ISHS Acta Horticulturae 411: VII International Workshop on Fire Blight
CHARACTERIZATION OF EXOPOLYSACCHARIDE SYNTHESIS BY ERWINIA AMYLOVORA |
| Authors: | K. Geider, P. Aldridge, S. Bereswill, P. Bugert, C. Langlotz |
| Abstract:
The Gram-negative bacterium Erwinia amylovora produces a capsule of the acidic exopolysaccharide (EPS) amylovoran. Amylovoran-deficient mutants are non-pathogenic. A chromosomal DNA region of 20 kb for amylovoran synthesis and the insertion sites of several Tn5-mutations were characterized by nucleotide sequence analysis. The gene products could be involved in assembly and transport of the repeating units or in the synthesis of sugar precursors. Twelve genes for expression of the ams-operon are transcribed as a 16 kb mRNA. Transcription relies on a region upstream of the operon and primer extension analysis revealed the start of the mRNA 103 nucleotides in front of amsG. Since genes adjacent to the ams-operon are homologous to udk-dcd of Escherichia coli and the rfb-region of Salmonella thyphimuirum, the ams-operon of E. amylovora could be located at 44 min relative to the chromosomal map if E. coli. The biosynthesis of amylovoran is regulated by rcs-genes and is affected by factors of the environment like the presence of sorbitol, a typical sugar for rosaceous plants, or the salt concentration in the growth medium. | |
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