Cell Wall Replication in Escherichia coli , Studied by Immunofluorescence and Immunoelectron Microscopy

Abstract

Cell wall components of four different strains of E. coli (B; B/r, try-; O5; and O86: B7) were labeled with homologous fluorescent antibodies (FLG); the way the label was dispersed on further growth in media free of antibody was followed by fluorescence micrscopy. Fluorescence diminished diffusely along longitudinal wall but remained bright at cell poles (or cross walls); newly formed cross walls did fluoresce. In agreement, reverse labeling (preincubation in unlabeled antibody, followed by staining on the slide with homologous FLG) showed that stainability of longitudinal wall increased gradually and diffusely with increased time of incubation, whereas polar wall remained nonfluorescent or stained only faintly; newly formed poles (or cross walls), on the other hand, stained brightly. These observations were confirmed by electron microscopy, after immunoferritin labeling. Although the mode of cross-wall formation remained unclear, our findings refuted reported ideas of segmental or polar growth of cell wall in E. coli and supported the idea of wall replication by diffuse intercalation, as described for Salmonella.