N-131. Susceptibility of Extreme Halophiles to Mercury using Resazurin Reduction Kinetics

S. R. Slight, A. R. Harker, D. P. Breakwell;
Brigham Young Univ., Provo, UT.

The mercury concentration of Great Salt Lake has been measured at 0.1 μM and at 45 μM in the sediment and is reportedly increasing. While the accumulation of this heavy metal on the lake’s macrobiota has been studied, its effect on extremely halophilic microorganisms has not been investigated. The effect of Hg on respiration rate was examined using six extremely halophilic prokaryotes previously isolated from the lake. Two Bacteria (Pseudomonas stutzeri and Alkalibacillus salilacud), and four Archaea (Halobacterium salinarum, Natrinema altunense, Halorubrum tebenquichense, and Haloarcula hispanica) were used in this study. Cultures were grown in a rich medium and then subjected to varying Hg concentrations. Respiration rates were measured using the resazurin reduction assay. All isolates showed a drastic reduction in respiration rate at 1 μM Hg2+. Respiration rates decreased between 23 and 90% of the control treatments, with no further decrease in respiration occurring at 5 μM Hg2+ in our bacterial isolates and 50 μM Hg2+ in the archaeal isolates. Complete elimination of respiratory activity was observed only in H. salinarum. Generally, Bacteria were still able to respire between 5-9% and Archaea between 0-3% of the control treatments. Mercury concentrations in the sediment approach maximum respiratory inhibition, but the bioavailability of this mercury is unknown. Rising mercury concentrations are beginning to be in the range where Hg will have significant impacts on respiration of extreme halophiles in Great Salt Lake.