Sequence analysis and characterization of plasmid pLK39 isolated from endophytic Salmonella sp. isolated from Solanum lycocarpum.

The complete nucleotide sequence of a small cryptic plasmid pLK39 isolated from endophytic Salmonella sp. was determined. This plasmid is 4,029 bp long with an overall GC content of 55.4 %. Sequence analyses of pLK39 revealed extensive homology to several plasmids: pRK10, pK, pSW200, pBERT, pST728/06-2, pSW100, pEC3, and pUCD5000. Using the ORF Finder program, 35 putative ORFs was identified, 30 showed more than 35 residues. After performing a search for homologous sequences to the pLK39 at BLASTn software on NCBI, it was ascertained that the plasmid has a ColE1-like replication origin and also a region of mobilization proteins from relaxase family (mobCABD). Besides these mobilization proteins, the pLK39 codes a putative DUF903 protein family, which is characterized as assumed external cytoplasmic membrane lipoprotein. A recombinant form of pLK39 carrying a kanamycin resistance gene is stably maintained in Escherichia coli cells grown in the absence of selection pressure. pLK39 was compatible with pUC18, pBR322, and pACYC184.