Results of electron-microscopic examination of Shigella flexneri cells, subjected to influence the bacteriocin-producing Lactobacillus acidophilus bacteria are presented. The response of shigellae to bacteriocinogenic lactobacilli was shown both on cellular and population levels. On population level the correlation of various morphological types of shigella cells with increase of involution, lysing and resting forms is revealed. At a cellular level the specific ultrastructural changes of shigella evidencing the significant destructive processes of the cells were revealed. In one case destabilization of shigella cellular wall was observed, that was manifested in expansion of periplasmic spaces and appearence of specific involution forms of the cells. In other cases, changes in the ultrastructural organization of shigella nucleoid were found out, manifested in disappearance of thin-fibrillar DNA and formation of electronic-dense globular structures of the cells.