Utra Violet Radiation Essay -- Environment, Purple Violet Pigment, Pho

Protection against solar UV radiations in organisms includes production of secondary metabolites such as pigments that can absorb UV and visible light. In this study, vioA gene coding for tryptophan 2-monooxygenase involved in the biosynthetic pathway of violacein-like purple violet pigment (PVP) was cloned and sequenced from an Antarctic bacterium Janthinobacterium sp. Ant5-2. A non-pigmented vioA mutant strain was obtained following mini-Tn10 transposon mutagenesis that produced a lesser amount of extrapolymeric substances (EPS) and exhibited a compromised survival to freeze-thaw cycles at 4ËšC. Survival of vioA mutant strain during exponential and stationary growth phase was significantly reduced when exposed to UVB (320 nm) and UVC (254 nm) (dose range: 0-300 J/m ²) light. Decreased viability of the mutant strain was noticed at 4ËšC upon nutrient deprivation and exposure to UV light. The pigment production was augmented in surviving cells following increased doses of both UVB and UVC. Interestingly, at higher doses i.e. 100 and 300 J/m ², pigmented wild-type strain showed better survival to harmful UVC than UVB. This could be attributed to the pigment structure, which has absorption maxima in the visible (575 nm) as well as in the UVC (270 nm) range. In conclusion, this study defines the photoprotective role of the PVP in Janthinobacterium sp. Ant5-2 against UV radiation using single gene mutation. Perhaps the photoprotective role of PVP in this bacterium is one of the key adaptive features that define their survival in Antarctic extreme conditions, especially during austral summer months. INTRODUCTION The high energy photons in solar UV radiation are considered to be the most damaging component to the biological macromolec... ...x, which is involved in quorum sensing mediated biofilm formation (Morohoshi et al., 2010). Therefore, it is likely that loss of vioA has affected the biofilm formation in Ant5-2. Moreover, colony morphology demonstrated that PVP had substantial effect on the structural organization of colony biofilms (Fig. 4). The mechanisms whereby pigment production control colony morphology and EPS production is likely to be a complex issue yet to be determined (Dietrich et al., 2008). Until recently, the potential role of pigments as secondary metabolites modulating the cellular physiology of microorganisms in extreme environments has been neglected (Hernandez & Newman, 2001). This study provides an evidence for the role of PVP as a secondary metabolite in UV resistance and suggests its functions of primary importance in Ant5-2 residing in Antarctic extreme conditions.