Page "Protein targeting" Paragraph 36

With some exceptions, Bacteria lack membrane-bound organelles as found in eukaryotes, but they may assemble proteins onto various types of inclusions such as gas vesicles and storage granules.

Bacteria may have a single plasma membrane ( Gram-positive bacteria ), or an inner membrane plus an outer membrane separated by the periplasm ( Gram-negative bacteria ).

Proteins may be incorporated into the plasma membrane, or either trapped in the periplasm or secreted into the environment, according to whether or not there is an outer membrane.

The basic mechanism at the plasma membrane is similar to the eukaryotic one.

In addition, bacteria may target proteins into or across the outer membrane.

Systems for secreting proteins across the bacterial outer membrane may be quite complex and play key roles in pathogenesis.

These systems may be described as type I secretion, type II secretion, etc.