Among the mechanisms to avoid nitrogenase inhibition by oxygen, cyanobacteria:
A) produce organic acids; aerobic heterotrophs consume available oxygen
B) develop heterocysts, thick-walled cells specialized in fixing nitrogen
C) perform photosynthesis by day and nitrogen fixation at night
D) form cell aggregates, favoring nitrogen fixation in the anaerobic interior
E) all of the above

Question

Quizplus · Accepted Answer

Cyanobacteria have evolved various strategies to protect nitrogenase from oxygen, including developing heterocysts (thick-walled cells that provide an anaerobic environment for nitrogen fixation), performing nitrogen fixation at night (when photosynthesis does not produce oxygen), and forming cell aggregates (where the interior can remain anaerobic). Some species may also influence their surrounding environment in ways that indirectly protect nitrogenase, such as by affecting oxygen levels, but the direct production of organic acids to consume oxygen is not a described mechanism for protecting nitrogenase in cyanobacteria. However, the options provided suggest a broad interpretation of strategies, including indirect effects on the oxygen environment, thus leading to the selection of "all of the above" to encompass the variety of adaptations cyanobacteria employ to mitigate oxygen exposure to nitrogenase.

Among the Mechanisms to Avoid Nitrogenase Inhibition by Oxygen, Cyanobacteria