The document provides an overview of bacterial structures and their functions, detailing both external structures like glycocalyx, flagella, and capsules, as well as internal structures such as cytoplasm, nucleus, and ribosomes. Key characteristics and functions of these structures are described, including the role of the cell wall in providing support, the function of flagella in locomotion, and the protective nature of capsules and endospores. Additionally, the document discusses plasmids, ribosomes, mesosomes, and other cellular components, emphasizing their importance in bacterial survival and adaptation.

1. Bacterial structures
and their functions
Iqbal Danish & fakiha javed
M.phil 1st Semester

2. Structures external to the cell
wall
Glycocalyx
Flagella
Pilli
Fimbrae
Capsule
Axial filament

3. Structures internal to cell wall
Cytoplasm
Cell membrane
Nucleus
Ribosomes
Inclusion bodies
Endospores
Mesosomes
Plasmid
Transposomes
Cell envelope
Lipopolysaccride
Techoic acid

4. Cell wall
 Cell wall is multilayer structure located external to
cytoplasm membrane
 Internally it is composed of peptidoglycan and external
structure vary according to the bacterial type
 Provide structural support t and maintain shape of cell
 Cell wall of acid fast bacteria have mycolic acid
 Sugar backbone with peptide side chains that are cross
linked
 Give rigid support, protect against osmotic pressure

5. flagella
Characteristics:
 Filamentous protein appendages attached to cell surface
 Have swimming movements incase of motile bacteria
 Have tactic behaviour(ability to move in response to
enviroment stimuli)
Composition
 Basal body
 Hook
 Long filament of polymerized protein called flagellin
Division on basis of locomotion
Polar(one area of cell)
Peritrichous(entire bacterial cell)

6. capsule
Characteristics:
 Bacteria produce or excrete high molecular weight of
polysaccride sugar coating called capsule
 Located outside the cell
Functions:
 Provide protection to bacteria from host
 Protect from phagocytosis
 Help in bacterial adhesion

7. Endospore
characteristics
 special structure formed by some bacteria(Bacillus,C
lostridium)
 Resistant to heat,chemicals,radiations and chemicals)
 Sporulation
 Spore to vegetative cycle

8. Pilli(fimbrae)
 Characteristics:
 Hair like filament short than flagella
 Composed of subunit of pillin
 Proteins are arranged in helical strand
 Mainly found in gram negative organisms
 Function:
 Attached to specific receptor
 Sex pilli(attachment)

9. Glycocalyx(slime layer)
Characteristics:
 Viscous,sticky,gelatinousPolysacchride coating external to
cell wall
 Adhere firmly to structres like skin,heart and catheter walls
 Important component of biofilm
Function:
 Adhesive property
 Antigenic sites

10. axial filament
characteristics:
 Bundle of fibrils
 Rotation of filament produce the movement
 Present in spirochetes

11. Structures internal to cell wall
Cytoplasm
 Thick,aqous,semitransparent and elastic material
 Contain ribosomes and various types of nutriental storage
granules
 About 80% water containing carbohydrates,proteins and
lipids

12. nucleus
 Consist of polyamine magnesium ions bond to negatively
charge circular super coiled double stranded DNA,small
amount of RNA and other proteins
 Cells genetic information which carries all the information's
requires for cell structures and function
 Purified nucleotides reveal that they composed of 60%
DNA 30% RNA 10% proteins by weight

13. plasmid
 Small circular non chromosomal double stranded DNA capable
of self replication
 Most frequently extra chromosomal but may become integrated
into bacterial DNA
 Function:
 Contain genes that confirm protective properties such as
antibiotics resistance are virulence factors are their own
transmissibility of other bacteria
 Plasmid play role in the lives of the organisms that have them
Types:
Episomes
Conjugate
colplasmid

14. Ribosomes
 Complex structure made of protein and RNA
 Shape of protein is determined by its amino acid sequence
 Risbosome present in cytoplasm loosly attach in plasma
membrane
 70S ribosome in prokaryotes,weight 2.7million

15. Inclusion bodies
 Several kind of deposits in cytoplasm
 Useful when enviroment is deficient
 Avoid osmotic pressure
 Metachromatic bodies use for storage

16. Mesosomes
 Structure invagination of plasma membrane
Two types
 Septal mesosomes
 Lateral mesosomes
 Functions:
 DNA replication
 Cell division
 secretion

17. Cytoplasmic membrane
 Composed of phospholipids bilayer
 Does not contain sterol
Cytochrome enzyme involved in electron transport and
oxidative phosporilation,lipids , enzymes and P binding
protein involved in cell wall biosynthesis
Function
 Selectively permeability and active transport
 Site of action of certain antibiotics such as polymixin

18. Transposomes
 Small piece of DNA that move bacteria rapidly from one
side to another between the DNA of the bacteria plasmid
and bacteriophage
 Also called jumping genes
Function:
 Code for antibiotic resistance and enzymes metabolic
enzymes and toxins
 May alter expression of neighboring genes are cause
mutation to genes into which they are inserted

19. Teichoic acid
 Are water soluble polymers containing a ribitole and
glycerol residue linked by phosphodiaster bonds
 Found in cell wall and is bonded to peptidoglycan
 Lipotechicacid is found in cell membrane and bounded to
membrane glycolipid in mesosomes specially
 Functions
 Important bacterial surface ,antigenic determinants
 It helps anchor the wall to membrane