Plasmids can be broadly classified into conjugative plasmids and non-conjugative plasmids. Plasmids are generally circular, but examples of linear plasmids are also known. This portion of the plasmid is highly conserved and found in nonpathogenic "Rhodococci" plasmids. This allows for amplification of transfected plasmids and extended temporal expression of desired gene products. The initial asRNAs discovered were in prokaryotes including plasmids, bacteriophage and bacteria. It often involves temperate bacteriophages and plasmids. Such beneficial plasmids may be considered bacterial endosymbionts. It has been shown that both plasmids and viral genomes can be transferred via MVs. Integrons may be found as part of mobile genetic elements such as plasmids and transposons. Restriction digests are frequently used to analyse purified plasmids. Certain bacteria also contain plasmids or other extrachromosomal DNA. Its genome has one finalized chromosome with no plasmids. TubZ functions in segregating low copy-number plasmids during bacterial cell division. Bacteria containing exogenous plasmids are called "transformants". Others replicate through a bidirectional replication mechanism ("Theta type" plasmids).