Transcript Microbiology

Microbiology
Course book
Khlood Noori Saeed
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SUBJECT OUTLINE
2015-2014
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Subject title
microbiology
Credit hours : 2
)Theory(2
Units 2
Unit
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Stage
second stage
Class schedule
120 minute, one sessions per
week
Duration 27 weeks
20 weeks
Course coordinator
Assistant Lecturer
Kazem. [email protected]
[email protected]
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Subject Description
.1
The lectures for this course will provide you with an introduction to the general
Microbiology and large amount of information about the outer and inner structure
of the bacteria and the main difference between the gram positive bacteria and
gram negative bacteria and how to control the bacterial diseases by chemical and
physical materials . Finally we classified types of bacteria.
Require Background or Experience .2
Many student know about medical microbiology and their effect on human in
infections
Subject Objective .3
A)Understand the fundamental concepts of microbiology and the scientific
vocabulary used in this field.
B) Classification of medical microorganisms according to morphological
characteristics
C) Knowing the common materials which are used for controlling pathogenic
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bacteria
and different pattern of diseases
.
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:Text book(s) and Readings
.
1)Prescott, L. M., Harley , J . P. and Klein, D. A.2000.Microbiology.pp.39-89
,Wm. C. Brawn publishing, U . S . A.
2)Levinson, W. and Jawetz , E. 2000 .Sterilization and Disinfection ,In
"Medical microbiology and immunology , examination and broad review , 6th
ed ., pp.78-81 " McGraw – Hill medical publishing division .
3(
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:Student Materials .5
Textbook and References .1
Lecture Notes .2
CD and internet resources .3
Collage Facilities .6
Classroom with Whiteboard and projection facilities .1
College library .2
data show3
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week- 1
Historical Preview
Microbiology : is defined as the science studying organisms or agents which cannot
be seen by eye and must be examined by microscope (objects less than about 1
mm).
Its subjects are viruses, bacteria, many algae and fungi, and protozoa.
Can be divided into virology, bacteriology, algeology, mycology etc.
Or on general, systematic, applied microbiology.
Microbiology dawn was in the end of 19th century .In general any organism
has a diameter of less than 1mm will be considered as microorganism (m-ms) .
Microorganisms are necessary for the production of bread, cheese, beer,
antibiotics, vaccines, vitamins, enzymes, they make possible the cycles of carbon,
oxygen, nitrogen , sulphur , and they also caused many diseases
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Week 2
Bacteria are :The smallest organisms that all machinery required for growth
and self replication.
Bacterial cell have rigid cell wall surrounding the cytoplasmic membrane .
The membrane provides the osmotic barrier while the wall protects the cell against
osmotic rapture in dilute media and against mechanical damage .
The cell wall and cell membrane together composed the cell envelope.
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week3
Capsule: Many bacteria synthesis large amount of extracellular
polymer when growing in their natural enviroments.
When the polymer forms condensed layer closely surrounding the cell it is called
capsule , and when it forms a loose network of fibrils extending outward from the
cell it called glycocalyx , sometimes masses of polymersare formed these
extracellular polymers called slime layer.
Capsule contributes to the invasiveness of pathogenic bacteria in protecting them
from phagocytosis.
The glycocalyx plays a role in the adherence of bacteria to surfaces in their
environment , including the cells of plant and animal hosts
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Week 4
Special components of G_ve cell wall
A)-Lipoprotein:
Molecule of an unusual lipoprotein cross link the outer membrane and
peptidoglycan layers ,the lipoprotein contain 57 amino acids , their function is to
stabilize the outer membrane and anchor it to p.g layers.
B)-Outer membrane:
Bilayered structure , the phospholipid of outer membrane are replaced by
lipopolysaccharides.
Function of outer membrane:
1-prevents leakage of periplasmic space proteins.
2-protects the enteric bacteria from bile salts and hydrolytic enzymes .
3-contain the minor proteins.
4-contain the porins that permit the passive diffusion of sugars , amino acids
,……etc.
5-contains numbers of enzymes like proteases and phospholipases.
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Week 5
Protoplast , Spheroplast and L-form
Removal of bacterial wall either by hydrolysis with lysozyme or treating with
penicillin { prevents the synthesis of cell wall} will liberate :
1-protoplast from G+ve .
2-spheroplast from G-ve
If such cells are able to grow and divide they are called L-forms . L-forms are
difficult to cultivate and usually require a solidified media with right osmotic
strength . Some bacterial species produce L-forms spontaneously or by antibiotics.
Cytoplasmic membrane:
It also called cell membrane , composed of proteins and phospholipids . The c.m of
prokaryotic cell is differing from those of eukaryotic cell by the absence of sterols
except mycoplasma.
Function of c.m :
1-selective permeability and transport of solutes.
2-electron transport and oxidative phosphorylation in aerobic species.
3-excretion of hydrolytic exoenzyes.
4-bearing the enzymes and carrier molecules that function in the biosynthesis of
DNA , membrane lipids, cell wall polymers.
