Triclosan enriches for<i>Dehalococcoides</i>-like<i>Chloroflexi</i>in anaerobic soil at environmentally relevant concentrations

Krzmarzick, Mark J.

doi:10.1111/1574-6968.12153

Cited by 34 publications

(20 citation statements)

References 27 publications

(33 reference statements)

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“…Custom R scripts were used to perform dual hierarchal clustering (utilizing R commands hclust of covariance, heatmap, and gplots library) and nonmetric multidimensional scaling (nMDS) of anaerobic community sequence data gathered from Illumina. (31) …”

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Triclocarban Influences Antibiotic Resistance and Alters Anaerobic Digester Microbial Community Structure

Carey

Zitomer

Hristova

et al. 2015

Environ. Sci. Technol.

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Triclocarban (TCC) is one of the most abundant organic micropollutants detected in biosolids. Lab-scale anaerobic digesters were amended with TCC at concentrations ranging from the background concentration of seed biosolids (30 mg/kg) to toxic concentrations of 850 mg/kg to determine the effect on methane production, relative abundance of antibiotic resistance genes, and microbial community structure. Additionally, the TCC addition rate was varied to determine the impacts of acclimation time. At environmentally relevant TCC concentrations (max detect = 440 mg/kg), digesters maintained function. Digesters receiving 450 mg/kg of TCC maintained function under gradual TCC addition, but volatile fatty acid concentrations increased, pH decreased, and methane production ceased when immediately fed this concentration. The concentrations of the mexB gene (encoding for a multidrug efflux pump) were higher with all concentrations of TCC compared to a control, but higher TCC concentrations did not correlate with increased mexB abundance. The relative abundance of the gene tet(L) was greater in the digesters that no longer produced methane, and no effect on the relative abundance of the class 1 integron integrase encoding gene (intI1) was observed. Illumina sequencing revealed substantial community shifts in digesters that functionally failed from increased levels of TCC. More subtle, yet significant, community shifts were observed in digesters amended with TCC levels that did not inhibit function. This research demonstrates that TCC can select for a multidrug resistance encoding gene in mixed community anaerobic environments, and this selection occurs at concentrations (30 mg/kg) that can be found in full-scale anaerobic digesters (U.S. median concentration = 22 mg/kg, mean = 39 mg/kg).

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confidence: 99%

Triclocarban Influences Antibiotic Resistance and Alters Anaerobic Digester Microbial Community Structure

Carey

Zitomer

Hristova

et al. 2015

Environ. Sci. Technol.

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“…Research to date has largely focused on organohalide respirers that dechlorinate anthropogenic pollutants and, in particular, on Dehalococcoides mccartyi, largely because of its ability to dechlorinate a large number of pollutants (14,15,16,17). Recently, several organohalide respirers have been detected in uncontaminated soils and sediments (18,19,20), and Dehalococcoides-like bacteria have been reported to grow in response to the amendment of enzymatically produced organochlorines (18). Nevertheless, there remains much about organohalide respiration that is unknown, particularly with respect to organisms whose niche lies in uncontaminated environments.…”

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Novel Firmicutes Group Implicated in the Dechlorination of Two Chlorinated Xanthones, Analogues of Natural Organochlorines

Krzmarzick

Miller

Yan

et al. 2014

Appl Environ Microbiol

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bAlthough the abundance and diversity of natural organochlorines are well established, much is still unknown about the degradation of these compounds. Triplicate microcosms were used to determine whether, and which, bacterial communities could dechlorinate two chlorinated xanthones (2,7-dichloroxanthone and 5,7-dichloro-1,3-dihydroxylxanthone), analogues of a diverse class of natural organochlorines. According to quantitative-PCR (qPCR) results, several known dechlorinating genera were either not present or not enriched during dechlorination of the xanthones. Denaturing gradient gel electrophoresis, however, indicated that several Firmicutes were enriched in the dechlorinating cultures compared to triplicate controls amended with nonchlorinated xanthones. One such group, herein referred to as the Gopher group, was further studied with a novel qPCR method that confirmed enrichment of Gopher group 16S rRNA genes in the dechlorinating cultures. The enrichment of the Gopher group was again tested with two new sets of triplicate microcosms. Enrichment was observed during chlorinated xanthone dechlorination in one set of these triplicate microcosms. In the other set, two microcosms showed clear enrichment while a third did not. The Gopher group is a previously unidentified group of Firmicutes, distinct from but related to the Dehalobacter and Desulfitobacterium genera; this group also contains clones from at least four unique cultures capable of dechlorinating anthropogenic organochlorines that have been previously described in the literature. This study suggests that natural chlorinated xanthones may be effective biostimulants to enhance the remediation of pollutants and highlights the idea that novel genera of dechlorinators likely exist and may be active in bioremediation and the natural cycling of chlorine.

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“…42 Reductive dechlorination was a suspected chemical transformation mechanism for TCC and TCS. Both compounds are polychlorinated (see Table 2) and susceptible to biological reductive dehalogenation, [43][44][45][46] implying that they could also be susceptible to abiotic reductive dehalogenation under appropriate conditions. Indeed, lesser chlorinated TCC homologs, 1-(3,4-dichlorophenyl)-3-phenylurea and 1-(4-chlorophenyl)-3-phenylurea, were detected in methanol in the impinger system after pyrolysis (Table 2).…”

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confidence: 99%

Emerging investigators series: pyrolysis removes common microconstituents triclocarban, triclosan, and nonylphenol from biosolids

Ross

Zitomer

Miller

et al. 2016

Environ. Sci.: Water Res. Technol.

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Reusing biosolids is vital for the sustainability of wastewater management. Pyrolysis is an anoxic thermal degradation process that can be used to convert biosolids into energy rich py-gas and py-oil, and a beneficial soil amendment, biochar. Batch biosolids pyrolysis (60 minutes) revealed that triclocarban and triclosan were removed (to below quantification limit) at 200°C and 300°C, respectively. Substantial removal (>90%) of nonylphenol was achieved at 300°C as well, but 600°C was required to remove nonylphenol to below the quantification limit. At 500°C, the pyrolysis reaction time to remove >90% of microconstituents was less than 5 minutes. Fate studies revealed that microconstituents were both volatilized and thermochemically transformed during pyrolysis; microconstituents with higher vapor pressures were more likely to volatilize and leave the pyrolysis reactor before being transformed than compounds with lower vapor pressures. Reductive dehalogenation products of triclocarban and suspected dehalogenation products of triclosan were identified in py-gas. Application of biosolids-derived biochar to soil in place of biosolids has potential to minimize organic microconstituents discharged to the environment provided appropriate management of py-gas and py-oil.

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Triclosan enriches forDehalococcoides-likeChloroflexiin anaerobic soil at environmentally relevant concentrations

Cited by 34 publications

References 27 publications

Triclocarban Influences Antibiotic Resistance and Alters Anaerobic Digester Microbial Community Structure

Triclocarban Influences Antibiotic Resistance and Alters Anaerobic Digester Microbial Community Structure

Novel Firmicutes Group Implicated in the Dechlorination of Two Chlorinated Xanthones, Analogues of Natural Organochlorines

Emerging investigators series: pyrolysis removes common microconstituents triclocarban, triclosan, and nonylphenol from biosolids

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