3a. Bacterial Cell Biology_v2_ Differences btn eukaryotic and prokaryotic cells_02Sept2024 [Compatibilit.pdf

Hematological principles

1. Freddie Bwanga
M.B;Ch.B, M Med (Microb), Ph.D.

Monday 02 Sept 2024
2-5pm
M. Med Class

2. Bacterial Growth
Bacterial Cell Division
Size

Shape

Bacterial cell structure

Bacterial DNA

Bacteria Ribosomes

Cell envelope structures

Capsules and Slime layers

Bacteria cell surface structures and Appendages
Bacteria Endospores

3. Bacterial Growth

4. Bacterial Growth Requirements

Bacterial Nutrition and Growth

«Nutrient Requirements:
Wi «Environmental factors for
Amer bacteria growth:

Carbon source (C) Temperature

Nitrogen source (N) Gas (oxygen)

Inorganic salts
S pH

Growth factors oo
Osmotic pressure

Sulfur source (S)

Phosphorus source (P)

5. Aerobic vS Anaerobic Bacteria

Effect of
Oxygen on
Growth

Bacterial
Growth in
Tube of Solid
Growth
Medium

Explanation
of Growth
Patterns

Explanation
of Oxygen's
Effects

a. Obligate Aerobes

Growth oceurs only where
high co

and superoxide
dismutase (SOD) allows
toxic forms of oxygen to be
neutralized: can use oxygen

b. Facultative
Anaerobes

Both aerobic an
anaerobic growth

Growth is best
oxygen is
x, but occurs:
throughout tube

Presence af enzymes
SOD

of oxygen to be

neutralized; can use

oxygen

©. Obligate
Anaerobes

Only anaerobic
growth: ceases

0)

Growth occurs
only where there
is no oxygen

neutralize harn
forms of oxygen:
‚anno! tolerate

d. Aorotolerant
Anaerobes

Only anserobic:
growth: but continues
in presence of
oxygen

Growth cour

Presence of one
enzyme, SOD. allow
harmful forms of
oxygen to be partially
neutralized; tolerates
oxygen

centration

ion of
‘oxygen has diffused into

of toxic forms of oxygen
if exposed to normal
atmospheric oxygen

6. 2
3
8
zg
3
o
LA
3
>
£
3
5
E
=
a
E
E
3

Bacterial Growth Curve

Log phase:
exponential
increase

in number

plateau in number
of living bacterial
cells; rate of cell
of living division and death
bacterial roughly equal

cells |

® Lag phase:

no increase in

number of living
==" bacterial cells

Stationary phase:

4 ) Death or
decline phase:
exponential
decrease in
number of
living bacterial
cells

Time

7. Fastidious Bacteria

These are Microorganisms that are difficult to grow in
the laboratory because they have complex or restricted
nutritional and/or environmental requirements growth

Special requirements may be temperature, pH,
oxygen availability/Concetration, special nutrient

sources

They are unable to grow unless these requirements are
stringently met in the laboratory.

8. Examples of Fastidious Bacteria

Fastidious Bacteria Example

Neisseria gonorrhoeae
Haemophilus influenzae
Treponema pallidum
Legionella pneumophila

Bordetella pertussis

Campylobacter jejuni
Helicobacter pylori (H. pylori)
Brucella species
Francisella tularensis
Bartonella henselae

Mycoplasma pneumoniae

A. pleuropneumoniae

9. Bacterial Cell Division

Binary fission

10. Principles of Bacterial Growth

Prokaryotic cells divide by binary
fission
One cell divides into two
Two into four etc.
Cell growth is exponential

Doubling of population with each cell
division

Exponential growth has important
health consequences

Generation time
Time it takes for population to double
A.k.a doubling time
Varies among species

11. Bacterial /Fungal Dividing Time

Organism (T) (min)

Bacillus cereus 49.0
Escherichia coli 52.0, 86.6
Proteus vulgaris 28.2
Enterobacter aerogenes 30.0
Enterococcus faecalis 25.9
Saccharomyces ellipsoideus 107.0
Saccharomyces cerevisiae 99

Methylobacterium extorquens 187.2
Caulobacter crescentus 68.7
Schizosaccharomyces pombe 108.3

« Mycobacterium smegmatis: about 3 hrs
« Pathogenic Mycobacterium: 18-24 hrs in
rich medium

12. SIZE OF BACTERIA

Cell size 0.1 to 5um in diameter, but may vary.
e.g.

