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Figure 1. Electron micrograph of an intact
Escherichia coli cell. LPs, lipopolysaccharide or outer membrane which is
present in Gram-negative bacteria and contains various porins which allow
diffusion of small molecules (up to penta-lysine) into the so-called
peri-plasmic space. Not seen in the micrograph is the rigid, electron dense
peptidoglycan layer of the cell wall, present in all Eubactericiae which
provides the cell with its shape and allows bacteria to accumulate
metabolites again large concentration gradients without bursting due to
influx of water. Closely opposed to the peptidoglycan layer is the plasma
membrane (PM).
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