BIOLUMINESCENCE INDUCTION RESPONSE AND SURVIVAL OF THE BIOREPORTER BACTERIUM PSEUDOMONAS-FLUORESCENS HK44 IN NUTRIENT-DEPRIVED CONDITIONS

Pseudomonas fluorescens HK44 is a bioluminescent bioreporter synthesiz ing light in the presence of naphthalene or salicylate. Upon immobiliz ation, HK44 is useful as an in situ or on-line biosensor of bioavailab le naphthalene and salicylate in waste streams or contaminated fields, The bioreporting efficacy of alginate/SrCl2-immobilized HK44 was inve stigated in simulated groundwater with different pH regimes. When indu ced with complex (salicylate plus auxiliary energy supplements) and si mple (salicylate as the sole energy supplement) inducer solutions, the specific light response was steadier at pH 6 than at pH 7 in a 35-day study. There was no bioluminescence response from cells incubated in groundwater samples with pH below 6. The rate of the luminescence reac tion was stable at pH 6 irrespective of the type of inducer solution, indicating the robust physiological status of the bioreporter bacteria . In addition, the quantity of light synthesized was at least one orde r of magnitude higher with complex inducer solution than with simple i nducer solution. The numbers of viable and cultivable cells remained c onstant in groundwater at pH 6 and 7 (approx. 10(7) g(-1) beads). The numbers decreased by four orders of magnitude (10(7) to 10(3)) to zero in groundwaters with pH below 6. This study suggested that HK44 is us eful for long-term biosensor applications in moderately acidic to neut ral groundwater conditions.