title: Ecophysiology and Comparative Genomics ofNitrosomonas mobilisMs1 Isolated from Autotrophic Nitrifying Granules of Wastewater Treatment Bioreactor.
abstract: Ammonia-oxidizing bacteria (AOB), which oxidize ammonia to nitrite in the first step of nitrification, play an important role in biological wastewater treatment systems.Nitrosomonas mobilisis an important and dominant AOB in various wastewater treatment systems. However, the detailed physiological and genomic properties ofN. mobilishave not been thoroughly investigated because of limited success isolating pure cultures. This study investigated the key physiological characteristics ofN. mobilisMs1, which was previously isolated into pure culture from the nitrifying granules of wastewater treatment bioreactor. The pure culture ofN. mobilisMs1 was cultivated in liquid mineral medium with 30 mg-N L-1(2.14 mM) of ammonium at room temperature under dark conditions. The optimum growth ofN. mobilisMs1 occurred at 27°C and pH 8, with a maximum growth rate of 0.05-0.07 h-1, which corresponded to a generation time of 10-14 h. The half saturation constant for ammonium uptake rate and the maximum ammonium uptake rate ofN. mobilisMs1 were 30.70 ± 0.51 μM NH4+and 0.01 ± 0.002 pmol NH4+cells-1h-1, respectively.N. mobilisMs1 had higher ammonia oxidation activity thanN. europaeain this study. The oxygen uptake activity kinetics ofN. mobilisMs1 were Km(O2)= 21.74 ± 4.01 μM O2and Vmax(O2)= 0.06 ± 0.02 pmol O2cells-1h-1. Ms1 grew well at ammonium and NaCl concentrations of up to 100 and 500 mM, respectively. The nitrite tolerance ofN. mobilisMs1 was extremely high (up to 300 mM) compared to AOB previously isolated from activated sludge and wastewater treatment plants. The average nucleotide identity between the genomes ofN. mobilisMs1 and otherNitrosomonasspecies indicated thatN. mobilisMs1 was distantly related to otherNitrosomonasspecies. The organization of the genes encoding protein inventory involved in ammonia oxidation and nitrifier denitrification processes were different from otherNitrosomonasspecies. The current study provides a needed physiological and genomic characterization ofN. mobilis-like bacteria and a better understanding of their ecophysiological properties, enabling comparison of these bacteria with other AOB in wastewater treatment systems and natural ecosystems.
authors.affiliation: Tsuneda Laboratory, Department of Life Science and Medical Bioscience, Waseda UniversityTokyo, Japan; Department of Biotechnology, Mandalay Technological University, Ministry of EducationMandalay, Myanmar.
authors.forename: Soe Myat
authors.initials: SM
authors.lastname: Thandar
authors.affiliation: Tsuneda Laboratory, Department of Life Science and Medical Bioscience, Waseda University Tokyo, Japan.
authors.forename: Norisuke
authors.initials: N
authors.lastname: Ushiki
authors.affiliation: Tsuneda Laboratory, Department of Life Science and Medical Bioscience, Waseda University Tokyo, Japan.
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Fujitani
authors.affiliation: Advanced Biomeasurements Research Group, Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology Ibaraki, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Sekiguchi
authors.affiliation: Tsuneda Laboratory, Department of Life Science and Medical Bioscience, Waseda University Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tsuneda
keywords: Nitrosomonas; ammonia oxidation; genomic properties; kinetics; nitrification; physiological characteristics; wastewater