Bacterial growth rates above 90 degrees C in Yellowstone hot springs.

Growth rates of bacteria living in boiling springs have been measured by determining rate of increase in cell numbers on microscope slides immersed in the springs. Distinction between growth and passive attachment was made with ultraviolet radiation. In all cases, slides irradiated at intervals had significantly fewer bacteria than controls. Estimated generation times ranged from 2 to 7 hours, values which are comparable to those of aquatic bacteria living in less extreme environments.