Chair of Medical Biology, Microbiology, Virology,
and Immunology
SIGNIFICANCE OF
MICROBIOLOGY IN NURSES’
PRACTICE. THE HISTORY OF
MICROBIOLOGY.
CLASSIFICATION AND
STRUCTURE OF
MICROORGANISMS.
Lecturer Prof. S.I. Klymnyuk
Lecture schedule
1. History of Microbiology.
2. Classification of bacteria.
3. Structure of bacterial cell
Microbiology is a science, which study
most shallow living creatures - microorganisms.
They were frequently named by microbes.
Before inventing of microscope humanity was
in dark about their existence. But during the
centuries people could make use of processes
vital activity of microbes for its needs. They
could
prepare a koumiss, alcohol, wine,
vinegar, bread, and other products. During
many centuries the nature of fermentations
remained incomprehensible.
Microbiology
learns
morphology,
physiology, genetics and microorganisms
systematization, their ecology and the other
life forms. The taxonomy of microbes is very
variable. They include prions, viruses,
bacteria, water-plants, fungi, protozoon and
even some multicellular organisms.
The Microorganisms are extraordinarily
widely spread in nature. They literally
ubiquitous forward us from birth to our death.
Daily, hourly we eat up thousands and
thousands of microbes together with air, water,
food. On our skin, in mouth and nasal cavities,
on mucous membranes and in bowels
enormous amount of microorganisms live and
act. Many of them are found in earth cortex
and in the air, and in the ocean’s, sea’s, river’s
water, on all of latitudes, mainlands and
continents.
Some microbes bring enormous use to humanity.
They are our good friends.
But among enormous amount of microorganisms,
which populate our planet, there are such, which bring
death to people, animals and plants. For them, our
enemies, does not exist geographic and state boundaries.
Disease which they cause, spread with striking speed.
Epidemics of flue and plague, cholera and smallpox,
measles and diphtheria affected sometimes whole
mainlands of our planet.
Only during one plague epidemic in 14 century in Europe
was killed 25 mln. people and 35 mln. in Аsia. The
countries Europe needed 100 years, to bring population
level down to outgoing level.
For the first time term “microbe" was
offered by French scientist Sh.Sedillot in
1878. It derives from Greek “microbe", that
means briefly living, or most shallow living
creature. Science, which learns the
microorganisms, was named by E.Duclaux
microbiology. For short development period
this science accumulated great factual
material. The separate microbiological
branches such as bacteriology, mycology,
protistology, virology quickly appeared.
Periods of microbiology
development
• Morphologic
• Physiologic
• Prophylactic
Development of
microbiological science
was interlinked with
art of glass and
diamonds
grinding.
This
brought
to
creation of the first
microscope by Hans
and Zacharian Jansen
in Holland in 1590.
The
discovery
of
microorganisms
is
associated with the
name of Antony van
Leeuwenhoek (16321723).
In 1683 Leeuwenhoek described the basic
bacterium
forms.
His
scientific
supervisions
Leeuwenhoek described in special letters and sent off
them to the London Royal Scientific Society. He sent
away about 300 letters. The Leeuwenhoek’s letters
brought on enormous surprise among English
scientists. They opened a fantastic world of invisible
creatures. He named them “living animals" (animalcula
viva) and in one of letter wrote: “In my mouth there are
more, than peoples in all English kingdom".
These wonderful discovery of Dutch
naturalist were the embryo, with which
science of bacteria developed. Namely from
these
times
starts
the
so-called
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.
However, using the primitive microscopes of that
time it was difficult to determine the difference between
separate bacteria species. Even celebrated founder of
scientific systematization of all of living organisms Karl
Linney renounced to classify the bacteria. He gave them
general name “chaos".
The important attempt to make microbes
systematization belongs to Danish naturalist O. Muller. In
1786 year he described 379 infusorians and some species of
bacteria. Ph. Ehrenberg. Was the first who offered the terms
“bacterium ", “spirillum", “spirochaeta ", “vibrio". The
great contribution in microorganisms systematization was
made by one of founders of Ukrainian microbiology L.
Zemkovsky (1822-1887). He described 43 new species of
microbes, got original vaccine against anthrax.
In the second half of XIX century
microbiology strongly affirms as independent science.
Namely these sciences were fruitful soil, on
which Pasteur's talent evinced.
He
studied
wine
"illness“,
fermentation, made Pasteurization
method, offered to grow microbes
on artificial nutrient media, he
proved, that on definite cultivation
conditions the pathogenic bacteria
lose its virulence, made vaccine
against anthrax, rabies.
Not less important are scientific works of celebrated
German scientist R. Koch.
