You are here
Search results
(1 - 5 of 5)
- Title
- A microbiological study of Erwinia amylovora exopolysaccharide ooze
- Creator
- Slack, Suzanne Marie
- Date
- 2016
- Collection
- Electronic Theses & Dissertations
- Description
-
Fire blight, caused by the pathogen Erwinia amylovora (Burrill) Winslow et al, is the most devastating bacterial disease of pome fruits around the world. The primary dispersal of E. amylovora is through ooze, a mass of exopolysaccharides and bacterial cells that is exuded from infected host tissue. Over the 2013 and 2014 field seasons, 631 ooze droplets (201 in 2013 and 435 in 2014) were collected from field inoculated trees. Populations of E. amylovora in ooze droplets range from 108 to 1011...
Show moreFire blight, caused by the pathogen Erwinia amylovora (Burrill) Winslow et al, is the most devastating bacterial disease of pome fruits around the world. The primary dispersal of E. amylovora is through ooze, a mass of exopolysaccharides and bacterial cells that is exuded from infected host tissue. Over the 2013 and 2014 field seasons, 631 ooze droplets (201 in 2013 and 435 in 2014) were collected from field inoculated trees. Populations of E. amylovora in ooze droplets range from 108 to 1011 colony forming units per micro liter (cfu/μl). In the host tissue surrounding the droplets even larger populations of E. amylovora reside in the surrounding 1 cm of tissue. Three apple cultivars with varying levels of resistance were also infected with four Michigan E. amylovora strains. Using scanning electron microscopy, host tissue was examined for the origin of the ooze droplets and erumpent mounds and small (10 μm) tears were the only bacterial sources observed. Genetic expression analysis indicated that E. amylovora cells in stem sections located above ooze drops and in ooze drops were actively expressing virulence genes. If disseminated to susceptible host tissue, these cells would be primed for infection. The current study suggests the following: high populations of E. amylovora are present in ooze droplets which larger populations found in darker pigmented, smaller volume droplets. These droplets are rupturing out from the parenchyma and epidermis of the host, with evidence of immense pressure being involved from SEM observations. Ooze droplet volume and population can vary between host cultivar and the virulence of a specific E. amylovora strain. Genetic expression analysis of virulent factors in E. amylovora indicated that the bacteria in ooze were primed and ready to infect a new susceptible host.
Show less
- Title
- Cyclic di-GMP regulates EPS secretion, biofilm formation, and motility in the plant pathogen Erwinia amylovora
- Creator
- Edmunds, Adam Christopher
- Date
- 2011
- Collection
- Electronic Theses & Dissertations
- Description
-
The second messenger cyclic di-GMP (c-di-GMP) is a nearly ubiquitous intracellular signal molecule known to regulate various cellular processes including biofilm formation, motility, and virulence. This intracellular concentration of this molecule is inversely governed by GGDEF-containing proteins (GCPs) and EAL-containing proteins (ECPs), which synthesize and degrade c-di-GMP, respectively. The role of this regulatory molecule in the plant pathogen and causal agent of fire blight disease, ...
Show moreThe second messenger cyclic di-GMP (c-di-GMP) is a nearly ubiquitous intracellular signal molecule known to regulate various cellular processes including biofilm formation, motility, and virulence. This intracellular concentration of this molecule is inversely governed by GGDEF-containing proteins (GCPs) and EAL-containing proteins (ECPs), which synthesize and degrade c-di-GMP, respectively. The role of this regulatory molecule in the plant pathogen and causal agent of fire blight disease,Erwinia amylovora was explored. In this study, it is demonstrated that E. amylovora contains three functional diguanylate cyclases (DGCs) that synthesize c-di-GMP: gcp1 , gcp3 , and gcp5 ; and two functional c-di-GMP specific phosophodiesterases (PDEs) that degrade c-di-GMP: ecp1 and ecp3 . C-di-GMP was not detected in the wild type strain. C-di-GMP was shown to positively regulate biofilm formation and secretion of the main expolysaccharide amylovoran and to inversely regulate swimming motility and virulence. A deletion of ecp3 resulted in a hyper-biofilm forming phenotype. Interestingly, over-expression of dgc1, which contains both an EAL and a GGDEF domain, resulted in no observable phenotypic differences from the wild type strain, even though over-expression of dgc1 increased the levels of c-di-GMP.
Show less
- Title
- Investigating carbohydrate utilization and virulence in Erwinia amylovora
- Creator
- Sweeney, Emma M.
- Date
- 2018
- Collection
- Electronic Theses & Dissertations
- Description
-
Fire blight, caused by the gram-negative bacterium Erwinia amylovora, is a destructive disease of apple and pear trees worldwide. A unique aspect of apple and pear physiology is the presence of sorbitol in the leaves and shoots, glucose on the flower stigma surface and sucrose in the flower nectary. Erwinia amylovora cells encounter all three carbohydrates at different stages of infection, and it is unknown how the carbohydrate utilization genes are regulated between these changing nutrient...
Show moreFire blight, caused by the gram-negative bacterium Erwinia amylovora, is a destructive disease of apple and pear trees worldwide. A unique aspect of apple and pear physiology is the presence of sorbitol in the leaves and shoots, glucose on the flower stigma surface and sucrose in the flower nectary. Erwinia amylovora cells encounter all three carbohydrates at different stages of infection, and it is unknown how the carbohydrate utilization genes are regulated between these changing nutrient environments. This thesis explores carbohydrate utilization by E. amylovora in relation to virulence, regulatory small RNAs (sRNAs), other virulence factors and host specificity. The findings presented here indicate that sorbitol utilization (srl) gene mutants of E. amylovora are amylovoran-deficient, and they are unable to obtain the energy base needed to infect apple shoots and immature pear fruits. Additionally, the sRNA Spot 42 does not regulate sorbitol as it does in Escherichia coli, and we hypothesize that E. amylovora has evolved to evade Spot 42 regulation in order to adapt to the high-sorbitol content of apple and pear hosts.
Show less
- Title
- Resistance against Erwinia amylovora induced in apple trees by acibenzolar-s-methyl
- Creator
- Maxson, Kimberly Lynn
- Date
- 2000
- Collection
- Electronic Theses & Dissertations
- Title
- Role of waaL and umuDC in Erwinia amylovora EA1189 in oxidative stress and ultraviolet radiation survival
- Creator
- Berry, Matthew
- Date
- 2009
- Collection
- Electronic Theses & Dissertations