Atrazine, a triazine class herbicide, frequently contaminates ground water and drinking water in the United States above the maximum contaminant level set by the Environmental Protection Agency of 3 parts per billion. Bioremediation, a novel approach to removing recalcitrant pollutants such as atrazine by microbial action, is considered as a cost-efficient and environmentally alternative method to traditional physio-chemical based remediation techniques. The model strain, Pseudomonas sp. ADP, is able use atrazine as a nitrogen source for survival and growth, and sequentially degrade the compound via a catabolic pathway. All genes in the catabolic pathway, AtzA – AtzF, are contained on a single 108-kb plasmid and encode for enzymes that mineralize atrazine into carbon dioxide and ammonia. Due to its complex heterogeneous structure, thick extracellular matrix, and increased transfer rates of genetic material, biofilms are explored as more efficient degraders of atrazine relative their planktonic counterparts. Genetic and chemical data was collected to determine the relative efficiency of atrazine degradation between Pseudomonas sp. ADP biofilms and planktonic cells. Biofilms were further probed by varying temperature of growth, and age of film. Real time reverse transcription quantitative PCR was used to determine the relative fold change in expression of each gene in strains’ catabolic pathway by mode of growth, biofilm growth temperature, and biofilm age. Complementarily, gas chromatographic data was collected to determine the temporal degradation of atrazine by Pseudomonas sp. ADP biofilms. Genes encoding for the enzymes AtzB-AtzF were upregulated in the biofilm mode of growth relative to planktonic cells. An increase in temperature of biofilm growth to 37oC significantly altered expression: AtzA, AtzB, an AtzC were down-regulated while AtzD, AtzE, and AtzF were upregulated. Chemical analysis demonstrated different degradation patterns of atrazine depending on the mode of bacterial growth. Our results suggest biofilms may be bacterial structures worth employing for remediation.

Temporal and temperature-dependence on expression of Atrazine-degrading genes in Pseudomonas sp. ADP biofilms

253rd National Meeting (2017)

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