Inhibitory and bioassay response of nitrifying bacteria
Abstract
Bacterial bioassay strategies have recently drawn an escalating level of technical interest given their expected ease of use, response sensitivity, and cost effectiveness. Four strategies are cited in the literature, including two mixed (i.e., aerobic heterotrophs and methanogens) and two specific (i.e., Vibrio fischeri and nitrifiers) culture methods. The latter genus-specific options have an inherent advantage in terms of their apparent reproducibility. Indeed, the Vibrio-based procedure (MicrotoxTM) is now widely applied as an analytical bioassay procedure. Unfortunately, though, the current sensitivities with most of these tests are typically cited at or above multiple-ppm levels. This research effort, therefore, attempted to improve upon this sensitivity with an advanced, respirometric-based procedure based on nitrifying bacteria. Seventeen organic chemicals and seven inorganic chemicals were tested using this new method. This so-called Nitrotox procedure, indeed, proved to be reproducibly more sensitive; for example, IC50 values of 0.20 mg/l for phenol, 0.3 mg/l for benzene, and 0.88 mg/l for chlorobenzene were identified. Improvements in sensitivity were also observed with cadmium, nickel, zinc, and cyanide; chromium and copper, though, actually showed lower toxicities. QSAR relationships were also developed for two classes (i.e., phenolic and benzene-related compounds) of chemicals using logKow as the key parameter. Successful QSARs were obtained for the phenol/chlorophenol group with a correlation coefficient of 0.99. A comparison of QSARs with Nitrotox and literature data (i.e., for MicrotoxTM and Nitrosomonas ) demonstrated the potential advantages of this new Nitrotox test. Overall, this improved method for nitrifier bioassay testing has several apparent attributes, in that it is not only simple and sensitive, but also rapid and inexpensive.
Degree
Ph.D.
Advisors
Alleman, Purdue University.
Subject Area
Environmental engineering|Toxicology|Microbiology|Environmental science
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