Dissociation of a population of Pectobacterium atrosepticum SCRI1043 in tobacco plants: formation of bacterial emboli and dormant cells.

The population dynamics of Pectobacterium atrosepticum SCRI1043 (Pba) within tobacco plants was monitored from the time of inoculation until after long-term preservation of microorganisms in the remnants of dead plants. We found and characterised peculiar structures that totally occlude xylem vessels, which we have named bacterial emboli. Viable but non-culturable (VBN) Pba cells were identified in the remnants of dead plants, and the conditions for resuscitation of these VBN cells were established. Our investigation shows that dissociation of the integrated bacterial population during plant colonisation forms distinct subpopulations and cell morphotypes, which are likely to perform specific functions that ensure successful completion of the life cycle within the plant.