(641a) Pseudomonas Sp. ADP Biofilms: Differentiation of Expression in Atrazine-Degrading Genes and Lectin Binding Analysis | AIChE

(641a) Pseudomonas Sp. ADP Biofilms: Differentiation of Expression in Atrazine-Degrading Genes and Lectin Binding Analysis

Authors 

Delcau, M. - Presenter, University of Iowa
Peeples, T. L., University of Iowa
Atrazine, the second most used herbicide in the United States, frequently contaminates soil and groundwater. This pollutant exceeds the maximum contaminant level set by the Environmental Protection Agency of 3 parts per billion in many water sources throughout the Midwest. A proficient alternative to physio-chemical remediation methods relies on enzymes within microbes to perform biotransformations on recalcitrant compounds to innocuous chemicals in a process known as bioremediation. Pseudomonas sp. ADP, a strain capable of degrading atrazine, completely mineralizes the contaminant into ammonia and carbon dioxide following a six-step catabolic pathway. Each enzyme, AtzA-AtzF, catalyzes the biotransformation of atrazine into various compounds, including cyanuric acid and urea.

Despite extensive studies on genetic expression and the biocatalytic capabilities of the strain Pseudomonas sp. ADP in the planktonic mode of growth, little has focused on the sessile lifestyle of the same strain as a biofilm. Biofilms demonstrate great promise is remediation efforts due to the presence of a self-secreted extracellular polymeric matrix for protection from the environment, increased genetic variation due to horizontal gene transfer, and high frequency of cell-to-cell communication via quorum sensing. Reverse transcription real time quantitative polymerase chain reaction was used to determine the differential expression of each atrazine-degrading gene in Pseudomonas sp. ADP cells grown as a biofilm and as planktonic cells. Genes AtzB, AtzC, AtzD, AtzE, and AtzF demonstrated an increase in expression in a sessile lifestyle relative to planktonic cells, conceivably indicating higher metabolic activity of the atrazine-degrading enzymes in the six-step pathway.

Pseudomonas sp. ADP biofilms were grown in a drip-flow reactor at various temperatures to establish differential expression of atrazine-degrading genes. Decreased expression for genes AtzA, AtzB, and AtzC and increases in expression for genes AtzD, AtzE, and AtzF were observed for biofilms grown at higher temperatures. These results give an increased understanding on assessing temperature-dependence of gene activity in strains capable of degrading recalcitrant compounds. Additionally, to further characterize the biofilms, the sugar moieties were identified and compositions were determined using fluorescent lectin binding analysis (FLBA) and laser scanning confocal microscopy. The results of these studies will help further knowledge on the application of biofilms in industrial remediation and other biocatalytic processes.