Correlation of NE 1545 Expression and Cell Size in Nitrosomonas europaea Exposed to Aromatic Hydrocarbons Caslin Gilroy Dr. Lewis Semprini Environmental Engineering

N. europaea Wastewater Treatment Plant

The process of nitrification exhibited by N. europaea is represented by the following reactions: 2H + + 2e - + NH 3 + O 2  NH 2 OH + H 2 O This step is catalyzed by the enzyme AMO H 2 O + NH 2 OH  NO H + + 4e - This step is catalyzed by the enzyme HAO Notice that there is a net gain of two electrons, which are used by the bacteria for energy

Why is this bacterium important? N. europaea prevents eutrophication in wastewater treatment plants.

Causes of Inhibition in Ammonia Oxidation N. europaea is very sensitive to common inhibitors (CN, heavy metals, pH shifts, and organics). Currently can monitor chemical inhibition, but cannot determine cause. Therefore cannot neutralize inhibitors and wastewater treatment plant failure can occur.

Solution Want to be able to detect nitrification inhibition AND determine cause of inhibition. Do this by identifying genes expressed in response to specific inhibitors. Create a biosensor to detect N. europaea’s gene expression and link expression to specific chemical contamination.

Shift in Cell Membrane Structure Membrane thickness decreased from nm to nm Control 40  M Benzene

Possible Biosensor Gene Identified NE 1545 linked to cell membrane size and organic compound exposure. Hypotheses:  Increased expression of NE 1545 is correlated with exposure to certain aromatic hydrocarbons.  Exposure to these hydrocarbons is correlated with a decrease in membrane thickness.

Batch Experiments

Nitrite Assay

Membrane Stability

Future Study Continued experimentation with NE 1545 to determine if it is an effective sentinel gene for our biosensor.

Acknowledgements Howard Hughes Medical Institute Dr. Lewis Semprini Dr. Tyler Radniecki Dr. Kevin Ahern