The spoIIJ gene, which regulates early developmental steps in Bacillus subtilis, belongs to a class of environmentally responsive genes.

The Bacillus subtilis spoIIJ locus is defined by a Tn917 insertion which leads to an oligosporogenous phenotype. Here we show that this mutation severely decreases transcription of spoIIA, spoIIE, and spoIIG, three operons involved in asymmetric septation, the earliest morphological event of sporulation. A 14.3-kilobase region overlapping the site of the spoIIJ::Tn917 insertion was cloned and the exact location of the spoIIJ gene was defined with various integrative plasmids carrying subfragments of that region. DNA sequencing established that spoIIJ is a monocistronic locus encoding a 606-amino-acid polypeptide which contains a canonical "transmitter" domain, indicating that spoIIJ is a new member of the "sensor" class of signal-transducing systems in bacteria. Thus, spoIIj, which is transcribed during vegetative growth, presumably under the control of sigma H, encodes a protein that could interact with major regulators of early sporulation stages, such as SpoOA and/or SpoOF.