Survival and expression of DNA repair genes in marine bacteria Pseudomonas pseudoalcaligenes NP103 and P-aeruginosa N6P6 in response to environmental stressors

摘要

A comparative response of marine bacteria Pseudomonas pseudoalcaligenes NP103 and P. aeruginosa N6P6 under pH stress and UV radiation (UVR) revealed that both their survival pattern and repair mechanism are species specific. In case of P. pseudoalcaligenes NP103, the survival was maximum at pH 8, which decreased with decline in pH of the medium. Whereas, in P. aeruginosa N6P6, maximum survival was observed at pH 7. On exposure to UVR at different doses (25-200 mJ/cm(2)) and increasing concentrations of Na+ (1-6%), considerable differences in the recovery (2% for P. pseudoalcaligenes NP103 and 3% for P. aeruginosa N6P6) from UVR induced damage was observed. The qRT-PCR analysis of DNA repair genes (recA and uvrA) of marine bacteria subjected to different pH conditions showed significant (P < 0.05) up-regulation of both genes at pH 6, indicating higher degree of DNA damage at low pH. Furthermore, exposure of UVR irradiated cell suspensions to visible light exhibited greater photo-reactivating capacity in P. pseudoalcaligenes NP103 as compared to P. aeruginosa N6P6. The present findings indicate that pH and UVR exposure have crucial role in dictating the light dependent and independent DNA repair pathway in marine bacteria. Further, we speculate that both these repair response to the environmental stressors varies with bacterial species.