Updated: Rotary motors in nature

Listening to the radio this morning, I heard about a bacteria called Bdellovibrio (silent ‘B’) that kills other bacteria – the programme was talking about its use as an antibiotic.

It is a fast-swimming bacteria, and this reminded me reminded me that some bacteria, including this one, swim using a real rotary motor attached to a long whip-like thing called a flagellum. The flagellum is interesting in it self, forming a cork-screw shape in the water as it is spun to give propulsion, but being constructed of more than one protein type along its length to give different stiffness to different parts – or so I understand.

Update: It looks like the motor is a stepper of some form, with switching of poles, described by this excellent paper in Microbiology: ‘Turning the flagella motor‘ – oh heck, I only got access once – good luck to you.

BTW, Some flagella motors are bi-directional, and others not, and there are also bacteria which don’t have rotary flagellum, but instead bend the base of a fixed flagellum so that it sweeps in a circle.


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