Composition of Lipopolysaccharides from Four Strains of Erwinia amylovora

Ray, T. C.; Smith, Andrew; Carter, K. J.; Hignett, R. C.

doi:10.1099/00221287-132-11-3159

Cited by 7 publications

(14 citation statements)

References 25 publications

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“…In agreement with the results of Ray et al. (37) for the structure of LPS, the absence of UDP-galactose in the galE mutant Eal/79-M1 also abolishes synthesis of the 0-specific side chain.…”

Section: Discussionsupporting

confidence: 81%

“…The high content of galactose makes the synthesis of the repeating unit sensitive to the availability of UDP-galactose. Galactose not only is the main sugar in the EPS amylovoran (45) but is also present in the 0-specific side chain of E. amylovora LPS (37). In contrast to results withAgrobacterium tumefaciens (48) Ley-Douderoff pathway.…”

Section: Discussionmentioning

confidence: 64%

“…By complementation with the galE gene on plasmid pEA200, we confirmed Billing's hypothesis. Strain S also shows an altered LPS structure (37). Besides the defect of a galE mutant in amylovoran synthesis, a change in LPS could also affect virulence.…”

Section: Discussionmentioning

confidence: 99%

“…Galactose is not only a constituent of amylovoran but also a component of the 0-specific side chain in LPS of E. amylovora (37). In addition to a defect in EPS synthesis, an alteration of the LPS structure could also interfere with pathogenicity.…”

Section: Methodsmentioning

confidence: 99%

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Genetics of galactose metabolism of Erwinia amylovora and its influence on polysaccharide synthesis and virulence of the fire blight pathogen

et al. 1994

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Galactose metabolism mutants of Erwinia amylovora were created by transposon insertions and characterized for their growth properties and interaction with plant tissue. The nucleotide sequence of the galE gene was determined. The gene, which encodes UDP-galactose 4-epimerase, shows homology to the galE genes of Escherichia coli, Neisseria gonorrhoeae, Rhizobium meliloti, and other gram-negative bacteria. Cloned DNA with the galE and with the gaiT and galK genes did not share borders, as judged by the lack of common fragments in hybridization with chromosomal DNA. These genes are thus located separately on the bacterial chromosome. In contrast to the gal operon of E. coli, the galE gene of E. amylovora is constitutively expressed, independently of the presence of galactose in the medium. The function of the galE gene but not of the galT or galK gene is required for bacterial virulence on pear fruits and seedlings. In the absence of galactose, the galE mutant was deficient in amylovoran synthesis. Subsequently, the galE mutant cells elicited host defense reactions, and they were not stained by fluorescein isothiocyanate-labelled lectin, which efficiently binds to amylovoran capsules ofE. amylovora. The mutation affected the side chains of bacterial lipopolysaccharide, but an intact 0 antigen was not required for virulence. This was shown with another mutant, which could be complemented for virulence but not for side chain synthesis of lipopolysaccharide.The gram-negative bacterium Erwinia amylovora is the causal agent of fire blight, a necrotic disease of rosaceous plants (49). To escape plant defense mechanisms and to cause symptoms, E. amylovora requires the capsular exopolysaccharide amylovoran (4, 20, 44). Amylovoran synthesis mutants are nonpathogenic (6, 47). A chromosomal cluster of ams genes necessary for amylovoran synthesis has been characterized (7). Cloned E. amylovora genes were able to complement mutants in the cps genes of the maize pathogen Erwinia stewartii, which are involved in exopolysaccharide (EPS) synthesis. The galE gene is adjacent to the cps gene cluster in E. stewartii (14). The dominant sugar in amylovoran is galactose (45). Consequently, disruption of the galactose metabolism affects the capsule synthesis and virulence of E. amylovora, and growth in the presence of galactose restores the ability to produce EPS (8). The genetics of gal genes in E. amylovora have not been resolved.Enterobacteria utilize galactose by the LeLoir pathway (1). The first reaction in this pathway is catalyzed by galactokinase (EC 2.7.1.6), which phosphorylates free galactose to galactose-1-phosphate. In the next steps, galactose-1-phosphate uridylyltransferase (EC 2.7.7.10) transfers the UDP residue from UDP-glucose to galactose-1-phosphate, and UDP-galactose 4-epimerase (EC 5.1.3.2) catalyzes the reversible conversions of UDP-galactose and UDP-glucose. In Escherichia coli, the structural genes galK, galT, and galE are organized in an operon which is induced by galactose (1). Two adjacent promoters are regulat...

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“…In agreement with the results of Ray et al. (37) for the structure of LPS, the absence of UDP-galactose in the galE mutant Eal/79-M1 also abolishes synthesis of the 0-specific side chain.…”

Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Genetics of galactose metabolism of Erwinia amylovora and its influence on polysaccharide synthesis and virulence of the fire blight pathogen

et al. 1994

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show abstract

“…EPS, sometimes referred to as amylovorin (Goodman et al, 1974;Bennet & Billing, 1978;Smith et al, 1990), lipopolysaccharide, LPS (Ray et al, 1986(Ray et al, , 1987, a high-molecular-mass levan (Gross et al, 1989) and a low-molecular-mass glucan (A. R. W. Smith personal communication). Since little is known about the possible role of the glucan in the pathogenicity of E.…”

Section: Bacterial Polysaccharidesmentioning

confidence: 99%