Dawn L. Arnold

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Phylogenetic analysis of the genus Pseudomonas: was conducted by using the combined gyrB and rpoD nucleotide sequences of 31 validly described species of Pseudomonas: (a total of 125 strains). Pseudomonas: strains diverged into two major clusters designated intrageneric cluster I (IGC I) and intrageneric cluster II (IGC II). IGC I was further split into two(More)
UNLABELLED Pseudomonas syringae pv. phaseolicola causes halo blight of the common bean, Phaseolus vulgaris, worldwide and remains difficult to control. Races of the pathogen cause either disease symptoms or a resistant hypersensitive response on a series of differentially reacting bean cultivars. The molecular genetics of the interaction between P. syringae(More)
The ability to form biofilms is seen as an increasingly important colonization strategy among both pathogenic and environmental bacteria. A survey of 185 plant-associated, phytopathogenic, soil and river Pseudomonas isolates resulted in 76% producing biofilms at the air-liquid (A-L) interface after selection in static microcosms. Considerable variation in(More)
The 154-kb plasmid was cured from race 7 strain 1449B of the phytopathogen Pseudomonas syringae pv. phaseolicola (Pph). Cured strains lost virulence toward bean, causing the hypersensitive reaction in previously susceptible cultivars. Restoration of virulence was achieved by complementation with cosmid clones spanning a 30-kb region of the plasmid that(More)
Bacterial pathogenicity to plants and animals has evolved through an arms race of attack and defense. Key players are bacterial effector proteins, which are delivered through the type III secretion system and suppress basal defenses . In plants, varietal resistance to disease is based on recognition of effectors by the products of resistance (R) genes .(More)
A recently emerging bleeding canker disease, caused by Pseudomonas syringae pathovar aesculi (Pae), is threatening European horse chestnut in northwest Europe. Very little is known about the origin and biology of this new disease. We used the nucleotide sequences of seven commonly used marker genes to investigate the phylogeny of three strains isolated(More)
DNA sequences flanking two avr genes (avrPpiA1 and avrPpiB1) from Pseudomonas syringae pv. pisi show a high degree of similarity. Specific primers designed from the conserved regions were used in PCR amplifications with all P. syringae pv. pisi races. As well as amplifying the expected avrPpiA- and avrPpiB-containing fragments, two additional fragments were(More)
Pseudomonas syringae pv. phaseolicola (Pph) race 4 strain 1302A carries avirulence gene avrPphB. Strain RJ3, a sectoral variant from a 1302A culture, exhibited an extended host range in cultivars of bean and soybean resulting from the absence of avrPphB from the RJ3 chromosome. Complementation of RJ3 with avrPphB restored the race 4 phenotype. Both strains(More)
SUMMARY Pathogenicity islands (PAIs) were first described in uropathogenic E. coli. They are now defined as regions of DNA that contain virulence genes and are present in the genome of pathogenic strains, but absent from or only rarely present in non-pathogenic variants of the same or related strains. Other features include a variable G+C content, distinct(More)
The co-evolution of bacterial plant pathogens and their hosts is a complex and dynamic process. Plant resistance can impose stress on invading pathogens that can lead to, and select for, beneficial changes in the bacterial genome. The Pseudomonas syringae pv. phaseolicola (Pph) genomic island PPHGI-1 carries an effector gene, avrPphB (hopAR1), which(More)