He
performed
classic
researches
on
etiology of anthrax, opened
tuberculosis
bacilli,
cholera vibrio, proposed to
isolate pure
bacterial
cultures on solid nutrient
media (gelatin, potatoes),
developed the preparations
staining methods by aniline
dye-stuffs,
method
of
hanging
drop
for
examination of bacteria
motility, offered apparatus
for sterilization
The Patriarch of world and Ukrainian microbiology I. Metchnikov
He studied inflammation
pathology, phagocytosis, bases
about antagonism of bacteria.
From
antagonists
preferred the
their base
medical
sour clotted
lactobacillin.
all
microbesI.Metchnikov
lactic bacteria. On
he offered three
preparations
milk, yogurt and
Now they are called by
eubiotics
Classic Metchnikov's researches defined a prophylactic
period in microbiology history.
In 1892 D. Ivanovskiy described an virus of mosaic
tobacco illness – new class of infectious agents
Microorganisms constitute a very
antique group of living organisms which
appeared on the Earth's surface almost
3000 million years ago.
There are natural and artificial 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
Procaryotae Kingdom has 4 Divisions according
to the structure of cell wall and Gram staining:
Gracilicutes (gracilis - thin, cutis - skin) – Gramnegative bacteria,
Firmicutes (firmus - firm) – Gram-positive bacteria,
Tenericutes (tener – soft, tender) – microbes without
cell wall,
Mendosicutes (mendosus - mistaket) – microbes wuth
atipical peptidoglican
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, on combinations of morphological and
physiological characteristics.
Some of the Major Groups of Bacteria in Bergey's Manual
Spirochetes
Very slender rods that are helically
coiled around a central axial filament;
includes the bacteria that cause
syphilis and Lyme disease
Gram-positive cocci
Bacteria that have a cell wall structure
that results in their staining bluepurple by the Gram stain procedure
and that are spherical; include the
streptococci and staphylo cocci
Endospore-forming rods Bacteria that form heat-resistant
bodies called endospores within their
and cocci
cells; include the bacteria that cause
gas gangrene, botulism, tetanus, and
anthrax
There are such levels of microorganisms’
organization: Species – Genus – Family – Class –
Division – Kingdom
Species is population of microbes, which
have the only source of origin, common
genotype, and during the present stage of
evolution are characterized by similar
morphological, biochemical, physiological
and other signs
If deviations from the typical species properties
are found on examination of the isolated bacteria, then
culture is considered a subspecies.
Infrasubspecies subdivisions
serovar (antigenic properties)
morphovar (morphological properties)
chemovar (chemical properties)
biovar (biochemical or physiological properties)
pathovar (pathogenic properties)
phagovar (relation to phages)
The term clone was applied to designate a
group of individuals arising from one cell
Population is an elementary evolutional
unit (structure) of a definite species
The term strain designates a microbial
culture obtained from the different sources or from
one source but in different time
Bacteria (Gk. bakterion - small staff) are
unicellular organisms lacking chlorophyll.
Morphological Classification of Bacteria
Morphologically, bacteria possess four main forms:
spherical (cocci)
rod-shaped (bacteria, bacilli, and clostridia)
 spiral-shaped (vibrios, spirilla and spirochaetes)
thread-shaped (non-pathogenic)
Cocci (Gk. kokkos berry). These forms of bacteria are
spherical, ellipsoidal, bean-shaped, and lanceolate. Cocci
are subdivided into six groups according to cell
arrangement, cell division and biological properties
Micrococci (Micrococcus).
The cells are arranged
singly or irregularly. They
are saprophytes, and live in
water and in air ( M. roseus,
M. luteus, etc.).
Diplococci (Gk. diplos
double) divide in one
plane and remain attached
in pairs. These include:
Meningococcus (causative
agent
of
epidemic
cerebrospinal meningitis,
and gonococcus, causative
agent of gonorrhoea and
blennorrhoea)
Pneumococcus (causative
agents of pneumonia)
Streptococci (Gk. streptos curved, kokkos berry) divide in
one plane and are arranged in chains of different length.
Some streptococci are pathogenic for humans and are
responsible for various diseases.
Tetracocci (Gk. tetra four) divide in two planes at right
angles to one another and form groups of fours. They
very rarely produce diseases in humans.
Staphylococci (Gk. staphyle cluster of grapes) divide in
several planes resulting in irregular bunches of cells,
sometimes resembling clusters of grapes. Some species
of Staphylococci cause diseases in man and animals
Sarcinae (L. sarcio
to tie) divide in three
planes at right angles
to one another and
resemble packets of
8, 16 or more cells.
They are frequently
found in the air.
