Download Bacterial flagellum

BIMM 130
Dr. Milton Saier
Bacterial Flagellum
Bacterial flagellum: 10 microns long (the helical period is ~2 microns); the size of the flagellum
is about 1 billion Da!
There are ~50 flagellum (flg, flh, fli) genes; about ~25 structural genes.
+ 2 mot + 6 che + 5 primary receptor genes encoding MCPs + many more secondary receptors
E. coli: ~10 flagelli; 20,000 rpm; H+; 30 /sec (~ 2 mm/min)
- other bacteria 1-1,000 flagelli (i.e., swarming), 101-105 rpm H+ or Na+; 10-200 /sec (~20
mm/min)
If E. coli was the size of a car, how fast would it go?
E. coli: 1   2 mm/min = 120 mm/hr = 0.12 meters/hr
Car: 5 meters  65 mph ~100 km/hr; max, 250 km/hr; size difference 5 x 106
0.12 meters/hr (5 x 106) = 0.6 x 106 meters/hr = 600 km/hr
But some bacteria swim 10x faster: 6,000 km/hr; faster than any jet airplane!
Motor:
a. Stator: MotAB is the ion selector (H+ or Na+) (Asai et al., 2003)
b. Rotor: the flagellum (FliFGMN). The C-terminal domain of FliG interacts with MotAB to
produce the torque.
FliG, FliM and FliN form a complex that interacts with MotAB; only their genes when mutated 
(1) fla, (2) mot and (3) che phenotypes, i.e., phenotypes corresponding to (1) an absence of flagelli,
(2) intact flagelli but no motor function, and (3) normal flagelli with an active motor but lacking
chemotactic responses.
MotAB complexes have been reconstituted in artificial membranes yielding channels specific for
H+ or Na+.
References:
(Terashima et al. 2008)
(Minamino et al. 2008)
bushing
OM
PG
IM
L-ring
rotor
P-ring
S-ring
M-ring

Stator
(MotA + MotB)
C-ring
FliG
Charged
ridge
Structure of the flagellar basal region and its
association with the bacterial cell envelope.
OM, outer membrane; PG, peptidoglycan
cell wall; IM, inner membrane.
References:
Anderson JK, Smith TG, Hoover TR. Sense and sensibility: flagellum-mediated gene regulation.
Trends Microbiol. 2010 Jan;18(1):30-7.
Asai Y, Yakushi T, Kawagishi I, Homma M. Ion-coupling determinants of Na+-driven and H+driven flagellar motors. J Mol Biol. 2003 Mar 21;327(2):453-63.
Egelman EH. Reducing irreducible complexity: divergence of quaternary structure and function
in macromolecular assemblies. Curr Opin Cell Biol. [Review]. 2010 Feb;22(1):68-74.
Minamino T, Imada K, Namba K (2008) Molecular motors of the bacterial flagella. Curr Opin
Struct Biol 18:693-701
Smith TG, Hoover TR. Deciphering bacterial flagellar gene regulatory networks in the genomic
era. Adv Appl Microbiol. [Review]. 2009;67:257-95.
Terashima H, Kojima S, Homma M (2008) Flagellar motility in bacteria structure and function
of flagellar motor. Int Rev Cell Mol Biol 270:39-85