+ Haemophillus influenzae 0.25x1.2um

« Escherichia coli 1.3x3um

+ Cyanobacteria 5x40um

13. Size Comparatives

100 pm

Organelles
Eukaryotic Celis

14. SHAPES OF BACTERIA

BACILLI

Streptococci
(Streptococcus
| pyogenes)
Diplococci Chain of bacilli
(Streptococcus (Bacillus anthracis)

pneumoniae) ag

ES

Flagellate rods
(Salmonella typhi)

Se”

Staphylococci Sarcina Spore-former
(Staphylococcus (Sarcina (Clostridium
aureus) ventriculi) botulinum)

OTHERS
A

Vibrios
(Vibrio cholerae)

on

Spirilla
(Helicobacter pylori)

MOIS

Spirochaetes
(Treponema pallidum)

15. la he OF BACTERIA
Coccus
ei

Coccobacillus 0000,

streptococcus tetra

Coccus

staphylococcus Filamentious Bacteria

Spirochete

16. Mycobacteria on ZN Stain

——

17. Actinomyces and Norcardia as examples of
Blamenhous, Bacteria _
, NAT,

EN.

18. Neisseria gonorhae as examples of
Gram negative diplococci

19. BACTERIAL BASIC CELL STRUCTURES
Celman
Plasma membrane

Cytoplasm.

Ribosomes
Plasmid
Pili

Bacterial Flagellum
Nucleoid (circular DNA)

20. Chromosome

Pilus (fimbria)

Inclusion

Flagellum ’ y \
“Sy a Capsule or
J ile slime layer

I Cell wall

/ Plasmid
Y

jr

Cell membrane

21. Bacterial cell (prokaryotic)

Chromosome

Pils (fimbria) \

\
Ribosomes \

Inclusion

Flagellum Y
EN capsule or
slime layer

/
Phsmid | Cell wal

Cell membrane

Assi ment, Read:

2.

Eukaryotic cell
Pinocytotic
vesicle

post

(in plants) >

Microfilament

cell
membrane —|

V
ua |

Microtubule’
Ribosomes.

Lysosome

Rough endoplasmic %$
reticulum

ifferences between eukaryotic and prokaryotic cell
Differences between gram positive and gram negative bacterial cell wall

Thylakoid y \ a

Y aa

Microvilli

à Centrioles
{in animals)

Golgi

Smooth
endoplasmic
| reticulum

à Nucleolus
Nuclear
chromatin

Mitochondrion

Nucleus
NY ‘cytoplasm
Nuclear pore

22. Stfücture of the Fungal Cell / 3

Table 1. Comparison of Selected Features of Fungi and Bacteria

Feature

Fungi

Bacteria

Cell type
Size of cell, diameter

Nuclear structure

Organelles

Cell membrane

Cell wall,
main constituent

Spores

Eukaryote
2-15 um

True nucleus with a well-defined
nuclear membrane

Mitrochondria, endoplasmic reticulum,
Golgi apparatus, vacuoles, others

Sterols present

Polysaccharides (e.g., glucans,
mannans, chitin); no peptidoglycan

Produce a wide variety of sexual
and asexual reproductive spores

Prokaryote
0.5-2.0 pm

No nuclear membrane

Sterols absent

Peptidoglycan

Endospores (not for reproduction)
some asexual reproductive spores

23. Bacterial DNA
Most bacteria have a haploid genome, a single
chromosome consisting of a circular, double
stranded DNA molecule
Bacterial DNA Plasmids

> Linear chromosomes have been found in Gram-positive Borrelia and Streptomyces
spp.

> One linear and one circular chromosome is present in the Gram-negative bacterium
Agrobacterium tumefaciens

Exceptions:

24. Bacterial DNA Replication, Transcription and
Translation

| nucleus

= cytoplasia
nucle enge.

F Translation
’ tein synthesis
a = A Protein si

y,

Pron

The Central Dogma of Molecular Biology

25. RNA Synthesis & Processing:
mRNA, tRNA, rRNA

y

DNA is the om Yom Y A
template with
the genes for all | Transcription

Chromosomal DNA ln er

(RNA synthesis)

forms of RNA

on 1 Yous GF exon 3

Nuclear ANA

ZA 4 RNA Splicing

exonz | exons

RNA synthesis and processing

26. « Are small particles composed of ribosomal
protein and ribosomal RNA (rRNA)

« Ribosome are 70s in size

¢ Part of the translation apparatus in the protein
synthesis (Ribosomal proteins and rRNA).

