Similar to flagella in bacteria, different archaeal species employ different numbers and patterns of archaella. Some species have one, others have many, either distributed peritrichously (all around) as in the Methanoregula formicica you just saw, or lophotrichously (clumped) as in this Thermococcus kodakaraensis. In T. kodakaraensis and related species, an additional structure–a large conical plate–is seen in the cytoplasm, perhaps providing leverage for the multiple motors. The plate has a unique structure (⇩) and may act as an organizing center akin to the polar PopZ structure we discussed in the last chapter (⇩). Note the two peaks on this cone; it may be in the process of replicating in preparation for division.
A leveraging plate must not be essential, however, because not all lophotrichous archaea use one (⇩).