Project description:Lytic bacteriophages able to infect and kill Dickeya spp. can be readily isolated from virtually all Dickeya spp.-containing environments, yet little is known about the selective pressure those viruses exert on their hosts. Here, we identified two spontaneous phage-resistant D. solani IPO 2222 mutants, DsR34 and DsR207, resistant to infection caused by phage vB_Dsol_D5 (ΦD5) that expressed a reduced ability to macerate potato tuber tissues compared to the wild-type, phage-susceptible D. solani IPO 2222 strain. Genome sequencing revealed that mutants had point mutations in two genes encoding: secretion protein HlyD (mutant DsR34) and elongation factor Tu (EF-Tu) (mutant DsR207). Both mutations impacted the proteoms of D. solani grown in rich and minimal media. Furthermore, DsR34 and DsR207 were characterized for features essential for their ecological success in a plant environment, including the ability to use various carbon and nitrogen sources, production of plant cell wall degrading enzymes, ability to form biofilms, siderophore production, swimming and swarming motility and virulence in planta. Compared to the wild-type ΦD5-susceptible D. solani strain, mutants DsR34 and DsR207 expressed reduced ability to macerate chicory leaves and to colonize and cause symptoms in growing potato plants. The implications of the ΦD5 resistance on the ecological performance of D. solani are discussed.
Project description:The DsbA oxidoreductase is a crucial factor responsible for introduction of disulfide bonds to the extracytoplasmic proteins in bacteria. A lack of the proper disulfides frequently leads to instability and/or loss of protein function. In pathogens, numerous envelope and extracellular proteins play important roles in pathogenesis; therefore, their improper disulfide bonding may lead to avirulent phenotypes. The importance of the DsbA function in phytopathogens has not been extensively studied yet. Dickeya solani is a bacterium from the Soft Rot Pectobacteriaceae group which is responsible for very high economic losses mainly on potato. In recent years, D. solani became the most abundant potato pathogen among Dickeya species in Europe. In this work, using the D. solani dsbA mutant, we demonstrated that a lack of the DsbA function caused loss of virulence. Mutant bacteria were deficient in most secreted virulence determinants and were not able to develop disease symptoms in the natural host, the potato plant. The SWATH-MS-based proteomic analysis revealed that the dbsA mutation led to multifaceted effects in the D. solani cells. First of all, the levels of the majority of plant cell wall degrading enzymes and proteins related to motility and chemotaxis were severely reduced. Furthermore, the protein profiles suggested induction of the envelope and cytoplasm stress responses in the mutant cells. Finally, the outer membrane barrier seemed to be disturbed by the mutation. Our results clearly demonstrate that the function played by the DsbA oxidoreductase is indispensable for D. solani virulence and a lack of DsbA significantly disturbs cellular physiology. A thorough analysis of proteomic research suggests that a lack of virulence may result from both, abnormalities of the disulfide deprived virulence determinants and the envelope stress-dependent repression of the virulence genes in the dsbA mutant.
Project description:An updated representation of S. meliloti metabolism that was manually-curated and encompasses information from 240 literature sources, which includes transposon-sequencing (Tn-seq) data and Phenotype MicroArray data for wild-type and mutant strains.
Project description:To identify differently expressed proteins in tuber tissue of potato cultivars and diploid interspecific hybrids of Solanum, differing in resistance to Dickeya solani, comparative analysis was performed. Two highly resistant (Bea and Humalda) and three susceptible (Irys, Katahdin, Ulster Supreme) potato cultivars, as well as the highly resistant (DG 00-270) and the susceptible (DG 08-305) diploid clones, were studied. DG 00-270 exhibited higher resistance to D. solani than the cultivars Bea and Humalda. Proteins were extracted from wounded potato tubers inoculated with bacteria at an early symptomatic phase and from controls, i.e., intact tubers and wounded mock-inoculated tubers. Protein profiles were analyzed using nano-liquid chromatography coupled with tandem mass spectrometry (LC-MS-MS/MS).
Project description:The Lon protein is a protease implicated in virulence of many pathogenic bacteria, including some plant pathogens. However, little is known about the role of Lon in bacteria from genus Dickeya. This group of bacteria include important potato pathogens, with the most aggressive species, D. solani. To determine the importance of Lon for pathogenicity and response to stress conditions of bacteria, we constructed a D. solani Δlon strain. The mutant bacteria showed increased sensitivity to certain stress conditions, in particular osmotic and high-temperature stresses. Furthermore, qPCR analysis showed an increased expression of the lon gene in D. solani under these conditions. The deletion of the lon gene resulted in decreased motility, lower activity of secreted pectinolytic enzymes and finally delayed onset of blackleg symptoms in the potato plants. In the Δlon cells, the altered levels of several proteins, including virulence factors and proteins associated with virulence, were detected by means of MS-SWATCH analysis. These included components of the type III secretion system and proteins involved in bacterial motility. Our results indicate that Lon protease is important for D. solani to withstand stressful conditions and effectively invade the potato plant.