Presentation1 of microbiology (2).pptx

Agricultural Microbiology (Plsc213)
Complied By Dr. Dawit getahun (Ph.D)
(Assistant professor in Plant Pathology)
ODA BULTUM UNVERSITY

Course Description
• Definition and historical development of Microbiology
• Types and structure of microscopes
• Culture techniques;
• Classification of microorganisms into different groups;
• Characteristics of bacteria;
• Microbes in rhizosphere and phyllosphere
– Morphology ,
– biology,
– nutrition,
– reproduction and classification of microorganism and other microorganisms of
agricultural importance;

 Microbiology of plant pathogenic microbes;
 Role of different microbes in nutrient transformations and nitrogen fixation
 Microbial interaction in the soil system;
 Like composting and decomposition of organic matter through microbes; biodegradation of
pesticides; mycorrhizae and
 Their role in agriculture and commercial use of bio fertilizers in agriculture.
Course Description

Objective of agricultural microbiology course
By the end of the course, students will be able:
 To know microorganisms of agricultural importance and techniques of their handling;
 To describe the importance of agricultural microbiology;
 To recognize microorganisms of agricultural importance: bacteria, fungi and viruses;
 To understand laboratory techniques for culturing and identification of microorganisms; and
 To describe the roles of microorganisms in agriculture.

1.1. General Introduction and Scope of Microbiology
What is microorganism?
Technically a microorganism or microbe is an organism that is microscopic
 So, they can be seen and studied only with the help of microscope
 They are an organism too small (less than 0.1 mm in size) to be seen by naked eyes.
 The human eye is not able to perceive (see) objects with a diameter of less than 0.1 mm size, therefore an
object must be required to magnify at least 0.1mm to preferably 0.2mm for clear vision.
 Being too small to be seen with unaided eyes, these organisms are termed as microorganisms.
Chapter 1. Introduction

What is microbiology?
 Microbiology often has been defined as the study of organisms and agents too small to be seen clearly by
the unaided eye.
 That is, the study of microorganisms.
 Because objects less than about 1mm in diameter cannot be seen clearly and
 Must be examined with a microscope, microbiology is concerned primarily with organisms and
 Agents this small and smaller.
 The term microbiology derived from three Greek words mikros [small] bios [life] and logos [study].
 The term microbiology was introduced by a french Chemist Louis Pasteur, who demonstrated that
fermentation was caused by the growth of bacteria and yeast.
 He is known as father of microbiology.
1.1. General Introduction and Scope of Microbiology

 Microbiology is the study of microorganisms which requires some form of magnification ( Microscope) to
be seen clearly
 Examples of microorganism:
 Viruses
 Bacteria
 Fungi
 Algae
 Protozoa's
 Most microorganisms are unicellular in which all the life processes are performed by a single cell.
 All living cells contain protoplasm which is a colloidal organic complex consisting of largely proteins,
lipids and nucleic acids.
1.1. General Introduction and Scope of Microbiology….

 Some organisms studies by microbiologists CAN be visualized without the aid of
amplification [bread molds (fungus) and filamentous algae]
 These organisms are included in the discipline of microbiology because of
similarities in properties and techniques used to study them
 Techniques necessary to isolate and culture microorganisms:
 Isolation
 Sterilization
 Culture in artificial media

• It is concerned with microbial
• Form, Structure,
• Reproduction,
• Physiology,
• Metabolism and
• Classification.
• It includes the study of
• Their distribution in nature,
• Their relation ship to each other and
• Other living organisms, their effects on human beings and on other animals and plants,
• Their abilities to make physical and chemical changes in our
environment and
• Their reactions to physical and chemical agents.

 Microbes Distribution in Nature:
They are Omnipresent: Generally microorganisms are everywhere in nature and grows where they get
food, moisture and temperature.
 Occurrence
• Air
• Soil
• Water, Oceans
• Food we eat
• Surfaces of our body (Skin) and inside alimentary canal also.

Scope of microbiology
 Microbiology has both basic and applied aspects
 Basic aspects are concerned with biology of microorganisms themselves and includes fields like
 Bacteriology.
 Mycology.
 Phycology.
 Protozoology.
 Microbial cytology and physiology.
 Microbial genetics.
 Molecular biology.
 Microbial ecology.
 Microbial Taxonomy.

• Applied aspects are concerned with practical problems.
• These are:
 Disease study.
 Water and waste water treatment.
 Food spoilage and food production.
 Industrial uses of microbes.
 Medical microbiology,
 Immunology,
 Industrial microbiology,
 Agricultural microbiology are widely studied fields of microbiology.
Scope of microbiology….

