MICROBES

Microscopic “bugs”

Viruses, Bacteria, Fungi.

Microbes 1
Microbes 2
Microbes 3
1) Microorganisms (Microbes) :-
i) Microorganisms are very small organisms
which cannot be seen with the unaided eye.
They can be seen only with a magnifying
glass or microscope.
ii) Microorganisms may be unicellular or
multicellular.
iii) Microorganisms may exist alone or in
colonies.
iv) Microorganisms are found in all kinds of
environment like ice cold climate, hot
springs, deserts, marshy lands etc. They are
also found inside the bodies of other
organisms.
 The approximate sizes of microbes can be approximated
by using the following rule of thumb:
PRIONS are proteins that are specially mutated in the brain. These are about 10
nanometers (1000 billionths of a meter.

VIRUSES are the smallest of all infectious agents, averaging about 100 nanometers
(100 billionths of a meter) in length. They have so few genes and proteins of their
own that in order to reproduce they need to commandeer the machinery of the cells
they invade.

BACTERIA vary widely in size and shape, but tend to be at least 10 times larger
than viruses, or at least 1 micrometer (1 millionth of a meter) long. They are single-
cell organisms that reproduce independently.

SINGLE-CELL ORGANISMS tend to be at least 10 times larger than bacteria, or

about .01 millimeter long.

MULTI CELLULAR ORGANISMS are so large they can usually be seen with the
naked eye. Tapeworms, for instance, can reach a length of 6 meters (20 feet).
2) Types of microorganisms :-

There are four main types of microorganisms. They

are :- bacteria, fungi, algae and protozoans.
Viruses are also considered as microorganisms. They
are different from other microorganisms because they
reproduce only in the body of host organisms like
bacteria, plants or animals.
Prions are proteins that mutate in the brain.

Eg :- Algae – Chlamydomonas, Spirogyra etc.

Fungi – Bread mould, Penicillium, Yeast, etc.
Protozoans – Amoeba, Paramaecium, etc.
Viruses – Influenza, Hepatitus, Measles, etc.
Parasites – intestinal worms, liver fluke, etc.
Prions – Mad Cow Disease
4) Harmful microorganisms :-
i) Some microorganisms cause diseases in plants and animals. Such
disease causing microorganisms are called pathogens.
ii) Some microorganisms grow in food substances and produce toxic
substances and makes the food poisonous.
iii) Some microorganisms spoil materials like clothing, leather, wood etc.

5) Disease causing microorganisms in Humans :-

Disease causing microorganisms enter our body through air, water,
food, contact or insects. These microorganisms are called
pathogens.
Diseases which can spread from an infected person to a healthy
person are called communicable diseases.
Eg :- cholera, common cold, chicken pox, tuberculosis etc.
Some insects and animals act as carriers of disease causing microbes.
Eg :- House fly, Female anopheles mosquito (malaria), Female aedes
mosquito (dengue fever) etc.
Some common human diseases caused by microorganisms:-

Human disease Causative Mode of

microorganism transmission
Chicken pox Virus Air / Contact
Polio Virus Air / Water
Measles Virus Air
Hepatitis – B Virus Water
Tuberculosis Bacteria Air
Typhoid Bacteria Water
Cholera Bacteria Water / Food
Malaria Protozoa Mosquito

Some common plant diseases caused by microorganisms :-

Plant disease Causative Mode of
microorganism transmission
Citrus canker Bacteria Air
Rust of wheat Fungi Air / Seed
Yellow mosaic of
Okra (Lady’s finger) Virus Water
bhindi
VIRUSES

Microbes 9
Microbes 10
Viral Disease in Humans

Copyright Pearson Prentice Hall

adenovirus

conjunctivitus

Microbes 12
Swine and avian flu viruses

Microbes 13
 Hendra virus
Horse flu

host
Microbes 14
 Adenovirus
electronmicrograph
and drawing

Microbes 15
 Cold Sores-These sores are caused by
the Herpes Simplex Virus (HSV 1).
 How frequently you get They
cause sores on or around the
mouth of those infected that
take a week to two weeks to
heal.
the sores depends on you,
and on the overall state of
your immune system.
 They say most people get
one to three episodes a year,
but some may have an
outbreak as frequently as
every month.
 There is no known cure for
the virus, since it lives in the
facial nerves and reactivates
whenever a weakened
immune system allows it to.
Microbes 16
Microbes 17
 SMALL POX
 Two viral skin
diseases that formerly
killed, but have now
been prevented or
eliminated by the use
of vaccines are
measles, and
smallpox.

Microbes 18
 The most common RETROVIRUS
symptoms of lupus
disease are skin rashes,
extreme fatigue,
arthritis, unexplained
fevers, and kidney.
 Lupus signs and
symptoms can
sometimes be
overlooked because
lupus is such a
mysterious disease.
Microbes 19
 Johns Hopkins
scientists say that a
retrovirus, which
inserted itself into the
human genome
thousands of years
ago, may be
responsible for some
cases of the
neurodegenerative STEPHEN HAWKING
disease amyotrophic
lateral sclerosis (ALS),
also known as Lou
Gherig''s disease. Microbes 20
 RETRO
VIRUS
 CAN CAUSE SOME
CANCERS

Microbes 21
 Feline Leukemia
 The disease caused by feline leukemia virus
(FeLV) belongs to the family and subfamily
Retrovirus oncoviruses.

