Dataset Information

Identification of wastewater bacteria involved in the degradation of triclocarban and its non-chlorinated congener.

ABSTRACT: Triclocarban (TCC) is an antimicrobial additive of personal care products that is only partially degraded during wastewater treatment. Bacteria responsible for its transformation are unknown. We obtained wastewater bacteria capable of using as the sole carbon source TCC or its non-chlorinated analog, carbanilide (NCC). Enrichments established using activated sludge amended with TCC and NCC, respectively, were maintained for 1 year through successive transfers. Enrichments displayed exponential growth after 2 weeks, reaching stationary phase after 1 month. The NCC enrichment was shown to accumulate aniline. Denaturing gradient gel electrophoresis of amplified 16S rRNA genes indicated markedly reduced community richness compared to the inoculum and a single, prominent taxonomic unit emerged in both chlorinated and non-chlorinated carbanilide enrichment cultures. Cloned 16S rRNA genes showed both enrichments were dominated by a single genotype related to uncharacterized organisms within the Alcaligenaceae. Of ?30 sequences from each enrichment, no other organisms were detected in the TCC enrichment while, a small, flanking community of alpha proteobacteria was detected in the NCC enrichment. Study results demonstrate that growth of wastewater bacteria on TCC and its lower chlorinated analog can be linked to bacteria within the family Alcaligenaceae. These organisms are promising agents for the bioremediation of hazardous phenylurea pollutants.

SUBMITTER: Miller TR

PROVIDER: S-EPMC2939305 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Identification of wastewater bacteria involved in the degradation of triclocarban and its non-chlorinated congener.

Miller Todd R TR Colquhoun David R DR Halden Rolf U RU

Journal of hazardous materials 20100730 1-3

Triclocarban (TCC) is an antimicrobial additive of personal care products that is only partially degraded during wastewater treatment. Bacteria responsible for its transformation are unknown. We obtained wastewater bacteria capable of using as the sole carbon source TCC or its non-chlorinated analog, carbanilide (NCC). Enrichments established using activated sludge amended with TCC and NCC, respectively, were maintained for 1 year through successive transfers. Enrichments displayed exponential g ...[more]

PMID: 20727675

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Project description:Triclocarban (TCC), a formerly used disinfectant, kills bacteria via an unknown mechanism of action. A structural hallmark is its N,N'-diaryl urea motif, which is also present in other antibiotics, including the recently reported small molecule PK150. We show here that, like PK150, TCC exhibits an inhibitory effect on Staphylococcus aureus menaquinone metabolism via inhibition of the biosynthesis protein demethylmenaquinone methyltransferase (MenG). However, the activity spectrum (MIC90) of TCC across a broad range of multidrug-resistant staphylococcus and enterococcus strains was much narrower than that of PK150. Accordingly, TCC did not cause an overactivation of signal peptidase SpsB, a hallmark of the PK150 mode of action. Furthermore, we were able to rule out inhibition of FabI, a confirmed target of the diaryl ether antibiotic triclosan (TCS). Differences in the target profiles of TCC and TCS were further investigated by proteomic analysis, showing complex but rather distinct changes in the protein expression profile of S. aureus Downregulation of the arginine deiminase pathway provided additional evidence for an effect on bacterial energy metabolism by TCC.IMPORTANCE TCC's widespread use as an antimicrobial agent has made it a ubiquitous environmental pollutant despite its withdrawal due to ecological and toxicological concerns. With its antibacterial mechanism of action still being unknown, we undertook a comparative target analysis between TCC, PK150 (a recently discovered antibacterial compound with structural resemblance to TCC), and TCS (another widely employed chlorinated biphenyl antimicrobial) in the bacterium Staphylococcus aureus We show that there are distinct differences in each compound's mode of action, but also identify a shared target between TCC and PK150, the interference with menaquinone metabolism by inhibition of MenG. The prevailing differences, however, which also manifest in a remarkably better broad-spectrum activity of PK150, suggest that even high levels of TCC or TCS resistance observed by continuous environmental exposure may not affect the potential of PK150 or related N,N'-diaryl urea compounds as new antibiotic drug candidates against multidrug-resistant infections.

Project description:The topical antiseptic agent triclocarban (TCC) is a common additive in many antimicrobial household consumables, including soaps and other personal care products. Long-term usage of the mass-produced compound and a lack of understanding of its fate during sewage treatment motivated the present mass balance analysis conducted at a typical U.S. activated sludge wastewater treatment plant featuring a design capacity of 680 million liters per day. Using automated samplers and grab sampling, the mass of TCC contained in influent, effluent, and digested sludge was monitored by isotope dilution liquid chromatography (tandem) mass spectrometry. The average mass of TCC (mean +/- standard deviation) entering and exiting the plant in influent (6.1 +/- 2.0 microg/L) and effluent (0.17 +/- 0.03 microg/ L) was 3737 +/- 694 and 127 +/- 6 g/d, respectively, indicating an aqueous-phase removal efficiency of 97 +/- 1%. Tertiary treatment by chlorination and sand filtration provided no detectable benefit to the overall removal. Due to strong sorption of TCC to wastewater particulate matter (78 +/- 11% sorbed), the majority of the TCC mass was sequestered into sludge in the primary and secondary clarifiers of the plant. Anaerobic digestion for 19 days did not promote TCC transformation, resulting in an accumulation of the antiseptic compound in dewatered, digested municipal sludge to levels of 51 +/- 15 mg/kg dry weight (2815 +/- 917 g/d). In addition to the biocide mass passing through the plant contained in the effluent (3 +/- 1%), 76 +/- 30% of the TCC input entering the plant underwent no net transformation and instead partitioned into and accumulated in municipal sludge. Based on the rate of beneficial reuse of sludge produced by this facility (95%), which exceeds the national average (63%), study results suggest that approximately three-quarters of the mass of TCC disposed of by consumers in the sewershed of the plant ultimately is released into the environment by application of municipal sludge (biosolids) on land used in part for agriculture.

Dataset Information

Identification of wastewater bacteria involved in the degradation of triclocarban and its non-chlorinated congener.

Publications

Identification of wastewater bacteria involved in the degradation of triclocarban and its non-chlorinated congener.

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