Sensory transduction in flagellate bacteria.

Flagellate bacteria can respond to a wide range of environmental chemicals and a variety of physical parameters, and integrate those responses. The most important thing for a cell is to maintain its energy level; bacteria therefore respond directly to any changes in their PMF. This has been likened to higher organisms responding to a physiological change, for example, a fall in blood glucose. In addition, if the PMF is high, the cell is free to respond to a limited range of metabolites and possibly move to an area that will allow an increased growth rate. Bacteria do not sense all amino acids, as the space available on the cytoplasmic membrane is limited, and a change in a few important metabolites is probably a good measure of the general environment around the cell. The sensory response does not require either transport into the cell or metabolism of the chemical, only the binding to the specific MCP. The cell could have a mutation in the pathway metabolizing the chemoeffector, but it would still respond to changes in the concentration of that compound. This taken with the ability of the cells to adapt to the stimulus has been considered to be the prokaryotic equivalent of smell and taste.