27. Ribosomal structure and subunits

70S ribosome
(2.3 x 108)

+Mg2+ t| —Mg2+

50S subunit 30S subunit
(1.45 x 106) (0.85 x 108)

5S RNA 23S RNA CON” 16S RNA
(4x 104) E ) (0.5 x 108)
®
+

Proteins Proteins
L1, 12.......„L $1, 82, 83...........,S21

28. Composed of:

> Cell / Cytoplasmic / Plasma membrane
> Cell wall — ¡.e. layer(s) outside cell membrane

In Gm positive bacteria, the cell wall is composed of
only the thick Peptidoglycan layer

In Gm negative bacteria, cell wall is composed of
= A thin Peptidoglycan layer
= Outer membrane

29. Chromosome

Pilus (fimbria)

slime layer

Cell wall

Cell membrane

30. Cell Envelope of Gram positive bacteria

I Un. ts
= == ==

ES
on $

on

Simple and has:
1. Cell/Cytoplasmic / Plasma membrane

2. Thick Peptidoglycans: Up to 40 sheets of peptidoglycan
comprising up to 50 - 90% of cell wall materials

31. Cell Envelope of Gram Positive Bacteria

. 7 Teichoic acid
Wall associated A)
protein @

|
A

>; — Lipoteichoic
| acid

ol oy
bo
|.-Peptidogiycan

Cytoplasmic
membrane

32. Cell Envelope of Gram Negative bacteria

Complex and multilayered with:
1. Cytoplasmic membrane / Inner / Plasma membrane
2. Single planar sheet of peptidoglycan

3. Outer membrane

33. Cell Envelope of Gram Neg bacteria

Lipopoiy-
saccharides

OUTER
MEMBRANE
PERIPLASMIC
, — SPACE

Murein Lipopratein!

INNER
MEMBRANE

CYTOSOL

34. Cell/Plasma/Cytoplasmic Membrane

35. Cytoplasmic /Cell/ Plasma membrane
(is a Phospholipid bi-layer)

Extracellular

UL er

Intracellular

Hydrophobic tail

Hydrophilic head

36. Cytoplasmic /Cell/ Plasma membrane
(It is a Phospholipid bi-layer)

Hydrophilic
head

Hydrophobic tails

Hydrophobic
tails

37. Function of Cytoplasmic Membrane
1. Selective permeability barrier

2. Electron transport and oxidative phosphorylation -
Cytochromes, dehydrogenase and other enzymes for
respiratory chain are located inside of the cytoplasmic
membrane

. Excretion of hydrolytic enzymes and pathogenic proteins

. Biosynthetic function - Subunits of cell wall and enzymes of
cell biosynthesis

5. Chemotactic systems - Attractants and repellants bind to
specific receptors in the bacteria cell membrane. Eg : 20
different chemoreceptor in Escherichia coli.

38. Cell Wall

39. Is the layer of the cell envelop that lies outside the
cytoplasmic membrane

Made up of Peptidoglycan only in Gr +ve bacteria

Made up of Peptidoglycan & outer membrane in gram
negative bacteria

Basis of the two major groups of bacteria (gram + & gram -)

High tensile strength

40. The Cell wall is the layer of the cell envelop
that lies outside the cytoplasmic membrane

OUTER MEMBRANE —| |
LIPOPROTEINS:
PEPTIDOGLYCAN ——4

—— PERIPLASMIC SPACE ——

ERAN INPI TENTE

41. Cell Wall Functions

« Shape and cellular integrity
« Essential role in cell division

« Serves as a primer of its own synthesis
« Major site for antigen determinant

42. Gram negative bacterial cell wall

0

0: “Th ¿Outside

ipopoly-
a E rot Porin ie
u polysacchari 7 A / (LPS)

membrane -ı aa » 0

N = alt A "| | r -
| j |
@ AN N (hh | JO — Phospholipid

> Lipoprotein
Periplasm À = a *Peptidiogiyéan. ‘

id aah naar

Inside

43. Peptidoglycan

44. Peptidoglycan

Complex polymer consisting of 3 parts:

1. Two sugar derivatives N-acetylmuramic acid
and N-acetyl glucosamine, which form the
backbone

2. Aset of identical tetrapeptide side chains

3. A set of identical peptide cross bridge

45. PEPTIDOGLY CANS

CH20H
Bacterial Cell wy alls L———

a

AS a

H3C EH NHC OCH;
oO" (lactatey
5
1 la
2 D-I=so-Slu
3. Ly
=NH2
CHOX peon US Das
| - o: i
e SleNAc 7

