Airborne micro-organisms: a technique for studying their survival

Abstract

The concentration of viable cells in an aerosol of micro-organisms is reduced by physical loss and biological decay. To study biological decay it is necessary to distinguish between the two processes. The preferred way of doing this is to mix the test aerosol with a tracer which is subject only to physical loss: the tracer and test cells should be mixed before dissemination.The recommended tracers for bacterial clouds are bacteria made radioactive by growing on a medium containing 32P, then killed with formaldehyde and washed. To ensure closest identity of physical behaviour it is necessary that the tracer should be of the same species as the cells under test.We are grateful to Mr E. O. Powell for helpful comment during the preparation of this paper.