A polar organelle is a structure at a specialised region of the

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

polar membrane A polarized membrane is a lipid membrane that has a positive electrical charge on one side and a negative charge on another side, which produces the resting potential in living cells. Whether or not a membrane is polarized is determined by the dis ...

that is associated with the flagellar apparatus. This flagellum-associated structure can easily be distinguished from the other membrane regions in ultrathin sections of embedded bacteria by

electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...

when the cell membrane is orientated perpendicular to the viewing direction. There, the membrane appears slightly thickened with a finely frilled layer facing the inside of the cell. It is also possible to isolate these polar organelles from the bacterial cells and study them in face view in

negatively stained In microscopy, negative staining is an established method, often used in diagnostic microscopy, for contrasting a thin specimen with an optically opaque fluid. In this technique, the background is stained, leaving the actual specimen untouched, an ...

preparations. The polar organelle bears a fine array of attached particles in hexagonal close packing and these have been shown to possess

ATPase ATPases (, Adenosine 5'-TriPhosphatase, adenylpyrophosphatase, ATP monophosphatase, triphosphatase, SV40 T-antigen, ATP hydrolase, complex V (mitochondrial electron transport), (Ca2+ + Mg2+)-ATPase, HCO3−-ATPase, adenosine triphosphatase) are ...

activity. The polar organelle is found in close juxtaposition to the points of insertion of the bacterial flagella into the plasma membrane, especially where multiple flagella bases are grouped in a region of the cell membrane. It may thus be inferred that the polar organelle could be of importance in the supply and transfer of

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of ...

to the bidirectional molecular rotational motor situated at the base of each individual bacterial flagellum (see also

electrochemical gradient An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and ...

References

Cell anatomy {{cell-biology-stub