DETECTION AND CHARACTERIZATION OF DENITRIFYING BACTERIA FROM A PERMANENTLY ICE-COVERED ANTARCTIC LAKE

Denitrifying bacterial strains were isolated from Lake Bonney, a perma nently ice-covered and chemically stratified lake in the McMurdo dry v alley region of Antarctica, using complex media at 4 degrees C. Three strains, identified as denitrifiers by their ability to produce nitrou s oxide using nitrate or nitrite as a respiratory substrate, were char acterized as to their temperature and salinity optima for aerobic grow th in batch culture; all three were psychrophilic and moderately halop hilic. Maximum growth rates of near 0.024 h(-1) were measured for all three strains. Growth rates projected to occur at in situ temperature and salinity imply generation times on the order of 100 h. Species spe cific polyclonal antisera were prepared against two of the strains, EL B 17 (from the east lobe of the lake at 17 m) and WLB20 (from the west lobe at 20 m). Both strains were subsequently detected and enumerated in the lake using the antisera. ELB 17 was present in both lobes belo w the chemocline, while WLB20 was present in the west lobe below the c hemocline but only in surface waters of the east lobe. These distribut ions are related to the observed chemical distributions which imply th e occurrence of denitrification in the west lobe of the lake and not i n the east lobe.