UV induced DNA damage and repair in marine bacteria

Abstract

The continuous depletion of the Earth's ozone layer by anthropogenic activities has fueled concern about the impact of increasing solar ultraviolet-B radiation (UV-B) on aquatic ecosystems. The DNA is one of the key targets for UV-induced damage in the aquatic organisms.. Thus, the aquatic organisms have developed a number of enzymes, repair and tolerance mechanisms to counteract the damaging effects of UV. The continuing ozone depletion not only caused DNA damage but also causes an abrupt collapse of primary photosynthetic production, resulting in subtle, community-level responses that could ultimately impact on higher trophic levels. The pH of oceans is also changing due to increase in amount of dissolved CO2 thus causing ocean acidification and disturbing the biogeochemical cycles in the marine environment. To study the consequences of ocean acidification, the response of marine bacteria (in terms of survival) under pH changes upon UVR exposure, preliminary work has been done on marine bacteria Pseudomonas pseudoalcaligenes NP103 and P. aeruginosa N6P6 isolated from Odisha coast. The sensitivity of the bacterium to UV-B under different dosages has been determined by colony counting and spectrophotometry growth method. The percentage survival calculated by colony counting method was about 0.005% and 0.004% for P. pseudoalcaligenes NP103 and P. aeruginosa N6P6 respectively (UVR exposure of 5 sec). The survival upon exposure to different UV dosage was studied spectrophotometrically. 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, optimum growth and survival was observed at pH 7. The preliminary findings suggest that pH has a crucial role in DNA repair system and response varies with bacterial species. Decline in ocean water pH from current pH 8.2-8.4 is expected to affect the survival of marine bacteria upon UV damage in some bacterial groups