This document provides information about the structures and functions of bacterial cell envelopes including capsules, slime, fimbriae, pili, and flagella. It discusses how capsules help bacteria attach and protect against phagocytosis. Slime layers surround bacterial cells and allow adhesion while protecting against chemicals. Fimbriae and pili aid in bacterial adhesion and conjugation. Flagella provide locomotion and allow bacteria to sense chemicals and exhibit chemotaxis. Bacteria are classified based on flagella placement including atrichous, monotrichous, lophotrichous, ampitrichous, and peritrichous types.

2. Student name Madiha Mustafa
Teacher name Prof.Raboia
Class B.S. Zoology
Topic Bacteria
Presentation #
1

3. Definition: Bacteria are microscopic , single-celled organisms that exist
in their million in every environment both in side and outside the other
organisms
Cell envelope is composed of cell wall . In some bacteria there is
capsule,slime,fimbria and pilia.
Capsule: Capsules are the outermost structure of bacterial cell. It is
a polysaccharide layer that lies outside the cell envelope and is thus deemed
part of outer envelope of bacterial cell. It is thicky layer. It makes the
Cell surface
BACTERIA

4. 1-Bacteria can attach with the substrate with their capsule. It also helps
bacteria to attach with each other and from colonies.
2- Capsule is a virulence factor in bacteria. It prevents phagocytosis. Thus it
enhances the ability of bacteria to cause disease. The capsule can protect cells
from engulfment by eukaryotic cells like macrophages. A capsule-specific
antibody is required for phagocytosis of bacteria. Immunity to one capsule type
does not result in immunity to the other types.
3- capsules also contain water. It protects the bacteria against desiccation.
4- capsule also excludes bacterial viruses and most hydrophobic toxic
materials like detergents.
Slime:-
defi: some bacteria are covered with loose, soluble shield of macromolecules
called slime .
It is an organized layer of extracellular material that surrounds bacterial cell. It
mostly consist of exopolysaccharides, glycoproteins and glycolipids. Slime layer
in bacteria is easily removed. A bacterial capsule is similar to slime. But a
capsule is well ordered structure and resistant to washing off. Slime performs

5. against phagocytosis.
2- It protects bacteria cells from environmental dangers antibiotics and
desiccation
3- The slime layer also allows bacteria to adhere to smooth surfaces .
4- It protects the bacteria from chemical sterilization with chlorine, iodine and
other chemicals.
Fimbria:-
defi: fimbriae is a short appendage found on many gram-positive and gram-
negative. These appendage ranges from 2-10 nanometers. It is thinner and
shorter
FUNCTIONS:
1- Fimbriae is used by bacteria to adhere to one another and to adhere to
animal cells
2- These are also essential for the virulence of some bacterial pathogens .
Pili:-

6. Functions:
1-pili are not involved in locomotion.
2-They are primarily involved in conjugation. Conjugation is a mating process.
3- some pili are used for attachment of bacteria with various surfaces.
Locomotory organ: Flagella
Flagella are extremely thin hair like appendages. They are originated from basal
body and come out through cell wall. The basal bodies are present just beneath
the cell membrane in the cytoplasm. Bacterial flagella are made up of about 20
protiens. Flagella are chiefly made up of a protein flagellin.

7. Bacteria are classified into 5 types
• Atrichous
• Monotrichous
• Lophotrichous
• Ampitrichous
• Peritrichous
Classification of bacteria
on the basis of flagella

8. Atrichous:
Bacteria without flagella are called Atrichous. Eg.
Monotrichous: Bacteria with single flagella. Eg.
Vibro cholerae
Lophotrichous: In this case, tuft of flagella
present at
single pole. Eg. Bartonella bacilliformis
Ampitrichous: Bacteria in which flagella present at
two poles. Eg. Spirillum serpend
Peritrichous: In this case, flagella surround the

9. 1- The primary function of flagella is locomotion. Flagella are used for
swimming through water, bacterial gliding and twitching. These movements also
change the buoyancy to allow vertical motion. Swimming bacteria frequently
move near 10 body lengths per second and a few as fast as 100. In twitching
motility, bacteria used their pili as a grappling hook. Bacteria repeatedly extend
it.
2- bacteria can detect a chemical signals with the help of flagella and move in
its response. Such type of behaviour is called Chemotaxis
Function of flagella