Relative humidity and the killing of bacteria. I. Observations on Escherichia coli and Micrococcus lysodeikticus.

Some observations on the ability of washed Escherichia coli and Mficrococcus lysodeikticus to form colonies when plated after having been freeze-dried and exposed to water vapor in vacuo will be presented in this paper. Serratia marcescens treated in this manner is rapidly killed within a rather narrowly limited range of relative humidities around 90 per cent (Monk and McCaffrey, 1957). It was of interest to determine whether other organisms would behave similarly.