Phytopathogenic Bacterium Pectobacterium carotovorum Cryptic Plasmids Distribution

Information on the extrachromosomal elements occurrence in phytopathogenic bacterium Pectobacterium carotovorum is insuffciently presented in modern scientifc literature. Data on the pectobacteria plasmid content are random.

The aim was to study the Pectobacterium carotovorum plasmids spectra, cryptic plasmids distribution and general characteristics.

Plasmid spectra of 54 strains of different origins were studied. Standard hot alkaline Kado and Liu method was used to isolate plasmids DNA [Kado C.J., Liu S.-T. Rapid procedure for detection and isolation of large and small plasmids. J. Bacteriol. 1981; 145 (3): 1365–1373].

It was found that 16 strains contained plasmids of various sizes. Isolated plasmids belonged to four discrete size classes: 2.5 – 6.8, 9.8 – 16.7, 47.7 – 64.5 and 129 kb. Approximately 50 % of the isolated P. carotovorum plasmids belonged to the second discrete size class with a size of 8.7 – 10.4 kb. Four large 129 kb P. carotovorum plasmids had unique primary DNA sequence according to results of restriction analysis.

Pectobacteria plasmids isolation results correlate with data obtained earlier that 30 % of strains contained plasmids [Tovkach FI. [Isolation and preliminary characterization of cryptic plasmids from Erwinia carotovora]. Microbiology. 2001; 70 (6): 804–810. Russian]. Strains` plasmid maintenance was associated with environmental and ecological niches where bacteria persisted. These extrachromosomal DNAs may present silent "selfsh", and probably prophage, replicons.