Allelic variations in dnaK of thermotolerant bacilli inhabiting thermal springs

Abstract

Abiotic stresses including high or low temperature are known to affect productivity in plants as well as microflora, and often heat shock proteins (Hsps) are induced in cells experiencing such heat stress. Hsp 70 which belongs to one of the five major families of Hsps, DnaK family, plays a vital role in the protection and recovery of cells damaged by heat stress. Further, the role of dnak gene encoding a protein related to Hsp70 in thermoregulation has been established already. In this study, we analyzed a set of thermotolerant bacilli for variation in the dnaK gene that codes for DnaK/Hsp70 protein. A part of the dnaK was amplified from seven different bacilli isolated from Manikaran hot springs, Himachal Pradesh, India. Phylogenetic analyses of dnaK in the set of strains generated four clusters, three representing highly thermotolerant strains and one, a moderately thermotolerant strain. However, analyses of deduced amino acid sequences generated only three clusters, two representing highly thermotolerant strains and one representing moderately thermotolerant strain. Comparison of DnaK of highly thermotolerant strain (M5) and moderately thermotolerant strain (M36) revealed polymorphism for 26 amino acids in the ATPase domain and for one amino acid in the substrate binding domain. It can be hypothesized that polymorphism in the DnaK could be linked to the difference in the temperature tolerance limit of the two strains.