FIG. 2.

Effect of temperature on exponential growth rate (solid circles) and on relative nitrogenase activity (bars). Growth rate was determined graphically from the mean OD₆₀₀ of duplicate liquid cultures (1). Relative nitrogenase activity was determined for cultures pregrown at 10°C (open bars) or 22°C (stippled bars) and subsequently incubated with acetylene at 4, 10, or 22°C. Acetylene reduction activity was expressed as the percentage of total GC peak area corresponding to the ethylene peak for each injection. Values are the means of duplicate cultures; error bars represent 1 standard deviation.