The Morphological Effects of Lactocin A 4357 on Lactobacillus bulgaricus Cells

Morphological effects of 8 hours treatment with Lactocin A 4357 to the sensitive bacterium (Lactobacillus bulgaricus ATCC 11842) were examined under light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results are as follows: 1) By adding of lactocin to L. bulgaricus the growth inhibition was showed, however, the morphological transformation was not recognized by SEM. 2) A number of metachromatic granules were observed in each cell body of L. bulgaricus before contact of lactocin, whereas are remarkable decrease and disappearance of these granules after contact of lactocin were recognized by both LM and TEM. 3) Although the mechanism of disappearance of metachromatic granules was unclear, its reason was speculated as the direct action of lactocin or the secondary effects of the regressive change and the death of cells by lactocin. 4) Mesosomes were observed by TEM in the cell body of L. bulgaricus and the number increased after contact of lactocin. The reason of the phenomenon is not clear, however, activity of lactocin must be the most important factor. 5) Hexastyle transformation of the cell body of L. bulgaricus after contact of lactocin and the beginning of plasmolysis at the comer of hexastyle were recognized by TEM. This phenomenon was regarded as a process of damage of cell body to death by action of the lactocin or a post-lethal damage These observations were considered to be a characteristic features in the morphology of the L. bulgaricus ATCC 11842 after affection of lactocin A 4357.