The document provides a detailed overview of bacterial morphology, focusing on classification based on shape, envelope structures, and internal components. Key elements discussed include the differences between gram-positive and gram-negative bacteria, unique components like teichoic acids and lipopolysaccharides, and structures such as flagella, pili, and endospores. It highlights the functions of various components in bacterial survival and adaptability, referencing a microbiology textbook for further context.

1. BACTERIAL MORPHOLOGY
Chapter 3A

2. CLASSIFICATION OF BACTERIA BASED ON SHAPE

3. COCCI/SPHERICAL OR ROUND-SHAPED
Staphylococcus aureus Streptococcus pneumoniae

4. BACILLI/ROD-SHAPED
Escherichia coli Salmonella typhi Haemophilus influenza

5. CURVED AND SPIRAL SHAPED
Vibrio cholerae Treponema pallidum Corynebacterium diphtheriae

6. ENVELOPE STRUCTURES
Glycocalyx
Outermost covering of some bacteria
A gelatinous substance located external to the cell wall
Composed of polysaccharide or polypeptide, or both
It is called capsule when strongly attached to the cell wall, called
slime layer if it is loosely attached
Aiding in the evasion of bacteria in phagocytosis, anti-body
response from the immune system and serve to protect the
organism from dehydration

7. ENVELOPE STRUCTURES
Cell Wall
Provides rigid support and shape to bacteria, it protects the bacteria from
osmotic damage and play a special role in cell division
Sometimes called the murein sacculus
Principal component is peptidoglycan called murein or mucopeptide
Multi-layered in gram-positive bacteria and single-layered in
gram-negative bacteria

8. SPECIAL COMPONENTS OF
GRAM-POSITIVE CELL WALLS
1. Teichoic acids
Comprise major surface antigens of gram-positive organisms and can
elicit antibody response
In some gram-positive organisms as Staphylococcus aureus, it function
for the attachment of the organism to the host cell
2. Polysaccharides
Include neutral sugars such as mannose, arabinose, rhamnose and
glucosamine and some acidic sugars as glucuronic acid and mannuronic
acid

9. SPECIAL COMPONENTS OF
GRAM-NEGATIVE CELL WALLS
1. Outer membrane
A bi-layered structure where inner-leaflet is composed of a lipopolysaccharide (LPS), special
protein channel for small or low-molecular-weight hydrophilic substances Lipid A-complex
glycolipid responsible for endotoxin activity, located in the outer leaflet of the outer
membrane
The inner core is a polysaccharide made-up of repeated units, also called
O antigen, which is unique for every species of bacteria
2. Lipoprotein
Functions to anchor the outer membrane to the peptidoglycan layer and stabilizes the outer
membrane
3. Periplasmic space
A fluid-filled space between the outer membrane and the inner plasma membrane
Contains enzymes for breakdown of large non-transportable molecules into transportable
ones and enzymes that serve to detoxify and inactivate antibiotics

10. GRAM-POSITIVE AND
GRAM-NEGATIVE BACTERIA

12. ACID-FAST CELL WALL
Possess an outer layer that is lipid-rich
Composed of large amounts of waxes that are known as mycolic
acids
The inner layer of the cell wall is made up of peptidoglycan but
the outermost layer is lipid-rich, happened to be hydrophobic
The hydrophobic nature of the cell wall protects them from harsh
chemicals such as strong acids and detergents

13. ACID-FAST BACTERIAL CELL WALL

14. PROJECTING STRUCTURES
Flagella
Thread-like structures made up entirely of molecules of the protein sub-unit
flagellin
They project from the capsule and are organs for motility
Four Types:
1. Monotrichous-single polar flagellum
2. Lophotrichous-a tuft of flagella at one end of the bacterium
3. Amphitrichous-flagella at both ends of the bacterium
4. Peritrichous-flagella all around the bacterium

15. TYPES OF FLAGELLA

16. PILI OR FIMBRIAE
Rigid appendages found on many gram-negative bacteria
Fine and short in comparison to flagella
Structural sub-units are called pilins
Function for motility and adherence to cell surface (common
pili) or attached to another bacterium during a form of
bacterial gene exchange called conjugation (sex pili)

17. PILI OR FIMBRIAE

18. AXIAL FILAMENTS
Also called endoflagella and found in spirochetes
Composed of bundles of fibrils
Arise from the ends of the bacterial cell and spiral around the
cell
Filaments rotate producing movement of the outer sheath of
the spirochetes propelling them forward

19. AXIAL FILAMENTS

20. CYTOPLASMIC MEMBRANE
Cell membrane is located beneath the cell wall, sometimes called
cell sac
Selectively permeable allowing transport of selected solutes
In aerobic organisms, it is the site of ETC and serves as the site of
ATP production, therefore serves the function of the mitochondria,
which are not found in prokaryotic cells
Contains the enzymes needed for the biosynthesis of DNA , cell wall
components and membrane lipids

21. INTERNAL STRUCTURES
Nucleoid
Not true nucleus where the genetic material is packaged in this structure
Bacteria possess a single, circular, double-stranded DNA
Mesosome
Function for cell division, also involved in the secretion of substances produced by
bacteria
Ribosomes
Bacterial ribosome is smaller (70S) and function for protein synthesis
Granules or Inclusion Bodies
Serve for storage of food and energy (e.g. metachromatic granules of C. diphtheriae
and much granules of M. tuberculosis)

22. INTERNAL STRUCTURES

23. ENDOSPORES
Produced by many bacteria when they are placed in a hostile
environment
Composed of dipicolinic acid which is resistant to heat, drying, chemical
agents and radiation; making it difficult to destroy
The process of spore production is called sporulation, occurs when the
environment is detrimental to bacteria
During favorable condition, the endospores revert to their vegetative
state through a process called germination
Some gram-positive, but never gram-negative, bacteria form spores

24. ENDOSPORES

25. REFERENCE BOOK:
F. A., Bartolome, E. P., Quiles (2020) Microbiology and Parasitology: A textbook and
Laboratory Manual for Health Sciences. 2nd Edition. p.51-58.