An origin of DNA replication from streptomycete phage ΦU1

A DNA fragment from phage PhiU1 containing an origin of DNA replication was identified. This fragment, designated ort, was able to support the maintenance in Streptomyces lividans of a plasmid lacking a functional Gram-positive ort. The sequence of the minimal ort fragment was determined and analyzed. The minimal fragment conferring replication origin function contained a number of direct and inverted repeats. The absence of an open reading frame in this ori fragment indicates that host factors alone were sufficient to initiate replication at ori.