What is agricultural microbiology
Scope of microbiology…
 Agricultural microbiology is a field of study concerned about
 Plant-associated microbes .
 Plant and animal diseases.
 It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter
and soil nutrient transformations.
 Agr. Microbiology also deals with BIOGEOCHEMICAL CYCLES like
 carbon cycle
Nitrogen cycle
Sulfur cycle
 Plant Microbe Interactions
Symbionts: beneficial relationships
Pathogen: harmful relationship

Microbiology– in context to agriculture
 Microbiology in general, has very diverse utility in agriculture, horticulture,
animal sciences, fisheries and forestry and hence studied as a agriculture
microbiology.
A big number of harmful microorganisms called pathogens are
responsible of plant diseases.
these microbial pathogens are found in the soil, air and water and can
infect the plant through the roots and leaves.

Therefore, getting inside into the causes, mode of dissemination, prevalence and control of those
diseases requires basic understanding of microbiology under sub-discipline called
A. Plant Pathology is basically the study of microorganisms that cause disease in plants.
• The microorganisms which cause diseases in the plants are called as plant pathogens.
B. Antagonism: In contrasting to plant pathogens, certain native microorganisms present in the soil feed upon (or
antagonistic to) these pathogens and can prevent the infection of crop plants.
 This particular behavior of microorganisms is called antagonism.
 Literally, antagonism is an interaction between two organisms where one organism benefits at the cost of
harm to another organism.
 In case of plant pathogens, antagonism usually involves competition between two microorganisms for
such as antimicrobial metabolites, secondary
metabolites, antibiotics and extracellular enzymes.
Microbiology– in context to agriculture….

C. Bio-pesticides: Some soil microorganisms produce compounds that stimulate the natural defense
mechanisms of the plant and improve its resistance to pathogens.
 Biopesticides is deffined as the compounds derived from some living organisms and used to manage
insect-pests by means of specific biological lethal effects.
 E.g. Bacillus thuringiensis (Bt), a bacterium capable of causing disease of Lepidoptera, Coleoptera
and Diptera, is a well-known insecticide).
 The (Bt toxin) has been incorporated directly into plants through the use of genetic engineering.
F. Food and Fermentation technology
Some of the promising examples where the microorganisms have been extensively used to aid up food
industries. Eg. Beer and wine production by yeast, bread making, processing of milk to dairy products by
lactic acid bacteria and the production of vinegar by acetic acid bacteria.

Modern agriculture seeks to introduce agricultural practices that are health and
maintain the long-term ecological balance of the soil ecosystem.
 In this context, use of biofertilizers, phytostimulators and biopesticides are examples.
 an environment friendly alternative of mineral fertilizers and chemical pesticides.
is the way of transferring bacterial genes from one organism to another.
• In this direction, the specific genes from particular bacteria that can kill certain insects but do not cause
harm to humans have been successfully transferred to plants as protein through Genetic engineering.
• This protein is toxic to the insects, so that when the insect feeds on the plant, the insect dies. E.g. Bt

G.Soil Microbiology
The soil is a favourable environment for a diverse range of microorganisms (Bacteria Fungi,
algea and protozea.
The activity of all these microorganisms is vital for the soil and is accountable for soil quality,
texture, structure and other properties as well.
deals with microorganisms associated with milk and milk products.
The science comprises of the study of the control and destruction of undesirable microorganisms
leading to spoilage of the milk and milk products on one hand while on the other,
also deals with intentional and directional introduction of beneficial microorganisms.

1.2. Historical Development of Microbiology
• With the advent of advanced tools and microscopic techniques, the field of microbiology is developing
day-by-day with the inclusion of practical application and aspects of human welfare.
 Obviously human have had to deal with microbes even before the recorded history.
 The first record of human using microbe comes from ancient tablets from mid east.
• Babylonians were using yeast to make beer over 8000 years ago and acetic acid bacteria to make
vinegar over 6000 years ago.
• About 5000 years ago, Persia (Now Iran) region recorded the wine making by using lactic acid
bacteria
• The roman God of mold and mildew was ―Robigus‖ and ―Robigo” which means crop rust. (Rust is
one of the plant disease caused by fungus). God Robigus was very much feared because of crop lost.
• About 2000 years ago, Romans proposed that diseases were caused by tiny animals. But, fundamentalist
religions had a strong hold over the progress.

Discovery of Microbiology
The real microbiology history starts from 1600s, when people began
to make crude lenses and microscopes.
 Robert Hooke (1665) (English scientist) is the first person to
report seeing microbes under the microscope/ lens.
 He was the first to use a lens to observe the smallest unit of tissues
he called “cells.”
 He also saw strands of fungi among the specimens of cells he
viewed .
 However, because his lenses were of poor quality he was
apparently unable to "see" bacteria.

