Biodegradation of triclosan by a wastewater microorganism.
Triclosan, a synthetic antimicrobial agent, has been considered as an emerging environmental contaminant. Here we reported a triclosan-degrading wastewater bacterial isolate, Sphingopyxis strain KCY1, capable of dechlorinating triclosan with a stoichiometric release of chloride. The stain can degrade diphenyl ether but not 2,4,4'-tribromodiphenyl ether and 2,2',4,4'-tetrabromodiphenyl ether, despite all these three compounds are structurally similar to triclosan. While strain KCY1 was unable to grow on triclosan and catechol, it could grow with glucose, sodium succinate, sodium acetate, and phenol. When grown with complex nutrient medium containing a trace amount of triclosan (as low as 5 μg/L), the strain could retain its degradation ability toward triclosan. The maximum-specific triclosan degradation rate (q(m)) and the half-velocity constant (K(m)) are 0.13 mg-triclosan/mg-protein/day and 2.8 mg-triclosan/L, respectively. As triclosan degradation progressed, five metabolites were identified and these metabolites continue to transform into non-chlorinated end products, which was supported by a sharp drop in androgenic potential. The activity of catechol 2,3-dioxygenase in the cell extract was detected. No triclosan degradation was observed in the presence of 3-fluorocatechol, an inhibitor of meta-cleavage enzyme, suggesting that triclosan degradation proceed via meta-cleavage pathway. Based on all the observations, a degradation pathway for triclosan by strain KCY1 was proposed.
Department of Civil Engineering, Texas A&M University, 205G WERC, 3136 TAMU College Station, TX 77843-3136, USA.
Do Gyun
DG
Lee
Fuman
F
Zhao
Yohannes H
YH
Rezenom
David H
DH
Russell
Kung-Hui
KH
Chu
D001673:Biodegradation, Environmental; D050557:Catechol 2,3-Dioxygenase / Q000378:metabolism; D002396:Catechols / Q000737:chemistry / Q000378:metabolism; D002712:Chlorides / Q000737:chemistry / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D055768:Halogenated Diphenyl Ethers; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D019800:Phenol / Q000378:metabolism; D010647:Phenyl Ethers / Q000737:chemistry / Q000378:metabolism; D011075:Polybrominated Biphenyls / Q000737:chemistry / Q000378:metabolism; D019346:Sodium Acetate / Q000378:metabolism; D042301:Sphingomonadaceae / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism; D014260:Triclosan / Q000737:chemistry / Q000378:metabolism*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism*
D002396:Catechols; D002712:Chlorides; D055768:Halogenated Diphenyl Ethers; D010647:Phenyl Ethers; D011075:Polybrominated Biphenyls; D013386:Succinates; D014874:Water Pollutants, Chemical; C511295:2,2',4,4'-tetrabromodiphenyl ether; D019800:Phenol; C031538:phenyl ether; D019346:Sodium Acetate; D014260:Triclosan; D050557:Catechol 2,3-Dioxygenase; D005947:Glucose; C034221:catechol