Microbes 22
RHINOVIRUS

 THE COMMON
COLD

Microbes 23
Influenza virus

Microbes 24
 Chickenpox!
Chicken Pox -The scientific
name is Varicella zoster
virus (VZV).

It is spread through the air,

and those infected are
contagious starting from
four or five days before the
rash occurs, until after all
the rash has scabbed.

Microbes 25
Papillomavirus – Warts!

Microbes 26
T2 Bacteriophage

Microbes 27
 A T4
bacteriophage
injecting DNA
into a cell.

Microbes 28
 HOW BIG IS TINY?

 Viruses are tiny and only seen with an

electron microscope.
 Their size is about 10 nanometers (nm)
 1mm = 1000 micrometers
 1 micrometer = 1000 nm
 Therefore 1nm = 1,000,000th of a mm

Microbes 29
 ARE THEY ALIVE?
 Virus cannot grow or reproduce on its own
but must be in a host cell.
 It injects its own DNA into the host cell
which causes the cell to make more
viruses.
 The cell bursts and releases lots of viruses
which move and infect lots of other cells.
 White blood cells then try to surround and
destroy the virus.
 Are they alive? – not really
Microbes 30
 Viruses can infect plants and animals and
even bacteria.
 Examples of viruses include:-
 Warts, myxomatosis, AIDs, influenza,
poliomyletis, Hendra, viral meningitus,
cold, some cancers, and some heart
conditions etc.

Microbes 31
Computer Virus

Microbes 32
BACTERIA

Microbes 33
Structure of a bacterium

Microbes 34
 THERE ARE 3 TYPES OF
BACTERIAL SHAPES / TYPES

 BACILLI ARE ROD SHAPE

 COCCI ARE SPHERICAL
 SPIRILLA ARE SPIRAL SHAPE

 Some have flagella or tails

Microbes 35
 THERE ARE 3 TYPES OF
BACTERIAL SHAPES / TYPES

 BACILLI ARE ROD SHAPE

 COCCI ARE SPHERICAL
 SPIRILLA ARE SPIRAL SHAPE

 Some have flagella or tails

Microbes 36
7) Food preservation :-
Food is spoilt by microorganisms. Spoilt food has bad smell and bad
taste and causes food poisoning. Food can be preserved by protecting
it from microorganisms. Food can be preserved by different methods.
They are :-
i) Chemical method :- Food like pickles can be preserved by using
chemicals like salts and edible oils. Jams and squashes can be
preserved by using sodium benzoate, sodium metabisulphite. These
chemicals are called preservatives.
ii) By using common salt :- Food items like fish, meat, amla, raw
mangoes, tamarind etc can be preserved by using common salt. It
prevents the growth of microbes.
iii) By using sugar :- Food items like jams, jellies, squashes etc. can be
preserved by using sugar solution. It prevents the growth of microbes.
iv) By using oil and vinegar :- Food items like pickles, vegetables, fish,
meat etc. are preserved by using oil and vinegar. It prevents the growth
of microbes.
v) By heat and cold treatments :- Heating food items kills microbes.
Similarly storing food items at low temperatures prevents growth of
microbes.
Bacteria

Microbes 39
Bacterial Disease in Humans

Copyright Pearson Prentice Hall

Bad bacteria

Penicillin
Ecoli (bacteria)

Microbes 42
Dental Plaque!

Microbes 43
Dental plaque bacteria

Microbes 44
Contact lens bacteria!

Microbes 45
Reproducing bacteria

Microbes 46
E.Coli dividing

Microbes 47
Binary fission E.Coli

Microbes 48
E.Coli (scanning electromicrograph)

Microbes 49
Leptospira (spiral bacteria)

Microbes 50
Bcaterial flagella

Microbes 51
FUNGI / YEASTS / MOULDS

Microbes 52
 Harmful Fungus
 Fungus can cause
things such as:

 Mould on food
 Athlete's Foot

 Dandruff

 Ringworm
Fungi

Microbes 54
Rhizopuz stonolifer - bread mould

Microbes 55
Bread mold spores

Microbes 56
PRIONS & VIROIDS

Microbes 57
 Viroids and Prions

 Viroids and Prions

 Otherviruslike particles that can cause
disease are viroids and prions.

Viroids cause disease in

plants.
Prions cause disease in
animals.
 Viroids
 Viroids
 Viroids are single-stranded RNA molecules that
have no surrounding capsids.
 Viroids enter an infected cell and synthesize new
viroids.
 They then disrupt the cell’s metabolism and stunt
the growth of the entire plant.
 Prions

 Prions
 Prions contain only protein—no DNA or RNA.
 Prions cause disease by forming protein clumps.
These clumps induce normal protein molecules to
become prions.
 Eventually, there are so many prions in the nerve
tissue that cells become damaged.
 Mad cow disease may be caused by prions.