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Microbiology

UNIT I : Scope and History

UNIT II : Microscopy and Staining

UNIT III : Growth and Culturing UNIT IV : Sterilization and Disinfection

UNIT V : The Bacteria

UNIT VI : Viruses

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Scope and History of Microbiology

Why Study Microbiology

The Microbes

Disease Causes by Microorganism History Roots

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SCOPE AND HITORY OF

MICRIBIOLOGY

Why Study Microbiology

Microorganisms are part of the humanenvironment and are there fore important to

human health and activities.

The study of microorganisms provides insight

into life processes in all forms of life.

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Scope of Microbiology

The Microbes

Microbiology is the study of all

microorganisms (microbes) in the

microscopic range.

This include :

bacteria,algae,fungi,viruses,and protozoa

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Diseases caused by

Microorganisme

Bacterial diseases:

Syphilis,tetanus,trachoma,meningitis,etc

Viral diseases : AID,Hepatitis,yellow

fever,etc

Protozoan disease : Malaria,Amebiasis

Helminth diseases : Trichinosis.

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The germ theory of disease

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Pasteur further contributions

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Kochs Contributions

Kochs Postulates:

1.The specific causative agent must be found inevery case of the disease.

2.The disease organism must be isolated in pureculture

3.Inoculation of a sample of the culture into ahealthy,susceptible animal must produce the

same disease.4.The disease organisms must be recovered from

the inoculated animal.

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II.Microscopy and Staining

Principles of microscopy

Light Microscopy

Electron Microscopy

Principles of staining

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MICROSCOPY

The technology of making very small

things in visible to the human eye.

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Comparison of Types of

Microscopy

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Metric Unit

Centimeter =0,01 m

Millimeter =0,001 m

Micrometer =0,000001 m Nanometer =0,000.000.001 m

Angstrom = 0,000.000.000.1 m

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III. Growth and Culturing of

Bacteria

Culture Media

Growth and Cell division

Phases of Growth Measuring Bacterial Growth

Factor Affecting Bacterial Growth

Culturing Bacteria

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CULTURE MEDIA

In nature, microorganims

are growth on nature media

or nutrients available in

water,soil,and living or dead

organic material.

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In The Laboratory

Microorganisms are grown in synthetic

media :

1.Defined synthetic media: consist of

known quantities of spesific nutrien

2. Complex media : consist of nutrients ofreasonably well known composition that

vary in composition from batch to batch.

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Commonly Used Media

Most routine laboratory cultures

make us of peptones,or fish

proteins. Other substances suchas yeast extract,serum, whole

blood, etc.

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Diasnostic Media.

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GROWTH AND CULTURING

1. Microbial growth can be defined as the

orderly increase in quantity of all cell

componen and in the number of cells of an

organims

2.Because of limited in crease in cell size

and the frequency of cell division, growth

in microorganism is measured by increasein cells number.

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Division Cell

Most cell division in bacteria occur bybinary fission,in which the nuclear bodydivides and the cell form are transverse

septum that separates the original cell intotwo cells.

Yeast cell and same bacteria divide bybudding, in which a small, new celldevelops from the surface of an existingcell.

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Growth and Cell Division

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Phases of Growth

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Phases of growth

Lag phase : Not increasing in cell number, metabolicallyactive.

Log phase : devide at exponential or logaritmic, rate andwith a constant generation time.these properties can beused to calculate both the number of generation time

and the generation. Stationary phase : The number of new cell produced

equals the number of cell dying.The medium containslimited nutriens and contains toxic quantities of wastematerials.

Decline phase ; death phase : many cells lose theirability to devide and eventually die. A logaritmicdecrease in the number of cell results.

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Measuring bacterial growth

Growth can be measured by serial dilution.

Growth also can be measure by direct

microscopic count, the most probable

number technique,filtration,observing or

measuring products of metabolism, and

obtaining the dry weight of cell.

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The technikque of serial dilution

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Methods of obtaining cultures

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The streak plate method.

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Spread plate method

Put 0,1 ml desired concentration(reached),

pour into surface of pre-poured agar then

spread with abent rod,next is

incubated.Bacterial colonies appear onlyon surface.

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pour plate method

1 ml of dilution (concentration reached) is

mixed with 9 ml of melted agar. Mix

throughly and pour entire petri dish. Cool

to hardness and incubate. Same coloniesappear on surface,many are bellow

surface.

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The streak plate method

A drop or bit of culture on a wire

inoculating loop is lightly streaked across

the top of the agar in region1.The loop is

flamed,the plate is rotated,and a feworganism are picked up from region 1 and

streaked out into region 2,The loop is

flames again and the process is repeatedin region 3.

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Principles of staining

A stain or dye is a molecule that can bind

to a structure and give it color.

Most microbial stain are cationic (positively

charged),or basic, dyes,such as

methylene blue.

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Comparison of Staining techniques

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The Gram Stain

The gram stain, was devised by Hans

christian Gram, in 1884.

The gram stain probabily the most

frequently used deferential stain.

Gram was testing new methods of staining

biopsy and autopsy material.

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Steps in gram staining

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Factors affecting bacterial growth.

1. Physical factor: pH, Temperature,

Oxygen

2. Nutritional factor :carbon sources.

Nitrogen sources, vitamin.

