Role of the Structural and Functional Genes Encoding Heat Shock Proteins in Biosurfactant Synthesis by Rhodococcus pyridinivorans 5Ap

Abstract—The role of groESL and dnaJ structural genes and hrcA regulatory gene, encoding the synthesis of heat shock proteins, in biosurfactant synthesis by R. pyridinivorans 5Ар was determined. The CIRCE binding sites for the regulatory protein coded by hrcA gene were revealed in the promoter regions of groESL, groEL2, and fmdB genes. GroESL and groEL2 genes expression during the late exponential phase in the medium with hexadecane at 42°C was higher than at 28°C (4.4 and 5.3 times, respectively). At the same time, no changes in expression of hrcA and fmdB genes were observed at two different temperature modes (28 and 42°C). In the absence of the negative regulator HrcA, groESL expression increased 14.4 and 3.5 times, that of groEL2, 9.6 and 2.7 times, and that of fmdB, 1.82 and 2.52 times at 28 and 42°C, respectively. Products of dnaJ and hrcA genes were required for trehalolipid synthesis at different temperature modes, with their role increasing at higher temperature (synthesis of trehalolipids by the mutant with impaired dnaJ gene decreased 1.8 and 2.5 times compared to 1.5 and 6.6 times, for the mutant with impaired hrcA at 28 and 42°C, respectively). At the same time, emulsifying activity of all mutant variants did not change at 28°C and decreased 1.4 and 1.9 times 42°C for the mutants with impaired groESL and hrcA genes, respectively. Our results indicated the complex chemical nature of the biosurfactants produce by R. pyridinivorans 5Ар (emulsifiers, including trehalolipids and compounds of other chemical composition). The Gro chaperones and the HrcA regulatory protein play the key roles in synthesis of these compounds at different temperature modes, while the dnaJ is required only for trehalolipid synthesis.