Acute Osmotic and pH Shock to Bioluminescent Bacteria Is Reversible in Terms of Luminescence Response

Bioluminescence inhibition (BLI) measurements in bioluminescent bacteria (BB) is perceived as a potential qualitative and quantitative indicator of hazardous materials. Acute but minor fluctuations in osmolarity and pH do not affect the living systems significantly. However, significant BLI is observed from marine BB due to acute osmolarity or pH changes that may affect the bioassay sensitivity. Often, real samples have low pH and osmolarity, interfering with the hazard assessment based on the principles of BLI. This anomaly in BLI measurements may lead to false positives. Therefore, modifications in existing analytical methods to overcome such practical constraints are envisaged. In the present research, a marine BB was utilized to study the luminescence reversal effect when exposed to stressful environments such as hypotonic (deionized water), acidic (50 μM to 50 mM HCl), and 0.1-100 ppm of Hg(II) for 0-30 min. Postincubation, the calcium alginate immobilized bioluminescent bacteria (biophotonic beads) were transferred to Boss media to observe any luminescence enhancement. The results showed that osmotic shock and low-strength acidic environments (50 μM to 0.5 mM HCl) at specified incubation times were not detrimental to the biophonic beads regarding luminescence response.