Resistance of Dickeya solani strain IPO 2222 to lytic bacteriophage ΦD5 results in fitness tradeoffs for the bacterium during infection.

Resistance to bacteriophage infections protects bacteria in phage-replete environments, enabling them to survive and multiply in the presence of their viral predators. However, such resistance may confer costs for strains, reducing their ecological fitness as expressed as competitiveness for resources or virulence or both. There is limited knowledge about such costs paid by phage-resistant plant pathogenic bacteria in their natural habitats. This study analyzed the costs of phage resistance paid by the phytopathogenic pectinolytic bacterium Dickeya solani both in vitro and in potato (Solanum tuberosum L.) plants. Thirteen Tn5 mutants of D. solani IPO 2222 were identified that exhibited resistance to infection by lytic bacteriophage vB_Dsol_D5 (ΦD5). The genes disrupted in these mutants encoded proteins involved in the synthesis of bacterial envelope components (viz. LPS, EPS and capsule). Although phage resistance did not affect most of the phenotypes of ΦD5-resistant D. solani such as growth rate, production of effectors, swimming and swarming motility, use of various carbon and nitrogen sources and biofilm formation evaluated in vitro, all phage resistant mutants were significantly compromised in their ability to survive on leaf surfaces as well as to grow within and cause disease symptoms in potato plants.

Pectobacterium parmentieri SCC 3193 Mutants with Altered Synthesis of Cell Surface Polysaccharides Are Resistant to N4-Like Lytic Bacteriophage ϕA38 (vB_Ppp_A38) but Express Decreased Virulence in Potato (Solanum tuberosum L.) Plants.

Pectobacterium parmentieri is a Gram-negative plant-pathogenic bacterium able to infect potato (Solanum tuberosum L.). Little is known about lytic bacteriophages infecting P. parmentieri and how phage-resistance influences the environmental fitness and virulence of this species. A lytic phage vB_Ppp_A38 (ϕA38) has been previously isolated and characterized as a potential biological control agent for the management of P. parmentieri. In this study, seven P. parmentieri SCC 3193 Tn5 mutants were identified that exhibited resistance to infection caused by vB_Ppp_A38 (ϕA38). The genes disrupted in these seven mutants encoded proteins involved in the assembly of O-antigen, sugar metabolism, and the production of bacterial capsule exopolysaccharides. The potential of A38-resistant P. parmentieri mutants for plant colonization and pathogenicity as well as other phenotypes expected to contribute to the ecological fitness of P. parmentieri, including growth rate, use of carbon and nitrogen sources, production of pectinolytic enzymes, proteases, cellulases, and siderophores, swimming and swarming motility, presence of capsule and flagella as well as the ability to form biofilm were assessed. Compared to the wild-type P. parmentieri strain, all phage-resistant mutants exhibited a reduced ability to colonize and to cause symptoms in growing potato (S. tuberosum L.) plants. The implications of bacteriophage resistance on the ecological fitness of P. parmentieri are discussed.

High-Quality Complete Genome Resource of Plant-Pathogenic Bacterium Dickeya solani IPO 2019, Isolated from Hyacinthus orientalis.

Dickeya solani is an emerging plant-pathogenic bacterium causing disease symptoms in a variety of agriculturally relevant crop species worldwide. To date, a number of D. solani genomes have been sequenced and characterized; the great majority of these genomes have, however, come from D. solani strains isolated from potato (Solanum tuberosum L.) and not from other plant hosts. Herewith, we present the first complete, high-quality genome of D. solani IPO 2019 (LMG 25990), isolated from the ornamental plant Hyacinthus orientalis. The genome of D. solani IPO 2019 consists of one chromosome of 4,919,542 bp, with a GC content of 56.2% and no plasmids. The genome contains 4,502 annotated features, 22 ribosomal RNA genes, 73 transfer RNA genes, and one CRISPR. We believe that the information on this high-quality, complete, closed genome of D. solani strain isolated from a host plant different from potato (i.e. hyacinth) will provide resources for comparative genomic studies and for analyses targeting adaptation and ecological fitness mechanisms present in Dickeya solani species.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.