Sunday, July 29, 2007
P73

Growth characteristics of an atrazine-degrading consortium of bacteria

Susan M. Adams, Lisa J. Broadhurst Brindel, and George E. Pierce. Biology, Georgia State University, 24 Peachtree Center Ave., Atlanta, GA 30303

Atrazine is currently the most commonly used herbicide in the United States (2 billion kg/year).  Use of atrazine has resulted in contaminated soils and groundwaters on a scale that exceeds EPA limits.  Additionally, there is evidence that atrazine is capable of prolonged environmental persistence.  It is well documented that selected microorganisms in pure culture are capable of partially degrading atrazine via N-dealkylation: a process that is somewhat hindered in nature.  By using a consortium of bacteria containing atrazine-degrading genes, it is possible to completely degrade the herbicide to cyanuric acid, then to urea, and finally to ammonia.  Initial methods evaluating the effectiveness of this mixed consortium, consisting of Variovox paradoxus, Ralstonia sp., Pseudomonas putida, Raoultella terrigina, and Shingobium yankoikuyae, involved measuring growth (OD600) of individual strains (pre-induced with 1000ppm atrazine and non-induced controls) utilizing atrazine or pathway intermediates as sole carbon sources.  Doubling time for non-induced strains was greater than 72 hours, except for S. yankoikuyae, which doubled in 24 hours when grown on atrazine or both atrazine and cyanuric acid: comparable with its growth rate on glucose.  Induction with atrazine resulted in an increased growth rate for all cultures with the exceptions of P. putida, which grew slowly even on glucose, and S. yankoikuyae, which grew more rapidly without being pre-exposed to atrazine.  Preliminary results suggest that S. yankoikuyae acts near the beginning of the atrazine degradation pathway, other strains in the consortium act upon intermediates, while the primary role of P. putida may occur later in the pathway.

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