Extracellular DNA controls expression of Pseudomonas aeruginosa genes involved in nutrient utilization, metal homeostasis, acid pH tolerance, and virulence.
Pseudomonas aeruginosa grows in extracellular DNA-enriched biofilms and infection sites. Extracellular DNA (eDNA) is generally considered a structural biofilm polymer required for aggregation and biofilm maturation. In addition, eDNA can sequester divalent metal cations, acidify the growth media, and serve as a nutrient source. Here we determine the transcriptome of planktonic P. aeruginosa grown in the presence of eDNA using RNA-seq. Transcriptome analysis identified 89 induced genes and 76 repressed genes in the presence of eDNA (FDR<0.05), and transcriptional lux fusions were used to confirm eDNA regulation. A large number of eDNA-induced genes appear to be involved in utilizing DNA as a nutrient. Several eDNA-induced genes are also induced by acidic pH 5.5, and growth in the presence of eDNA or acidic pH promoted an acid tolerance response in P. aeruginosa. The cyoABCDE terminal oxidase is induced at pH 5.5 and contributed to the acid tolerance phenotype. Quantitative metal analysis confirmed that DNA binds to diverse metals, which helps explain why many genes involved in a general uptake of metals were controlled by eDNA. Growth in the presence of eDNA also promoted intracellular bacterial survival and influenced virulence and during the acute infection model of fruit flies. The diverse functions of the eDNA-regulated genes underscore the important role of this extracellular polymer in promoting antibiotic resistance, virulence, acid tolerance, and nutrient utilization; phenotypes that contribute to long-term survival.