A Method for investigating the Cause of Death of Airborne Bacteria

Abstract

WHEN bacteria are sprayed into the air their ability to survive depends on a large number of factors. The usual criterion for deciding if they are alive or dead depends on the appearance of visible colonies on an agar plate after the organisms have been recovered from the air and subjected to certain laboratory handling techniques. Since, by this method, it is usually difficult or impossible to determine the cause of death, it would be an advantage to be able to distinguish between death resulting from a breakdown of the cell's productive capacity (for example, its enzyme systems) or loss of its reproductive power (for example, nucleoprotein integrity). Attempts have been made to produce a laboratory technique enabling this differentiation to be made. The principle is to label the organisms with a suitable phage. Following aerosolization and recovery of the cells a comparison is made between the degree of lysis of the test cells (containing phage) and the survival of control (phage-free) cells. If the extent of lysis in the test cells is different from the survival-level of control cells then deductions can be made as to whether death is attributable to failure of the cell's productive or reproductive powers. The argument is best demonstrated by example.