Few studies deal with the understanding of disease ecology, especially in the agricultural domain. Soft rot Pectobacteriaceae are major plant pathogens that frequently co-infect potato tubers. Exploring their ecological relationships can provide valuable insights for effective monitoring and preventing disease. The study of Barny et al (2024) explores the dynamics of synthetic communities of soft rot Pectobacterium species (SRP) following in vitro and in vivo inoculations, focusing on the implications for disease development. To delve into co-infection dynamics, the authors constructed mixed populations comprising six strains, with three strains from each of two species. Through inoculations of both liquid cultures and potatoes, they observed outcomes using amplicon sequencing targeting the gapA gene, along with monitoring bacterial population sizes and symptoms on potato tubers. Results reveal intriguing patterns: competition among strains of the same species, cooperation through trophic interactions, and interference due to toxicity. Thanks to a modelling approach, they suggest that the presence of a cheater strain may be favoured when it is associated with an aggressive strain. This finding is crucial for field sampling strategies, as there is a risk that during an outbreak, only the cheater strain may be detected, potentially overlooking the problematic aggressive strain. 

While the study conducted by Barny et al. (2024) provides valuable insights into strain interactions, it also highlights areas for further exploration to enhance understanding. First, the extent to which different species occupy similar niches in real agricultural scenarios remains unclear. Additionally, comparative genomics analysis on strains and investigating specific gene candidates could offer valuable mechanistic insights into strain dynamics. These areas for future research offer chances to build up our knowledge base in this field and improve how we understand the interactions between bacteria in nature. The implications of the study extend beyond plant pathogens like SRP. Similar scenarios of complex diseases involving closely related species or strains competing within the same niche are observed in human pathogens as well.

Reference

Barny, M.-A., Thieffry, S., Gomes de Faria, C., Thebault, E., Pedron, J. (2024). Bacterial pathogens dynamic during multi-species infections. https://doi.org/10.1101/2023.12.06.570389