A Pseudomonas plant pathogen uses distinct modes of stationary phase persistence to survive bacteriocin and streptomycin treatments

Abstract

Antimicrobial treatment of bacteria often results in a small population of surviving tolerant cells, or persisters, that may contribute to recurrent infection. Antibiotic persisters are metabolically dormant, but the basis of persistence to membrane-disrupting biological compounds is less well-understood. We previously found that the model plant pathogen Pseudomonas syringae pv. phaseolicola 1448A (Pph) exhibits persistence to tailocin, a membrane-disrupting biocontrol compound with potential for sustainable disease control. Here we compared physiological traits associated with persistence to tailocin and to the antibiotic streptomycin, and established that both treatments leave similar frequencies of persisters. Microscopic profiling of treated populations revealed that while tailocin rapidly permeabilizes most cells, streptomycin treatment results in a heterogeneous population of redox and membrane permeability states. Sorting cells according to redox reporter intensity identified streptomycin persisters among the low-redox fraction, but tailocin persisters were only cultured from the fraction with intermediate redox activity. Cells from culturable fractions were able to infect host plants, while nonculturable redox-active cells were not. Tailocin and streptomycin were effective in eliminating all persisters when applied sequentially, in addition to eliminating cells in other viable states. This study identifies distinct redox states associated with antibiotic persistence, tailocin persistence, and virulence, and demonstrates that tailocin is highly effective in eliminating dormant cells.