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 of Vibrio parahaemolyticus have drawn attention to make detailed study on their genomes. The pathogenicity of V. parahaemolyticus has been associated with thermostable-direct hemolysin (TDH) and/or TDH-related hemolysin (TRH). The present study evaluated characteristics of tdh and trh genes, considering the phylogenetic and in silico functional features of V. parahaemolyticus and other bacteria. Fifty-two tdh and trh genes 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 that tdh and trh are highly distinct and also differ within the V. parahaemolyticus strains 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 nonpandemic tdh sequences. 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 pandemic V. parahaemolyticus. Experimental evidences are needed to recognize the importance of substitutions and deletions in the tdh and trh genes.

Effects of salinity and shaking condition on the growth and virulence of Vibrio parahaemolyticus

“…We did not observe in any case the production of hemolysin and chitinase. That V. parahaemolyticus XN9 did not show hemolytic characteristics was predictable as hemolytic activity is much more frequently found in clinical isolates but not environmental ones (Bhowmik et al, 2014). Chitinase, on the other hand, generally plays an important role in the degradation of the crustacean rich biopolymer chitin, converting it into nutrients for marine bacteria (Frederiksen et al, 2013).…”

Cell‐free production of pore forming toxins: Functional analysis of thermostable direct hemolysin from Vibrio parahaemolyticus

“…KP positive bacterial strains contain one or two TDH gene copies . In total, five different TDH gene variants have been described which share a sequence identity >96.7% . Apart from KP effect, TDH is known to exhibit the so called Arrhenius effect, where the hemolytic activity is inactivated when the protein is heated at 60°C and is reactivated by further heating at 90°C for 15 min .…”

“…In O3:K6 pandemic strains, two TDH genes termed TDH1 and TDH2, are present and are responsible for the Kanagawa phenomenon. The gene TDH2 holds 97.2% homology with TDH1 and was found primarily responsible for the phenotypic expression of hemolytic activity . Very recently, these bacterial strains were reported to exhibit antibiotic resistance .…”