Roesler, C. S. University of Connecticut, roesler@uconnvm.uconn.edu
Culbertson, C. S. USGS, cculbert@usgs.gov
McLeroy-Etheridge, S. L. University of Connecticut, stm98002@uconnvm.uconn.edu
Oremland, R. USGS, roremlan@usgs.gov

 
PHYSIOLOGICAL CHARACTERISTICS OF A NOVEL EUKARYOTIC PHOTOTROPH ISOLATED FROM THE HALOALKALINE MONO LAKE, CALIFORNIA
 
A novel unicellular phototroph was isolated from meromictic Mono Lake, where it occupies two niches: the upper mixolimnion that undergoes seasonal variations while remaining oxygenic, hyperalkaline and hypersaline, and the deep anoxic monimolimnion that is additionally characterized by extreme methane, sulfide and ammonia concentrations. Maximal cell concentrations occur at the chemocline indicating the organism's ability to adapt not only to these conditions but also to extreme gradients, while still accounting for nearly half of the lake's annual primary production. With this in mind, the growth and photosynthesis of the organism were assessed over broad ranges in salinity, pH and light under controlled conditions. Growth rates of 0.25-1.3 [d-1] were observed over the salinity range 0-260 ppt and the pH range 4-12. Cell-specific maximal photosynthetic rates were less sensitive to pH (0.75-1.6 [pgC/cell/hr]) than to salinity (0.1-1.3 [pgC/cell/hr]). The potential for considerable acclimation to dim blue light, which would be encountered in the monimolimnion, was indicated by maximal growth and photosynthetic rates at growth irradiances below 50 [uE/m2/s] and the presence of five structurally-unique carotenoids. The organism's adaptability to extreme conditions yields photosynthetic carbon fixation under a multitude of circumstances and likely contributes to sustenance of the Mono Lake ecosystem.
 
Day: Tuesday, Feb. 2
Time: 03:45 - 04:00pm
Location: Sweeney Center
 
Code: SS27TU0345S