Isolation and characterization of marine bioluminescent bacteria for toxicity bioassays and biotechnological applications

Toxic heavy metals pollution posed severe health hazards to the environment and biodiversity. Therefore, the development of rapid and non-invasive bioassays is in the race to monitor toxic chemicals using novel approaches. This study isolated and characterized an intense blue luminescence-producing marine bacteria, Vibrio campbellii STF1, for biosensing applications. Species-level identification of this strain was confirmed based on various phenotypic tests and multilocus sequence approach using 16s rRNA, toxR, and luxA gene sequence analysis. Fatty acid methyl ester analysis revealed the presence of three predominant fatty acids C15:0 anteiso (21.73%), C17:0 anteiso (11.27%), and C19:0 anteiso (9.08%) in STF1. Luciferase enzyme from V. campbellii STF1 was extracted, partially purified, and molecular masses (alpha subunit 40 kDa and beta subunit 37 kDa) were determined by SDS-PAGE gel for in vivo assays. MALDI-TOF-MS analysis of V. campbellii cells’ protein extracts showed distinct mass spectral peaks at m/z of 2615, 3948, and 4232 da. V. campbellii STF1 is resistant to heavy metal lead, while other metals such as cadmium, copper, and mercury inhibited its growth and luminescence. Crude ethyl acetate extraction of V. campbellii demonstrated antibacterial activity against Shigella dysenteriae type 5 with a maximum inhibition zone of 27.0±1.0 mm.