TY - JOUR
T1 - Nitrite oxidation kinetics of two Nitrospira strains
T2 - The quest for competition and ecological niche differentiation
AU - Ushiki, Norisuke
AU - Jinno, Masaru
AU - Fujitani, Hirotsugu
AU - Suenaga, Toshikazu
AU - Terada, Akihiko
AU - Tsuneda, Satoshi
N1 - Funding Information:
This research was supported by a Grant-in-Aid for Young Scientists (B) from the Japan Society for the Promotion of Science (JSPS) (16K18609) (to H.F.) and by the Large Research Projects program of the Institute for Fermentation, Osaka (to S.T.).
Publisher Copyright:
© 2017 The Society for Biotechnology, Japan
PY - 2017/5/1
Y1 - 2017/5/1
N2 - Nitrite oxidation is an aerobic process of the nitrogen cycle in natural ecosystems, and is performed by nitrite-oxidizing bacteria (NOB). Also, nitrite oxidation is a rate-limiting step of nitrogen removal in wastewater treatment plants (WWTPs). Although Nitrospira is known as dominant NOB in WWTPs, information on their physiological properties and kinetic parameters is limited. Here, we report the kinetic parameters and inhibition of nitrite oxidation by free ammonia in pure cultures of Nitrospira sp. strain ND1 and Nitrospira japonica strain NJ1, which were previously isolated from activated sludge in a WWTP. The maximum nitrite uptake rate (Vmax_NO2) and the half-saturation constant for nitrite uptake (Km_NO2) of strains ND1 and NJ1 were 45 ± 7 and 31 ± 5 (μmol NO2−/mg protein/h), and 6 ± 1 and 10 ± 2 (μM NO2−), respectively. The Vmax_NO2 and Km_NO2 of two strains indicated that they adapt to low-nitrite-concentration environments like activated sludge. The half-saturation constants for oxygen uptake (Km_O2) of the two strains were 4.0 ± 2.5 and 2.6 ± 1.1 (μM O2), respectively. The Km_O2 values of the two strains were lower than those of other NOB, suggesting that Nitrospira in activated sludge could oxidize nitrite in the hypoxic environments often found in the interiors of biofilms and flocs. The inhibition thresholds of the two strains by free ammonia were 0.85 and 4.3 (mg-NH3 l−1), respectively. Comparing the physiological properties of the two strains, we suggest that tolerance for free ammonia determines competition and partitioning into ecological niches among Nitrospira populations.
AB - Nitrite oxidation is an aerobic process of the nitrogen cycle in natural ecosystems, and is performed by nitrite-oxidizing bacteria (NOB). Also, nitrite oxidation is a rate-limiting step of nitrogen removal in wastewater treatment plants (WWTPs). Although Nitrospira is known as dominant NOB in WWTPs, information on their physiological properties and kinetic parameters is limited. Here, we report the kinetic parameters and inhibition of nitrite oxidation by free ammonia in pure cultures of Nitrospira sp. strain ND1 and Nitrospira japonica strain NJ1, which were previously isolated from activated sludge in a WWTP. The maximum nitrite uptake rate (Vmax_NO2) and the half-saturation constant for nitrite uptake (Km_NO2) of strains ND1 and NJ1 were 45 ± 7 and 31 ± 5 (μmol NO2−/mg protein/h), and 6 ± 1 and 10 ± 2 (μM NO2−), respectively. The Vmax_NO2 and Km_NO2 of two strains indicated that they adapt to low-nitrite-concentration environments like activated sludge. The half-saturation constants for oxygen uptake (Km_O2) of the two strains were 4.0 ± 2.5 and 2.6 ± 1.1 (μM O2), respectively. The Km_O2 values of the two strains were lower than those of other NOB, suggesting that Nitrospira in activated sludge could oxidize nitrite in the hypoxic environments often found in the interiors of biofilms and flocs. The inhibition thresholds of the two strains by free ammonia were 0.85 and 4.3 (mg-NH3 l−1), respectively. Comparing the physiological properties of the two strains, we suggest that tolerance for free ammonia determines competition and partitioning into ecological niches among Nitrospira populations.
KW - Activated sludge
KW - Affinity for nitrite
KW - Affinity for oxygen
KW - Free ammonia
KW - Growth parameters
KW - Inhibitory constant
KW - Nitrospira
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U2 - 10.1016/j.jbiosc.2016.12.016
DO - 10.1016/j.jbiosc.2016.12.016
M3 - Article
C2 - 28202306
AN - SCOPUS:85011949541
SN - 1389-1723
VL - 123
SP - 581
EP - 589
JO - Journal of Bioscience and Bioengineering
JF - Journal of Bioscience and Bioengineering
IS - 5
ER -