The effect of heavy metals on microbial alad δ-aminolevulinate dehidrataz)enzyme in contaminated environment

Delta-aminolevulinate dehydratase (ALAD) activity has been used in prokaryotesand eukaryotes as a biomarker for environmental lead (Pb) exposure and toxicity.Microorganisms are sensitive indicators of toxicity at the fundamental level ofecological organization, but bacterial biomarker studies are focused on thePseudomonas strains in Group I and E coli.The objectives of the present work were to determine if Burkholdoria gladiolibelonging to group II, due to its 16SrRNA similarity, can be used as biomarker inmetal contamination and compare its possible usage with Pseudomonasaeruginosa which are classified in Group I. and Citrobacter freundii (previouslyknown as Esherichia freundii and Bacterium freundii).iIn this study, ALAD activity in an environmental strains of Burkholdoria gladioli,Pseudomonas aeruginosa, Citrobacter freundii were investigated to evaluatepotential inhibition by Pb and other toxic metals.When the ALAD activity of Burkholdoria gladioli was tested, Co and Pbdecreased activity by %27, and %71, respectively. In addition to these findings,Zn increased the activity up to %26. These effects were found to be statisticallymeaningful (p<0.05). It was determined that the increase of lead concentrationinhibites the ALAD activity at each of the three strains. There was a statisticallysignificant dose-response relationship between ALAD activity in cells ofBurkholdoria gladioli and Pb. (Pearson correlation coefficent = -0.665; r2 = 0.665,and p<0.001). The strongest ALAD inhibition which was measured was 90% atBurkholdoria gladioli when protein extracts were incubated with 750µM of Pb.The relationship between Pb and ALAD activity was statistically described by[ALAD Activity] = 0.476-0.000597 x [Pb].According to the obtained results, we suggest that the ALAD of Burkholdoriagladioli can be used as a biomarker for lead contamination in the environment.2006, 54 PagesKeywords: ALAD, Pseudomonas, Biomarker, Lead, Metals, rRNA groupii