Morphology-of-bacteria-_1_ microbiology.ppt

Bacterial morphology refers to the shape, size, and arrangement of bacterial cells. Bacteria exhibit various shapes and structural forms that help in their identification and classification. The main types of bacterial morphology include:

1. Cocci (Spherical)

Shape: Round or spherical.

Examples:

Staphylococcus (clusters)

Streptococcus (chains)

Diplococcus (pairs)

Tetrads (groups of four)


Arrangement: Can appear in clusters, chains, or pairs based on their division patterns.


2. Bacilli (Rod-shaped)

Shape: Cylindrical or rod-like.

Examples:

Escherichia coli (single rods)

Bacillus anthracis (chains of rods)

Clostridium (single or pairs)


Arrangement: Often seen as single rods, chains, or palisades (side-by-side arrangement).


3. Spirilla (Spiral-shaped)

Shape: Spiral or corkscrew-like, rigid.

Examples:

Spirillum (rigid spirals)

Campylobacter (curved rod or "comma" shape)



4. Spirochetes (Flexible spirals)

Shape: Thin, flexible, helical spirals.

Examples:

Treponema pallidum (causes syphilis)

Borrelia burgdorferi (causes Lyme disease)



5. Vibrio (Comma-shaped)

Shape: Curved, comma-like.

Examples:

Vibrio cholerae (causes cholera)



6. Pleomorphic (Variable shapes)

Shape: Bacteria that can have various shapes.

Examples:

Mycoplasma (lacks a rigid cell wall, variable shape)

Corynebacterium (club-shaped rods)



7. Filamentous

Shape: Long, thread-like or filamentous chains.

Examples:

Streptomyces (produces antibiotics)

Nocardia



8. Coccobacilli

Shape: Short, oval, intermediate between cocci and bacilli.

Examples:

Haemophilus influenzae



9. Diplobacilli

Shape: Rods arranged in pairs.

Examples: Certain species of Moraxella.


Arrangement:

Bacterial cells may exhibit different arrangements based on their division patterns:

Diplo-: Pairs (e.g., diplococci, diplobacilli).

Strepto-: Chains (e.g., streptococci, streptobacilli).

Staphylo-: Clusters (e.g., staphylococci).

Palisades: Side-by-side arrangement (commonly seen in bacilli).


Size:

Bacterial size typically ranges between 0.2 to 2.0 micrometers in diameter for cocci and 1 to 10 micrometers in length for bacilli.

This diversity in morphology helps microbiologists to identify bacteria and understand their functions, pathogenicity, and ecological roles.

2. Microorganisms – heterogeneous group of
several classes of living beings.
Kingdom – Protista & Monera.

3. Based on differences in cellular organization
and biochemistry : 2 groups :- Prokaryotes
Eukaryotes
Prokaryotes – Bacteria, Blue-green algae.
Eukaryotes – Fungi, other algae, slime moulds,
protozoa.

4. Bacteria and blue-green algae.
Bacteria – Unicellular
No true branching
0.2-1.5 µm width, 2-5 µm length

6. Fungi, algae (except blue-green algae), protozoa.

7. Character Prokaryotes Eukaryotes
Nuclear membrane Absent Present
Nucleolus Absent Present
Chromosome One Two or more
Mitochondria,
lysosomes,Golgi
apparatus, Endoplasmic
reticulum
Absent Present
Sterols in Cytoplasmic
membrane
Absent Present
Muramic acid in cell wall Present Absent

10. 1) Cocci - Spherical cells.
2) Bacilli - Straight rod like cells.
3) Vibrios - Curved rod shaped
4) Spirilla - Spirally twisted, non-flexuous
rods
5) Spirochetes-Slender, flexuous, spiral
filaments

11. Spherical/ Oval cells.
Based on arrangement:
Diploccocci- pairs
Streptococci-chains
Staphylococci-grape like clusters

13. Rod-shaped cells.
Based on arrangement and shape:

Discretely aaranged
Chains - Streptobacilli
Chinese letter pattern - Corynebacteria

