MOLECULAR-BASIS OF A BACTERIAL CONSORTIUM - INTERSPECIES CATABOLISM OF ATRAZINE

Pseudomonas sp. strain ADP contains the genes, atzA, -B, and -C, that encode three enzymes which metabolize atrazine to cyanuric acid, Atraz ine-catabolizing pure cultures isolated from around the world contain genes homologous to atzA, -B, and -C. The present study was conducted to determine whether the same genes are present in an atrazine-catabol izing bacterial consortium and how the genes and metabolism are subdiv ided among member species. The consortium contained four of more bacte rial species, but two members, Clavibacter michiganese ATZ1 and Pseudo monas sp. strain CN1, collectively mineralized atrazine, C. michiganes e ATZ1 released chloride from atrazine, produced hydroxyatrazine, and contained a homolog to the atzA gene that encoded atrazine chlorohydro lase. C. michiganese ATZ1 stoichiometrically metabolized hydroxyatrazi ne to N-ethylammelide and contained genes homologous to atzB and atzC, suggesting that either a functional AtzB or -C catalyzed N-isopropyla mine release from hydroxyatrazine. C. michiganese ATZ1 grew on isoprop ylamine as its sole carbon and nitrogen source, explaining the ability of the consortium to use atrazine as the sole carbon and nitrogen sou rce, A second consortium member; Pseudomonas sp, strain CN1, metaboliz ed the N-ethylammelide produced by C. michiganese ATZ1 to transiently form cyanuric acid, a reaction catalyzed by AtzC. A gene homologous to the atzC gene of Pseudomonas sp. strain ADP was present, as demonstra ted by Southern hybridization and PCR. Pseudomonas sp. strain CN1, but not C. michiganese, metabolized cyanuric acid. The consortium metabol ized atrazine faster than did C. michiganese individually. Additionall y, the consortium metabolized a much broader set of triazine ring comp ounds than did previously described pure cultures in which the atzABC genes had been identified, These data begin to elucidate the genetic a nd metabolic bases of catabolism by multimember consortia.