Prevention of Surface-Associated Calcium Phosphate by the Pseudomonas syringae Two-Component System CvsSR.

CvsSR is a Ca-induced two-component system (TCS) in the plant pathogen pv. tomato DC3000. Here, we discovered that CvsSR is induced by Fe, Zn, and Cd However, only supplementation of Ca to medium resulted in rugose, opaque colonies in Δ and Δ strains. This phenotype corresponded to formation of calcium phosphate precipitation on the surface of Δ and Δ colonies. CvsSR regulated swarming motility in pv. tomato in a Ca-dependent manner, but swarming behavior was not influenced by Fe, Zn, or Cd We hypothesized that reduced swarming displayed by Δ and Δ strains was due to precipitation of calcium phosphate on the surface of Δ and Δ cells grown on agar medium supplemented with Ca By reducing the initial pH or adding glucose to the medium, calcium precipitation was inhibited, and swarming was restored to Δ and Δ strains, suggesting that calcium precipitation influences swarming ability. Constitutive expression of a CvsSR-regulated carbonic anhydrase and a CvsSR-regulated putative sulfate major facilitator superfamily transporter in Δ and Δ strains inhibited formation of calcium precipitates and restored the ability of Δ and Δ bacteria to swarm. Lastly, we found that glucose inhibited Ca-based induction of CvsSR. Hence, CvsSR is a key regulator that controls calcium precipitation on the surface of bacterial cells. Bacteria are capable of precipitating and dissolving minerals. We previously reported the characterization of the two-component system CvsSR in the plant-pathogenic bacterium CvsSR responds to the presence of calcium and is important for causing disease. Here, we show that CvsSR controls the ability of the bacterium to prevent calcium phosphate precipitation on the surface of cells. We also identified a carbonic anhydrase and transporter that modulate formation of surface-associated calcium precipitates. Furthermore, our results demonstrate that the ability of the bacterium to swarm is controlled by the formation and dissolution of calcium precipitates on the surface of cells. Our study describes new mechanisms for microbially induced mineralization and provides insights into the role of mineral deposits on bacterial physiology. The discoveries may lead to new technological and environmental applications.