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Bacterial soft rot causes major crop losses annually and can be caused by several species from multiple genera. These bacteria have a broad host range and often infect produce through contact with soil. The main genera causing bacterial soft rot are Pectobacterium and Dickeya, both of which have widespread geographical distribution. Because of many recent renaming and reclassifications of bacteria causing soft rot, identification and characterization of the causative agents can be challenging. In this work, we surveyed commercially available produce exhibiting typical soft rot symptoms, isolating pectinolytic bacteria and characterizing them genetically and phenotypically. We found that in our sampling, many samples were from the genus Pectobacterium; however, other genera were also capable of eliciting symptoms in potatoes, including an isolate from the genus Chryseobacterium. Genomic analyses revealed that many of the Pectobacterium isolates collected share prophages not found in other soft rot species, suggesting a potential role for these prophages in the evolution or fitness of these isolates. Our Chryseobacterium isolate was most similar to C. scophthalmum, a fish pathogen, suggesting that this isolate may be a crossover pathogen. [ABSTRACT FROM AUTHOR]

Erwinia amylovora is the causative agent of the devastating disease fire blight of pome fruit trees. After infection of host plant leaves at apple shoot tips, E. amylovora cells form biofilms in xylem vessels, restrict water flow, and cause wilting symptoms. Although E. amylovora is well known to be able to cause systemic infection, how biofilm cells of E. amylovora transit from the sessile mode of growth in xylem to the planktonic mode of growth in cortical parenchyma remains unknown. Increasing evidence has suggested the important modulatory roles of Hfq‐dependent small RNAs (sRNAs) in the pathogenesis of E. amylovora. Here, we demonstrate that the sRNA RprA acts as a positive regulator of amylovoran exopolysaccharide production, the type III secretion system (T3SS), and flagellar‐dependent motility, and as a negative regulator of levansucrase activity and cellulose production. We also show that RprA affects the promoter activity of multiple virulence factor genes and regulates hrpS, a critical T3SS regulator, at the posttranscriptional level. We determined that rprA expression can be activated by the Rcs phosphorelay, and that expression is active during T3SS‐mediated host infection in an immature pear fruit infection model. We further showed that overexpression of rprA activated the in vitro dispersal of E. amylovora cells from biofilms. Thus, our investigation of the varied role of RprA in affecting E. amylovora virulence provides important insights into the functions of this sRNA in biofilm control and systemic infection. [ABSTRACT FROM AUTHOR]