Sensitivity of an Oligotrophic Lake Planktonic Bacterial Community to Oxygen Stress

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Abstract
Dissolved oxygen at approximately four times normal saturation (42 mg liter −1 ) inhibited the growth and metabolism of summer planktonic bacteria in the surface water of alpine oligotrophic Mountain Lake (Giles County, Va.). Data were derived from growth of CFU on membrane filters, d -[ U - 14 C]glucose incorporation into the extractable lipid of these CFU, and respiration and assimilation of d -[ U - 14 C]glucose by lake water samples. Statistically significant (α < 0.05) differences were not detected in either CFU or 14 C incorporation in lipid when superoxide dismutase (30 U ml −1 ) or catalase (130 U ml −1 ) was added to the medium. Thus, exogenous oxygen by-products apparently are not responsible for the observed inhibition of growth and metabolism.