Chair of Microbiology, Virology, and
Immunology
THE HISTORY OF MICROBIOLOGY.
CLASSIFICATION AND STRUCTURE OF
MICROORGANISMS.
Lecturer As. O. B Kuchmak
Lecture schedule
1.
2.
3.
4.
History of Microbiology.
Classification of bacteria.
Structure of bacterial cell
The physiology of microorganisms.
Growth, reproduction and
respiration of bacteria.
Why Study Microbiology?

Pharmaceuticals


Vaccines/Antibiotics
Biotechnology

Bioremediation

Pathogenicity

Fundamental Biology
Microbiology
The study of microorganisms
 Microorganisms
living
things too small to be seen
with the unaided eye
 Microorganisms = Microbes
Microorganisms
Divided into six groups
 Bacteria
 Archae
 Algae
 Fungi
 Protozoa
 Viruses
History of Microbiology
 Microbes
discovered >300yrs
 Known to man during the mid
1800s
 Period of progress began &
continues to the present
Periods
of microbiology development
 Morphologic
 Physiologic
 Prophylactic
Morphological period
in microbiology history
(XVII middle of age).
It is also called micrographycal period, as the
study of microorganism came only to
description of their dimensions and forms.
Biological properties and their significances for
man
still
a
long
time
remained
incomprehensible.
Experimental phase
 Leeuwenhoek
 Pasteur
 Koch
 Lister
Before 17th century, study of microbiology was
hampered by the lack of appropriate tools to
observe microbes.
 Robert Hooke: In 1665 built a compound light
microscope and used it to observe thin slices of
cork. Coined the word cell.
 Anton van Leeuwenhoeck: In 1673 was the
first person to observe live microorganisms
which he called “animalcules” (bacteria,
protozoa), using single-lens microscopes that he
designed. He observed 50,000 different
specimens, reported findings to the Royal Society
of London
Jenner ( 1796)  Smallpox
immunity / Vaccine
 Edward
Pasteur’s Contributions:

Pasteurization: Developed a process in
which liquids are heated (at 65oC) to kill
most bacteria responsible for spoilage.

Disease Causes: Identified three different
microbes that caused silkworm diseases.

Vaccine: Developed a vaccine for rabies
from dried spinal cords of infected rabbits.

Directed Pasteur Institute until his death in
1895.
French Chemist Pasteur
(1861)
 Joseph
Lister (1859): Used
disinfectant to treat surgical wounds,
greatly reducing infection rates.
Considered the father of antiseptic
surgery.
 Robert
Koch (1876):

First person proved that microorganisms
caused diseases

Only specific microorganisms caused
specific diseases
Studied anthrax  affects cattle & humans
Proved that Bacillus anthracis causes
anthrax in cattle.



Later identified bacterium that causes
tuberculosis.
Study of viruses
 Iwanoski (1892) studying
diseases of tobacco plants
 Discovered TMV
 Filterable viruses
Prophylactic period
After 1914
Classic Metchnikov's
researches defined a
prophylactic period in
microbiology history.
The Patriarch of world and Ukrainian
microbiology - I. Metchnikov

Paul Ehrlich (1910): Search for “magic bullet”.
 Discovered
salvarsan, an arsenic derivative, was
effective against syphilis. (1st synthetic drug to
come in to widespread use)

Alexander Fleming (1928): Discovered that
penicillin produced by the mold Penicillium notatum
was able to prevent microbial growth.
 Penicillin