Virulent species have
not been encountered
Rods. Rod-shaped or cylindrical forms are subdivided
into bacteria, bacilli, and clostridia. Bacteria include
those microorganisms which, as a rule, do not produce
spores (colibacillus, and organisms responsible for
enteric fever, paratyphoids, dysentery, diphtheria,
tuberculosis, etc.). Bacilli and clostridia include
organisms the majority of which produce spores (hay
bacillus, bacilli responsible for anthrax, tetanus,
anaerobic infections, etc.)
According to their arrangement, cylindrical forms can be
subdivided into three groups:
monobacteria
monobacilli
C. tetani
E. coli
Y. pestis
C. botulinum
diplobacteria
K. pneumoniae
diplobacilli
streptobacteria
streptobacilli
Haemophilus ducreyi
Bacillus anthracis
(chancroid)
(anthrax)
Spiral-shaped bacteria
Vibriones (L. vibrio to
vibrate) are cells which
resemble a comma in
appearance.
Typical
representatives of this
group
are
Vibrio
cholerae, the causative
agent of cholera, and
aquatic vibriones which
are widely distributed in
fresh water reservoirs.
Spirilla (L. spira coil) are coiled forms of bacteria
exhibiting twists with one or more turns. Only one
pathogenic species is known {Spirillum minus} which
is responsible for a disease in humans transmitted
through the bite of rats and other rodents (rat-bite fever,
sodoku)
Spirochaetes (L. spira curve, Gk. chaite cock, mane)
differ from bacteria in structure with a corkscrew
spiral shape
Borrelia. Their cells have
large, obtuse-angled, irregular
spirals, the number of which
varies from 3 to 10. Pathogenic
for man are the causative
agents of relapsing fever
transmitted by lice (Borrelia
hispanica), and by ticks
(Borrelia persica, etc.). These
stain blue-violet with the
Romanowsky-Giemsa stain
Leptospira (Gk. leplos thin, speira coil) are characterized by
very thin cell structure. The leptospirae form 12 to 18 coils
wound close to each other, shaping small primary spirals. The
organisms have two paired axial filaments attached at
opposite ends (basal bodies) of the cell and directed toward
each other.
Leptospira
interrogans
which is pathogenic for
animals and man cause
leptospirosis
Treponema (Gk. trepein turn, nema thread) exhibits thin,
flexible cells with 6-14 twists. The micro-organisms do not
appear to have a visible axial filament or an axial crest
when viewed under the microscope
A typical representative is the
causative agent of syphilis
Treponema pallidum
Properties of prokaryotes and eukaryotes
Prokaryotes
Eukaryotes
The nucleoid has no membrane
separating it from the cytoplasm
Karyoplasm is separated from the
cytoplasm by membrane
Chromosome is a one ball of double Chromosome is more than one,
twisted DNA threads. Mitosis is There is a mitosis
absent
DNA of cytoplasm are represented DNA of cytoplasm are represented
in plasmids
in organelles
There aren’t cytoplasmic organelle There are cytoplasmic organelle
which is surrounded by membrane which is surrounded by membrane
The respiratory system is localized The respiratory system is localized
in cytoplasmic membrane
mitochondrion
There are
cytoplasm
ribosome
70S
in There are ribosome 80S
cytoplasm
in
Peptidoglycan are included in cell’s Peptidoglycan aren’t included in
wall (Murein)
cell’s wall
The structure of procaryotes
Nucleus. The prokaryotic nucleus can
be seen with the light microscope in
stained material. It is Feulgenpositive, indicating the presence of
DNA. Histonelike proteins have
recently been discovered in bacteria
and presumably play a role similar to
that of histones in eukaryotic
chromatin
The DNA is seen to be a single,
continuous,
"giant"
circular
molecule with a molecular weight of
approximately 3 X 109. The
unfolded nuclear DNA would be
about 1-3 mm long (compared with
an average length of 1 to 2 µm for
bacterial cells)
Plasmids are small circular DNA molecules that can be
thought of as carrying extra genes that can be used for
special situations. There may be several different plasmids
in one cell and the numbers of each may vary from only
one to 100s in a cell.
Plasmids:
R, Col, Hly, Ent, Sal
The cytoplasmic constituents of prokaryotic cells invariably
include the prokaryotic chromosome and ribosomes.
