Sir,SEIF CUHAS MWANZA

1. Introduction to bacterial cell

2. Cell
 Fundamental unit of life
 A single cell is isolated from other cells by a
membrane and contain within it chemicals and
subcellular structure.
 Compartmentalization is a prerequisite for life

3. Cell chemistry
 Chemical components
Proteins
Nucleic acids
Lipids
Polysaccharides
Collectively are called: Macromolecules

4. Characteristics of living system
 Metabolism
 Reproduction or Growth
 Differentiation
 Communication (Quorum Sensing)
 Movement
 Evolution

5. Cell Structure

7. Flagella
 Are filamentous protein structures attached to the cell
surface that provide the swimming movement for most
motile prokaryotes.
 Prokaryotic flagella are much thinner than eukaryotic
flagella.
 Diameter of a prokaryotic flagellum is about 20
nanometers

8. Location of flagella

9. Demonstration of motility

10. Use of electron microscope

11. Fimbriae and pilli
• Heavy hair-like structures made of protein
• Fimbriae and pilli are interchangeable terms
- Composed of protein.
• Fimbriae are shorter and than flagella, and slightly
smaller in diameter.
• Nothing to do with bacterial movement.

12. Fimbriae and pilli
 Are common in Gram-negative bacteria
 Fimbriae are most often involved in adherence
 In E. coli, a specialized type of pilus, the F or sex
pilus,
- numerous common pilli is quite different

14. Cell envelope
 Capsule
 Cell Membrane
 Cell wall

15. Capsule
 Polysaccharide layer outside of the cell wall polymer.
 A true capsule is a discrete detectable layer of
polysaccharides deposited outside the cell wall.
 A less discrete structure or matrix which embeds the
cells is a called a slime layer or a biofilm.

16. Capsule

20. Function of capsule
 Like fimbriae, slime layers, and glycocalyx,
capsules, often
- mediate adherence of cells to surfaces.
 Capsules also protect bacterial cells from
engulfment

21. Function of capsule
 Capsules in certain soil bacteria protect cells
from effects of drying or desiccation.
 Capsular materials (e.g. dextrans) reserves of
carbohydrate for subsequent metabolism.

22. Cell wall
 Maintains the overall shape of the bacteria cell
 They are an essential structure for viability
 They are composed of unique components found
nowhere else in nature.
 They are one of the most important sites for attack
by antibiotics.

23. Cell wall
 They provide ligands for adherence and receptor
sites for drugs or viruses.
 They provide for immunological distinction and
immunological variation among strains of bacteria.

24. Cell wall gram positive and gram negative

25. Peptidoglycan
 Peptidoglycan is a complex polymer consisting, of three
parts:
 a backbone composed of alternating N-
acetylglucosamine and N-acetylmuramic acid;
 a set of identical tetrapeptide side chains
 and peptide cross-bridges

27. Gram-positive
 Contain teichoic and teichuronic acids
 Account for up to 50% of the dry weight of the wall and
10% of the dry weight of the total cell.
 In addition, some gram-positive walls may contain
polysaccharide molecules.
 There are two types of teichoic acids: wall teichoic acid
(WTA), and membrane teichoic acid a.k.a lipoteichoic
acids (LTA).

29. Gram-negative

30. Structure of LPS

31. Structure of LPS
 O-antigen a complex polysaccharide,
- composed of repeating units of five to eight
monosaccharides (galactose, rhamnose, mannose)
 Core oligosaccharride
 Lipid A

32. Plasma membrane
 Is the most dynamic structure of a prokaryotic cell.
 Main function is a s a selective permeability barrier
 It sequesters the molecules of life in a unit, separating it
from the environment.
 It allows passage of water and uncharged molecules up
to mw of about 100 daltons.

33. Plasma membrane
 Composed of 40% phospholipid and 60% protein.

34. Function of plasma membrane

35. Transport

37. The Periplasm
 Between the inner (plasma) and outer membranes of
Gram-negative bacteria and spirochetes.
 The peptidoglycan sheet resides within the periplasm.
 The periplasm is a very active compartment of the
cell.

39. Cytoplasm
• Consists of an aqueous solution of three groups of
molecules:
• macromolecules such as proteins (enzymes), mRNA
and tRNA;
• small molecules that are energy sources, precursors
of macromolecules, metabolites or vitamins;
• various inorganic ions and cofactors
• The primary structural components found in the
cytoplasm are the nucleoid and ribosomes, and possibly
some type of inclusion.

42. Inclusions

43. Endospore
 A bacterial structure sometimes observed as an
inclusion is actually a type of dormant cell.
 Bacillus
 Clostridium.
 Thermoactinomyces,
 Sporolactobacillus,
 Sporosarcina,
 Sporotomaculum,
 Sporomusa,
 Sporohalobacter.

44. Why spores are heat
resistance?
 Dehydrated state.
 The presence in the core of large amounts (5–15% of
the spore dry weight) of calcium dipicolinate.