EVIDENCE FOR EXISTENCE OF LECTINS ON THE RUMINAL BACTERIA FROM STEERSFED ROUGHAGE AND CONCENTRATE DIETS

Mixed rumen bacteria, isolated by centrifugation from the rumen of ste ers fed a roughage (R) or concentrate (C) diet, were used to determine if lectins are present on rumen bacteria, based on hemagglutination ( HA) and HA inhibition assays in vitro. Rumen bacteria from steers fed either diet agglutinated erythrocytes from cattle, sheep, pigs, and ra ts, suggested that lectins exist on rumen bacteria, Bacterial HA titer s from steers receiving the R diet were much higher (p<0.001) than tho se from steers fed the C diet, depending on the erythrocyte source use d. Centrifugation at 20,000xg for 30 min fractionated the rumen bacter ia into upper (U) and lower (L) layers, The HA titers of the U bacteri al fractions were significantly higher (p<0.001) than those of the L f ractions, A remarkable reduction or complete disappearance of HA titer s following treatment of rumen bacteria with protease, trypsin, sodium dodecyl sulfate (SDS) or sodium periodate indicates that rumen bacter ial lectins are probably glycoproteins. Lectin specificity for sacchar ides (galactose, lactose, N-acetyl-D-galactosamine, methyl-alpha-D-gal actopyranoside and methyl-beta-D-galactopyranoside) and glycoproteins (mucin, fetuin, and thyroglobulin) was found in the RU, RL, and CU bac terial fractions; no specific binding was determined in the CL fractio ns, The potential role of lectins in mediating the attachment of rumen bacteria to feed particles, rumen epithelia and other microorganisms is discussed.