ABSTRACT
Characteristic feature of the most of Selenomonas ruminantium cryptic plasmids is the presence of short, conserved sequences encompassing the gene for replication protein creating a potential rep gene cassette. PCR-based experiment was designed to analyse the genetic organization of putative plasmid rep modules and to assess S. ruminantium plasmid biodiversity. Analysed PCR amplicons contained single open reading frames encoding for putative replication proteins. While most of the derived protein sequences were often found to be conserved among putative plasmid molecules, at noncoding regions, genetic variability was observed to various extents. Complete nucleotide sequence of a plasmid was determined that contained probably a new rep gene only distantly related to known selenomonas Rep proteins but at noncoding regions shared high homology with already known plasmids. Our results document considerable structural instability and sequence variability of analysed rep gene cassettes and suggest a modular structure of S. ruminantium plasmids potentially accessible for rep gene module exchanges.
Subject(s)
Bacterial Proteins/genetics , Plasmids/genetics , Selenomonas/genetics , Amino Acid Sequence , Bacterial Proteins/chemistry , Base Sequence , DNA Replication , Gene Order , Molecular Sequence Data , Open Reading Frames , Sequence AlignmentABSTRACT
The complete nucleotide sequence of pSRD192 plasmid from Selenomonas ruminantium 19D has been obtained and analyzed. The plasmid, 2334bp in length, was shown to replicate by rolling circle replication mechanism. By PCR method variability of pSRD192-like plasmids was investigated and another variant of pSRD192-like plasmid; the pSRM22 plasmid 2338bp in length; was detected and characterized. Both pSRD192 and pSRM22 plasmids share an identical rep gene and origins of replication to that of another S. ruminantium pONE429 plasmid. Other than that there are additional regions of sequence similarity between the three plasmids, interspersed with divergent regions. The sequence comparisons suggest structural instability of pSRD192-like rolling circle replication plasmids.
