Bacterial Chemotaxis to Atrazine and Relateds-Triazines

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Abstract
Pseudomonassp. strain ADP utilizes the human-mades-triazine herbicide atrazine as the sole nitrogen source. The results reported here demonstrate that atrazine and the atrazine degradation intermediatesN-isopropylammelide and cyanuric acid are chemoattractants for strain ADP. In addition, the nonmetabolizeds-triazine ametryn was also an attractant. The chemotactic response to theses-triazines was not specifically induced during growth with atrazine, and atrazine metabolism was not required for the chemotactic response. A cured variant of strain ADP (ADP M13-2) was attracted tos-triazines, indicating that the atrazine catabolic plasmid pADP-1 is not necessary for the chemotactic response and that atrazine degradation and chemotaxis are not genetically linked. These results indicate that atrazine and relateds-triazines are detected by one or more chromosomally encoded chemoreceptors inPseudomonassp. strain ADP. We demonstrated thatEscherichia coliis attracted to thes-triazine compoundsN-isopropylammelide and cyanuric acid, and anE. colimutant lacking Tap (the pyrimidine chemoreceptor) was unable to respond tos-triazines. These data indicate that pyrimidines and triazines are detected by the same chemoreceptor (Tap) inE. coli. We showed thatPseudomonassp. strain ADP is attracted to pyrimidines, which are the naturally occurring structures closest to triazines, and propose that chemotaxis towards-triazines may be due to fortuitous recognition by a pyrimidine chemoreceptor inPseudomonassp. strain ADP. In competition assays, the presence of atrazine inhibited chemotaxis ofPseudomonassp. strain ADP to cytosine, and cytosine inhibited chemotaxis to atrazine, suggesting that pyrimidines ands-triazines are detected by the same chemoreceptor.

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