Effects of simulated acidic precipitation on the colonization and ice nucleation activity of Pseudomonas syringae pv. syringae and Erwinia herbicola

Precipitation over the eastern United States has been increasing in acidity, particularly within the last three decades. The average annual pH of rain in this area is about 4.2. The foliar surface, or phylloplane, of soybean can be damaged by rain acidified to pH 2.9. Simulated acidic precipitation has an overall inhibitory influence on soil microbial processes. The effect acidic precipitation may have on epiphytic microorganisms has not been examined. Bacteria are among the most numerous residents on the phylloplane.