NHC OC Ha

o
47 murio

NHC OCHS
{=}

| EShds for Gram + bacteria;
L “la ¿direct amide link for Gram-
D-isoglutamié acid

|
3 Lye 7

|
4 D-Ala

46. D-alaninine vS B-Lactam Rings

O
HOLA y

NHo

47. N.B
1. Gram positive bacteria have up to 40 sheets of peptidoglycan
comprising up to 50-90% of cell wall materials

2. Gram negative bacteria have tor 2 sheets of peptidoglycan
comprising up to 5 - 20% of cell wall materials

3. Archaebacteria lack peptidoglycan

4. Some Eukaryotic cells have a cell wall with cellulose (plants), or
chitin(fungi) instead of peptidoglycan

48. LIPOPOLYSACHARIDES

49. LIPOPOLYSACHARIDES (LPS) of gram -ve cell wall

Consist of;

1. Complex Lipid A (Fatty acids- caproic, lauric, myriastic, palmitic
and stearic acids (Not glycerol)

2. Core Polysaccharides - similar in all gram neg bacteria of
same genus

3. Terminal series of repeat units of O-polysaccharides. This is
the so called O-antigen responsible for antigenic variability in gram
negative bacteria ( >2500 antigenic types in Salmonella)

50. LIPOPOLYSACHARIDES (LPS) of gram -ve cell wall

à Outside

O-polysacı Bu
(

Lipopoly-
Core Prot roel accharde
ae D hi A (LPS)

| 6 0 0 00 |
) har E wr ri Ll ‘| la
, ii cesses! eco UAL
4 * D a — Lipoprotein

Peptidogiyé:
Cytoplasmi a”

AO vei or un 4 Lia

Periplasm

51. Lipid A
« Lipid A, aka endotoxin, is a component of
the lipopolysaccharides, found on the
outer membrane of Gram-negative
bacteria

¢ The lipid A portion is a disaccharide
comprised of two glucose units
connected through B(1 > 6) linkages and
six esterified FA-derived acyl groups

52. Lipid A Structure

1 phosphate group
o

Il
SON

Hy H3C

ndary Hao

chain

53. Lipid A, Core Polysaccharide and O Antigen

an

54. Function of LPS

» LPS is an endotoxin (Toxicity attributed to
Lipid A only) e.g.: Salmonella, shigella and
Escherichia coli pathogenicity

« Major surface antigen. This is the so called
O-antigen - >2500 antigenic types in
Salmonella

55. Capsules
and

Slime layers

56. Capsules and Slime layers

Slimy or gummy material secreted by many procaryotes on their surfaces
General term: glycocalyx.

Extracellular polymer of polysaccharide (with one exception, the poly-D
glutamicacid capsules of Bacillus licheniformis).

May be thin or thick, rigid or flexible

Functions
+ Attachment of pathogenic microorganism to their host, eg: Streptococcus
mutans and dental caries.

+ Anti-phagocytic
+ Antigenic structure - used for typing

57. BACTERIAL CELL SURFACE STRUCTURES
8 APPENDAGES

58. 1. Pilli & Fimbriae
Rigid surface structures in many gram -ve bacteria
Shorter and finer than flagella.
Consisting of structural protein subunits called pillins

Pilli are longer than fimbriae and only 1 or a few pilli are present on the
surface.

Functions:

Pilli

» For adherence

» Sex pilli (F-pilli): Attachment of donor 8. recipient cell in bacteria conjugation
» Antigenic structures e.g.: Antigenic variation in N. gonorrhoae

Fimbriae:

« 2? Enable bacteria to stick to inert surfaces, or to form pellicle or scums on
the surface liquids

59. Surface structures cont'd

2. Flagella

Thread like surface appendages composed entirely of protein
subunits called flagellin arranged to form a helical structure
(12-13nm in diameter).

Functions
¢ Organ of locomotion in most of bacteria (some bacteria
move by gliding and by gas vesicles).

» They are highly antigenic (H-antigen in Salmonella)

60. BACTERIA ENDOSPORE

61. BACTERIA ENDOSPORE

Endéshors À

Spore coat

Formed in adverse conditions such as hash conditions e.g
nutritional depletion, high temperatures, etc.

Very resistant to heat and other harmful agents like drying,
radiation, acids and chemical disinfectants

Location important in classification: Central, Subterminal, Terminal

62. Spore Structure — shapes
Core, cortex, spore coat, and exosporium

— Spore coat

63. Uses of Spores in Microbiology

« Bacillus stearothermophilus spores

Are used to monitor the success of
sterilization in autoclaves

« Bacillus anthracis - spores
—Used in ??biological warfare