15. Comma shaped
Eg: Vibrio cholerae

16. Spirally twisted
Eg: Spirillum minus

17. Slender, flexuous filaments
Gram negative
Motile
Eg: Treponema, Leptospira

19. 1) Aerobic:
Eg: Pseudomonas
2) Facultative anaerobes
Eg: E.coli, Klebsiella, Staphylococcus

3) Anaerobic
Eg: Bacteroides spp, Fusobaterium

20. Gram stain:
1) Gram positive:
Gram + cocci : Staphylococci, Streptococci
Gram + bacilli: Clostridium
2) Gram negative:
Gram –ve cocci: Neisseria
Gram –ve bacilli: E. coli, Klebsiella,
Pseudomonas, Salmonella

24. 1) Cell wall.
2) Cytoplasmic membrane.
3) Capsule and slime layer
4) Cytoplasm: Ribosomes
Intracytoplasmic inclusions
Mesosomes
Nucleoid

25. 5) Cell appendages- Flagella
Fimbriae
6) Spores

27. Tough , rigid structure.
10-25 nm in thickness ,
Functions :
Shape
Protection against osmotic damage
Rigidity
Role in cell division
Target sites for antibiotics, lysozymes.
Bacterial antigens - virulence, immunity

28. 28
CytoplasmCytoplasm Cell membrane
Cell Wall

29. Chemical structure:
Rigid part of cell wall- Peptidoglycan.
Made up of: N-acetyl muramic acid
N-acetyl glucosamine

30. Components
Peptidoglycan – thicker than that of Gram
negative bacteria.
Teichoic acid – constitutes major surface
antigens of G+ bacteria.

32. Components
Lipid rich outer membrane
Lipoprotein layer – connects peptidoglycan
layer to outer membrane.
outer membrane proteins.
Lipopolysaccharide (LPS) – constitutes
endotoxin. Lipid A + polysaccharide-LPS

33. Periplasmic space – space between inner and
outer membranes.
Peptidoglycan – rigid part

36. Differential staining
Plasmolysis
Microdissection
Reaction with specific antibodies
Mechanical rupture of cell
Electron Microscopy

37. Character Gram positive Gram negative
Thickness Thicker Thinner
Periplasmic space Absent Present
Lipids Absent/small Present
Teichoic acid Present Absent
Peptidoglycan 16-80nm 2nm

38. Cell wall defects are due to:
Antibiotics, bacteriophages, lysozymes
4 types:
Mycoplasma – naturally occuring
L-forms - due to effect of penicillin
Protoplasts – derived from Gram positive
Spheroplasts – derived from Gram negative
Pleomorphism

39. 5-10 nm thick, composed of lipoproteins,
carbohydrates
Elastic, semipermeable layer, controls the flow of
metabolites to and from the protoplasm
Passage through the membrane depends on
molecular size of the particles, presence of specific
enzymes in the membrane (permeases)
Electron microscopy shows the presence of 3
layers constituiting a ‘unit membrane’

40. Functions:
Osmotic barrier
Site of enzymes
Semipermeable membrane, thus control
movement of metabolites

41. Amorphous viscid bacterial secretion.
Polysaccharides or polypeptide
Slime layer – loose undemarcated secretion.
Capsule – sharply defined structure.

42. Functions:
Bacterial virulence – by inhibiting phagocytosis
Protects bacteria from deleterious agents like
lytic enzymes, bacteriophages
Capsular material is antigenic –thus useful in
identification, typing of the species

43. Examples of Capsulated organisms:

Streptococcus pneumoniae
Klebsiella spp
Haemophilus influenzae
Bacillus anthracis
Cryptococcus neoformans ( fungus)

44. Negative staining by-India ink, Nigrosin
Serological methods- Quellung phenomenon to
show capsular swelling
Special capsular staining – here copper salts
are used as mordants for staining the capsule

