This document provides an overview of a unit on bacterial flagella from a microbiology course. It describes the structure of flagella including the filament, hook, and basal body. It discusses the different types of flagella including monotrichous, amphitrichous, lophotrichous, and peritrichous. It explains the mechanism of flagellar movement including how rotation propels bacteria and the roles of chemotaxis in bacterial movement toward attractants and away from repellents.

1. ACADEMIC YEAR 2021-2022
I SEM CORE: MICROBIAL PHYSIOLOGY AND METABOLISM
(ZMBM13)
UNIT-1
FLAGELLA
S.ASHIFA BEGAM
REG NO:20211232516106
I M.SC MICROBIOLOGY
ASSIGNED ON: 05/12/2021
TAKEN ON:11/01/2022
SUBMITTED TO,
DR.S.VISWANATHAN,
ASSISTANT PROFESSOR & HEAD.

2. BACTERIAL CELL STRUCTURE.
STRUCTURE EXTERNAL TO CELL WALL.
FLAGELLA.
STRUCTURE.
TYPES.
MECHANISM OF FLAGELLAR MOVEMENTS.
CHEMOTAXIS.
FUNCTIONS.
REFERENCES.

3. Structure external to the cell wall.
The bacterial cell wall.
Structure internal to cell wall.

4. Flagella
Pili
Fimbriae
Capsule
Sheaths
Prosthecae
Stalks

5. FLAGELLA

6. Most motile prokaryotes move by use of thread like
locomotor appendages extending outward from the plasma
membrane and cell wall called flagella.
Bacterial flagella are slender, rigid structure, about 2 nm
across and up to 15- 20 nm long.
Flagella is made up of flagellin protein.

7. STRUCTURE

8. FILAMENT BASAL BODY HOOK

10. The longest and most obvious portion is the flagellar
filament, which extends from the cell surface to the tip.
The filament is a hollow, rigid cylindrical constructed of
subunits of the protein flagellin.
Flagellin molecular weight ranges from 30,000 to 60,000
daltons, depending on the bacterial species.
The filament ends with a capping protein.
Some bacteria have sheaths surrounding their flagella.
For example, Bordello vibrio has a membranous structure
surrounding the filament.
Vibrio cholerae has a lipopolysaccharide sheath.

12. A short, curved segment, the flagellar hook, connects the
filament to its basal body and act as a flexible coupling.
The hook and basal body are quite different from the
filament.
The hook is made up of different protein subunits.

14. A basal body is embedded in the cell.
The basal body is the most complex part of flagellum.
In E. coli and most gram-negative bacteria, the basal body has
four rings.
L, P, MS, and C, which are connected to a central rod.
The outer L and P rings are anchored with the
lipopolysaccharide and peptidoglycan layers, respectively.
MS rings are anchored in the cell envelope.
The C ring is anchored in the cytoplasmic side.
Typical Gram- positive bacteria have only two rings.
An inner ring connected to the plasma membrane.
An outer one propaply attached to the peptidoglycan.

16. The rotor portion of the motor seems to be made primarily of a
rod, the M ring, and a C ring joined to it on the cytoplasmic side
of the basal body.
These two rings are made up of several proteins; FliG is
particularly important in generating flagellar rotation.
The two most important proteins in the stator part of the motor
are MotA and MotB.
These form a proton channel through the plasma membrane,
MotB also anchors the Mot complex to cell wall-peptidoglycan.
There is some evidence that MotA and FliG directly interact
during flagellar rotation.
The rotation is driven by proton or sodium gradients movement.

18. TYPES

19. MONOTRICHOUS AMPHITRICHOUS
LOPHOTRICHOUS PERITRICHOUS

20. Monotrichous bacteria have one flagellum.
If it is located at one end, it is said to be a polar flagellum.

21. Amphi means on both side.
It have a single or bunch of flagellum at each pole.
It is a polar flagellum.

22. Lopho means tuft.
It have a cluster of flagella at one end.
It is a polar flagellum.

23. Peri means around.
In peritrichous bacteria, the flagella are spread evenly over
the whole surface of bacteria.
It is a non-polar flagellum.

24. MECHANISM
OF FLAGELLAR
MOVEMENT

25. The flagellum is very effective swimming device.
The surrounding water seems as thick and viscous as
molasses.
The cell must bore through the water with its corkscrew-
shaped flagella, and if flagellar activity ceases, it stops almost
instantly.
Despite such environmental resistance to movement,
bacteria can swim from 20 to almost 90 micrometer/second.
The filament is in the shape of a rigid helix, and cell moves
when this helix rotates just like propellars on a boat.
The flagellar motor can rotate very rapidly.
The E. coli motor rotates 270 rps.
Vibrio alginoluticus averages 1,100 rps.

27. Monotrichous, polar flagella rotares in clockwise direction
during normal forward movement, whereas the cell itself
rotates slowly clockwise.
It stop and tumble randomly by reversing the direction of
flagellar rotation(backward).

28. To move forward, the flagella rotates in clockwise direction.
As they do so, they bend at their hooks to form a rotating
bundle that propels the cell forward.
Clockwise rotation of the flagella disrupts the bundle and the
cell tumbles.

29. Spirochetes are helical bacteria that travel through viscous
substances such as mucus or mud by flexing and spinning
movements caused by a special axial filament composed of
periplasmic flagella.
It is also called as axial fibrils and endoflagella.

30. The swimming motility of the helical bacterium Spiroplasma
is accomplished by the formation of bends in the cell body
that travel the length of the bacterium.

31. Gliding motility, is employed by many bacteria:
Cyanobacteria, Myxobacteria and Cytophagas, and some
Mycoplasma.
Although there are no visible external structures associated
with gliding motility, it enables movement along surfaces at
rates up to 3m/second.

32. CHEMOTAXISS

33. Bacteria do not always move aimlessely but are attracted by
such nutrients as sugars and aminoacids and are replled by
many harmful substances and bacterial waste products.
Movement toward chemical attractants and away from
repllents is known as chemotaxis.

34. Chemotaxis may be demonstrated by observing bacteria in the
chemical gradient produced.
When a thin capillary tube is filled with an attractant and lowered
into a bacterial suspension.
As the attractant diffuses from the end of capillary, bacteria
collect and swim up the tube.
The number of bacteria within the capillary after a short length of
time reflects the strength of attraction and rate of chemotaxis.

36. Positive and negative chemotaxis also can be studied with Petri
dish cultures.
If bacteria are placed in the center of a dish of semisolid agar
containing an attractant.
The bacteria will exhaust the local supply and then swim
outward following the attractent gradient they have created.
When a disk of repellent is placed in a Petri dish of semisoild
agar and bacteria.
The bacteria will swim away from the repellent, creating a clear
zone around the disk.
Bacteria can respond to very low levels of attractants.
The magnitude of their response increasing with attractant
concentration.

38. Attractants and replellents are detected by chemoreceptors.
About 20 attractant chemoreceptors and 10 repellants
chemoreceptors for repellents have been discovered thus far.

39. FUNCTIONS

40. They help an organism in movement.
They act as a sensory organs to detect temperature and pH
changes.
Few eukaryotes use flagellum to increase reproduction rates.
Recent researches have proved that flagella are also used as
a sceretory organelle. For example., in Chlamydomonas.

41. 1. Prescott’s Microbiology
2. Microbiology Principles and Explorations- Jacquelyn G. Black.
3. www.microbenotes.com
4. www.biologydictionary.net
5. www.microbeonline.com

45. Communication skills.
Confidence.
Gained subject knowledge better.
Presentation skills.
Searching capability increased.
Learn time management.