Comparative proteome analysis of four Erwinia amylovora strains with different pathogenicity

Abstract

Fire blight, caused by the bacterium Erwinia amylovora, affects most species of the Malaceae and some species in other families of the Rosales. The severity of the disease results from its destructive character on the one hand and the lack of effective control methods on the other hand. To gain a better insight into the degree of virulence and the sensitivity to oxidative stress, the proteome of four strains of Erwinia amylovora was studied. The strains used were E. amylovora LMG2024 and PD437, which are moderately pathogenic, PFB5, which is highly, and BG16, which is very highly pathogenic. The bacteria were grown in fluid MM2 medium until the exponential phase. Proteins were extracted and analysed by two-dimensional electrophoresis. Differentially regulated protein spots were excised, trypsinized and analysed by LC-ESI-MS/MS. The MS/MS spectra were searched with Sequest and Mascot against an ORF-database, which is based on the sequencing data of Erwinia amylovora produced by the Sanger Institute and can be obtained from ftp://ftp.sanger.ac.uk/pub/pathogens/era/. The identified ORF-protein sequences were blasted against the NCBInr database to know their possible function. For analysis by mass spectrometry, 27 spots were selected. Some proteins (e.g., peroxiredoxin and 5,10-methylenetetrahydrofolate reductase) are more expressed in the moderately pathogenic strains LMG2024 and PD437, while others (e.g., GADPH) are more expressed in the highly virulent strains PFB5 and BG16. In the most pathogenic strain, BG16, some important proteins are strongly expressed: the OxyR, a protein which is a sensor of oxidative stress; the uracil-DNA glycosylase involved in DNA repair; and the gluthathione-S-transferase involved in detoxification. This might implicate a possible relation between resistance against oxidative stress and virulence.