Bacterial Locomotion: Flagellar Structure and Movement Mechanism
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LOCOMOTION
IN
BACTERIA
TYPES
OF
MOVEMENT
A.
FLAGELLAR
STRUCTURE
OF
FLAGELLA
FLAGELLAR SYNTHESIS
AND
ASSEMBLY
MECHANISM
OF
FLAGELLAR
MOVEMENT
B.
GLIDING
MOVEMENT
FLAGELLA
AND
INTELLIGENT
DESIGN
DEBATE
.
A.
FLAGELLAR
MOVEMENT
:
Most
motile
bacteria
move
by
use
of
flagella,
threadlike locomotor
appendages extending
from
the
plasma
membrane
and
cell
wall. They
are
slender,
rigid
structure
,
about
20nm
across
and
up
to
15
or
20
μm
long.
Transmission
electron
microscope
studies
have
show
that
the
bacteria
flagellum
is
composed
of
three
parts:
A.
Filament
:
The
longest
and
most
obvious
portion
is
the
filament,
which extend
from
the
cell
surface
to
the
tip.
B.
Basal
body
:
A basal
body
is embedded in the
cell.
The basal body attaches the
flagellum
to
the
cell
wall
and plasma
membrane.
It
is
composed
of a
small
rod
instead
into
a series of
ring.
C
.
Hook
: A short,
curved segmented, the
hook is
present
outside
the
cell
wall
and
connects
filament
to
the
basal
body.
The
hook and
basal
body
are quite different
from
the
filament
.
Slightly
wider
than the
filament,
the
hook
is
made
of
different
protein
subunit.
A.
gram-negative
B.
gram-positive
bacteria
An
enlarged
view
of
the basal
body
of an
E.coli
flagellum.
All
four
rings
(L,P,S
and
M)can be
clearly
seen.
The
uppermost
arrow
is
at
the junction
of
the
hook and
filament.
•
The
synthesis
of
flagella
is
a
complex
process
involving
at
least
20
to
30
genes.
•
Beside the
gene
for
flagellin,
10
or
more
genes code
for
hook &
basal
body
proteins.
•
Other
genes
are
concerned
with
the
control
of
flagellar
construction
or
function.
•
It
is
not
known
how
the
cell
regulates
or
determines
the
exact location of
flagella.
•
The
filament
is
in
the
shape
of
a
rigid
helix,
and
the
bacterium
moves
when this
helix
rotates.
•
The
basal
body
act
as
motor
and
cause
rotation.
•
Flagellar
rotation determines the nature
of
bacterial
movement
•
This
diagram
of
a
G
ram-negative
flagellum
shows
some
important
component
and
the
flow
of
proton
that
drives
rotation.
Five
of
the
many
flagellar
proteins
are
labeled
(Mot
A,
Mot
B,
Fli
G,
Fli
M, Fli N)
.
•
Spirochetes
shows several
types
of
movement
such
as
flexing,
spinning,
free
swimming
and
creeping
as
they
are
flexible
and helical
bacteria
and
lake
flagella.
•
Just
within
the
cell envelop
they
have
flagella
like
structure
which
are
know
as
periplasmic
flagella
or
axial
fibrils.
•
The
axial
fibrils
are
present
in
the
space
between
inner
and
outer
membrane
of
cell
envelope.
•
Some
bacteria
such
as
the
species
of
cyanobacteri
(eg.
Cytophaga)
and
mycoplasma show
gliding
movement.
When
come
in
contact
to
a
solid
surface.
•
However
no
organelles
are
associated
with
the
movement
.
•
In
the members
of cytophagales and cyanobacteria ,
movement
helps
to
find
out
the
substratum
eg.
Wood,
bark,
etc
for
anchorage
and
reproduction.
•
They
secrete
slime
with
the
help
of
which
they
get
attached
to
substratum.
Bacterial locomotion involves intricate flagellar structures composed of filaments, basal bodies, and hooks. The synthesis of flagella is a complex process controlled by numerous genes. The rotation of the flagellar helix acts as a motor, determining the direction of bacterial movement.
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Presentation Transcript
LOCOMOTION IN BACTERIA TYPES OF MOVEMENT A. FLAGELLAR STRUCTURE OF FLAGELLA FLAGELLAR SYNTHESIS ANDASSEMBLY MECHANISM OF FLAGELLAR MOVEMENT B. GLIDING MOVEMENT FLAGELLA AND INTELLIGENTDESIGN DEBATE .
A. FLAGELLAR MOVEMENT: Most motile bacteria move by use of flagella, threadlike locomotor appendages extending from the plasmamembrane and cell wall. They are slender, rigid structure , about20nmacrossand upto15or20 m long.
Transmission electron microscope studies have show thatthe bacteria flagellum is composed of threeparts: Filament : The longest andmostobvious portion is the filament, which extend from the cell surface to thetip. Basal body: A basal body is embedded in thecell. The basal body attaches the flagellum to the cell wall and plasma membrane. It is composed of a small rod instead into a series ofring. A. B.
C. Hook : A short, curved segmented, the hook is presentoutside the cell wall and connects filament to the basal body. The hook and basal body are quite differentfrom the filament . Slightly wider than the filament, the hook is made of different proteinsubunit.
A.gram-negative B. gram-positivebacteria
An enlarged view of the basal body of an E.coli flagellum. Allfour rings (L,P,S and M)can be clearly seen. The uppermost arrow is at the junction of the hook and filament.
Thesynthesisof flagella isacomplexprocess involvingat least 20 to 30genes. Beside the gene for flagellin,10 or hook & basal bodyproteins. Othergenesareconcernedwiththecontrol of flagellar construction orfunction. Itis notknown howthecell regulatesordeterminesthe exact location of flagella. more genes codefor
Thefilamentisintheshapeof arigid helix,and the bacterium moves when this helixrotates. Thebasal bodyactas motorandcauserotation. Flagellar rotation determines the nature ofbacterial movement
This diagramof a Gram-negative flagellum shows some important component and the flowof proton that drives rotation. Five of the manyflagellar proteins are labeled (Mot A, Mot B, Fli G, Fli M, Fli N) .
Spirochetes shows several types of movement suchas flexing, spinning, freeswimmingandcreepingastheyare flexible and helical bacteria and lakeflagella. Just within the cell envelop they have flagella like structurewhichareknowasperiplasmicflagellaoraxial fibrils. Theaxial fibrilsarepresentinthespace between inner and outer membrane of cellenvelope.
Some bacteria such as the species of cyanobacteri (eg. Cytophaga) and mycoplasma show gliding movement. Whencomeincontacttoasolid surface. However no organelles are associated withthe movement. In the members of cytophagales and cyanobacteria , movement helps to find outthesubstratum eg.Wood, bark, etc for anchorage andreproduction. Theysecreteslimewiththehelpof whichtheyget attached tosubstratum.