5-bearing the receptors and other proteins.
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Week 6
Cytoplasmic Ultrastructures:
*Mesosomes
One or more large irregular invaginations of the plasma membrane
.There are 2 types of them: a-septal mesosomes
b-lateral
mesosomes
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Week 7
*Sheath
It is a filamentous structure enables bacteria to attach to solid surfaces .These
sheaths afford protection against predators and parasites.
*Flagella
Flagella is thread-like appendage [long filamentous appendage] extending outward
from the cytoplasmic membrane , their main function is motility.flagellum
composed of many subunits of protein flagellin.
Flagella consist of a single very small filament made up of 3 fibers of protein
flagellin .prokaryoyic flagella attached to astruture called the hook which in turn
attached to the basal body.
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Week 8
Spores
Some bacteria are able to produce tough, dormant structures called
endospores which allow them to survive when stressed.
Endospores are hardy, defensive structures that enable some bacteria to
survive harmful environmental conditions, such as starvation, high
temperatures, desiccation, chemical disinfectants and extremes in pH.
Each endospore is produced by a vegetative cell, an active bacterial cell
that undergoes metabolism, divides and goes about the daily business of
being alive.
The ability to form endospores, a process called sporulation, Bacteria
that can do this neat trick are few, but include the notable
genera Clostridium and Bacillus.
When a vegetative cell of an endospore-forming bacteria detects that
essential nutrients are running out it begins to sporulate, a process that
takes about 8-10 hours and results in the formation of one endospore
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Week 9
Bacterial growth curve:
When bacteria are inoculated into a new culture media it shows a characteristic growth curve which has
four phases :
lag phase, bacteria adapt themselves to growth conditions. It is the period where the
individual bacteria are maturing and not yet able to divide. During the lag phase of the bacterial growth
cycle, synthesis of RNA, enzymes and other molecules occurs.
log phase (sometimes called the logarithmic phase or the exponential phase) is a period
characterized by cell doubling. The number of new bacteria appearing per unit time is proportional to
the present population. If growth is not limited, doubling will continue at a constant rate so both the
number of cells and the rate of population increase doubles with each consecutive time period. The
actual rate of this growth (i.e. the slope of the line in the figure) depends upon the growth conditions
and the medium is soon depleted of nutrients and enriched with wastes.
The stationary phase is often due to a growth-limiting factor such as the depletion of an essential
nutrient, and/or the formation of an inhibitory product such as an organic acid. Stationary phase results
from a situation in which growth rate and death rate are equal. The number of new cells created is
limited by the growth factor and as a result the rate of cell growth matches the rate of cell death. The
result is a “smooth,” horizontal linear part of the curve during the stationary phase.
At death phase,(Decline phase) bacteria die. This could be due to lack of nutrients, a temperature
which is too high or low, or the wrong living conditions.
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Week 10
Factors affecting growth
Microorganisms are affected by the physical nature of their
environment. Environmental factors such as temperature , pH , osmotic
pressure and radiation , influence the growth of microorganism.
1-Temperature
Play a very important role in the cell cycle . The optimum temperature for
enzyme activity in microorganism is depending on the ecological site of the
species and the enzyme locations . Above the optimum temperature ,
enzymes become denatured and the rate of growth drops , producing what
is called the maximum growth .Below the optimum temperature range the
rate of growth decrease slowly until a point is reach , called the minimum
growth temperature , where growth ceases
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Week 11
4-Acidity and pH:
The pH of a solute describes the hydrogen ion concentration (H+) .The pH greatly
influences the structure and function of proteins and enzyme and microbial growth
rates . M.O vary in their pH tolerance ranges . Fungi show a wide pH range
growing well over a pH range of 5-9 compared to most bacteria , which grow well
over a pH range of 6-9 .
In general M.O may divide into three categories:
A-Alkalophiles:
Grow in a pH range of 7-11 with an optimum of 10.
B-Neutrophiles:
Grow in a pH range of 4-9 with an optimum near neutrality.
C-Acidophiles:
Live at low pH values and can be divided into facultative such as fungi
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Week 12
Nutrition of microorganisms
*Carbon and energy sources for bacterial growth:
All living M.O require a source of energy .M.O that use
energy (light) are called phototrophs. M.O that use an
organic form of carbon are called chemotrophs. M.O
that oxidize inorganic compounds are called lithotrophs .
M.O that use organic carbon are heterotrophs and M.O that
use CO2 as a sole source of carbon for growth are called
.
autotrophs
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Week 13
Requirements of Nitrogen , Phosphorus , and Sulfur
Nitrogen: is needed for the synthesis of amino acids , purines , pyrimidines ,
nucleic acids , enzymes , and vitamins.
Phosphorus: is present in nucleic acids , phospholipids , nucleotides like ATP ,
several cofactors , some proteins , and other cell components.
Sulfur: is needed for the synthesis of substances like amino acids (cysteine ,
methionine , thiamine , biotin ) and some carbohydrates.