came into use 10 yrs later
-By the 1940s known as the
“wonder drug”
Rene Dubos (1939): Discovered two antibiotics
(gramidin and tyrocidine) produced by bacterium
(Bacillus brevis).
Classifications system.
Bergey's Manual
of Determinative Bacteriology – the
"bible" of bacterial taxonomy.
There
are
such
levels
of
microorganisms’
organization:
Species – Genus – Family – Class –
Division – Kingdom
35 of the major groups of bacteria are
distinguished primarily on morphological
characteristics, namely: cell shapes (rods,
cocci, curved, or filament forming); spore
production; staining reactions; motility.
Other groups are defined based on their
metabolism,
or
combinations
of
morphological
and
physiological
characteristics.
Some of the Major Groups of Bacteria
in Bergey's Manual
Very slender rods that are helically
coiled around a central axial filament;
Spirochetes
includes the bacteria that cause
syphilis and Lyme disease
Bacteria that have a cell wall structure
Gram-positive that results in their staining bluepurple by the Gram stain procedure
cocci
and that are spherical; include the
streptococci and staphylococci
Bacteria that form heat-resistant bodies
Endosporeforming rods and called endospores within their cells;
include the bacteria that cause gas
cocci
gangrene, botulism, tetanus, and
anthrax
Bacteria (Sing. Bacterium)

Small, single-celled (unicellular) organisms.

Procaryotes: “Before nucleus”.
Lack the following structures:
 Nuclear
membrane around DNA
 Membrane
bound organelles
Mitochondria
Chloroplasts
Golgi
apparatus
Endoplasmic
Lysosomes
reticulum
Property
Prokaryotic
Eukaryotic
0.5 - 10μm
5-100μm
Present in all bacteria
Except in Mycoplasma
Present in Fungi & Algae
No Sterol Except in
Mycoplasma
Has sterols
4- Nuclear
Membrane
Absent
Present
5- Nucleus
Absent
Present
6- Chromosome
Single chromosom
[not associtred with
protein
More than one
[associated with histone]
7- Mitochondria
Absent
Present
Sedimentation coefficient
70S
Sedimentation coefficient
80S
Asexual (binary fusion)
Sexual & Asexual
Bacteria, Chlamydia,
Rickettsiae
Fungi & Protozoa
1- Size
2- Cell Wall
3- Cytoplasmic
Membrane
8- Ribosome
9- Reproduction
10- Example
Bacterial Identification and
Classification








Shape - cocci, bacilli, spiral
Arrangement - single, pairs, chains,
clusters
Size
Gram-positive vs. Gram-negative
Aerobic vs. anaerobic
Physical/structural characteristics
Biochemical characteristics
DNA analysis
The Dimension of Bacteria
Relative size of a bacterial cell compared
to other cells including viruses.
Gross morphology of bacteria


Size - 1 to 10 mm - aids in identification
Shape
Coccus - round
Bacillus - rod
- Fusiform, coccobacilli
Spirillum - corkscrew
- Flexible, undulating - spirochetes
- Curved - vibrios
Cocci groupings
Coccus
Diplococcus
Streptococcus
Tetrad
Sarcinae
Staphylococcus
Chains of cocci
Streptococcus pyogenes
Clusters of cocci
Staphylococcus aureus
Sputum smear
Bacillus shaped bacteria
Pseudomonas aeruginosa
Escherichia coli
Bacillus shaped bacteria
Fusobacterium
Bacillus chains
Bacillus anthracis
Palisades arrangement
Corynebacterium diphtheriae
Curved bacteria
Vibrio cholerae
Campylobacter
Curved bacteria
Spirilla
Borrelia burgdorferi
Bacterial surface structures
Cell Envelope
 Cytoplasmic
 Cell
membrane
wall
Cell wall-less bacteria
 No peptidoglycan layer
 Cell membrane contains sterols for
stability
Mycoplasma pneumoniae
Cytoplasmic Membrane
 Phospholipid bilayer
 “Fluid mosaic” model
 Embedded proteins for active transport
 Enzymes for energy generation
 Photosynthetic pigments
Cell membrane
Peripheral
Membrane
Protein
Phospholipid
Integral
Membrane
Protein
Peripheral
Membrane
Protein
Function of Cytoplasmic Membrane
Selective permeability to different
molecules.
 Active transport aided by permease.
 Play a role in DNA replication.
 Cell wall biosynthesis.
 Mesosomes ----- cell division.

