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Application of single‐ and multiphasic michaelis‐menten kinetics to predictive modeling for aquatic ecosystems
Author(s) -
Lewis David L.,
Holm Harvey W.,
Hodson Robert E.
Publication year - 1984
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620030406
Subject(s) - microcosm , pollutant , michaelis–menten kinetics , environmental chemistry , aquatic ecosystem , kinetics , population , biochemical engineering , transformation (genetics) , enzyme kinetics , adaptation (eye) , chemistry , environmental science , ecology , biology , biochemistry , enzyme , enzyme assay , physics , demography , quantum mechanics , neuroscience , sociology , active site , engineering , gene
The transport, fate and effects of many toxic chemicals in aquatic ecosystems are largely mediated by microbial transformations. In our research, we have assumed that the transformations are a result of enzymatic reactions, and thus follow Michaelis‐Menten kinetics. Using diverse field‐collected and laboratory microcosm microbiota, we obtained sufficient experimental data to reach some general conclusions concerning the strengths and weaknesses of using Michaelis‐Menten kinetics in making environmental predictions. We concluded that this approach is best suited to predicting microbial transformations for pollutant concentrations of approximately 10 −7 M or lower. The approach also is applicable to high pollutant concentrations (saturated systems), provided that toxic effects of the pollutant and adaptation are considered. Unfortunately, most experiments have been conducted in the upper 10 −7 to 10 −4 M pollutant concentration range, which may approach saturation for a portion of enzymatic systems in a mixed population. This range is ideal for analytical purposes, but could be confounded by mixed‐order and multiphasic kinetics, toxic effects of the pollutant and adaptation. Adaptation, mass‐transport effects, multiphasic kinetics of pollutant uptake and transformation, and suppression of transformation by diauxie, biologically produced inhibitors, and other xenobiotic chemicals are some of the factors that we believe need to be more thoroughly evaluated to improve predictive modeling capabilities.