Peculiarities of diesel fuel degradation by strain Rhodococcus sp. NDT23 under high salinity conditions

Degradation of diesel fuel by the halotolerant strain Rhodococcus sp. NDT23 under increased salinity conditions was studied. The strain NDT23 was isolated from diesel-contaminated soil sample which collected at a distance of 3 m from the salt dump of the plant of PJSC Uralkali (Solikamsk, Perm region, Russia). On the basis of 16S rRNA gene analysis it was shown that the strain NDT23 is phylogenetically close to Rhodococcus fascians DSM 20669T and Rhodococcus cercidiphylli YIM 65003T (100% similarity). The presence of alkane-1-monooxygenase (alkB) gene in the strain NDT23 was found to have the highest similarity (99.10-100%) with alkB genes of Rhodococcus strains isolated from soil and plant tissues. The ability of the strain NDT23 to degrade diesel fuel (DF) in the medium without salt and at concentrations up to 100 g/L NaCl was detected. A positive effect of NaCl at a concentration of 50 g/L on the degradation of DT by the studied strain was revealed. Moreover, the presence of NaCl in the medium improved the biodegradation of long-chain hydrocarbons (C14-C20) by the strain NDT23 to a greater extent than short-chain hydrocarbons (C9-C13). It is shown that such an increase in the degradation activity of the strain NDT23 is due to an increase in the hydrophobicity of their cell walls in the presence of NaCl in the medium.