Bacteria have a variety of morphologies and internal structures that allow them to thrive in diverse environments. They range in size from 0.5-5.0 micrometers and can have cocci, bacilli, or spiral shapes. The cell wall provides structure and protection, while the plasma membrane regulates what enters and exits the cell. Inside, bacteria contain ribosomes for protein synthesis, storage materials like glycogen and polyhydroxybutyrate, and structures like flagella, pili and gas vacuoles that perform important functions. Bacteria display remarkable diversity in their cellular structures, allowing them to colonize nearly every habitat on Earth.

1. Morphology & Ultrastructure
of Bacteria
Dr. RACHANA CHOUDHARY
Department of Microbiology
Shri Shankaracharya Mahavidyalaya Junwani, Bhilai

2. INTRODUCTION
• Bacteria are the first organisms to
appear on earth
• That thrive in diverse environments.
• These organisms can live in soil, the
ocean and inside the human gut.
• Humans' relationship with bacteria is
complex.
• Some bacteria are harmful, but most
serve a useful purpose.
• They support many forms of life, both
plant and animal, and they are used in
industrial and medicinal processes.

3. GENERAL CHARACTERISTICS OF
BACTERIA
•Bacteria are Microscopic, Single-celled organisms.
•They lack organelles such as chloroplasts and
mitochondria, and they do not have the true nucleus.
•Bacteria also have a cell membrane and a cell wall .
•The cell membrane and cell wall are referred to as the cell
envelope.
•Asexual Reproduction by binary fission.
•However, some bacteria can also exchange genetic
material among one another in a process known as
horizontal gene transfer.

4. MORPHOLOGY OF BACTERIA
Morphology of Bacteria include:
•Size
•Shape
•Arrangement

5. Size of bacteria
•Bacterial cells are about one-tenth the size of
eukaryotic cells.
• typically 0.5–5.0 micrometers in length.
•Thiomargarita namibiensis is up to half a
millimeter long
•Epulopiscium fishelsoni reaches 0.7 mm
•Mycoplasma, which measure only 0.3 micrometers.
•E. coli , is 1.1 to 1.5 µm wide by 2.0 to 6.0 µm
long.
•Spirochaetes 500 µm in length.
•Cyanobacterium Oscillatoria is about 7 µm in
diameter.

6. Shapes of Bacteria
•Coccus
•Chain = Streptoccus
•Cluster = Staphylococcus
•Bacillus
•Chain = Streptobacillus
•Coccobacillus
•Vibrio = curved
•Spirillum
•Spirochete
•Square
•Star

7. Arrangement in bacteria
Chapter 4

8. Arrangement on the Basis of Presence of
flagella
1. Atrichpus :Absence of
flagella
2. Monotrichous; 1 flagella
3. Lophotrichous; tuft at one
end
4. Amphitrichous; both ends
5. Peritrichous; all around
bacteria

9. ULTRASTRUCTURE OF BACTERA
•Flagella
•Pili & Fimbriae
•Capsule & Slime Layers
•Cell Wall
•Plasma Membrane
•Mesosomes
•Cytoplasmic Inclusions
•Nucleoid
•Plasmids

10. Flagella
•Flagellum (singular) is hair like helical structure
emerges from cell wall and cell membrane
•It is responsible for motility of the bacteria
•Size: thin 15-20nm in diameter.
•Single flagella can be seen with light microscope
only after staining with special stain which increase
the diameter of flagella.
•Non-contractile
•Single protein subunit - flagellin

11. STRUCTURE OF FLAGELLA
Flagella has three parts. Basal body, Hook and filament
Basal body:
• it is composed of central rod inserted into series of rings which is
attached to cytoplasmic membrane and cell wall.
• L-ring: it is the outer ring present only in Gram -ve bacteria, it
anchored in lipopolysaccharide layer.
• P-ring: it is second ring anchored in peptidoglycan layer of cell wall.
• M-S ring: anchored in cytoplasmic membrane.
Hook:
• it is the wider region at the base of filament.it connects filament to the
motor protein in the base.length of hook is longer in gram +ve
bacteria than gram –ve bacteria
Filament:
• it is thin hair like structure arises from hook.

