title: Mechanisms of ammonium assimilation by Chlorella vulgaris F1068: Isotope fractionation and proteomic approaches.
abstract: Removal of ammonium (NH4(+)-N) by microalgae has evoked interest in wastewater treatment, however, the detailed mechanisms of ammonium assimilation remain mysterious. This study investigated the effects of NH4(+)-N concentration on the removal and biotransformation efficiency by Chlorella vulgaris F1068, and explored the mechanisms by (15)N isotope fractionation and proteome approaches. The results showed NH4(+)-N was efficiently removed (84.8%) by F1068 at 10mgL(-1) of NH4(+)-N. The isotope enrichment factor (ε=-2.37±0.08‰) of (15)N isotope fractionation revealed 47.6% biotransformation at above condition, while 7.0% biotransformation at 4mgL(-1) of NH4(+)-N (ε=-1.63±0.06‰). This was due to the different expression of glutamine synthetase, a key enzyme in ammonium assimilation, which was up-regulated 6.4-fold at proteome level and 18.0-fold at transcription level. The results will provide a better mechanistic understanding of ammonium assimilation by microalgae and this green technology is expected to reduce the burden of NH4(+)-N removal for municipal sewage treatment plants.
authors.affiliation: Department of Environmental Science and Engineering, Xiangtan University, Xiangtan 411105, PR China.
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.affiliation: Department of Environmental Science and Engineering, Xiangtan University, Xiangtan 411105, PR China.
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.affiliation: Department of Environmental Science and Engineering, Xiangtan University, Xiangtan 411105, PR China. Electronic address: gefei@xtu.edu.cn.
authors.forename: Fei
authors.initials: F
authors.lastname: Ge
authors.affiliation: Department of Biological and Food Engineering, Xiangtan University, Xiangtan 411105, PR China.
authors.forename: Nengguo
authors.initials: N
authors.lastname: Tao
authors.affiliation: Department of Environmental Science and Engineering, Xiangtan University, Xiangtan 411105, PR China.
authors.forename: Qiongzhi
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Consortium on Health, Environment, Research and Education (CHEER), and Department of Science and Environmental Studies, Hong Kong Institute of Education, Tai Po, Hong Kong, China.
authors.forename: Minghung
authors.initials: M
authors.lastname: Wong
mesh_terms: D064751:Ammonium Compounds / Q000493:pharmacokinetics*; D001426:Bacterial Proteins / Q000378:metabolism*; D001711:Biotransformation; D048408:Chlorella vulgaris / Q000145:classification / Q000378:metabolism*; D020869:Gene Expression Profiling / Q000379:methods; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis / Q000737:chemistry; D020543:Proteome / Q000378:metabolism; D040901:Proteomics / Q000379:methods; D015398:Signal Transduction / Q000502:physiology; D013045:Species Specificity
chemical_list: D064751:Ammonium Compounds; D001426:Bacterial Proteins; D009587:Nitrogen Isotopes; D020543:Proteome; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
keywords: (15)N isotope fractionation; Ammonium removal; Microalgae; Proteomic; Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR)