A trait based approach to bacterial biofilms in soil

One of the greatest challenges of living in the soil environment is that microorganisms must contend with fluctuations in water availability. Biofilm production is a trait that may helps bacteria persist through moisture conditions that are suboptimal for growth and reproduction. Using an alginate knockout of Pseudomonas aeruginosa, we demonstrate that biofilm production increased survivorship and created a more favorable moisture niche. Although biofilm production is assumed to incur a fitness cost, we were unable to detect a trade-off along a moisture gradient. In addition to increasing desiccation tolerance, biofilm production altered the soil environment in ways that were consistent with niche construction. Specifically, biofilm production increased soil water retention, but this did not facilitate the growth of an unrelated, desiccation-sensitive soil bacterium. In sum, our findings suggest that biofilm production is a response and effect trait that may influence the distribution and abundance of microorganisms in soil environments.