Submitted to: Plasmid Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 22, 2006
Publication Date: March 1, 2007
Citation: Miller, W.G., Heath, S., Mandrell, R.E. 2007. Cryptic plasmids isolated from Campylobacter strains represent multiple, novel incompatibility groups. Plasmid. 57(2):108-117. Interpretive Summary: Plasmids are small, circular DNA molecules found often in bacteria. Sometimes, they contain genes important for disease or genes that confer resistance to antibiotics. Because they are found in a number of bacteria, they are also valuable research tools, permitting the insertion of new genes into bacteria or mutating the existing repertoire of genes. Campylobacter spp., the number one cause of human bacterial gastroenteritis, contain a large variety of plasmids both large and small. In this study, three plasmids from the same multi-drug-resistant Campylobacter coli strain were isolated, characterized and their DNA was sequenced. While they do not contain any apparent virulence determinants or antibiotic resistance genes, they are novel and belong to a new class of small plasmids, which can be used readily in Campylobacter research. Additionally, these plasmids contain common sequences, suggesting that these plasmids may undergo cycles of plasmid fusion and plasmid separation, mediated by these common regions, to form new plasmids or exchange genetic information.
Technical Abstract: Three small, cryptic plasmids from the multi-drug-resistant (MDR) Campylobacter coli strain RM2228 and one small, cryptic plasmid from the MDR Campylobacter jejuni strain RM1170 were sequenced and characterized. pCC2228-1 has some similarity to Firmicutes RepL-family plasmids that replicate via a rolling-circle mechanism. pCC2228-2 is a theta-replicating, iteron-containing plasmid (ICP) that is a member of the same incompatibility (Inc) group as previously described Campylobacter shuttle vectors. The other two ICPs, pCC2228-3 and pCJ1170, represent a second novel Inc group. Comparison of the four plasmids described in this study with other characterized plasmids from C. jejuni, C. coli, C. lari, and C. hyointestinalis suggests that cryptic plasmids in Campylobacter may be classified into as many as eight Inc groups. The plasmids characterized in this study have several unique features suitable for the construction of novel Campylobacter shuttle vectors, e.g. small size, absence of many common multiple-cloning site restriction sites, and Inc groups not represented by current Campylobacter shuttle plasmids. Thus, these plasmids may be used to construct a new generation of Campylobacter shuttle vectors that would permit transformation of environmental Campylobacter isolates with an existing repertoire of native plasmids.