Discovery of Microbiology…
 Anton van Leeuwenhoek (1632–1723): Dutch businessman
(merchant) was the first microbiologist and the first person to
observe bacteria using a single-lens microscope of his own
design in the 1670s .
 His first microscopes were able to give clear images at
magnifications of 50 to 300 diameters
 His best lenses could magnify 300-500X . Observed a variety
of things including pond water, rain water, blood and
scrapings from his own teeth using his own Microscope.
 He described live microorganisms that he observed as
Animalcules which means small animals.
He is sometimes called the “father of microbiology”
 Considered as ‘Father of Bacteriology’

1.2.1. Theories on the origin of life (spontaneous generation theory)
• Where did microbes come from? The hypothesis that living organisms arise from nonliving matter is
called spontaneous generation
• Spontaneous Generation theory is belief that all living things originated spontaneously from
inanimate/non-living matter, without the need for a living progenitor to give them life.
• Spontaneous generation also called abiogenesis,
 It became difficult to disprove this doctrine, because of lack of experimental proof.
 Later, Francesco Redi in 1665 performed experiments and showed that maggots that develop in putrefying
meat are the larval stages of flies and will never develop in putrefying meat if it is protected from flies
laying eggs.
 He was the first to disprove SG of animals.

• Where did microbes come from? The hypothesis that living organisms arise from nonliving matter is
called spontaneous generation.
• Spontaneous Generation is the Theory that belief life come from inanimate objects or non-living things.
 Spontaneous generation also called abiogenesis.
• The belief in the spontaneous generation theory was introduced by Aristotle, who lived around 350 BC.
 According to Aristotle, it was: "readily observable that aphids arise from the dew which falls on plants,
mice from dirty hay.”
 This theory is NOT true but it was believed for almost for 2000 years. Even in1700's and 1800's
 It became difficult to disprove this doctrine, because of lack of experimental proof.
 This theory was disproven by the experiments that used the scientific method as early as the 17th century and
completely rejected in the 19th century
1.2.1. Theories on the origin of life (spontaneous generation theory)

Spontaneous Generation/ Abiogenesis…
• In 1665 Francesco Redi disproved abiogenesis theory for the
first time at the macroscopic level by demonstrating flies did
not arise spontaneously from decaying meat.
• Hypothesis: maggots came from the eggs of flies
• Experiment procedure
• He put some meat inside jars and covered them. No
maggots grew.
• Antagonists claimed life needed fresh air to grow so the
experiment was invalid.
• Redi repeated the experiment but used gauze to cover the
jars allowing fresh air in, but keeping flies out. No
maggots grew.
 Conclusion: Because there were no maggots in or around
the jar it was concluded that the maggots came from the fly
eggs.
Open jar Covered jar Sealed jar

Spontaneous Generation/ Abiogenesis theory…
 John Needham (1713 –1781)
 In England, John Needham challenged Redi's findings by conducting an experiment in which he placed a
broth, or “gravy,” into a bottle, heated the bottle to kill anything inside, then sealed it.
 Days later, he reported the presence of life in the broth and announced that life had been created from
nonlife.
 In actuality, he did not heat it long enough to kill all the microbes.
Conclusion: He thought organic matter contained a vital force that could confer the properties of
life on nonliving matter.
 He supports or prove abiogenesis

 In 1670 Jablot conducted an experiment in which
 he divided a hay infusion that had been boiled into two
containers:
 a heated container that was closed to the air and a
heated container that was freely open to the air.
 Only the open vessel developed microorganisms.
 This further helped to disprove abiogenesis.

 Procedure/ : Spallanzani put broth /gravy into four flasks
 Flask 1 – left open to the air
 Flask 2 – was sealed
 Flask 3 – was boiled and left open
 Flask 4 –was boiled then sealed
 Results
 Flask 1 – left open to the air– Turned cloudy (microbes found)
 Flask 2 – was sealed – Turned cloudy (microbes found)
 Flask 3 – was boiled and left open – Turned cloudy (microbes found)
 • Flask 4 – was boiled then sealed – Did not turn cloudy (NO MICROBES)
Spontaneous Generation theory…
 Lazzaro Spallanzani (1729-1799): He refused the Needham’s experiment.
 Hypothesis: Microbes come from the air. Boiling will kill microbes.
 was the first to provide evidence that MO do not develop spontaneously.
 He believed microbes move through the air and could be killed by boiling.
 He boiled beef broth for an hour and then sealed the flasks.
 No microbes appeared following incubation.

