Genetic transformation system for a psychrotrophic deep-sea bacterium: Isolation and characterization of a psychrotrophic plasmid

A versatile system that permits generic manipulation of a psychrotrophic de ep-sea bacterium, pseudoalteromonas sp. PS1M3, has been developed. A crypti c indigenous plasmid, pPS1M3, of 3.1 kb from the above strain was isolated and characterized. The nucleotide sequence analysis of plasmid pPS1M3 revea led the presence of one open reading frame, and its deduced amino acid sequ ence was identified as the essential protein for plasmid maintenance. Trans formation with the pPS1M3 harboring antibiotic resistance genes by electrop oration was fully successful using the pPS1M3-cured strain as a host. This plasmid was quite stable under nonselective culture conditions For about 10 0 generations at 4 degreesC. The copy number of this plasmid in the cell wa s about 5 copies per chromosome.