Interspecies interaction extends bacterial survival at solid–air interfaces

Abstract

Despite the ubiquity of biofilms in natural and man-made environments, research on surface-associated cells has focused primarily on solid–liquid interfaces. This study evaluated the extent to which bacterial cells persist on inanimate solid–air interfaces. The desiccation tolerance of bacterial strains isolated from indoor air, as well as of a test strain (Pseudomonas aeruginosa), was determined at different levels of relative humidity (RH) using the large droplet inoculation method in an aerosol chamber. The cells survived longer at lower (25 and 42%) than at high RH (95%). Four of the seven indoor strains selected for further study showed extended period of survival following deposition as 0.05–0.1 ml of washed culture followed by desiccation, each with different effects on the survival of the test strain, P. aeruginosa. A strain closely related to Arthrobacter species afforded the highest level of protection to the test strain. Even though the desiccation-tolerant strains survived when they were deposited as bioaerosols, the protective role towards the test strain was not observed when the latter was deposited as a bioaerosol. These, which are often-unculturable, bacteria may go undetected during routine monitoring of biofouling, thereby allowing them to act as reservoirs and extending the habitat range of undesired microorganisms.