12. STRUCTURE OF FLAGELLA

13. FUNCTION OF FLAGELLA
1. That acts primarily as an organelle of
locomotion/movement in the cells.
2. They act as sensory organs to detect temperature
and pH changes.
3. Few eukaryotes use flagellum to increase
reproduction rates.
4. Recent researches have proved that flagella are
also used as a secretory organelle.
For eg., in Chlamydomonas

14. Pili & Fimbrae
• Both fimbriae and pili are hair like appendages on bacterial
cell wall. They originate from cytoplasm that protrudes
outside after penetrating the peptidoglycan layer of cell wall.
• Fimbriae are made up of 100% protein called fimbrilin or
pilin which consists of about 163 amino acids
• Smaller than flagella
• Adhere bacteria to surfaces
• E. coli has numerous types
• K88, K99, F41, etc.
• Antibodies to will block adherance
• F-pilus; used in conjugation
• Exchange of genetic information
• Flotation; increase
Chapter 4

15. Function of Pili & Fimbrae
•Fimbriae have the adhesive properties which attach
the organism to the natural substrate or to the other
organism.
•Fimbriae agglutinate the blood cells such as
erythrocytes, leucocytes, eplithelial cells, etc.
•Fimbriae are equipped with antigenic properties as
they act as thermolabile nonspecific agglutinogen.
•Fimbriae affect the metabolic activity.
• The sex pili make contact between two cells. Since
they posses hollow core, they act as conjugation
tube.
Chapter 4

16. Capsule & Slime Layers
• Some bacteria have an additional layer outside of the cell
wall called the glycocalyx. This coating of macromolecules
protects the cell and helps it adhere to surfaces.
• Slime Layer: glycoprotein molecules are loosely associated
with the cell wall. Bacteria that are covered with this loose
shield are protected from dehydration and loss of nutrients.
• Capsule: The glycocalyx is considered a capsule when the
polysaccharides are more firmly attached to the cell wall.
Capsules have a gummy, sticky consistency and provide
protection as well as adhesion to solid surfaces and to
nutrients in the environment.

17. Cell Wall
•Peptido-glycan Polymer (amino
acids + sugars)
•Unique to bacteria
•Sugars; NAG & NAM
•N-acetylglucosamine
•N-acetymuramic acid
•D form of Amino acids used not
L form
•Hard to break down D form
•Amino acids cross link NAG &
NAM

18. CHEMICAL STUCTURE OF BACTERIAL
CELL WALL

20. Chapter 4

21. Fig :-gram positive bacteria
(A) cell wall
(B) view after gram staining
A
B

22. FIG : gram negative bacteria
(A) cell wall
(B) view after gram staining
(A)
(B)

23. Difference - Gram positive and Gram
negative
Gram positive
•Composed of thick
layers peptidoglycan.
•Gram staining
procedure, gram-
positive cells retain the
purple coloured stain.
•Produce exotoxins
Gram negative
•Composed of thin layers
of peptidoglycan.
•Gram staining
procedure, gram-
negative cells do not
retain the purple
coloured stain.
•Produce endotoxins

24. Difference - Gram positive and Gram
negative

25. FUNCTION OF CELL WALL
• Determine shape of bacteria
• Strength prevents osmotic rupture
• 20-40% of bacteria
• Unique to bacteria
• Some antibiotics effect directly
• Penicillin

26. Plasma Membrane /Cell Membrane
•The bacterial cytoplasmic/Cell membrane is a
fluid phospholipid bilayer that encloses
the bacterial cytoplasm.
•The cytoplasmic membrane is semipermeable and
determines what molecules enter and leave
the bacterial cell.
•Water can penetrate
•Flexible
•Not strong, ruptures easily
•Osmotic Pressure created by cytoplasm

28. FLUID MOSAIC MODEL
• This model was first proposed by S.J. Singer and Garth L.
Nicolson in 1972.
• Describes the structure of the plasma membrane as a mosaic
of components-including phospholipids, cholesterol,
proteins, and carbohydrates.
• Range from 5 to 10 nm in thickness.
• The proportions of proteins, lipids, and carbohydrates in the
plasma membrane vary with cell type.
• For example,
• Myelin contains 18% protein and 76% lipid.
• The mitochondrial inner membrane contains 76% protein and
24% lipid.

