FIG 3.

Exploring the relationship between RH and E. coli airborne survival. CELEBS and bulk measurements of the survival of E. coli MRE162 and K12 at room temperature (18 to 21°C). A and C datapoints show the mean, error bars show the standard deviation. B and D datapoints show the results of individual measurements, the middle line shows the mean, the error bars show the standard deviation. (A) Survival of E. coli MRE162 over 3 h in bulk solutions of NaCl. The light blue points show the survival in a more dilute solution with a water activity of 0.95 and the dark blue points show the survival in a more concentrated solution with a water activity of 0.76. n = 5 for all measurements. (B) The airborne survival of E. coli K12 (beige points) and an OtsA deficient mutant of E. coli K12 (green points) after 2 and 10 min of levitation at 50% ± 1% RH, in LB broth droplets. (C) Comparison of the survival of E. coli MRE162 after 1 h of levitation in LB broth droplets at 80% RH (lighter beige points labeled Aerosol 80% RH) to the survival over 3 h in a bulk solution of concentrated LB broth matching the concentrations of all components in an airborne droplet equilibrated to 80% ± 1% RH (orange points labeled bulk Aw 0.8). For all measurements in the bulk solution n = 6, for the CELEBS measurement n = 3. (D) The airborne survival of E. coli MRE162 after 5 min at 30% ± 1% RH, in LB broth droplets with either a third or three times the initial solute concentration compared to the survival in LB broth with a normal initial solute concentration; *, P < 0.05; ***, P < 0.001.