Their function is not precisely known. Electron micrographs of mesosomes reveal a spherical, swiss cheese structure. Figure 3 - An electron micrograph of a mesosome. Mesosomes are often found near septa or dividing lines in bacteria and seem to be involved with segregation of newly replicated chromosomes. Although the width of the cell membrane is fixed, the area is not.
Some bacteria have complex infoldings.
These are attached to the cytoplasmic membrane but serve to increase its area. Below is a picture of the intercytoplasmic membrane of Rhodobacter sphaeroides Figure 4 - The intercytoplasmic membrane of Rhodobacter sphaeriodes These infoldings are found in photosynthetic and rapidly respiring bacteria. The infolding provides additional surface area and contact with the environment needed for high metabolic rates. Membranes and Antibiotics Several antibiotic are targeted at the membrane, including Polymyxin B and Gramicidin. To get around this, these antibiotics are used topically or in very low doses.