Explains what bacteria is and where it exists. A key feature of nearly all prokaryotic cells is the cell wall, which maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment. The cell walls of prokaryotes differ in structure from those of eukaryotes. In eukaryotes that have cell walls, such as plants and fungi, the walls are usually made of cellulose or chitin. In contrast, most bacterial cell walls contain peptidoglycan, a polymer composed of modified sugars cross-linked by short polypeptides. Using a technique called the Gram stain, developed by the 19th-century Danish physician Hans Christian Gram, scientists can categorize many bacterial species according to differences in cell wall composition. Gram-positive bacteria have simpler walls with a relatively large amount of peptidoglycan. Gram-negative bacteria have less peptidoglycan and are structurally more complex, with an outer membrane that contains lipopolysaccharides (carbohydrates bonded to lipids). LEARN ABOUT: - Bacteria - The number of viruses on earth is staggering - Pathogenic yeasts - Helminths - Harnessing bacteria - Microbes on the tree of life - Living and working together - Archaea - Protozoa LEARN ABOUT: - Bacteria - The number of viruses on earth is staggering - Pathogenic yeasts - Helminths - Harnessing bacteria - Microbes on the tree of life - Living and working together - Archaea - Protozoa The bacterial flagellum has three main parts (the motor, hook, and filament) that are themselves composed of 42 different kinds of proteins.The cells of prokaryotes are simpler than those of eukaryotes in both their internal structure and the physical arrangement of their DNA. The genome of a prokaryote is structurally different from a eukaryotic genome and in most cases has considerably less DNA. Prokaryotes generally have circular chromosomes, whereas eukaryotes have linear chromosomes.

2. Bacteria
Morphology, growth and reproduction

3. Contents
• Bacterial characteristics
• Bacterial morphology
• Size of bacteria
• Shape of bacteria
• Bacterial anatomy
• Bacterial growth
• Reproduction in bacteria

4. Bacterial characteristics
• Unicellular
• Circular DNA
• No organelles
• 1/10th the size of eukaryotic cells
• Flagella-long hair-like structure used for
movement
• Reproduce asexually –Binary Fission

5. Bacterial morphology
Size of bacteria:
• Bacteria are so small because of that their size is measured in a
micron (u )
• Generally cocci are about 1u in diameter and bacilli are 2 to 10 u in
length and 0.2 to 0.5 u in width
• The limit of resolution with unaided eye is about200 u because of
that bacteria can be only visualized under microscope.

6. Shape of bacteria
On the basis of general shape,
bacteria are classified into three
categories.
• Cocci
• Bacillus
• Spiral shaped bacteria

7. Cocci
The cocci are spherical or oval bacteria
having one of several distinct
arrangements based on their planes of
division. Types of cocci are following:
• Cocci in cluster – staphylococci
• Cocci in chain – streptococci
• Cocci in pair- diplococci
• Cocci in group of four – tetrad
• Cocci in group of eight – sarcina

8. Bacillus
Bacilli are rod-shaped bacteria. Bacilli all divide
in one plane producing a bacillus,
streptobacillus, palisade or diplobacillus Bacillus
is a single cell of bacteria.
When rod shaped bacteria occur in pairs then
arrangement of cells is known as diplobacilli.
When the bacilli are arranged in chains, as the
cells divide in one plane, this type is called
streptobacillus.
The bacilli bend at the points of division
following the cell divisions, resulting in a palisade
arrangement.
Coccobacillus are so short and stumpy that they
appear ovoid. They look like coccus and bacillus.
Examples of rod shaped bacteria are Escherichia
coli, Bacillus subtilis, Pseudomonas.

9. Spiral shaped bacteria
The spiral shaped bacteria are spirally
coiled. Spirals come in one of three
forms, a vibrio, a spirillum, or a
spirochete.
• Vibrio is curved or comma-shaped rod.
• Spirillum is a thick, rigid spiral.
• Spirochete is a thin, flexible spiral.
Examples of spiral shaped bacteria are
Vibrio, Hyphomicrobium.

