16S rDNA restriction fragment length polymorphism analysis of psychrotrophic vibrios from Japanese coastal water

Restriction fragment length polymorphism (RFLP) analysis was carried out fo r 136 natural isolates belonging to the family Vibrionaceae. These were col lected from inshore areas of Japan, mainly in winter. Twenty-eight 16S rDNA genotypes were obtained by digestion with four restriction endonucleases ( HhaI, DdeI, RsaI, and Sau3AI). To estimate the genetic relationships, 53 in formative fragments were scored by their presence or absence. A dendrogram was constructed using the unweighted pair group method with the arithmetic averages algorithm. Five RFLP groups (groups I to V) were obtained. Group I corresponded to Vibrio splendidus-like strains. It was confirmed that this group was not only found in Otsuchi Bay, but also in broad coastal areas o f Japan. Group II strains were not identified as previously known Vibrio sp ecies. Group III strains were regarded as members of the Vibrio main group, which is a major phylogenetic group deduced from 16S rRNA gene analysis in the family Vibrionaceae. The RFLP profile indicated that Group IV strains were closely related to V. hollisae. Group V strains showed RFLP patterns w hich have not been observed previously. From the clustering analysis, it wa s concluded that group V strains were not Vibrio species. Most of the isola tes studied were not identified as previously described species. It suggest s that many psychrotrophic vibrios in cold marine environments remain as un known species.