Sensitivity of an Oligotrophic Lake Planktonic Bacterial Community to Oxygen Stress

Abstract

Dissolved oxygen at approximately four times normal saturation (42 mg liter-') 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-14C]glucose incorporation into the extractable lipid of these CFU, and respiration and assimilation of D-[U-14C]glucose by lake water samples. Statistically significant (a < 0.05) differences were not detected in either CFU or 14C incorporation in lipid when superoxide dismutase (30 U ml-) or catalase (130 U ml-') was added to the medium. Thus, exogenous oxygen by-products apparently are not responsible for the observed inhibition of growth and metabolism.

Response of an Antarctic Lake Heterotrophic Community to High Dissolved Oxygen

“…Water samples for DO were field fixed and later analyzed by the modified Winkler technique (3). HDO atmosphere was maintained by the application of pressurized oxygen in a modified pressure cooker for CFU experiments or to the head space in butyl rubber-sealed serum bottles for carbon assimilation-respiration experiments as previously described (14). Containers were not purged to avoid removal of normal atmospheric gases.…”

“…The pressure applied (11 lb/in2 [75.8 kPa]) would be equivalent to that sustained in 28 ft (ca. 8.5 m) of water and has no physiological effect (2,13,14).…”

“…D-[U-14C]glucose assimilated and respired under ADO and HDO conditions were measured as previously described (14). Values were not corrected to disintegration per minute as relative differences were sufficient and quench was negligible in all samples.…”

“…(ii) Glucose was available as a high-specific-activity carbon compound and is a central metabolite in a variety of microbial carbon pathways. (iii) The use of the same labeled compound as for our previous work (14) represents the only way a comparison between two ecosystems carn be made. Figure 1 shows the depth profile of DO concentrations in Lake Hoare.…”

“…Most research concerning oxygen toxicity has involved the very sensitive anaerobes (6,15), microaerophiles (10,16,17), and the facultative aerobe Escherichia coli (7). Interestingly, except for our investigations of the oligotrophic Mountain Lake, Va. (14), no investigations of the community responses to HDO conditions have been conducted, and no studies have ever been made on perpetual HDO environments such as Lake Hoare. Consequently, we undertook this investigation of the influence of HDO versus ADO on the assimilation and respiration of D-[U-14C]glucose and CFU on both the planktonic and benthic heterotrophic bacterial communities of Lake Hoare.…”