10. Bacterial structure
• Cell Wall
• Plasma Membrane
• Cytoplasm
• Bacterial capsule
• Flagella
• Fimbria / pilli
• Endospores(spores)

11. Bacterial anatomy (structure)
• In the bacteria the outer layer or cell envelop or bacteria consist of
two things
(a) rigid cell wall
(b) underlying cytoplasmic membrane
• plasma membrane:
• It includes granules, ribosomes, mesosomes and circular DNA.
• Some bacteria in addition to possess additional structures such as
gelatinous material which cover it is called as capsule and when it
is too thin it is called as microcapsule.

12. Cell wall
• Introduction:
most cell posses a cell envelop consisting of cell wall and underlying
cytoplasmic membrane.
• Definition:
“the tough, rigid structure which surrounds bacterial cell it is called as
cell wall”
• Thickness: 10-20nm
• Weight: 20-25% of dry weight of bacterial cell wall

13. Cell wall structure
Chemical structure of cell wall is made up of a Peptidoglycan Polymer
(amino acids + sugars)
That structure is unique to all bacteria
Sugars; NAG & NAM
N-acetylglucosamine
N-acetymuramic acid
Amino acids cross link NAG & NAM

14. Made of peptidoglycan – a combination of protein and
polysaccharides
It is present in both gram positive & negative bacteria.
Some bacteria called Gram negative bacteria have an additional
layer of membrane that contains lipopolysaccharide
- this extra layer inhibits the uptake of antibiotics – protecting the
bacteria

15. Gram positive and gram negative bacteria
The type of cell wall is used by doctors to
help diagnose disease.
The bacteria are stained with a special
stain called Gram stain.
• Bacteria without the extra membrane,
appear purple. These are Gram positive
(Gram +) bacteria.
• Bacteria with the extra membrane
appear pink. These are Gram negative
( Gram -) bacteria.

16. Cytoplasmic membrane
Definition:
“Thin semi permiable membrane which lies just beneath the cell wall
that is called as cytoplasmic membrane”
• The whole bacterial cytoplasm is bound peripherally by very thin,
elastic and semi permiable cytoplasmic membrane also known as cell
membrane.
• It is 5-10nm in width
• Electron microscope shows the presence of three layer constituting a
unit membrane structure.
• Chemically the membrane consist of phospholipid with small amount
of protein.

17. Cytoplasm
“Bacterial cytoplasm is suspension of organic and inorganic solutes in
viscous watery solution”
It is not exhibiting protoplasmic streaming and it lacks endoplasmic
reticulum or mitochondria. It contains ribosomes, mesosomes, inclusion
and vacuoles.
All the organills which cytoplasm contains is as follows.
Ribosomes:
Ribosomes appear as small granules and pack the whole cytoplasm.
These are strung together on strands of mRNA to form polymers. the
code of mRNA is translated in to peptides sequence t this place. The
ribosomal particles become linked up and travels along the mRNA
strand.

18. Polysomes:
They are the group of ribosomes linked together like beads of chain by
messanger RNA
Mesosomes:
They are vesicular, convulated or multilaminted structures formed as
invagination of plasma membrane in cytoplasm . They are more
prominent in the gram positive bacteria.
Two types of mesosomes
(a) septal mesosomes:
It is attached to bacterial chromosomes and involved in DNA segregation
and in formation of cross wall during cell division.
(2) Lateral mesosomes:
They are at lateral side

19. 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.

20. Bacterial capsule
“ It is an outer covering of thick jelly like material that surrounds the bacterial
cell wall”
Width: 0.2 micrometer
• Contains about 90% water and 2% solid
• The solid constitutes may be complex polysccharide (pneumococcus
klebsiella, (enterobacter) or polypeptides (anthrax bacillus) or hyaluronic acid
(streptococcus).
• The capsule is best seen in pathological specimens like pus, blood, sputum,
and exudates
(1) By ordinary stain (gram or acid fast) capsule can not be stained, it apper as
halo arround the stained bacterial body.
(2) In negative staining (india pink preparation), capsule appears as clear halo
around the bacterium as link can not penetrate capsule.

