Thermophilic denitrifying bacteria: A survey of hot springs in Southwestern Iceland

Samples of water, sediment and bacterial mat from hot springs in Grandalur and Hveragerdi areas in southwestern Iceland were screened at 70°C and 80°C for thermophilic denitrifying bacteria by culturing in anaerobic media containing nitrate or N,O as the terminal oxidant.The springs ranged in temperature from 65-100°C and included both neutral (pH 7-S.5) and acidic (pH 2.5-4) types.Nitrate reducing bacteria (nitrate + nitrite) and denitrifiers (nitrate + N2) were found that grew at 70°C but not at 80°C in nutrient media at pH 8. Samples from neutral springs that were cultured at pH 8 failed to yield a chemolithotrophic, sulfur-oxidizing and nitrate-reducing bacterium, and samples from acidic springs that were cultured at pH 3.5 seemed