Construction of DnaJ Database for Medically important Bacteria to determine Species Definition

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Bacteria is phylogenetically classified with 16S rDNA gene sequence variationThe information is especially useful to find phylogenetic position of unidentified bacteria, however, the sequence variation among closely related species are almost identical in many cases. Bacterial species is genetically defined as, "Species is a population of strains, which shares more than 70% chromosome similarity ". However, methods to measure this chromosome DNA similarity are different from one laboratory to another and as a result, the similarity values of same species group are different among different laboratories. So Judicial commission announced to accumulate at least 5 different house keeping gene sequences, which are more variable than 16SD rDNA and useful to determine bacterial species.We focused on DnaJ sequences and collected the sequences of medically important bacterial groups. Staphylococcus, Streptococccus, Legionella, Mycobacterium, Vibrio, Aeromonas and members of Family Enterobacteriaceae.The sequence variation of dnaJ is bigger than 16S rDNA. M. gastri and M. kansasiishares identical 16S rDNA sequence, however, type strains and clinical strains of these species were different more than 4%. Vibrio alginolyticus and Vibrio parahaemolyticus group, Vibrio cholerae and Vibrio mimicus group also shares identical 16S rDNA sequences, however, their dnaJ sequence are 4 to 7 percent different. Generally, DnaJ variation in a genus ranged from 75% to 100%,. On the Other hand, Variation of 16S rDNA within a genus ranged from 90 to 100%.These data supported that the dnaj sequence information is extremely useful to define species and also to design specific sequence to detect bacteria at species level.