The algal mats of a number of hot springs in the Lower Geyser Basin of Yellowstone National Park were destroyed by a brief violent hailstorm on August 30, 1967. The rate of recovery of the algal mat at Mushroom Spring was studied by quantitative methods. In the temperature range of 65-71 C a unicellular cyanophycean alga is the sole photosynthetic component. The doubling times during the recovery period for three stations were: Station I (71 C), 17 days; station II (68 C), 10.5 days; station III (65 C), 10 days. The algal mat had returned to apparently normal size by 152 days after the catastrophe. The significance of these observations for the conservation of hot spring communities is discussed.

SUMMARYWhen growing cells of Escherichia coli were treated with chloramphenicol or erythromycin for 1 hr. and then suspended in antibiotic-free medium, there was a 45 min. lag before growth resumed. By eliminating growth factors or other essential nutrients during antibiotic treatment, it was possible to show that the lag occurred only when ribonucleic acid (RNA) synthesis could take place and did not require the synthesis of deoxyribonucleic acid (DNA). This antibiotic-induced RNA was apparently abnormal and was degraded when the antibiotic was removed. This degradation is a hydrolytic process and does not require the presence of a complete growth medium. During the recovery from the antibiotic-induced lag, DNA and protein synthesis did not occur, but RNA synthesis occurred, even though this new RNA synthesis was not required for the lag to be overcome. When antibiotictreated cells were suspended in phosphate buffer, a decrease in optical density of the suspension occurred which resembled a lytic process, but lysis apparently did not occur. Although these results clarify considerably earlier observations on antibioticinduced lag, they leave unsolved the question of why the antibiotic-induced RNA is abnormal, and how it brings about the lag.