Abstract
Objectives: The current study focuses on the isolation of bioluminescent bacteria from the gut of Sea urchin and using its luminescence property as a potential biosensor for detecting chromium toxicity in water. Methodology: Bioluminescent bacteria, JAAKP J2 was isolated from the gut of Pseudoboletia indiana species of Sea urchin collected from Pondicherry university beach. The morphological, biochemical, enzyme profiling and molecular characterization through 16S sequencing were performed to identify the strain. Growth kinetic assays and spectrophotometric analysis under chromium stress condition were performed on bioluminescent strains for luminescence inhibition studies. The bioluminescent bacteria was then immobilized in nutrient agar cubesand used as a biosensor for the detection of hexavalent chromium concentration in water samples. Findings: The morphological, biochemical and molecular characterization revealed that the isolate JAAKP J2 was closely related to Vibrio campbellii. Industrially important enzymes like Protease, Lipase, Agarase, Cellulase, Xylanase and Gelatinase were also screened in this study. The developed biosensor using bioluminescence property of the isolate was able to detect the level of chromium toxicity in water samplesat concentration not more than 9 mg L-1 . Further we have elucidated a possible hypothetical pathway for reduction in luminescence property due to ROS (Reactive oxygen species) caused by hexavalent chromium toxicity in bacteria. Novelty: The study is first of its kind in isolation of bioluminescent strain from sea urchin and using it as a biosensor for heavy metal detection in water. Our study also throws lights on futuristic approach of detecting other heavy metals like lead, zinc, cadmium, mercury in water samples by bacterial luminescence. Keywords: Bioluminescent Bacteria, Biosensor, Chromium Toxicity, Enzyme Profiling, Sea Urchin
Highlights
Marine ecosystem forms the largest aquatic system in the world enclosing more than 70 percent of the planet
The heavy metal chromium is extensively being used in various industrial processes and is generally discharged into the natural water sources
Through our growth kinetic studies it is evident that Vibrio campbellii is capable of producing luminescence at the stationary phase of its growth cycle
Summary
Marine ecosystem forms the largest aquatic system in the world enclosing more than 70 percent of the planet. Most marine bacteria are halophiles which thrive in extreme salt conditions in a much broader way than other life forms[1]. Vibrios are generally salt loving with different species opting for different concentration of salt requirements[2]. The purpose ofproducing bioluminescence varies from organism to organism, generally as a defense mechanism, predation or mating etc[3]. Bioluminescent bacteria are commonly found in ocean water,there they generally prevails in the digestive tracts of marine fishes, persist as parasites in crustaceans and insects or as light organ symbionts in teleost fishes and squids[4]. The major organisms capable of exhibitingbioluminescence comprises of four bacterial genera: Vibrio, Photobacterium, Shewanella, and Photorhabdus[5]. The members of Vibrionaceae are well documented for understanding the underlying mechanism of bacterial bioluminescence[7]
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