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

我们再次证实了发酵菌在牛奶中的凝集作用，并试图阐明这种凝集作用的机制。各菌株（乳酸乳球菌亚种）的脱脂乳培养。鲜奶中以1%的添加率添加Cremoris。在4flC静置17小时后，测定上层（奶油层）、中间层和底层的细菌细胞数量。试验11株菌株中，底层细菌细胞数均高于中间层。洗涤后的细菌细胞与初乳乳清反应后，我们在细菌细胞的电泳图谱中发现了源于IgM的条带，并证实只有这条条带与抗牛IgM反应。我们得到的一些结果表明，IgG也可以粘附在细菌细胞上。我们证实了不同菌株间IgM的凝集能力有很大差异。此外，在某些菌株的牛血清中，IgM和IgG的最大稀释率相差约250倍。此外，5%乙醇和1 M-NaCl的存在对IgM.4的凝集能力没有影响。将细菌细胞多肽转录的PVDF膜与初乳反应后，我们证实膜上的一些条带与抗牛IgM反应。由于该条带的反应活性特别高（M.W.=约52,000），因此该多肽可能是IgM.5的受体。我们已经证实，生鲜奶静置几小时后，牛奶中IgM的分布变得不均匀，本研究结果为IgM与细菌细胞的粘附促进了牛奶中发酵菌的分布不均匀提供了积极的证据。

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.