Water-to-Air Fractionation of Bacteria.

Differences in the ability of bacterial species to be transported from water to air by bursting bubbles were investigated. Bubbles were generated in suspensions of mixed bacterial cultures, and the concentration was measured for each species in the top jet drop ejected. This concentration divided by the concentration in the bulk menstruum is the concentration factor (CF). Bubbles were generated 2 cm below the liquid surface, and jet drops with diameters from 34 to 136 mum were studied. Serratia marinorubra and Micrococcus euryhalis had CFs which were generally 10 to 100 times greater than those of Escherichia coli, Pseudomonas bathycetes, and spores of Bacillus subtilis. P. bathycetes never had a CF significantly greater than 1 at any drop size, and spores of B. subtilis had a maximum CF of 4. E. coli had a maximum CF of 6 for 1- or 2-day old cultures, but this increased to 80 when a 5-day-old culture was used. This change in the CF with age of the cells indicates that composition of the cell may be a factor influencing its ability to concentrate in jet drops.