spore. The combination of 0.1 mmol/L D-cycloserine and 1 mmol/L L-alanine could trigger spore germination induced by L-alanine effectively.