29. FLUID MOSAIC MODEL

31. The structure of a phospholipid molecule:

32. Functions of the Plasma Membrane
•A Physical Barrier
•Selective Permeability
•Endocytosis and Exocytosis
•Cell Signaling

33. MESOSOMES
• Mesosome is formed by an extension
of the plasma membrane into the cell
wall.
• These extensions are usually in the
form of vesicles, tubules, and
lamellae.
The main use of mesosomes are
• Synthesis of a cell wall.
• DNA replication.
• Distribution of daughter cells,
respiration, secretions, etc.

34. CYTOPLASMIC INCLUSIONS
Cytoplasmic inclusions found in bacteria.
1. Ribosomes
2. Polyphosphates
3. Poly-β-hydroxybutyrate
4. Glycogen
5. Gas Vacuoles
6. Magnetosomes
7. Sulfur Globules
8. Carboxysomes.

35. 1.RIBOSOMES
• Small granular bodies of 10-20 nm in diameter freely lying
in the cytoplasm and composed of ribosomal ribonucleic
acid (rRNA) and proteins.
• Bacterial ribosomes are thought to contain about 80-85% of
the bacterial RNA.
• Sometimes, they are found in small groups called
polyribosomes ox polysomes.
• Generally, the ribosomes are a few hundred in number in
each bacterial cell, but when the cell undertakes active
protein synthesis, they increase in number to as many as
15,000-20,000 per cell about 15% of the cell mass.
Chapter 4

36. Structure of Ribosome
• Sedimentation coefficient of 70S ( 50S + 30S),
• Ribosomes are functional only when the two subunits are
combined together.
• The association and dissociation of two subunits of ribosomes
depend on the concentration of Mg++ ions.
50S subunit
• 23S rRNA , 5S rRNA and 34 different proteins ( L1 to L34)
30S subunit
• 16 rRNA and 21 different proteins (S1 to S21).

38. Models of Ribosome

39. Functions of Ribosome
• Ribosomes are the sites of protein synthesis in bacteria
• There are three sites on the ribosome: the acceptor site, where
the charged tRNA first combines; the peptide site, where the
growing polypeptide chain is held; and exite site.
• During each step of amino acid addition, the ribosome
advances three nucleotides (one codon) along the mRNA and
the tRNA moves from the acceptor to the peptide site.
• Termination of protein synthesis takes place when a nonsense
codon, which does not encode an amino acid, is reached.

40. 2. Polyphosphates (Volutin Granules or
Metachromatin Granules):
• Many bacteria and microalgae accumulate inorganic phosphates in the
form of granules of polyphosphates.
• It is a liner polymer of orthrophosphates joined by ester bonds.
• Because they were first described in Spirillum volutans and they bring a
about metachromatic effect also called ‘volutin granules’ and
‘metachromatin granules’.
• They composed of polymetaphosphate, common in diphtheria bacillus
,certain lactic acid bacteria.
• Polyphosphates are also used as source of phosphate for phospholipids.
• In some cells the polyphosphates act as an energy reserve and can serve as
energy source in reactions.

41. 3. Poly-β-hydroxybutyrate (PHB):
• Poly- β -hydroxybutyrate (PHB), is one of the most common lipid formed.
• the monomers (units) joined by easter-linkages of adjacent molecules.
• It readily stained with Sudan black.
• PHB, which is a long-term energy storage,
• is used as an energy and carbon source .
• Some bacteria produce co-polymers of PHB often referred to as poly-β-
hydroxy-alkanoate (PHA).
• a copolymer containing approximately equal amounts of poly-β-
hydroxybutyrate (PHB) and poly-β- hydroxyvalerate (PHV) has had the
greatest market success thus far.
• they are more cost-effective, the conventional petroleum-based plastics
still make up virtually the entire plastics market today.