Cell wall

Two major groups of bacteria based
on structure of cell wall

Gram positive
 Thick

peptidoglycan layer
Gram negative
 Thin
peptidoglycan layer
 Outer membrane containing LPS

Gram stain is crucial first step
toward identification
Peptidoglycan (cell wall)
Cell Wall
 Gram positive cell wall



Thick peptidoglycan (PG) layer
Acidic polysaccharides
Teichoic acid and lipoteichoic acid
 Gram-negative cell wall




Thin peptidoglycan (PG) layer
Lipopolysaccharide layer
Porins
Periplasmic space
Gram-positive cell envelope
Gram-negative cell envelope
Cell Wall Structures
Structures associated with gram-positive and gram-negative cell walls.
Function of Cell Wall


Maintenance of the shape (due to rigidity of
peptidoglycan).
Protects the cytoplasmic membrane cell
contents


Rigidity
Cell wall is osmotically insensitive
Hypotonic solution – cell burst.
 Hypertonic solution – cell shrank.
 Isotonic solution – bacteria is life.

L Forms
Mutations can cause some bacteria to lose the
ability to synthesize the cell wall and are called L
forms.
Capsules

are important for
 Adhesion
(Associated with virulence in bacteria)
 Avoidance of immune response
(Protects bacteria from phagocytic
cells)
 Protection from dehydration
Capsule
Streptococcus
pneumoniae
Klebsiella pneumoniae
Bacillus anthracis
External structures

Pili (Fimbriae) play roles in
Adhesion
 Exchange of genetic material
 Avoidance of immune response


Flagella are important for


Motility (dispersal)
Antigenic determinant (“H” antigens)
Number and location species specific
Pili and flagella
Fimbriae are smaller than
flagella and are important
for attachment.
Salmonella
Pili
Pili enable conjugation to occur, which is the transfer of
DNA from one bacterial cell to another (“mating”).
Flagellar Structure
Three components of a flagellum: filament, hook and basal body
It composed of protein subunits called flagellin.
Flagellar Arrangement
(a) Monotrichous
(c) Amphitrichous
(b) Lophotrichous
(d) Peritrichous
Bacterial Motility
The rotation of the flagella enables bacteria to be motile.
Internal Structures
 Cytoplasm
 Genome
 Inclusion bodies
 Endospore
Cytoplasm
 Gelatinous solution containing
water, nutrients, proteins, and
genetic material
 Site for cell metabolism
Chemical Analysis of Microbial
Cytoplasm



70% water
Proteins
96% of cell is composed of 6 elements:






carbon
hydrogen
oxygen
phosphorous
sulfur
nitrogen
69
Bacterial Genome
Most bacteria contain a single circular double strand of DNA called a nucleoid.
Prokaryotic Ribosome
A ribosome is a
combination of RNA and
protein, and is the site
for protein synthesis
Composed of large
(50S) and small (30S)
subunits
S = Svedverg unit,
measures molecular size
Inclusion Bodies
Inclusion bodies enable a cell to store nutrients and to survive in
nutrient depleted environments
Bacterial Spores
Some bacteria, notably those of the
genera Bacillus and Clostridium, develop
a highly resistant resting phase or
endospore that does not grow or
reproduce and exhibit absolute dormancy
(not detectable metabolism).
Endospores
Bacillus anthracis

Vegatitive form


The bacteria actively growing, non spore
stage of a bacterium.
Sporulation:

Formed on exposure to unfavorable
condition,E.g.,
Nutrient depletion
 Changes






Moisture,
Temperature,
pH or
Oxygen tension
Spore requires 10-15 hours to form.
Endospore formation
Germination
Mature endoscope are metabolically inert
 Changes in the environment



Retuning to vegetative state within 15
minutes.
In the process of germination the spores
absorb water and swell, the protective
coat disintegrates and a single vegatitive
cell emerges.