The complete nucleotide sequence of the Bacillus coagulans plasmid pBC1 was determined. The sequence revealed an open reading frame encoding a polypeptide of 259 amino acids. This open reading frame shows sequence similarity to genes coding for replication-associated proteins in a group of gram-positive bacterial plasmids known to replicate via single-stranded intermediates. A region required for replication in cis, when the intact replicon is supplied in trans, was identified as well.