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Abstract
Klebsiella pneumoniae strains k11 and m5a1 which differ greatly in their ability to produce slime had similar ratios of nitrogenase activity when grown on agar under atmospheres of nitrogen, air or oxygen. With both strains, the rate of acetylene reduction was not significantly different when measured under air compared to nitrogen but was decreased under oxygen, which also restricted growth. Strain k11, the more slimy of the two strains produced more slime, as measured viscometrically, when the atmosphere above the agar contained a greater proportion of oxygen up to 50% O2. Strain m5a1 gave no detectable response to increased oxygen concentration other than decreased growth and nitrogenase activity under high oxygen concentration. Despite the superficial correlation between enhanced slime production and resistance to the potentially damaging effects of oxygen on nitrogenase in air-grown nitrogen-fixing Klebsiella, slime probably contributes only marginally to that resistance.
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