Examination of polynucleotide sequence relationships among 11 strains of Vibrio anguillarum biotype 2 isolated from moribund fish in North America and Japan demonstrated the highly conserved character of this group of fish pathogens and, moreover, confirmed its discrete nature from V. anguillarum biotype 1. Additional molecular analyses of the V. anguillarum biotype 2 strains revealed the universal presence of a multicopy plasmid with a molecular mass of approximately 20 × 106 daltons and a mole percent guanine plus cytosine of 44. The plasmid of strain DF3K was representative of this molecular species and was designated pMJ101. Subsequent DNA–DNA hybridizations using nick translation-labeled pMJ101 as a probe indicated all the 20 × 106 dalton plasmids were either identical or highly conserved, and, furthermore, that pMJ101 was apparently unrelated to either the virulence plasmid, pJM1, of V. anguillarum biotype 1 or to representatives of common plasmid incompatibility groups. The lack of relatedness between pMJ101 and pJM1 was further supported by differences in their restriction endonuclease cleavage patterns.
Nick-translation of metaphase chromosomes: in vitro labeling of nuclease-hypersensitive regions in chromosomes.
