Agglutination of Erwinia stewartii Strains with a Corn Agglutinin: Correlation with Extracellular Polysaccharide Production and Pathogenicity

Abstract

A bacterial agglutinin was extracted from ground corn (WI hybrid 64A x W117) seed with phosphate-buffered saline (pH 6.0) and precipitated with (NH4)2SO4 at 70% saturation. The activities of this agglutinin against 22 strains of Erwinia stewartii (agent of bacterial wilt of corn) that varied in virulence were determined. Specific agglutination (agglutination titer per milligram of protein per milliliter) values were correlated negatively with virulence ratings. Strains with high specific agglutination values (15 or higher) were avirulent or weakly virulent; strains with low specific agglutination values (10 or lower) were highly virulent, with two exceptions. Avirulent strains produced butyrous colonies and released only small amounts of extracellular polysaccharide (EPS) into the medium, and the cells lacked capsules; virulent strains produced fluidal colonies and released large amounts of EPS, and the cells were capsulated. There was a strong correlation between the amount of EPS produced by each strain (as determined by increase in viscosity of the medium) and the specific agglutination value; in contrast, lipopolysaccharide compositions were similar in all strains. When cells of six fluidal strains were washed by repeatedly centrifuging and resuspending them in buffer, they were agglutinated more strongly by corn agglutinin than were unwashed cells. When avirulent cells were washed, their specific agglutination values did not increase significantly. Eight EPS-deficient mutants of E. stewartii, selected for resistance to the capsule-dependent bacteriophage K9, had lower virulence but higher specific agglutination than did their corresponding wild-type parents. Production of EPS appears to be essential for virulence; EPS may prevent agglutination of bacteria in the host, thus allowing their multiplication.

Rhizobium meliloti competitiveness and the alfalfa agglutinin

“…These are the same strains that did not nodulate earlier than their HA parents. Thus, it seems that there is a 3 4 5 6 7 8 9…”

Identification and characterization of three novel EsaI/EsaR quorum‐sensing controlled stewartan exopolysaccharide biosynthetic genes in Pantoea stewartii ssp. stewartii

“…This mode of growth requires the production of large amounts of stewartan exopolysaccharide (EPS), which impedes the flow of xylem sap, leading to plant wilt. Stewartan EPS is a high‐molecular‐weight heteropolysaccharide and represents the primary virulence factor in P. stewartii (Bradshaw‐Rouse et al. , 1981; Jumel et al.…”

Interactions between Clavibacter michiganensis and its host plants

“…As bacterial EPS are mostly acidic, they can also act as ion exchangers, concentrating minerals and nutrients as well as binding toxic compounds. Particularly in the context of the pathogenic interaction with plant cells, EPS may prevent recognition of the pathogen by the plant defence system, block agglutinins or lectins and detoxify phytoalexins or reactive oxygen species (Bradshaw-Rouse et al, 1981;Romeiro et al, 1981;Young and Sequeira, 1986;Kiraly et al, 1997). Furthermore, EPS mediate adhesion to abiotic and biological surfaces and may also promote infection and colonization of the host plant, a prerequisite for disease development (Tharaud et al, 1994;Bermpohl et al, 1996;Saile et al, 1997).…”