Temperature Optimum of Non-sulphur Bacteria from a Spring at 90° C

Abstract

IT is well established that bacteria live in hot springs at temperatures greater than 90° C depending on altitude^1–4. We have studied the physiology and temperature optima of these organisms by growing them on coverslips and measuring directly the uptake of various radioactively labelled compounds⁵. The bacteria were obtained from an unnamed spring, known to us as “pool A”, which is in the Lower Geyser Basin of Yellowstone National Park⁴, and which has a temperature of 90°–91.5° C and is therefore just below the boiling point for this altitude. It has a pH of 8.6–8.9 and a low sulphide content (0.096 µg/ml.). Our work on Boulder Spring, a superheated spring with a relatively large sulphide content (3.1 µg/ml.), revealed that the bacteria in that spring incorporated radioactively labelled compounds only when sulphide was present⁶, yet the uptake by bacteria from pool A was inhibited by sulphide.