Advances on using a bioluminescent microbial biosensor to detect bioavailable Hg (II) in real - Review

Review:

Advances on using a bioluminescent microbial biosensor to detect bioavailable Hg (II) in real samples (by: G. S. Costa, A. M. Salgado, P. R. G. Barrocas)

This reviews the use of microbial biosensor in detecting bioavailable mercury. Ever since the industrial revolution, trace metal pollutants has accumulate progressively in the natural ecosystem, one of which is mercury (Hg). Due to the influence of anthropogenic activities and indiscriminate use by men, the normal traces of Hg in ecosystem increase and deaths have already been reported upon consumption of contaminated aquatic organism. There are various types of Hg base on forms and chemical species so it is important to determine its bioavailability and toxicity. Traditional analytical method does not distinguish bioavailable species to inert ones, so biosensors are used as an alternative analysis device to diagnose environmental condition because of its sensitivity, selectively and relatively low cost. New biosensors use microbial sensors like the use of luminescence. The main objective of the study is to investigate and apply genetically engineered E. coli MC1061 and a luminometer as the biological element and the transducer respectively to detect Hg concentration.

 The method of the study revolved around the addition of Hg into the agar mediums prepared. The LB medium was used in the form of agar or broth. The independent variables measured were the cell concentration and mercury concentration. All experiments were performed on three time frames (20, 45 and 60 minutes). Calibration of Hg concentration standard was also followed. Complex environmental samples were studied as well (i.e. landfill slurries). Luminometer was used to detect the luminescence of the bacteria upon the addition of Hg. Moreover, bioassays were obtained from after cell growth at 150 rpm and 30 º C. Concentration was measured through the dry weight. The medium where the bacteria are grown are controlled with specific conditions for the detection of mercury.

            Results show that only M9NO₃ medium showed significant results from 20 to 45 minutes. Th4 coefficient determination (R2) adjusted for M9NO3 using 20 minutes was 51.30%, while for

45 minutes, R2 was 93.96%. At the three locations identified, the bioluminescent bacteria showed high specificity in the detection of mercury (Hg) at controlled samples. The study concluded that bioluminescent biosensor has a high potential on the detection of bioavailable mercury and other complex environmental samples.

            All in all, the researcher was successful in using the bioluminescent biosensor in detecting Hg concentration because the luminescence of the bacteria reflected the amount of concentration of Hg. A decrease of luminescence is equal to increased Hg; he was able to recommend it as a detector of other complex environmental samples as well.