Cloning and dependence pattern of the sporulation operon spoVH

The spoVH locus, involved in the sporulation of Bacillus subtilis, was cloned in derivatives of the temperate bacteriophage luminal diameter 105. Two recombinant phages were obtained which contained 4.2 kilobases of chromosomal DNA. Both phages only partially complemented a mutation in the spoVH operon, spoVH516. Nevertheless, analysis of the cloned locus with integrational plasmids showed that the complete operon had been cloned. A spoVH'-lacZ transcriptional fusion was constructed, and this indicated that the spoVH operon was expressed 2.25 h after the start of sporulation. The distribution of beta-galactosidase in sporulating cells containing a spoVH'-lacZ fusion showed that spoVH was expressed in the spore compartment; lac fusion experiments were also used to study spoVH expression in the presence of other sporulation mutations. Expression of spoVH was prevented by mutations in any of the stage 0 or stage II loci and also by mutations in spoIIIA, spoIIIB, and spoIIIE. A similar pattern of dependence was found previously for the expression of spoVA, which is also expressed in the spore compartment.