Bacterial conjugation: electron microscope observations on thin sections.

Abstract
Empty-appearing bubbles are formed by the Hfr strain of Escherichia coli. These often connect 2 cells, 1 of which often appears to be leaky in conjugating mixtures. Labeling experiments with bacteriophage T6 indicate that the leaky-appearing cell in conjugating pairs may represent the donor cell (Hfr). Simple mesosomes sometimes connect the cell membrane to the nucleoplasm. The DNA seems to pass directly from cell to cell in some cases.