This document provides an overview of bacterial cell structure and components. It discusses that bacteria are single celled organisms enclosed by a membrane. The key components of a bacterial cell include: proteins, nucleic acids, lipids and polysaccharides. Bacteria exhibit characteristics of living things like metabolism, reproduction, differentiation and communication. Structures inside and on the bacterial cell include flagella, fimbriae, cell wall, cell membrane, capsule, periplasm and cytoplasm. The document describes the differences between gram positive and gram negative cell walls.

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.