*Growth factors:
Autotroph or heterotrophy , may require small amounts of certain organic
compounds for growth because they are essential substances that the organism is
unable to synthesize from available nutrients . Such compounds are called
growth factors . This is required in small amounts by cells because they play a
specific role in biosynthesis .
Growth factors are organized into three categories:
A) purines and pyrimidines
B) amino acids
C)vitamins
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Week 14
Control of microbial growth
The rate of microbial growth and death influenced by a number of
environmental parameters. Some agents destroy all forms of microbes ,
whereas other agents only inhibit their growth . A nutrient may be
essential for growth in low concentrations ; it may be toxic at higher
concentration.
Control of microbial growth by antimicrobial agents:
A number of inhibitory chemicals are employed for the control of
microbial growth .
The principal reasons for microbial control are:
1-To prevent transmission of disease and infection .
2-To prevent decomposition and spoilage.
3-To prevent contamination of materials used in pure culture work in
.
laboratories
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Week 15
Microbial and microbiostatic agents act by:
1-Destruction : by
a-heat (boiling , oven )
b-chemical agents( disinfectants)
c-radiation (X-ray , UV )
d-Mechanical agent ( crushing , scattering by ultrasonic
vibrations)
2-Removal: (especially bacteria )by
a-filtering
b-high – speed centrifugation
3-Inhibition: by
a-low temperature ( refrigeration , dry ice )
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Week 16
A-Physical parameters:
1-Temperature(heat): It used to sterilize materials , sterilization by heat can be divided
into:
a-moist heat.
b-dry heat
2-Filtration:It is a common technique for separating microorganisms
Of different size , but it is also useful for sterilization.
3- Radiation: it is used for controlling microbial growth , can be characterized as either
non ionizing such as (UV) light which is absorbed by DNA at wavelength 240-280 nm. It has
low penetrability and is used primarily for irradiation of air and flats, also it can be used in
hospitals , or ionizing such as X-rays and gamma rays , which are characterized by their
ability to impart their energy to molecules ; such as water , Ionizing radiation has been used
for sterilization of pharmaceuticals and disposable medical supplies such as gloves , plastic
items , catheters .
4-Osmotic pressure.
5-pH.
6-Drying: it causes the ceases of metabolism in cells because of unavailable humidity.
7-Lyophilization: ( freeze – drying ) is a more practical way of preserving M.O for
storage . The principle of lyophilization is that the culture broth is dried in a glass vial while
in the frozen state by removing the water through a process called sublimation .That is water
is removed from the frozen state as a vapour by using ahigh vacuum system.
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Week 17
B-Chemical parameters (agents )
Compounds have the ability to kill or prevent growth or metabolism of
M.O.
Typical properties must found in these chemical agents are :
1-Antimicrobial activity 2-Solubility 3-Stability 4-Non-toxic
5-Homogenicity
6-Acting only with M.O
7-Capacity to penetrate
Into M.O cell 8-Non-corrosive and non-staining to human.
9-Have a good smell 10-Detergent capacities 11-Availability
Factors limited the chosen chemicals:
1)Nature of the chemical material: some chemical material can
be used to sterilize tools but not human skin.
2)Species of M.O:it was found that bacteria E.coli is more resistant
than S. aureus also it was found that spores are more resistant than
vegetative cells.
3)Environmental conditions: such as temperature , pH , time ,
chemical concentration , and the presence of organic compound in the
media
, which affect the activity of the chemicals
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Week 18
Surface active agents:
Such as soaps and detergents , they have the property of lowering surface tension ,
and thereby increase the wetting power of the water in which they are dissolved .
They permit mechanical removal of microbes on the skin's surface.
5-Alkylating agents ( aldehyde compounds) :
The most active alkylating agents are formaldehyde , glutaraldehyde , β –
propiolactone , and ethylene oxide. Formaldehyde : is mainly used as a
preservation and because of its irritation of tissue and odor it is seldom used as a
disinfectant .Formalin: is a 37% solution of formaldehyde gas and is used for the
preservation and fixation on tissue it combine with proteins and nucleic acids
causing death to cell. Glutaraldehyde: it is active against bacteria and viruses in
2% solution , but spores are destroyed only after 10 h. β-propiolactone :
is used in the gaseous phase to sterilize liquids . It is effective against bacteria ,
fungi , viruses and spores , but it use has been restricted because of its potential
carcinogenic properties
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Week 19
Antibiotics
Materials produced by microorganisms
metabolism , it has low molecular weight , have the
ability to inhibit another microorganisms growth
when it used in little concentrations.
In 1877 , Pasteur and Gobert noticed that bacteria
P.aeruginosa produce material called later
pyocyanin , which inhibit Bacillus anthracis growth
.In 1929 Fleming noticed an inhibition zone around
Penicillium notatum colonies ,which contaminate
petri dish cultivated with Staphylococcus.
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Week 20
1-Inhibition of cell membrane
function: they change
permeability of the microbial cell
.
2-Inhibition of cell wall synthesis
:
3-Inhibition of nucleic acids
synthesis:
4-Inhibition of protein synthesis:
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