The present communication deals with construction of immobilized robust biophotonic bead using P. leiognathi, a marine luminescent bacterium for their possible application in monitoring of environmental toxicants. Immobilization efficiency of agar, carrageenan and sodium alginate was evaluated separately in terms of luminescence response and was recorded as 30.3, 77.4 or 99.5%, respectively. Under optimized storage conditions, the luminescent response of P. leiognathi in the immobilized state was studied over a period of 30 days. These biophotonic beads were further used as a rapid and reliable optical biosensing tool for the detection of heavy metals [Hg(II), As(V) or Cd(II)] and pesticide [2,4-dichlorophenoxyacetic acid (2,4-D)] in water systems. The concentration range for the detection of Hg(II), As(V), Cd(II) and 2.4-D was 2-32 ppm, 4-128 ppm, 16-512 ppm and 100-600 ppm, respectively, while corresponding sensitivity threshold was 2.0 ppm. 4.0 ppm. 16.0 ppm and 100 ppm. A comparison of inhibition constant (K-d)(or EC20) values indicated that the sensitivity thresholds rank as Hg(II) > As(V) > Cd(II) > 2.4-D. Moreover, the time taken for the detection of heavy metals and pesticide was less than 30 min. Using the bioluminescence inhibition method, the concentration of heavy metals and pesticide could be predicted. (c) 2012 Elsevier B.V. All rights reserved.