The ribosomes of prokaryotes are smaller than cytoplasmic
ribosomes of eukaryotes. Prokaryotic ribosomes are 70S in
size, being composed of 30S and 50S subunits. The 80S
ribosomes of eukaryotes are made up of 40S and 60S
subunits. Ribosomes are involved in the process of
translation (protein synthesis), but some details of their
activities differ in eukaryotes, Bacteria and Archaea. Protein
synthesis using 70S ribosomes occurs in eukaryotic
mitochondria and chloroplasts, and this is taken as a major
line of evidence that these organelles are descended from
prokaryotes
Some inclusions in bacterial cells
Cytoplasmic
inclusions
Where found
Composition
Glycogen
Many bacteria e.g. E. Polyglucose
coli
Polybetahydroxyutyric
acid (PHB)
Many bacteria e.g.
Pseudomonas
Polyphosphate (volutin Many bacteria
granules)
Corynebacterium
diphtherieae
Sulfur globules
Ppolymerized hydroxy
butyrate
e.g. Linear or cyclical
polymers of PO4
Phototrophic purple
and green sulfur
bacteria and
lithotrophic colorless
sulfur bacteria
Elemental sulfur
Volutin granules
Neisser's staining
Loeffler's technique
The cell envelope is a descriptive term for the
three layers of material that envelope or enclose
the protoplasm of the cell. The cell protoplasm
(cytoplasm) is surrounded by the plasma
membrane, a cell wall and a capsule
Bacterial plasma membrane are composed of 40 percent
phospholipid and 60 percent protein. The phospholipids are
amphoteric molecules with a polar hydrophilic glycerol "head"
attached via an ester bond to two nonpolar hydrophobic fatty
acid tails, which naturally form a bilayer in aqueous
environments. Dispersed within the bilayer are various structural
and enzymatic proteins which carry out most membrane
functions.
Mesosome
The predominant functions of bacterial membranes are:
1. Osmotic or permeability barrier;
2. Location of transport systems for specific solutes (nutrients and ions);
3. Energy generating functions, involving respiratory and photosynthetic
electron transport systems, establishment of proton motive force, and
transmembranous, ATP-synthesizing ATPase;
4. Synthesis of membrane lipids (including lipopolysaccharide in Gramnegative cells);
5. Synthesis of murein (cell wall peptidoglycan);
6. Assembly and secretion of extracytoplasmic proteins;
7. Coordination of DNA replication and segregation with septum
formation and cell division;
8. Chemotaxis (both motility per se and sensing functions);
9. Location of specialized enzyme system.
Cell wall
Most prokaryotes have a rigid cell wall. The cell wall is an
essential structure that protects the cell protoplast from
mechanical damage and from osmotic rupture or lysis.
The osmotic pressure against the inside of the plasma
membrane may be the equivalent of 10-25 atm.
The cell walls of all Bacteria contain a unique type of
peptidoglycan called murein. Peptidoglycan is a polymer of
disaccharides (a glycan) cross-linked by short chains of
amino acids (peptides), and many types of peptidoglycan
exist. All Bacterial peptidoglycans contain Nacetylmuramic acid and N-acetylglucosamine, connected by
a beta1,4-glycoside bond. Then there is connections with
peptide side chain that contains L-alanine, (L-ala), Dglutamate (D-glu), Diaminopimelic acid (DAP), and Dalanine (D-ala).
Structure of peptidoglycan
Differences between Gram-positive and Gram negative cells
Capsules
Most prokaryotes contain some sort of a
polysaccharide layer outside of the cell wall polymer
Only capsule of B. anthracis consist of polypeptide
(polyglutamic acid)
Functions of capsules
Like fimbriae, capsules, slime layers, and
glycocalyx often mediate adherence of cells to
surfaces. Capsules also protect bacterial cells from
engulfment by predatory protozoa or white blood
cells (phagocytes), or from attack by antimicrobial
agents of plant or animal origin. Capsules in
certain soil bacteria protect them from perennial
effects of drying or desiccation.
