Analysis by RNA-Seq of Xylella fastidiosa evidences transcriptional regulation exerted by calcium that is correlated with prolonged biofilm formation over time
L. DE LA FUENTE (1), J. Parker (1), H. Chen (1) (1) AUBURN UNIVERSITY, U.S.A.

The functions of calcium (Ca) in bacteria are less characterized than in eukaryotes, where its role has been studied extensively. The plant-pathogenic bacterium Xylella fastidiosa has several virulence features that are enhanced by increased Ca concentrations, including biofilm formation. However, the specific mechanisms driving modulation of this feature are unclear. Characterization of biofilm formation over time showed that 4mM Ca supplementation produced denser biofilms that were still developing at 96 hrs, while biofilm in non-supplemented media had reached the dispersal stage by 72 hrs. To identify changes in global gene expression in X. fastidiosa grown in supplemental Ca, RNA-Seq of batch culture biofilm cells was conducted at three 24-hr time intervals. Results indicate that a variety of genes are differentially expressed in response to Ca, including genes related to attachment, motility, exopolysaccharide synthesis, biofilm formation, peptidoglycan synthesis, regulatory functions, iron homeostasis, and phages. Collectively, results demonstrate that Ca supplementation induces a transcriptional response that promotes continued biofilm development, while biofilm cells in non-supplemented media are driven towards dispersion of cells from the biofilm structure. These results have important implications for disease progression in planta, where xylem sap is the source of Ca and other nutrients for X. fastidiosa, and our previous research has shown that host plants increase the concentration of Ca in leaves and xylem sap after pathogen infection.

Abstract Number: P6-140
Session Type: Poster