A Dual Stressor System Negatively Impacts In vivo Luminescence from Bioluminescent Bacteria

Cellular health requires an intricate balance of prooxidants and antioxidants. Enzymatic and non-enzymatic molecules that maintain this balance succumb to oxidative insults beyond certain levels. Therefore, it becomes necessary to probe cellular health through the estimation of antioxidant enzymes/ molecules, NADH/NAD⁺ and GSH/GSSG inside a viable cell. This approach demands skilled personnel, considerable time, expensive kits, and reagents. Therefore, there is a search for potent alternatives that can precisely estimate cellular health in real time. In the present study, we exposed bioluminescent bacteria (BB, OD₆₀₀: 0.1) to model prooxidants, viz. H₂O₂ and Hg (II) at different concentrations to study in vivo luminescence kinetics under nutrient-rich (cultivation media: Luria-Bertani broth, 2.5 %, and NaCl, 1.5 %) and nutrient-starved conditions (2.5 % NaCl). Further, we investigated the effect of a dual stressor system at low-dose (10 μL Hg (II) at 1.00 ppm in the presence of 10 μL of 10 ppm H₂O₂) on luminescence response from a cell suspension of BB (50 μL, OD₆₀₀: 0.1). The results showed that luminescence recovery in BB was delayed as the concentration of stressors increased. Moreover, a low-dose stimulatory effect (enhanced luminescence) was observed when Hg(II) at 0.142 ppm was exposed individually but in presence of H₂O₂ at 1.42 ppm were inhibitory.