8. Molecular formal inversion - C.

Bacteria. In bacterial brain-mind homologues there are formal inversions in cell-to-cell systems rather like the virus-to-cell inversions in the previous post. One example is the fimbriae mechanism. The fimbriae are very fine hair-like protein filaments that grow out from the surface of a bacterium and enable it to adhere to other cells. The presence or absence of fimbriae on E. coli is determined by inversion of the promoter region of the gene called fim A, as shown.

There is another kind of bacterial formal inversion switch that works on larger protein outgrowths called flagella. For example, as in the sketch shown in post 4, a flagellum (or motor unit) of E. coli works by rotating clockwise or anticlockwise. When the bacterium detects an attractant chemical, the molecular brain-mind homologue of the cell signals the 5 to 10 flagella to rotate anticlockwise and collect into a sort of pony-tail that drives the cell in a 'run' towards the chemical. When a repellent chemical is detected, the flagella rotate clockwise and fly apart so that the cell is said to 'tumble' at an angle to the run and away from the chemical. The run and tumble effect is yet another example of the formal inversion principle being deployed in the interests of survival.