Studies on the relation between the agglutination of milk fat globule and the uneven distribution of bacteria in raw bovine milk

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We reconfirmed the agglutination of starter bacteria in cow's milk and tried to elucidate the mechanism of this agglutination.1. Skim milk culture of each strain (Lactococcus lactis subsp. cremoris) was added to fresh raw milk at the rate of 1 %. After the milk had stood still at 4flC for 17 hours, bacterial cell numbers of upper layr (cream layr), intermediate layr and bottom layr were determined. Bacterial cell number of bottom layr was higher than that of intermediate layr in all the test 11 strains.2. After washed bacterial cells were reacted with colostrum whey, we could find the band originated in IgM in the electrophoretic pattern of the bacterial cells and confirm that only this band reacted with anti-bovine IgM.We obtained some results that IgG was also suggested to adhere to bacterial cells.3. We confirmed that the agglutination abilities of IgM differed considerably among different strains. Moreover, about 250 times difference of maximum dilution rate was recognized between bovine serum IgM and IgG in case of certain strain. Additionally, there was not any effect of the existence of either 5% ethanol or 1 M-NaCl on the agglutination ability of the IgM.4. When the PVDF membrane transcribed polypeptides of bacterial cell was reacted with colostrum, we confirmed that some bands on the membrane reacted with anti-bovine IgM.As the reactivity of the band (M.W.= about 52,000) was especially high, this polypeptide was suggested to be a receptor of IgM.5. As we have confirmed the distribution of IgM in cow's milk became uneven a few hours after standing fresh raw milk, the present results gave positive evidence that uneven distribution of starter bacteria in cow's milk was promoted by the adhesion of IgM to bacteria cell.