The complete sequence of a Bacillus cereus member of the SNF2 family of putative helicases showed conservation of all seven motifs typical of this family. Bcsnf predicted a protein of 1064 aa where the conserved SNF2 domain was located at the carboxy terminus, whereas the 633 amino-terminal aa showed no homology to any protein in the databases. A putative transcriptional start was identified by primer extension, indicating that Bcsnf is not a part of a larger operon. No phenotypical changes were observed after insertional inactivation of Bcsnf. The completely sequenced genomes of Mycoplasma genitalium and Haemophilus influenzae contain one ORF each with similarity to the SNF2 family: MG018 and HI0616, respectively. A phylogenetic tree of the SNF2 family showed that BcSNF and MG018 were most closely related, and appeared closer to the eukaryotic members of the SNF2 family than to the two other bacterial members of the family, HepA from Escherichia coli and HI0616.