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The hexagonal array structure of chemosensory systems is invariant across species, and even across domains. As you can see in this Methanospirillum hungatei, the arrays have the same architecture in archaea as in bacteria, with 12 nm center-to-center spacing between the hexagons. This strong conservation indicates the importance of chemotaxis for cells’ fitness, and suggests that evolution had already honed it to a relatively optimal form in the common ancestor of all these cells.