Overlapping oriC and centromere-like functions in secondary genome replicons determine their maintenance independent of chromosome I in Deinococcus radiodurans

Abstract

The Deinococcus radiodurans multipartite genome system (MGS) consists of chromosome I (ChrI) and secondary genome elements; Chr II and megaplasmid (MP). The sequences upstream to parAB operons in Chr II (cisII) and MP (cisMP) helped an E. coli plasmid maintenance in D. radiodurans and showed sequence specific interactions with DnaA and ParBs. The cells devoid of cisII ({Delta}cisII) or cisMP ({Delta}cisMP) showed reduced {gamma} radiation resistance and copy number of Chr II and MP. Fluorescent Reporter-Operator System (FROS) developed for ChrI, ChrII and MP in {Delta}cisII or {Delta}cisMP mutants showed no change in wild type pattern of Chr I localization. However, the relative copy numbers of Chr II and MP had reduced while anucleate cells had increased in mutants. These results suggested that cisII and cisMP elements contain both ori and centromere-like functions, and like other MGS bacteria, the Chr I and secondary genome are maintained independently in D. radiodurans.