Open AccessKinetics of CH 4 oxidation in oxic soils exposed to ambient air or high CH 4 mixing ratios
Author(s) -
Bender Martin,
Conrad Ralf
Publication year - 1992
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1992.tb05783.x
Subject(s) - cambisol , soil water , chemistry , environmental chemistry , anaerobic oxidation of methane , kinetics , saturation (graph theory) , methane , soil science , geology , physics , mathematics , organic chemistry , quantum mechanics , combinatorics
The kinetic parameters of CH 4 oxidation ( K m , V max , apparent threshold = Th a ) were measured using different oxic soils (cultivated cambisol, forest luvisol, meadow cambisol, paddy soil) both in a fresh state and after 3 weeks preincubation under high CH 4 mixing ratios (20%). The preincubation resulted in an increase of the most probable number of methanotrophic bacteria. In fresh soils, CH 4 oxidation followed Michaelis‐Menten kinetics with a low K m (30–51 nM CH 4 ), low V max (0.7–3.6 nmol CH 4 h −1 g −1 dw soil), and low Th a (0.2–2.7 ppmv CH 4 ). In preincubated soils, CH 4 oxidation exhibited biphasic kinetics in which two different CH 4 saturation curves were apparently superimposed on each other. Eadie‐Hofstee plots of the data showed two activities with different kinetic parameters: a high‐affinity activity with low K m (13–470 nM CH 4 ), low V max (2.1–150.0 nmol CH 4 h −1 g −1 dw) and low Th a (0.3–4.1 ppmv CH 4 ) being similar to the kinetic parameters in fresh soils; and a low‐affinity activity with high K m (1740–27 900 nM CH 4 ), high V max (270–3 690 nmol CH 4 h −1 g −1 dw) and high Th a (11–45 ppmv CH 4 ) being similar to the kinetic parameters known from methanotrophic bacteria. The low‐affinity activity was also observed in a soil over a deep natural gas source which was permanently exposed to high CH 4 mizing ratios (>5% CH 4 ). Bacteria culturable as methanotrophs are probably responsible for the low‐affinity activity which is typical for the soils exposed to high CH 4 mixing ratios. However, the bacteria responsible for the high‐affinity activity are still unknown. This activity is typical for the soils exposed to only ambient CH 4 mixing ratios. Both high‐ and low‐affinity activities were inhibited by autoclaving and by acetylene.