The Effect of Oxygen Tension on the Oxygen Uptake of Lake Bacteria

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Abstract
The O2 tension of lakewater was adjusted at different levels by treating the water with either tank O2 or N2. The water containing bacteria was incubated in 145 ml. glass-stoppered bottles in a water bath and the O2 content was detd. by the Winker method. The rate of O2 consumption by bacteria from Lake Mendota and other Wisconsin lakes was independent of the O2 tension within the examined range of 0.3 to 36.48 mg. per liter. Multiplying bacteria used 51-93 X 10-12 mg. of O2 per cell per hr. during the first day in lake water but progressively less as the more readily oxidizable organic matter was oxidized; upon enrichment with glucose or glycerol the lake bacteria consumed from 69 to 214 X 10-12 mg. of O2 per cell per hr. The respiratory rate of neither mixed nor pure cultures of "resting" cells was influenced by the O2 tension of enriched lake water until the conc. of O2 was reduced to less than 0.3 mg./l. Preservative concs. of phenol, CH20 and toluol inhibited the respiration of bacteria but the effect was not influenced by the O2 tension of the water.