21. Flagella
“These are long, sinnous contractile filamentous appendages known as flagella”.
• Composed of a flagellin subunit.
• Usually sheathed (covered).
• Rotates by way of a basal body in the bacterial cell.
• These are organs of locomotion . ex:-Escherichia coli salmonella, vibrio ,
pseudomonas, etc.
• The number of f lagella varies up to 10 to 20 per cells according to species of
bacteria.
• These are extremely thin (diameter)12 to 30 nm, helical shaped structure of
uniform diameter throughout their length .
• these are 3 to 20 nm long.
• Each flagellum consist of hook & basal body. It originates in a spherical body
located just inside cell wall.

22. Arrangement / types
• Monotrichous; 1 flagella
• Lophotrichous; tuft at one end
• Amphitrichous; both ends
• Peritrichous; all around
bacteria

23. Fimbria / Pilli
“Fimbria are filamentous , short , thin , straight , hair like appendage”.
• This is 0.1 to 1.5 µ long & less than 4 to 8 nm thick.
• They are also called as Pili.
• Fimbriae are seen only in some gram negative bacteria.
• Each bacterium may have 100 to 500 Fimbriae on all over the body of
bacteria.
• They project from cell surface as a straight filaments.
• They are best developed in freshly isolated strains & in liquid culture.
• They are composed of protein known as pillin (molecular weight 18000
Daltons).

24. Endospores (spores)
• Dormant cell
• Produced when starved
• Resistant to adverse conditions - high temperatures - organic solvents
- desiccation - UV radiation
• contain calcium dipicolinate and Calcium
• Bacillus (anthracis and cereus)and
• Clostridium (tetanus, perfringens, botulinum

25. Bacterial growth
Bacterial Growth - an increase in bacterial
numbers
- does not refer to an increase in
size of the individual cells
•How to determine bacterial growth?
directly – through counting
indirectly – through measuring their metabolic
activity

26. Bacterial growth
Bacteria ‘s growth can be take place by binary fission and
during that so many phases happen during it:
1. Entrance of basic nutrients into the cell
2. Conversion of nutrient components
3. Replication of chromosomes
4. Increase in size and mass
5. Division of cells into two daughter cell

27. Growth cycle
Bacterial growth is regulated by nutritional environment. When suitable
environment is there that time bacterium is incubated, its growth leads
to increase in number of cells which allow definite course.
• The growth curve has got four phases:
• Lag phase
• Log phase(logarithmic) or exponential phase
• Stationary phase
• Decline phase

29. Lag phase
When microorganisms introduced into fresh medium
1. no immediate increase in cell number
2. no cell division
Lag phase may be due to
1. Cells may be old
2. Depletion of nutrients
3. No essential co-factors and ribosomes
4. Medium may be different
5. Microorganism may be injured

30. Log phase
Microorganisms grow and divide at maximum rate due to
1. Their genetic potential
2. Nature of medium
3. Condition Growth is constant and in geometric progression (2n)
Generation time will be minimum
Each cell divide at slightly different moment
Population is uniform in terms of chemical and physiological properties
under which they are growing
Used for biochemical and physiological studies

31. Stationary phase
• Growth ceases and growth curve become horizontal
• Final population depends on nutrient availability
• Total number of viable cells remains constant
• Microbial population enter stationary phase due to
• 1. nutrient limitation
• 2. oxygen availability
• 3. accumulation of toxic wastes

32. Decline phase
• Nutrient depletion or due to build-up of toxic wastes
leads to death of viable cells
• Death of microbial population as like exponential
phase
• Total number of cells remains constant, because cells
• simply fail to lyse

33. Bacterial reproduction
Bacteria reproduces by the following ways:
• Binary fission
• Budding
• Spore formation

34. Binary fission
Simplest type of asexual
reproduction.
Binary Fission involves a one celled
organism.
Binary Fission produces new
daughter cells.
Binary Fission begins with DNA but
doesn’t exchange genetic info.
The cells become an exact
replication of each other.

35. Budding
• This is when a child grows
out of the parent.
• When the cell splits off the
nucleus divides equally
but it’s cytoplasm divides
unequally.
• The parent and child could
stay connected and form a
colony or separate.

36. Spore formation
• Spores contain a nucleus and a
small amount cytoplasm.
• Spores sprout out of decaying
materials releasing spores to
make more sprouts.
• Species of the genus Stretomyces
and related bacteria produce
many spores per organism by
developing crosswalls at the
hyphal tips: each spores gives rise
to new organism.