1. Bacterial Morphology and Structure

2. Bacterial cells Morphology
Cocci: sphere, 1μm
Bacilli: rods , 0.5-1 μm in width -3 μm in length
Spiral bacteria: 1~3 μm in length and   μm in width.
Unit for measurement Micron or micrometer, μm:
1μm=10-3mm
Size: Varies with kinds of bacteria, and also related to their age and external environment

3. Bacterial Shapes and Arrangements

4. Structure of Bacteria Essential structure Cell wall cell membrane
Cytoplasm
Nuclear material
Particular structures
Capsule
flagella
pili
Spore

5. Gram Stain
1884: Christian Gram: First publication for the Gram stain method.
Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet.

6. Cell Wall of Bacteria

7. Cell Wall: common peptidoglycan layer
A back bone of N-acetyl glucosamine and N-acetyl muramic acid: Both discovered in Gram positive and Gram negative bacteria.
A set of identical tetrapeptide side chain attached to N-acetyl-muramic acid: different components and binding modes in Gram positive and Gram negative bacteria.
A set of identical peptide cross bridges: only in Gram positive bacteria

8. Special Components of Gram Positive Cell Wall
Teichoicacid

9. Special Components of Gram Negative Cell Wall
lipopolysaccharide

11. Functions of Cell Wall Maintaining the cell's characteristic shape
The rigid wall compensates for the flexibility of the phospholipid membrane
keeps the cell from assuming a spherical shape
Countering the effects of osmotic pressure
Providing attachment sites for bacteriophages
Providing a rigid platform for surface appendages- flagella, fimbriae, and pili all emanate from the wall and extend beyond it
Play an essential role in cell division
Be the sites of major antigenic determinants of
The cell surface
Resistance of Antibiotics

12. Wall-less forms of Bacteria
 When bacteria are treated with 1) enzymes that are lytic for the cell wall e.g. lysozyme or 2) antibiotics that interfere with biosynthesis of peptidoglycan, wall-lles bacteria are often produced
Usually these treatments generate non-viable organisms. Wall-less bacteria that can not replicate are referred to as sphero-plasts (when an outer membrane is present) or protoplasts(if an outer membrane is not present).
L-form bacteria, also known as L-phase bacteria, L-phase variants, and cell wall-deficient (CWD) bacteria, are strains of bacteria that lack cell walls

13. Cell membrane
Site of biosynthesis of DNA, cell wall polymers and membrane lipids. Selective permeability and transport of solutes into cells
Electron transport and oxidative phosphorylation
Excretion of hydrolytic exoenzymes

14. Mesosomes
Mesosomes are folded invaginations in the plasma membrane of bacteria that are produced by the chemical fixation techniques used to prepare samples for electron microscopy. Although several functions were proposed for these structures in the 1960s, and are no longer considered to be part of the normal structure of bacterial cells.

15. Cytoplasm Composed largely of water, together with proteins, nucleic acid, lipids and small amount of sugars and salts 
 Ribosomes: numerous, 15-20nm in diameter with 70S; Distributed throughout the cytoplasm; sensitive to streptomycin and erythromycin site of protein synthesis  
 Plasmids: extra-chromosomal genetic elements 
 Inclusions: sources of stored energy, e,g volutin

16. Plasmid Plasmids are small，circular/line，
extrachromosomal，double-stranded DNA molecules。
They are capable of self-replication and contain genes that confer some properties，such as antibiotic resistance，virulence factors。
Plasmids are not essential for cellular survival. 

17. Cell Inclusions and Storage Granules
Bacteria have different methods of nutrient
storage that are employed in times of plenty, for
use in times of want.
Inclusions are aggregates of various compounds
 that are normally involved in storing energy reserves 
or building blocks for the cell
Inclusions accumulate when a cell is grown in 
the presence excess nutrients and they are 
often observed under laboratory conditions.

18. Nucleus Lacking nuclear membrane absence of nucleoli, hence
known as nucleic material or nucleoid
one to several per bacterium.

19. Capsules and slime layers
These are structures surrounding the outside of the cell envelope.
They usually consist of polysaccharide; however, in certain bacilli they are
composed of a polypeptide (polyglutamic acid). 
They are not essential to cell viability and some strains within a species will
 produce  a capsule, whilst others do not.
 Capsules are often lost during in vitro culture.
  Functions
Attachment
Protection from phagocytic
engulfment.
Resistance to drying.
Depot for waste products.
Reservoir for certain nutrients.
Protection
A bacterial capsule is similar, but is a well
ordered structure that is resistant to washing off

20. Flagella Some bacterial species are mobile and possess
locomotory organelles - flagella. 
Flagella consist of a number of proteins including flagellin
The diameter of a flagellum is thin, 20 nm, and long with some having a length 10 times the diameter of cell.
Due to their small diameter, flagella cannot be seen in the light microscope unless a special stain is applied.
Bacteria can have one or more flagella arranged in clumps or spread all over the cell.
Functions
Identification
of Bacteria
Pathogenesis
 Motility of bacteria

21. Flagellum Structure

22. Pili Pili are hair-like projections of the cell
They are known to be receptors for certain
 bacterial viruses
Chemical nature is pilin
Classification and Function 
a. Common pili or fimbriae: fine , rigid numerous,
related to bacterial adhesion
 b. Sex pili: longer and coarser, only 1-4, related to
bacterial conjugation

23. Endospores(spores)
A bacterial spore is a spore or spore- like structure produced by bacteria
Spore formation in bacteria is not a method of reproduction but simply a method of surviving in an unfavorable conditions
Produced when starved
Contain calcium dipicolinate
DPA, Dipicolinic acid
E.g.Bacillus and Clostridium
Dormant cell
Resistant to adverse conditions
- high temperatures
- organic solvents

24. Thanks