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1. Session 2:
Basic concept of microbiology in detecting disease 2
Dr Jesca malele (MD)

2. Learning objectives
 At the end of this session students should
be able to:
a) Describe characteristics of prokaryotic cell and eukaryotic cells
b) Describe structure and function of each part of bacteria cell
c) Compare eukaryotic cell and prokaryotic cell

3. prokaryotic and eukaryotic cells
 Microbial cells have evolved into 2 different types of cells ,the Eukaryotic
and prokaryotic cells
 This is based on their structure and the complexity of their organization.
 Fungi, protozoa, and helminths are eukaryotic,
 bacteria are prokaryotic

4. prokaryotic cell
 Prokaryotic cells: Are simple unicellular organism without a distinct nucleus
and other specialized cell structures.
 Example of prokaryotic cell is bacterial cell.

5. Characteristics of prokaryotic cells
I. The genetic material (DNA, RNA) of prokaryotic cells is not membrane-
bounded
II. Prokaryotes have no true nucleus and other membrane-bound structures
known as organelles.
III. They normally possess just a single chromosome that is separated from
other cell contents by a membrane.
 The characteristics of prokaryotic cells apply to the bacteria, cyanobacteria
(formerly known as blue-green algae) and archaebacteria.

6. Eukaryotic cell
 Eukaryotic cells: Are cells that contain nucleus, a sack
like structure that encloses a cell’s genetic materials.
 The presence of nucleus differentiates eukaryotic cell
from prokaryotic cell

7. Characteristics of eukaryotic cells
i. Eukaryotic cells have nucleus enclosed within nuclear membrane
ii. Eukaryotic cells contain cellular organelle such as mitochondria, lysosome,
ribosomes

8. Parts of bacteria cells and their function
Bacterial cell is comprised of the following parts
i. Cell wall
ii. Capsule
iii. Flagella
iv. Pilli (Fimbriae)
v. Cytoplasmic/Plasma membrane
vi. Mesosomes
vii. Cytoplasm
viii. Ribosomes
ix. Nucleoid material (DNA and RNA)
 N.B Not all bacteria possess all of these components

9. structure and organization of bacteria
cell

10. Parts of bacteria cells and their function
Cell wall :Is the outer most supporting layer which protects the internal
structure of a cell
Function
i. Protection of internal structures (supporting layer)
ii. Gives shape to the cell
iii. Confers stability to osmotic pressure (mucopeptide toughens the cell wall)
iv. Role in division of bacterial
v. Offers resistance to harmful effect of environment

11. Parts of bacteria cells and their function
Capsule: Is gelatinous secretion of bacteria which gets organised as a thick coat
around cell wall .
Function
i. Protection against deleterious agents (antibacterial agents) example lytic
enzymes
ii. Contributes to the virulence of pathogenic bacteria by inhibiting
phagocytosis

12. Parts of bacteria cells and their function
Flagella: Are long contractile filamentous appendages
Function :They are organs of movements
Pilli : Are (Fimbriae) hair like filaments that extend from the cell surface. They
are shorter and straighter than flagella
Function
i. They are organs of adhesion
ii. Facilitate transfer of genetic materials from one bacteria to another

13. Parts of bacteria cells and their function
Cytoplasmic/plasma membrane: Is a thin and elastic layer surrounding a
cytoplasm. It is made of lipoproteins and phospholipids :
Function
i. Controls the movement of water, ions, nutrients and excretory substances
in and out of the cell.
ii. Secrets extracellular hydrolytic enzyme

14. Parts of bacteria cells and their function
 Cytoplasm : Is a viscous watery solution or soft gell containing a variety of
organic and inorganic solutes
 Function
 Supports cellular structures like ribosome, nutrient granules, metabolites
plasmids and nucleoid materials

15. Parts of bacteria cells and their function
 Mesosomes : Is the invagination of the cytoplasm membrane
 Function
i. Sites of respiratory enzymes in bacteria
ii. Coordinates nuclear and cytoplasmic division during binary fission
iii. Responsible for compartmenting DNA at sporulation

16. Parts of bacteria cells and their function
Ribosomes : Are small granules and pack the whole cytoplasm.
 Function :They are the sites for protein synthesis
Nucleoid(site for DNA or RNA) :Is the area of the cytoplasm in which DNA and
RNA are located
 Function
i. To store genetic information
ii. Responsible for mutation of a bacteria

17. Parts of bacteria cells and their function
 Plasmid : Are extra chromosomal DNA capable of independent replicfation.
They are found in the cytoplasm
 Function
i. They carry the genes and structures of medical importance example
antibiotic resistance
ii. Resistance to heavy metals such as mercury
iii. Resistance to ultraviolet light

18. Comparison between prokaryotic and
eukaryotic cells
Similarities between Prokaryotes and Eukaryotes
i. They both have DNA and RNA as their genetic material
ii. They are both membrane bound
iii. They both have ribosomes
iv. They have similar basic metabolism
v. They are both diverse groups

19. Distinguishing featbetween prokaryotic and
eukaryotic cells
features prokaryotes eukaryotes
nucleus No enclosing membrane Enclosed by a membrane
Nucleolus absent present
Cell membrane composition Sterols are present Sterols are abscent
Cell wall composition Usually contain peptidoglycan Usually contain cellulose or
chitin
Mitochondria and chloroplast absent May be present
Location of the chromosomes In the cytoplasm usually
attached to cell membrane
In the nucleus separated from
cytoplasm by nuclear
membrane
reproduction Normally asexual Asexual or sexual
pilli Present absent
size Typically 1-5 micrometer Normally greater than 10
micrometer
Chromosome number One(1) More than one(1)

20. THE END