Open AccessRegulation of nitrogen fixation by different nitrogen sources in the filamentous non‐heterocystous cyanobacterium Microcoleus sp.
Author(s) -
Sroga Grażyna E
Publication year - 1997
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.1574-6968.1997.tb10457.x
Subject(s) - nitrogenase , nitrogen fixation , cyanobacteria , urea , biochemistry , nitrogen , chloramphenicol , biology , chemistry , bacteria , organic chemistry , genetics , antibiotics
The pattern of N 2 fixation, the synthesis and activity of nitrogenase under different nitrogen sources was studied in the filamentous, non‐heterocystous cyanobacterium Microcoleus sp. grown under defined culture conditions. Cells grown under a 10 h light/14 h dark (10L/14D) cycle with N 2 as an inorganic nitrogen source showed highest nitrogenase activity (acetylene reduction) at the end of the light phase and then a decrease after entering the dark phase. Nitrogenase synthesis was neither suppressed after 7 days of growth with 2 mM NaNO 3 or 0.2 mM (NH 4 ) 2 SO 4 or 0.3 mM urea nor with 20 mM NaNO 3 or 3 mM (NH 4 ) 2 SO 4 or 4 mM urea under the 10L/14D cycle. Western immunoblots tested with polyclonal antisera against the Fe‐protein revealed the following: (1) the Fe‐protein was synthesized in cells grown with N 2 as well as in cells grown with NaNO 3 or (NH 4 ) 2 SO 4 under the 10L/14D cycle; (2) the Fe‐protein was found in cells grown with urea under the 10L/14D cycle, but not in the darkness; (3) only one protein band, corresponding to the Fe‐protein, was found in cells harvested during the light phase of the 10L/14D cycle under the tested conditions. No nitrogenase activity was observed when chloramphenicol was added to the cultures 4 h before the onset of the light period. This observation suggest de novo synthesis of nitrogenase in Microcoleus sp.