Electron Microscopic Observations on the Penetration of Bdellovibrio bacteriovorus into Gram-negative Bacterial Hosts

Abstract

The progressive stages in Bdellovibrio bacteriovorus penetration into two strains of Escherichia coli were examined by use of electron microscopic techniques. The initial change observed in the ultrastructure of the host following parasitic attack was the swelling of the cell envelope at the site of attachment. The Bdellovibrio then appeared to pierce the center of this swelling, forming a pore in the outer wall layers of the host. The edges of this entry pore constricted the Bdellovibrio throughout its penetration into the host cell. Although partial disruption of the cytoplasmic membrane was always apparent, the parasite did not appear to actively penetrate through this barrier. An attempt is made to correlate the fine structural changes involved in penetration with the physiological data that have accumulated to date.

Intraperiplasmic growth of Bdellovibrio bacteriovorus 109J: N-deacetylation of Escherichia coli peptidoglycan amino sugars

“…It was shown in the previous paper (19) that the peptidoglycan layer of the substrate organism was partially solubilized by a glycanase during bdellovibrio penetration. It was proposed that this enzymatic activity made the entry pore in the substrate cell's peptidoglycan layer that has been seen in electron micrographs (1,7,17). With completion of penetration, however, this glycanase activity came to a sharp halt.…”

“…One prominent feature of the glycanase is the very sharp termination of its activity with completion of bdellovibrio penetration. We proposed that the glycanase activity was involved in making the entry pore in the peptidoglycan of the substrate cell that has been seen by electron microscopy (1,7,17).…”

Morphogenesis of Cysts in Azotobacter vinelandii

“…solution for 2.5 hr prior to dehydration in a series of acetone solutions at 1-hr intervals. After dehydration, the cells were embedded in a mixture of Epon 812 and Epon 815 (1). Sections were prepared with diamond knives (Ge-Fe-Ri, Frosinone, Italy) on a Porter-Blum MT-2 ultramicrotome (Ivan Sorvall, Inc., Norwalk, Conn.), mounted on 300-mesh copper grids, and poststained with a simplified lead citrate stain (2) for 5 min.…”

Novel bacterium infecting an African snail

“…The filaments, thicker than the 12-to 19-nm diameter of most bacterial flagella (2), in size and structure resemble the thick polar flagella of some vibrios (17,19), pseudomonads (18), and Bdellovibrio bacteriovorus (1,5,6,29)…”