Figure 1. A hypothetical growth curve for a culture of Escherichia coli. The four phases of growth are given.

Figure 2. The cell envelope of Escherichia coli. The dark blue rounded rectangle denotes the inner (cytoplasmic) membrane; the red blue rounded rectangle denotes the outer membrane. The thin black rounded rectangle just inside the outer membrane denotes the peptidoglycan layer. In the enlargement of the inner membrane enlargement the light blue ovals denote the head groups of the phospholipid molecules and the wavy black lines are the fatty acid chains of the phospholipids. The grey shapes denote protein molecules. In the enlargement of the outer membrane structure the designations are the same except that the green boxes denote the lipid A head groups and the chains of differing shapes represent the sugars of the oligosaccharides.

Figure 3. The donor and recipient cells are denoted by rounded rectangles and the chromosomes by ovals. In the mating pair, for simplicity, only the chromosome transferred by the donor is shown. The chromosome from which it was copied is not shown. The lower left is an enlargement of the alignment step of homologous recombination in the recipient cell. The X denotes genetic exchange.

Figure 4. Two Escherichia coli cells undergoing conjugation; one strain has fimbriae. Fimbriae are abundant short filaments that extend from the cell surface and play a key role in the attachment of the organism to cells of its animal hosts.