Evidence for propagation of aerobic bacteria in particles suspended in gaseous atmospheres.

One factor involved in the possibility that airborne microbes might contaminate the Jovian atmosphere, is whether microbes have the capacity to propagate in air. Prior to these studies, the evidence was that the airborne state was lethal to microbes. By mixing an aerosol of aerobic bacteria with another containing 14C glucose, we were able to detect the presence of 14CO2, showing that the airborne cells were metabolically active. In the same type of experiment, we were able to show that thymidine was incorporated into the acid-insoluble fraction of samples, indicating the formation of DNA. Finally, we were able to show, both by an increase in numbers of viable cells and a parallel increase in particle numbers, that at least two new generations of cells could occur. As of this writing, evidence for propagation of anaerobic bacteria has been negative.