Shikimate kinase is an enzyme in the pathway of aromatic amino acid biosynthesis. The gene for this enzyme of Bacillus subtilis, aroI, was cloned and its nucleotide sequence determined. The gene consists of 186 amino acid codons. The enzyme shares 40.4% and 26.2% amino acid identity with Escherichia coil shikimate kinase I (AroK) and II (AroL), respectively. The amino acid sequence contains a motif for ATP-binding. aroI is an important marker gene at the 25/360 position on the B. subtilis chromosome.