Cell-length heterogeneity: a population-level solution to growth/virulence trade-offs in the plant pathogen Dickeya dadantii

Abstract

Necrotrophic plant pathogens acquire nutrients from dead plant cells, which requires the disintegration of the plant cell wall and tissue structures by the pathogen. Infected plants lose tissue integrity and functional immunity as a result, exposing the nutrient rich, decayed tissues to the environment. One challenge for the necrotrophs to successfully cause secondary infection (infection spread from an initially infected plant to the nearby uninfected plants) is to effectively utilize nutrients released from hosts towards building up a large population before other saprophytes come. In this study, we observed that the necrotrophic pathogen Dickeya dadantii exhibited heterogeneity in bacterial cell length in an isogenic population during infection of potato tuber. While some cells were regular rod-shape (<10μm), the rest elongated into filamentous cells (>10μm). Short cells tended to occur at the interface of healthy and diseased tissues, during the early stage of infection when active attacking and killing is occurring, while filamentous cells tended to form at a later stage of infection. Short cells expressed all necessary virulence factors and motility, whereas filamentous cells did not engage in virulence, were non-mobile and more sensitive to environmental stress. However, compared to the short cells, the filamentous cells displayed upregulated metabolic genes and increased growth, which may benefit the pathogens to build up a large population necessary for the secondary infection. The segregation of the two subpopulations was dependent on differential production of the alarmone guanosine tetraphosphate (ppGpp). When exposed to fresh tuber tissues or freestanding water, filamentous cells quickly transformed to short virulent cells. The pathogen adaptation of cell length heterogeneity identified in this study presents a model for how some necrotrophs balance virulence and vegetative growth to maximize fitness during infection.

Evolution of Pseudomonas aeruginosa toward higher fitness under standard laboratory conditions

“…To facilitate the comparison of phenotypic data and transcriptional profiles, the WBN clones are arranged along x axis in the same order as they are arranged by DESeq2 clustering analysis. chemotaxis, motility, and the rapid growth has been described as typical in various bacterial species [67][68][69][70]. Also, two thirds of all the clones showed a decreased expression of cyclases that produce the intracellular signaling molecule c-di-GMP.…”

“…More specifically, we found a group of clones that exhibited a decreased expression of rsmZ and rsmY , associated with an increased expression of the T3SS and decreased expression of the T6SS, and another group of clones with a decreased expression of chemotaxis transducers and an induced T6SS. Notably, the trade-off between chemotaxis, motility, and the rapid growth has been described as typical in various bacterial species [ 67 – 70 ]. Also, two thirds of all the clones showed a decreased expression of cyclases that produce the intracellular signaling molecule c-di-GMP.…”

Pseudomonas syringae pv. phaseolicola Uses Distinct Modes of Stationary-Phase Persistence To Survive Bacteriocin and Streptomycin Treatments

“…In recent years, it has become clear that pathogenicity to plants is often a heterogeneously expressed trait, with essential virulence factors produced in a population-bistable manner in P. syringae and other plant pathogens ( 51 , 52 ). The virulent state is associated with a suppression of genes involved in active growth processes ( 53 , 54 ). This study links one avirulent Pph subpopulation to an increased metabolic rate.…”

Identification of Three Type II Toxin-Antitoxin Systems in Model Bacterial Plant Pathogen Dickeya dadantii 3937

“…Bacterium length was measured from pole to pole with the ImageJ software [ 33 ]. Cell length was measured for 100 bacteria for each of the tested cultures as described in [ 63 , 64 ]. The same procedure was conducted using the E. coli K-12 MG1655 strain.…”