Phylogenetic andIn SilicoFunctional Analyses of Thermostable-Direct Hemolysin andtdh-Related Encoding Genes inVibrio parahaemolyticusand Other Gram-Negative Bacteria

Abstract

Emergence and spread of pandemic strains ofVibrio parahaemolyticushave drawn attention to make detailed study on their genomes. The pathogenicity ofV. parahaemolyticushas been associated with thermostable-direct hemolysin (TDH) and/or TDH-related hemolysin (TRH). The present study evaluated characteristics oftdhandtrhgenes, considering the phylogenetic andin silicofunctional features ofV. parahaemolyticusand other bacteria. Fifty-twotdhandtrhgenes submitted to the GenBank were analyzed for sequence similarity. The promoter sequences of these genes were also analyzed from transcription start point to −35 regions and correlated with amino acid substitution within the coding regions. The phylogenetic analysis revealed thattdhandtrhare highly distinct and also differ within theV. parahaemolyticusstrains that were isolated from different geographical regions. Promoter sequence analysis revealed nucleotide substitutions and deletions at −18 and −19 positions among the pandemic, prepandemic, and nonpandemictdhsequences. Many amino acid substitutions were also found within the signal peptide and also in the matured protein region of several TDH proteins as compared to TDH-S protein of pandemicV. parahaemolyticus. Experimental evidences are needed to recognize the importance of substitutions and deletions in thetdhandtrhgenes.