title: Carboxyl-modified single-walled carbon nanotubes negatively affect bacterial growth and denitrification activity.
abstract: Single-walled carbon nanotubes (SWNTs) have been used in a wide range of fields, and the surface modification via carboxyl functionalization can further improve their physicochemical properties. However, whether carboxyl-modified SWNT poses potential risks to microbial denitrification after its release into the environment remains unknown. Here we present the possible effects of carboxyl-modified SWNT on the growth and denitrification activity of Paracoccus denitrificans (a model denitrifying bacterium). It was found that carboxyl-modified SWNT were present both outside and inside the bacteria, and thus induced bacterial growth inhibition at the concentrations of 10 and 50 mg/L. After 24 h of exposure, the final nitrate concentration in the presence of 50 mg/L carboxyl-modified SWNT was 21-fold higher than that in its absence, indicating that nitrate reduction was substantially suppressed by carboxyl-modified SWNT. The transcriptional profiling revealed that carboxyl-modified SWNT led to the transcriptional activation of the genes encoding ribonucleotide reductase in response to DNA damage and also decreased the gene expressions involved in glucose metabolism and energy production, which was an important reason for bacterial growth inhibition. Moreover, carboxyl-modified SWNT caused the significant down-regulation and lower activity of nitrate reductase, which was consistent with the decreased efficiency of nitrate reduction.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Xiong
authors.initials: X
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Yinglong
authors.initials: Y
authors.lastname: Su
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Yinguang
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Wan
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Mu
authors.initials: M
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Haining
authors.initials: H
authors.lastname: Huang
mesh_terms: D004249:DNA Damage / Q000187:drug effects / Q000235:genetics; D058440:Denitrification / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects* / Q000235:genetics; D004734:Energy Metabolism / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D005947:Glucose / Q000378:metabolism; D037742:Nanotubes, Carbon / Q000009:adverse effects*; D050901:Nitrate Reductase / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics
chemical_list: D037742:Nanotubes, Carbon; D009566:Nitrates; D012264:Ribonucleotide Reductases; D050901:Nitrate Reductase; D005947:Glucose