Dynamics of Bacterial Pathogen Interactions During Multi-Species Infections in Potato

Core Concepts

Intraspecific competition, cooperation through trophic interactions, and toxicity interference contribute to the maintenance of diversity within the soft rot Pectobacteriaceae species complex infecting potato.

Abstract

The study investigated the dynamics of co-infections by soft rot Pectobacteriaceae (SRP) species in potato tubers. The authors set up 16 synthetic communities, each containing 6 strains from 2 different SRP species, and inoculated them on potato tubers or in liquid medium. They used Illumina sequencing of the gapA gene to track the relative abundance of each strain over time.
Key insights:

The outcome of the synthetic communities differed greatly between potato tubers and liquid medium, with more strains being outcompeted in potato tubers. This suggests that competition mechanisms involving secreted toxins are more important in the structured environment of potato tubers.
Competition was strain-specific rather than species-specific, with the fate of the 3 strains of the same species often differing within a community.
The species P. aquaticum, which is unable to cause disease symptoms on its own, was able to persist and even become dominant in some communities, likely by acting as a "cheater" that benefits from the nutrient release by other SRP species without contributing to plant cell wall degradation.
Modeling indicates that the cost of plant cell wall degrading enzyme production, the rate of potato degradation, and the diffusion of degraded substrates could favor the persistence of cheater species like P. aquaticum.
The complexity of inter-strain competition, involving toxin production and resistance, as well as trophic interactions, likely contributes to the maintenance of high diversity within the SRP species complex and the regular shifts in dominant species observed in potato disease outbreaks.

Stats

The number of bacterial generations achieved within each inoculated potato tuber ranged from 0.9 to 13.7, with a median of 8.9.

Quotes

"Cooperation for virulence, exemplified by cheating behavior of P. aquaticum, and the complexity of competition between strains, are two mechanisms that likely contribute to the maintenance of the SRP complex diversity."
"The fact that competition occurs at the strain level rather than the species level probably also explains the regular appearance of new species responsible for epidemic outbreaks."

Key Insights Distilled From

Bacterial pathogens dynamic during multi-species infections

by Barny,M.-A.,... at www.biorxiv.org 12-06-2023

https://www.biorxiv.org/content/10.1101/2023.12.06.570389v4

Deeper Inquiries

How might the dynamics of the synthetic SRP communities evolve as the infection progresses from the potato tuber to the stem during natural field conditions?

In natural field conditions, the dynamics of the synthetic SRP communities are likely to evolve as the infection progresses from the potato tuber to the stem. The environmental conditions within the potato tuber and stem are different, leading to distinct interactions between the SRP species. In the potato tuber, where nutrients are released upon SRP infection, competition through the production of toxic compounds and resistance mechanisms is intensified. This can result in the outcompetition of certain strains within the synthetic communities. Additionally, the presence of structured environments within the potato tuber may enhance the production and efficiency of antimicrobial molecules, further influencing the dynamics of the SRP communities.
As the infection progresses to the stem, the interactions between the SRP species may change. Factors such as nutrient availability, oxygen levels, and host immune responses in the stem can impact the competition and cooperation dynamics within the SRP communities. Some strains that were outcompeted in the potato tuber may find a more favorable niche in the stem, leading to shifts in the composition of the synthetic communities. The temporal and spatial succession of different SRP species in epidemic outbreaks may also play a role in shaping the dynamics of the synthetic communities as the infection progresses through the plant.

How might the dynamics of the synthetic SRP communities evolve as the infection progresses from the potato tuber to the stem during natural field conditions?

In natural field conditions, the dynamics of the synthetic SRP communities are likely to evolve as the infection progresses from the potato tuber to the stem. The environmental conditions within the potato tuber and stem are different, leading to distinct interactions between the SRP species. In the potato tuber, where nutrients are released upon SRP infection, competition through the production of toxic compounds and resistance mechanisms is intensified. This can result in the outcompetition of certain strains within the synthetic communities. Additionally, the presence of structured environments within the potato tuber may enhance the production and efficiency of antimicrobial molecules, further influencing the dynamics of the SRP communities.
As the infection progresses to the stem, the interactions between the SRP species may change. Factors such as nutrient availability, oxygen levels, and host immune responses in the stem can impact the competition and cooperation dynamics within the SRP communities. Some strains that were outcompeted in the potato tuber may find a more favorable niche in the stem, leading to shifts in the composition of the synthetic communities. The temporal and spatial succession of different SRP species in epidemic outbreaks may also play a role in shaping the dynamics of the synthetic communities as the infection progresses through the plant.

How might the dynamics of the synthetic SRP communities evolve as the infection progresses from the potato tuber to the stem during natural field conditions?

In natural field conditions, the dynamics of the synthetic SRP communities are likely to evolve as the infection progresses from the potato tuber to the stem. The environmental conditions within the potato tuber and stem are different, leading to distinct interactions between the SRP species. In the potato tuber, where nutrients are released upon SRP infection, competition through the production of toxic compounds and resistance mechanisms is intensified. This can result in the outcompetition of certain strains within the synthetic communities. Additionally, the presence of structured environments within the potato tuber may enhance the production and efficiency of antimicrobial molecules, further influencing the dynamics of the SRP communities.
As the infection progresses to the stem, the interactions between the SRP species may change. Factors such as nutrient availability, oxygen levels, and host immune responses in the stem can impact the competition and cooperation dynamics within the SRP communities. Some strains that were outcompeted in the potato tuber may find a more favorable niche in the stem, leading to shifts in the composition of the synthetic communities. The temporal and spatial succession of different SRP species in epidemic outbreaks may also play a role in shaping the dynamics of the synthetic communities as the infection progresses through the plant.