42. 4. Glycogen:
• It is a polymer of glucose units composed of long
chains.
• It is dispersed more evenly throughout the cytoplasmic
matrix as small (about 20 – 100 nm in diameter) and is
a storage reservoir tor carbon and energy.
• Glycogen is also known as ‘animal starch’ and, besides
prokaryotes, is found in fungi.

43. 5. Gas Vacuoles:
• Gas vacuoles, small, hollow, cylindrical structures.
• These structures confer buoyancy on cells by decreasing their
density and live a floating existence.
• Each about 75 nm in diameter with conical ends & 200-1,000
nm in length.
• floatation due to gas vacuoles are seen in cyanobacteria
(blooms).
• Two different proteins, GvpA and GvpC ,compose the gas
vesicle wall.
• GvpA composes 97%, GvpC, the protein in minor amount of
3%, of total gas vesicle protein.

44. Gas Vacuoles

45. 6. Magnetosomes:
• Magnetosomes are the inorganic inclusion bodies of iron usually
in the form chains of magnetite (Fe3O4).
• Some species magnetosomes containing greigite (Fe3S4) and
pyrite (FeS2).
• Magnetosome bacteria are called magnetotactic bacteria (e.g.,
Aquaspirillum magnetotacticum).
• It is vary in shape from square to rectangular to spike-shaped .
• They are 40 to 100 nm in diameter , made up of phospholipids,
proteins, and glycoproteins.
• Its proteins probably play a role in precipitating F3+ as Fe3O4 in
the developing magnetosome.

47. 7. Sulphur Globules:
• Sulphur globules present in the bacterial cells
growing In H2S rich environment ( purple
sulfur bacteria (Beggiatoa and Thiothrix).
• They oxidize H2S into elemental sulfur (H2S
→ S°) which accumulates sulfur globules.
• elemental sulfur remain until the H2S source is
reduced.
• sulfur globules occur in the periplasm rather
than the cytoplasm.

48. 8. Carboxysomes
• Carboxysomes are polyhedrical bodies ,100 nm in diameter.
• They contain, apart from a little DNA, the enzyme ribulose-1,
5- bisphosphate carboxylase (RUBISCO).
• Rapid CO2 fixation .
• The carboxysome is insoluble.
• Photoautotrophic (cyanobacteria) and chemolithoautotrophic
(sulfur bacteria, nitrifying bacteria) that use Calvin cycle for
CO2 fixation produce carboxysomes.
• The carboxysomes appear to be an evolutionary adaptation to
bacteria under strict autotrophic environment.

49. Nucleoid
•The nucleoid (meaning nucleus-like) is an
irregularly-shaped region within the cell of a
prokaryote that contains all or most of the genetic
material.
•In contrast to the nucleus of a eukaryotic cell, it is
not surrounded by a nuclear membrane.

50. Plasmids
•A plasmid is a small, extrachromosomal DNA
molecule within a cell.
•It is physically separated from chromosomal DNA
and can replicate independently.
•They are most commonly found as small circular,
double-stranded DNA molecules in bacteria;
however, plasmids are sometimes present in archaea
and eukaryotic organisms.

52. Types of plasmid on the basis of function
•Fertility F-plasmids
•Resistance Plasmids
•Virulence Plasmids
•Degradative Plasmids
•Col Plasmids

53. CONCLUSI0N
• Most of the Bacteria in humans live a harmonious existence
with human cells, but disease and infection can be caused
when this balance is disrupted or when the body or immune
system is weakened.
• The beneficial uses of bacteria include the production of
traditional foods such as yogurt, cheese, and vinegar.
• Also important in agriculture for the compost and fertilizer
production.
• Bacteria are used in genetic engineering and genetic changes.
• have an important role to play in the breakdown of human
waste in sewage plants.

54. REFERENCES
•Textbook of Microbiology by R.P.Singh .
•Textbook of Microbiology by R.C. Dubey &
Maheshwari.
•Textbook of Botany by Dr. Y.D.Tyagi.
•www. Google.com

55. THANK YOU