They provide virulent properties of bacteria
(S. pneumoniae, B. anthracis)
Flagella
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, and they lack the typical 9 + 2
arrangement of microtubules. Their diameter is about 20
nanometers, well-below the resolving power of the light
microscope. The flagellar filament is rotated by a motor
apparatus in the plasma membrane allowing the cell to swim
in fluid environments. Bacterial flagella are powered by
proton motive force (chemiosmotic potential) established on
the bacterial membrane, rather than ATP hydrolysis which
powers eukaryotic flagella
The ultrastructure of a bacterial flagellum
Outer membrane
Peptidoglуcan
layer
Periplasmic space
Plasma membrane
According to a pattern in the attachment of flagella motile microbes can
be divided into 4 groups: (1) monotrichates, bacteria having a single
flagellum at one pole of the cell (cholera vibrio, blue pus bacillus), (2)
amphitrichates, bacteria with two polar flagella or with a tuft of flagella
at both poles (Spirillum volutans), (3) lophotrichates, bacteria with a tuft
of
flagella
at
one
pole
(blue-green
milk
bacillus,
Alcaligenes faecalis), (4) peritrichates, bacteria having flagella
distributed over the whole surface of their bodies (colibacillum,
salmonellae of enteric fever and paratyphoids A and B)
Flagella
The flagella of Proteus vulgaris demonstrated by
electron microscopy
Fimbriae and Pili are interchangeable terms used to
designate short, hair-like structures on the surfaces of
prokaryotic cells
Like flagella, they are composed of protein. Fimbriae are
shorter and stiffer than flagella, and slightly smaller in
diameter. Generally, fimbriae have nothing to do with
bacterial movement
Fimbriae are most often involved in adherence of bacteria to
surfaces, substrates and other cells in nature
Common pili (almost always called fimbriae) are usually
involved in specific adherence (attachment) of prokaryotes
to surfaces in nature. In medical situations, they are major
determinants of bacterial virulence because they allow
pathogens to attach to (colonize) tissues and/or to resist
attack by phagocytic white blood cells.
Pili of the second class (sex-pili) provide conjugation
process
Endospores. Endospores are
highly
heat-resistant,
dehydrated
resting
cells
formed intracellularly in
members of the genera
Bacillus and Clostridium.
Endospores
are
small
spherical or oval bodies
formed within the cell. A
spore is formed at a certain
stage in the development of
some microorganisms and
this property was inherited in
the process of evolution in the
struggle for keeping the
species intact.
Spore
The sporulation process begins when nutritional
conditions become unfavorable, depletion of the
nitrogen or carbon source (or both) being the most
significant factor. Sporulation involves the
production of many new structures, enzymes, and
metabolites along with the disappearance of many
vegetative cell components.
Spore formation
Properties of Endospores
1. Core. The core is the spore
protoplast. It contains a
complete nucleoid, all of the
components of the proteinsynthesizing apparatus, and an
energy-generating
system
based on glycolysis. A number
of vegetative cell enzymes are
increased in amount (eg,
alanine racemase), and a
number of unique enzymes are
formed (eg, dipicolinic acid
synthetase). The energy for
germination is stored as 3phosphoglycerate rather than
as ATP.
2. Spore wall. The innermost
layer surrounding the inner
spore membrane is called the
spore wall. It contains normal
peptidoglycan and becomes
the cell wall of the
germinating vegetative cell.
3. Cortex. The cortex is the
thickest layer of the spore
envelope. It contains an
unusual type of peptidoglycan,
with many fewer cross-links.
Cortex
peptidoglycan
is
extremely
sensitive
to
lysozyme, and its autolysis
plays a key role in spore
germination.
4. Coat. The coat is composed of
a keratinlike protein containing
many intramolecular disulfide
bonds. The impermeability of
this layer confers on spores their
relative resistance to antibacterial
chemical agents.
5. Exosporium. The exosporium
is a lipoprotein membrane
containing some carbohydrate.
Germination
The germination process occurs in 3 stages:
1. Activation. Even when placed in an environment that
favors germination (eg, a nutritionally rich medium),
bacterial spores will not germinate unless first activated
by one or another agent that damages the spore coat.
Among the agents that can overcome spore dormancy are
heat, abrasion, acidity, and compounds containing free
sulfhydryl groups.
Germination
2. Initiation. Once activated, a spore will initiate
germination if the environmental conditions are favorable.
Different species have evolved receptors that recognize
different effectors as signalling a rich medium: thus,
initiation is triggered by L-alanine in one species and by
adenosine in another. Binding of the effector activates an
autolysin that rapidly degrades the cortex peptidoglycan.
Water is taken up, calcium dipicolinate is released, and a
variety of spore constituents are degraded by hydrolytic
enzymes.
Germination
3. Outgrowth. Degradation of the cortex and outer layers
results in the emergence of a new vegetative cell consisting
of the spore protoplast with its surrounding wall. A period
of active biosynthesis follows; this period, which
terminates in cell division, is called outgrowth. Outgrowth
requires a supply of all nutrients essential for cell growth.
In bacilli and clostridia, spores are
located (1) centrally, in the centre of the
cell (causative agent of anthrax); (2)
terminally, at the ends of the rod
(causative agent of tetanus); (3)
subterminally, towards the ends
(causative agents of botulism, anaerobic
infections, etc.)
The spores of certain bacilli are capable of
withstanding
boiling
and
high
concentrations of disinfectants. They are
killed in an autoclave exposed to saturated
steam, at a temperature of 115-125 C, and
also at a temperature of 150-170 C in a
Pasteur hot-air oven.