Pectobacterium versatile beta-lactamase, a common good of the soft rot Pectobacteriaceae species complex

Little is known about the role of antibiotics and associated resistance in microbial ecosystems in the absence of clinical antibiotic pressure. The Soft Rot Pectobacteriaceae (SRP) species complex, which comprises 37 bacterial species that are collectively responsible for the severe rotting of many crops, is an interesting model to analyse the role of {beta}-lactam and {beta}-lactamases in natural ecosystems. In particular, within this complex, most Pectobacterium versatile strains harbour a {beta}-lactamase called BlaPEC-1. The aim of our work was to analyse the role of BlaPEC-1 during infection. To this end, two blaPEC-1-deleted strains were constructed and compared with their wild-type counterparts in vitro and in potato tuber infections. In vitro, the BlaPEC-1 {beta}-lactamase enables P. versatile to resist ampicillin or carbapenem produced by Pectobacterium brasiliense. In mono-infections on potato tubers, blaPEC-1-deleted strains were unaffected in terms of virulence, fitness or association with commensal bacteria. In mixed infections, the BlaPEC-1 {beta}-lactamase proved necessary for the coexistence of P. versatile with the carbapenem-producing strain, and also for the protection of carbapenem-sensitive strains both in vitro and in planta. Interestingly, in planta protection was observed even if the blaPEC-1 gene was repressed and bacteria expressing BlaPEC-1 were in the minority within the symptom. These results indicate that BlaPEC-1 exerts a true {beta}-lactamase function during the infection process and acts as a public good of the SRP species complex. Finally, our results highlight the important role of {beta}-lactamase in maintaining of strains diversity in natural ecosystem. Statements relating to our ethics and integrity policiesThe data shown in this paper are available within the article and supplementary materials. The funding of the ANR, ANR-19-CE35-0016-03, is acknowledged. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication. The authors declare that there are no conflicts of interest. All applicable local, national and international regulations and conventions, as well as normal scientific ethical practices, were followed in the preparation of this work. This manuscript has not been previously or simultaneously published or submitted elsewhere and was critically reviewed and approved by all co-authors before submission. The CRediT of all authors is provided.