 These assumptions provoked Louis Pasteur (1822- 1895) to settle the matter once and for all.
 In 1862, Louis Pasteur conducted experiments to disprove the theory of Spontaneous Generation.
 He prepared flasks, with long, narrow, goose-neck openings heated the nutrient broth in the flask
and
 thus the air carrying the germs were allowed to settle in the goose-neck.
 When the flasks were cooled, the air entering through the gooseneck retained the germs, and under
these conditions the broth remained clear.
 He also showed by further studies that ‘used’ cotton filters, when examined under the microscope,
revealed the presence of microscopic organisms.
 However, Spallanzani couldn’t convince people because it was thought that air was necessary for
spontaneous generation and he couldn’t figure out how to let in air without also letting in microbes.

Louis Pasteur experiment
 Pasteur’s Swan/goose neck flasks could supply air but could also trap ambient germs from
entering broth

Set of experiments
involving a goose
necked flask.
Boiled broth in a flask
with a straight neck and
left it exposed to air,
organisms grew
Boiled with his goose-
necked flask, nothing
grew
The S-shape of this second
flask trapped dust particles
from the air
Preventing the air from
reaching the broth
He could allow air to get
into the flask but not the
particles in the air,
Pasteur proved that it was
the organisms in the dust
that were growing in the
broth
Resolved the controversy
of Abiogenesis versus
biogenesis
Established the
theory of Biogenesis
Pasteur’s Experiment in Flow Chart

 Conclusion of Pasteur's experiment
 The hypothesis was supported by the data therefore it was accepted.
 Because the broth did not turn cloudy and dust was observed trapped in the neck of the
S-Shaped flask,
 it was concluded that the microbes came from cells of organisms riding on dust
particles.
Louis Pasteur experiment….
 Pasteur is called father of microbiology because of his enormous contribution.
 Father of “Modern Bacteriology” and “Founder of microbiology”
 Father of Pasteurization and Fermentation

 John Tyndall (1820-1923) proved that dust carried the germs.
 He showed that sterile infusions placed in a dust free chamber could remain sterile indefinitely even if
kept exposed to air.
 During his experimentation he concluded that bacteria have phases one relatively thermo labile
(growing phase destroyed by boiling for 5 min.) and
 One thermo resistant (bacterial spores cannot be destroyed even by boiling for 5 ½ hours).
 He developed a method of sterilization by discontinuous heating, later called Tyndallization,
which could be used to kill all bacteria in infusions.
 He found that discontinuous boiling for 1 min on 5 successive occasions would make the infusion sterile
whereas continuous boiling for 1 hr. would not.
 Pasteur and Tyndall’s experiments finally disproved the Doctrine of Spontaneous generation
(S.G.).

1.2.2. The germ theory of disease (Koch's Postulates)
The germ theory of disease states that many diseases are caused by microorganisms
such as bacteria, viruses, protozoa, or fungi.
These diseases are caused by the growth and replication of microorganisms.
The germ theory of disease was devised by Louis Pasteur.
He also performed various experiments to demonstrate the relationship between
microorganisms and diseases.
 Building on the early work of Louis Pasteur and the germ theory of disease, Robert Koch established the
basic scientific requirements used to demonstrate that each specific disease is caused by a specific
microorganism.
 These requirements were based on Koch’s experiments with anthrax isolated from diseased hosts, and
are known as “Koch’s Postulates”. Koch’s Postulates consist of the following four rules:

1. A specific disease is caused by a specific organism. A specific organism can
always be found in association with a given disease
2. The organism should be isolated and grown in the lab into a pure culture.
3. When the artificially cultured organism inoculated into health but susceptible
animal it should produce symptoms of the same diseases
4. The organism should be re-isolated from artificially infected animal and grown
into pure culture in the lab.

There are four Kotch’s postulate on diseased plant
 To demonstrate Koch’s Postulates, you must do the following:
 (i) Describe and record the symptoms shown.
 (ii) Isolate the suspected pathogen from the infected plant material and establish a
pure culture.
 (iii) Inoculation of new healthy plant material.
 (iv) Re-describe and record the symptoms shown by the new plant. Check that these
are the same as your original observations.
 (v) Re-isolate the organism. Check that this is the same as that isolated previously.

Drawbacks (Limitations) of Kotch’s postulate
1. Not every microorganism associated with diseases. ex. Normal flora do not cause diseases
2. Many health people carry pathogens but do not exhibit symptoms of the disease
(carriers)
3. Certain disease develops only when an opportunistic pathogen invades a weakened host.
Opportunistic microorganisms can cause diseases only in immune compromised individuals.
4. Not all diseases are caused by microorganisms.
Ex. Diabetes, Asthma, hypertension etc.
5. Some microbes are very difficult or impossible to grow in the laboratory in artificial media,
such as most viruses and some bacteria
ex. Treponema pallidivm and M.leprae are uncultivable organisms

1. Emphasizes the importance of lab cultivation of microorganism in
artificial growth media
2. Showed that a specific microbe has specific activity
3. Contributed to the development of pure culture

Presentation1 of microbiology (2).pptx

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