Open AccessEffect of oxygen level on simultaneous nitrogenase and sMMO expression and activity in Methylosinus trichosporium OB3b and its sMMO C mutant, PP319: aerotolerant N 2 fixation in PP319
Author(s) -
Kim Hyung J,
Graham David W
Publication year - 2001
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.1574-6968.2001.tb10746.x
Subject(s) - nitrogenase , methane monooxygenase , mutant , chemistry , biochemistry , methanotroph , molecular mass , enzyme , microbiology and biotechnology , biology , nitrogen fixation , gene , anaerobic oxidation of methane , catalysis , organic chemistry , nitrogen
Soluble methane monooxygenase (sMMO) expression and activity were monitored under conditions that either promoted or suppressed the expression of nitrogenase in Methylosinus trichosporium OB3b wild‐type (WT) and in its sMMO‐constitutive mutant, PP319. Both WT and mutant cultures had reduced sMMO activity and protein levels under elevated O 2 conditions (188 μM) compared with low O 2 conditions (24 μM). Simultaneous N 2 fixation also reduced sMMO activity in both cultures when O 2 was low. However, when O 2 levels were increased, nitrogenase expression ceased and sMMO activity was reduced by ∼77% in the WT, whereas sMMO and nitrogenase expression and activity in PP319 were relatively unaffected by the higher O 2 levels. Western immunoblot analysis showed that the nitrogenase Fe protein resolved as two components (apparent molecular mass of 30.5 and 32 kDa) in both the WT and PP319 when O 2 levels were low. When O 2 levels were high, only the 32‐kDa form of the Fe protein was present in PP319, whereas neither form was detectable in the WT. Aerotolerant N 2 fixation appears to be associated with the 32‐kDa Fe protein in M. trichosporium OB3b.