Plasmids for making multiple knockouts in a radioresistant bacterium Deinococcus radiodurans.

The gene knockouts are mostly created using homologous recombination-based replacement of target gene(s) with the expressing cassette of selection marker gene(s). Here, we constructed a series of plasmids bearing the expressing cassettes of genes encoding different antibiotics markers like nptII (KanR ), aadA (SpecR ), cat (CmR ) and aac(3) (GenR ). D. radiodurans is a radioresistant Gram positive bacterium that does not support the independent maintenance of colE1 origin-based plasmids. Using these constructs, the disruption mutants of both single and multiple genes involved in segregation of secondary genome elements have been generated in this bacterium. Unlike single mutants, the double and triple mutants showed growth retardation under normal growth conditions and the synergistic effects with Topoisomerase II inhibitor on the growth of this bacterium. Thus, these plasmids could be useful in creating multiple deletions/disruptions in bacteria that do not support independent maintenance of colE1 origin-based plasmid.