46. QUELLUNG REACTION

47. Colloidal system, contains organic and
inorganic solutes in a viscous watery solution
Contains:
Nucleoid
Enzymes
Ribosomes
Mesosomes
Inclusions
Vacuoles
No mitochondria and endoplasmic reticulum

48. No nuclear membrane or nucleolus
Single chromosome arranged in the form of a
circle
Double stranded DNA
Demonstration - electron microscopy

49. Extra-nuclear genetic material consisting of DNA in
the cytoplasm
Not essential for the life of the cell but confers
certain properties like drug resistance and
toxigenicity

50. Plasmids can be transmitted from one
bacterium to another by conjugation or
through a bacteriophage
They can be transferred to daughter cells
during cell division by binary fission

51. Ribosomes:
Centres of protein synthesis
Composed of ribosomal RNA and ribosomal proteins

52. Mesosomes
Vesicular, multi-laminated structure
Formed as invaginations of plasma membrane
into cytoplasm
Centre of respiratory enzymes, are analogous to
mitochondria of eukaryotes
They are more prominent in Gram positive
bacteria
Play a role in binary fission

53. Sources of stored energy , most frequent in
bacteria growing under conditions of nutritional
deficiency

Seen as: poly-metaphosphate granules
lipid granules
polysaccharide granules
sulphur granules

54. Fluid filled cavities.

55. 5-20 µm in length, 0.01-0.02 µm in diameter
Thread-like appendages
Composed of a protein-flagellin
Organs of locomotion

56. Parts:
Filament
Hook
Basal body-has outer and inner rings

58. Arrangements:
Monotrichous – Single polar flagellum
eg: Vibrio cholerae
Amphitrichous – Single flagellum at both ends
eg: Alcaligenous faecalis
Lophotrichous – tuft of flagella at one/both ends
eg: Spirilla
Peritrichous – flagella arranged all around the cell
eg: Salmonella typhi

59. A-Monotrichous
B-Lophotrichous
C-Amphitrichous
D-Peritrichous

60. Dark ground microscopy
Special staining techniques to increase the
thickness of flagella
Electron microscopy
Indirect methods– to detect motility:
1) Spreading type of growth on solid media (eg:
swarming)
2) Hanging drop
3) Growth in semisolid agar eg: Craige’s tube
method

62. Hair- like appendages projecting from cell surface
Shorter and thinner than flagella about 0.5µm long,
less than 10 nm thick
Found in some Gram negative bacteria
Composed of protein named pilin
Types: Common pili
Sex or F (fertility) pili
Col I (colicin) pili

64. They originate in cell membrane
They are unrelated to motility and are present in
both motile and non-motile bacteria
Functions:
Adhesion-this property helps to anchor the
bacteria to the necessary microenvironment
Fimbriae are antigenic
Transfer of genetic material ( by F pili during
conjugation)

65. Detection of fimbriae:
 Electron microscopy
 Hemagglutination :
Fimbriated bacteria ( eg: E.coli, Klebsiella)
agglutinate RBCs of guinea pigs, horse, pigs
strongly, human and sheep RBCs weakly. This
can be specifically inhibited by D-mannose

66. These are resistant resting stage of bacteria
formed in unfavourable environmental conditions
This process is called Sporulation
Are called Endospores as they are formed within
parent bacterial cell
Highly resistant to heat, drying & chemical agents
Sporulation is not a method of reproduction

68. Shape: Oval
Spherical
Position: Central
Sub-terminal
Terminal
Bulging, non-bulging spores

69. Demonstration: Gram’s staining
Modified ZN staining
Uses: Indicators for proper sterilisation
(Bacillus stearothermophilus)

70. Sporulation is triggered by the onset of
unfavourable conditions
Eg: depletion of nutrients, accumulation of
metabolites or changes in the favourable
conditions like moisture, temperature, pH, oxygen
tension in the environment
Spores are much more resistant than the vegetative
forms to exposure to disinfectants, drying and
heating

71. Examples of spore forming bacteria:
 Bacillus anthracis,
 Clostridium tetani,
 Cl. welchii,
 Cl. botulinum