Dickeya solani
1. Classification
a. Higher order taxa
Domain: Bacteria; Phylum: Proteobacteria; Class: Gammaproteobacteria; Order: Enterobacterales; Family: Pectobacteriaceae; Species: Dickeya solani
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NCBI: [1] |
2. Description and significance
Describe the appearance, habitat, etc. of the organism, and why you think it is important.
- Include as many headings as are relevant to your microbe. Consider using the headings below, as they will allow readers to quickly locate specific information of major interest*
3. Genome structure
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?
4. Cell structure
Interesting features of cell structure. Can be combined with “metabolic processes”
5. Metabolic processes
D. solani is a facultative anaerobe, capable of conducting both aerobic respiration and fermentation, depending on the amount of oxygen present. The percentage of oxygen-dependent genes in D. solani, including virulence genes, is much lower than those of other microorganisms, including other Dickeya species [5]. This feature allows D. solani to infect potatoes, its primary host, under a wide range of oxygen conditions [5]. After initial contact with a potential host, there is only a small change in transcription of plant-tissue specific virulence genes within D. solani, meaning that global reprogramming of D. solani’s metabolism is not required for the successful infection of a plant host [8]. The slow onset of this gene expression allows D. solani to colonize the host and grow into a larger bacterial population before beginning the infection process [8]. D. solani can often be found inhabiting the tubers of a potato plant, while D. Dianthicola, a related bacterium, can be found residing in the stems of the same plant [3]. Genome sequence analysis of D. solani and comparison to the genome of D. dianthicola revealed that each species had a few hundred genes to it, including metabolism-related genes. The metabolic differences between the two species include differences in carbon and nitrogen source utilization, allowing D. solani and D. dianthicola to exploit distinctive niches in the same habitat, contributing to their coexistence on the same host [9].
6. Ecology
D. solani is a plant pathogen that most commonly infects the tubers on potatoes, but can often be found on other ornamental plants [3]. Since its first observation in 2004, D. solani has been rapidly spreading throughout Europe and damaging crops, leading to significant economic losses. The pathogenic success of D. solani stems from its ability to maximize its metabolic activity in temperate climates. The recent rise in temperatures and precipitation rates in Europe have contributed to an increase in its population levels that is expected to continue [2]. D. solani is able to coexist with other bacterial pathogens in the same host plant, allowing it to colonize previously infected plants. It is more common for D. solani to inhabit the tubers, while related competitor D. dianthicola may reside in the stems [3].
7. Pathology
D. solani infection is a common cause of blackleg and soft-rot in potato stems and tubers, resulting in widespread crop loss in Europe (3). The aggressive infection of D. solani is a result of its genetic diversity and mechanism of infection. D. solani interaction with host tissues induces the expression of a complex network of virulence genes, including pectin lyase genes, integral membrane proteins, and structural proteins, tailoring cellular metabolism and environmental interactions to increase infection efficiency (7). D. solani has an increased capacity to instigate symptoms at a lower inoculum level than other Dickeya species, likely due to its assorted pectate lyase genes that encode for enzymes that more efficiently degrade plant cell walls (9, 3). The virulence of various strains of D. solani is affected by mutations in assorted genes, with strains that possess incomplete adhesion protein genes being more virulent than those that have complete cell adhesion protein genes (10). Incomplete adhesion proteins cause increased mobility within a host and contribute to more aggressive infection and faster spread (10). D. solani exploits alternative carbon sources not used by other pathogens, which facilitates coexistence with other organisms on the potato host (9). D. solani has only 1% of its genes thermoregulated, allowing it to cause infection across a spectrum of environmental conditions (11). However, optimal performance is observed at higher temperatures, where pectin lyase genes are upregulated and biofilm formation is stimulated (11).
8. Current Research
Current research on D. solani focuses on the characteristics that lead to its aggressiveness as a plant pathogen. Much of the recent literature on this bacterium focuses on its pathology, due to its high virulence and ability to rapidly spread; these characteristics allow D. solani to cause great economic losses in agriculture [12]. Research has shown that D. solani has the ability to infect hosts under a wider range of environmental conditions than comparable plant pathogens; only 1.46% of its genes are oxygen-dependent, making it more effective at infecting plants at different oxygen availabilities than other disease-causing species [5]. Much of the current research has also found that D. solani is able to infect potatoes under a larger range of temperatures and density load than other species. When comparing D. solani to other plant pathogenic bacteria in tubers, researchers found that D. solani was able to inoculate the tubers at densities and at a wider range of temperature of 21-27 ℃. [5]. Recent studies have investigated D. solani at the genomic level to understand the severity of its virulence. One recent study found that different D. solani strains had key variability in virulence features like production of proteases, cellulases, and motility, while the rest of its genome remained largely conserved [10]. When looking at the virulence of a strain with an intact adhesin gene, scientists found that its virulence was lower than strains where this gene had been disrupted. They concluded that D. solani’s aggressiveness as a pathogen is related to motility, rather than adherence to plant material [10]. Ultimately, D. solani is more virulent than other species, with greater variability among species strains that could factor into the aggressiveness of the bacterium [6]. In response to economic losses and the aggressiveness of D. solani in causing soft rot, research has also expanded into diagnostic methods and prevention of D. solani infection. One study looked at the diagnostic ability of serological testing on potato crops suspected of infection. Serological tests were found to lack the specificity to screen potato crops for D. solani effectively, with only 68% of isolates being identified by the antibodies [13]. Instead, new immunoassay technologies with increased sensitivity capabilities for D. solani are an active area of research and implementation [13]. Another study looked into 46 different bacteriophages as potential treatments to prevent D. solani infection. Researchers found 6 T7-like bacteriophages that, when combined in a viral cocktail and treated in vivo in the potatoes, significantly disease progression in the potatoes [14].
9. References
It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035. Edited by [Mary Campion, ], student of Jennifer Bhatnagar for BI 311 General Microbiology, 2021, Boston University