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Physical factors

A.Optimum pH

Bacteria are clasified as

1. Acidophiles :pH below 5,4. Exm:Lactobacilus

2. Neutrophiles (pH 5,4 -8,5). Ex : Bacteria

that causes disease in human.

3.Alkaliphiles : pH 7,0-11,5. Ex

:Agrobacterium,alcaligenes faecalis.

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B.Temperature

Bacteria are clasified as :

1.Psychrophiles( 150C-200C )

a. Obligate psychrophiles (cannot growabove 200C ).Ex.Bacillus globisporus.

b.Facultative psychophiles (grow best

below 200

C). Ex.Xanthomonas sp

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2. Mesophiles (250C 400C)

3.Thermophiles(500C -600C) Ex. Bacillus

stearothermophilus.

C.Oxygen

a.aerobes (require oxygen to grow).

Ex:pseudomonas

b.anaerobes(do not requere it).

Ex:Bacteroides.

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Nutritional factors

Carbon sourcesAutotrophs : us CO2 as carbon source

Heterotroph :require glocose or organic

carbon source

.Nitrogen sources : sulfur,phosphorus,Iron,etc.

.Sulfur and phosphorus :Amino acid,organic

phosphate .

.Vitamin :B12, K (small amount or as a coenzyme.

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Sterilization and Disinfection

1.Principles of Sterilization and

Disinfection

2.Chemical antimicrobial agents

a.potency of chemical agent

b.Mechanisms of action

c.specific chemical agent

3. Physical antimicrobial agents.

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Sterilization

Refers to the killing or

removal of all organisms

in any material or on

object.

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Disinfection

Refers to the reduction in

numbers of pathogenic

organism on obyects or

in materials so that theorganisms no longer

pose a disease threat

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TERM OF RELATED TO STERILIZATION

AND DISINFECTION

ANTISEPTIC : A chemical agent that can

safely be used externally on living tissue to

destroy microorganisms or to inhibit their

growth

Disinfectant : A chemical agent used on

inanimate obyects to destroy

migroorganisms . Most disinfectant do notkill spores.

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SANITIZER :A chemical agent typically

used on food-handling equipment and

eating utensils to reduse bacterial

numbers so as to meet public healthstandards. Sanitization may simply refer to

thorough washing with only soap or

detergent. Bactericide : An agent that kills bacteria.

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POTENCY OF CHEMICAL AGENT

The potency of chemical agent is affected by

time,

temperature,

pH,

Concentration of the agent.

M h i f ti f h i l

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Mechanisms of action of chemical

agent

Action of chemical agent antimicrobial agent canbe grouped according to their effects on protein,cell membranes and other cell components.

Reactions that alter protein include hydrolysis,oxidation,and attachment of atoms or chemicalgeoups to protein molecules. Such reactiondenature protein, rendering them nonfungtional.

Reactions of other chemical agents damagenucleic acids and energy-producing systems.Demage to nucleic acids is an important meansof inactivating viruses.

SPECIFIC CHEMICAL

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SPECIFIC CHEMICAL

ANTIMICROBIAL AGENTS

Soaps and detergents aid in the removal

of microbes,oils,and dirt but do not

sterilize.

Among the agent containing heavymetals, silver nitrate is used to kill

gonococci, and mercury containing

compounds are used to disinfectinstrument and skin.

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Acid are commonly used as food

preservatives, alkali in soap helps destroy

microorganisms.

Alkohols are used to disinfectants

Among the agents containing halogens,

chlorine is use to kill pathogens in water,

and iodine is major ingredient in severalskin disinfectants.

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Phenol derivatives can be used on skin,

instruments,dishes, and furniture, and to

destroy discarded cultures they work well

in the presence of organic materials.

Oxidizing agents are particularly useful in

disinfecting puncture wounds.

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Alkylating agents can be used to disinfect

or sterilize a variety of materials, but all

are carcinogens.

Same dyes, plant oils, sulfur containing

subtances and nitrates can be used as

disinfectans or food preservatives.

PHYSICAL ANTIMICROBIAL

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PHYSICAL ANTIMICROBIAL

AGENTS

Heat destroys microorganisms by

denaturing protein, melting

lipids,and when open flame isused,by incineration.

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Dry heat,Moist heat,Pasteurization

Dry heat is used to sterilize metal obyects and

glassware.

Flame is used to sterilize inoculating loops and

the mouths of culture tubes. Autoclave uses moist heat underpresure, is a

common instrument for sterilization and is very

efective when proper procedures are followed.

Pasteurization kill most patogens milk,does not

sterilize.

Refrigeration freezing drying and

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Refrigeration, freezing,drying,and

Freeze-drying.

Can be used to retard the growth

of microorganisms.

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Radiation

Used to control microorganisms

includes ultraviolet light, ionizing

radiation,and some timesmicrowaves and strong sunlight.

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Sonic and Ultra sonic waves

Can kill microorganisms but are

used mostly for sonication,the

disruption of cell by sound waves

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Filtration

Can be used to sterilize

subtances that are destroyed by

heat, to separate viruses, and tocollect microorganisms from air

and water samples.

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Osmotic pressure

High concentrations of sugar or

salt create osmotic presure that

plasmolisis of cell and preventsgrowth of microorganisms in

gightly sweetened or salted foods.

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