ANALYSIS OF THE GENOME OF VIBRIO-COSTICOLA - PULSED-FIELD GEL-ELECTROPHORETIC ANALYSIS OF GENOME SIZE AND PLASMID CONTENT

The genome organization of the moderate halophile Vibrio costicola has been investigated. To estimate its genome size, large restriction fra gments of genomic DNA were separated by pulsed-field gel electrophores is (PFGE) after digestion with restriction endonucleases. Enzymes SfiI and MboI generated 25 and 6 restriction fragments, respectively. The genome size of V. costicola E-367 was estimated to be 2,505 kb (SfiI) or 2,259 kb (MboI). Genomic DNA digested with SfiI also permitted the calculation of the genome sizes of five additional V. costicola strain s, which ranged from 2,100 to 2,600 kb. Besides, three plasmids, desig nated pVC1, pVC2 and pVC3 (of 2.95 kb, 19 kb and 21 kb, respectively), as well as a megaplasmid, were detected in V. costicola E-367. The re striction map of pVC1 was determined following the use of 14 restricti on enzymes, showing cleavage sites for BamHI, BglII, HindII and SalI. Plasmid pVC1 is a candidate for use in the development of cloning vect ors suitable for genetic manipulation of V: costicola. An interesting finding is that the DNA of V. costicola is likely to be highly methyla ted because digestion with MboI yields few cleavage sites. Additionall y, different MboI restriction patterns were observed when this moderat e halophile was grown at different salinities. This suggests that the methylation system of this halophile may be affected by the salinity o f the growth medium.