Abstract
Background: The bacterium Pantoea ananatis is associated with devastating diseases in many crops that cause serious economic losses. We previously isolated strain DZ-12 from maize brown rot leaves and, genome sequencing revealed that it belongs to P. ananatis and contains a large, endogenous plasmid, pDZ-12. Virulence plasmids are essential for pathogenesis in many bacterial pathogens. However, nothing was known regarding the role of this plasmid in P. ananatis pathogenicity in maize. Results: Here, we eliminated the endogenous plasmid from P. ananatis by substituting its native replicon with a temperature-sensitive replicon. The resulting temperature-sensitive plasmid could be cured by growing cells at high temperature (37 °C). Loss of pDZ-12 from P. ananatis DZ-12 led to decreased disease severity in maize plants, suggesting the endogenous plasmid was important for pathogenesis. Meanwhile, loss of pDZ-12 also affected the ability of the bacterium to form biofilms. The method described here, which is efficient and needs only two steps to cure the endogenous plasmid without antibiotic resistance, was also shown to work in Bacillus subtilis, and may be generally applicable in bacteria. Conclusions: This study provides the first evidence that the endogenous plasmid of P. ananatis DZ-12 is important for pathogenesis in maize plants and in the ability of this species to form biofilms. It also presents the first report on curing plasmid DNA from P. ananatis.
Exploring the pathogenic function of an endogenous plasmid of Pantoea ananatis by a simple and efficient plasmid elimination strategy