What is Microbiology?
Microbes, or microorganisms are minute living
things that are usually unable to be viewed with the
What are some examples of microbes?
Bacteria, fungi, protozoa, algae, viruses are
Some are pathogenic
Many are beneficial
Dr.T.V.Rao MD 3
Study of different
Dutchman anton van leeuwenhoek observed
microorganisms>>”animalcules” suspended in a drop of
pond water in front of a ground hand lens
ROBERT HOOKE built simple compound microscope and observed
structure of thin layer of cork>>used the word “CELLS”
Theory of spontaneous generation: from non-living matter
Theory of biogenesis: from preexisting living cells
LOUIS PASTEUR>>Pasteur’ experiment>>boiled nutrient broth in a
flask & curved it in to S-shape>>after cooling>>bacteria trapped in
curve but no organism in flask; dicovered souring in alcohol is due
to fermentation and can be prevented by heating wine at56oC for
30mins…..now called PASTEURISATION>>
IGNAZ SEMMELWEIS was concerned at high incidence of puerperal
fever and latter instituted hand washing in chlorinated solutions;
ridiculed by colleagues and was dismissed; died of
JOHN SNOW: transmission of cholera due to contamination of the
river Thames….later confirmed by ROBERT KOCH in German
Bacteriology is the study of bacteria.
Mycology is the study of fungi.
Parasitology is the study of protozoa and
Recent advances in genomics, the study of an
organism’s genes, have provided new tools for
Proteomics is looking at the gene products
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Classification of micro-organisms
All living organisms are classified into:
Organisms that can cause disease are many and varied
Parasites 3/10/2014Dr.T.V.Rao MD 10
Relevance of Classification
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Prokaryotic cells Eukaryote cells
Small cell (< 5µm) Larger cells (> 10 µm)
Always unicellular Often multicellular
No nucleus or any membrane bound organelles Always have nucleus and membranes bound
DNA circular, without proteins DNA is linear and associated with proteins to
Ribosomes are small 70S Ribosomes are large 80S
No cytoskeleton Always have cytoskeleton
Motility by rigid rotating flagellum made from
Motility by flexible waving cilia or flagella
made from tubulins.
Cell division is by binary fission Cell division is by meiosis and mitosis.
Reproduction is always asexual Reproduction is sexual and asexual.
Summary of differences between
prokaryote and eukaryote cells
Prokaryotic Cell Structure
• Prokaryotic cells are about 10 times smaller
than eukaryotic cells.
• prokaryotes are very simple cells when
compared with eukaryotic cells,
• Reproduction of prokaryotic cells is by binary
fission, the simple division of one cell into two
For energy, use
photosynthesisDr.T.V.Rao MD 15
Capsule stain. The capsule stain is an example of a negative staining technique. The
bacterial cells and the background stain, but the capsules do not. The capsules are
seen as unstained “halos” around the bacterial cells.
Binary fission. Note that DNA replication must occur before the actual
splitting (fission) of the parent cell.
Viruses lack many of the attributes of cells, including the ability
to replicate. Only when it infects a cell does a virus acquire the
key attribute of a living system: reproduction
A viral particle consists of a nucleic acid molecule, either DNA
or RNA, enclosed in a protein coat, or capsid
Viruses are known to infect all cells, including microbial cells.
Host-virus interactions tend to be highly specific
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Discovery of Virus
a Russian chemist, 1892
Tobacco Mosaic Disease
Walter Reed, USA
Yellow fever virus
Ist human virus
Tobacco mosaic disease,
caused by the tobacco
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A virus is not a cell!
Viruses are replicated only when
they are in a living host cell
Consist of DNA or RNA core
Core is surrounded by a protein
Coat may be enclosed in a lipid
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What are Viruses
Viruses Dependent on Host cells
for necessary functions and
Contain either DNA or
RNA never both.
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Complex, large organisms
Eukaryotes (as are
Divided into yeasts &
Cause a range of diseases
Invasive & allergic
Many diseases are
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Absorb or ingest
May be motile via
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Multicellular Animal Parasites
Parasitic flatworms and round worms are called Helminths.
Microscopic stages in life cycles.
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are called pathogens.
Pathogenic microorganisms have
special properties that allow
them to invade the human body or
When a microorganism overcomes
the body’s defenses, a state of
Diseases and Infections
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Pathology, Infection, and Disease
Pathology is the scientific study of disease.
Pathology is concerned with the
effects of disease – structural and functional changes
brought about by disease.
Infection is the invasion and growth of pathogens in the body.
A host is an organism that shelters and supports the growth of
Disease is an abnormal state in which part or all of the body is
not properly adjusted or is incapable of performing normal
Infection disease – presence of particular microorganism in part
of the body where is not usually found. 3/10/2014Dr.T.V.Rao MD 29
Classifying Infectious Diseases
Communicable diseases are transmitted directly
or indirectly from one host to another.
Chicken pox, genital herpes,
A contagious disease is one that is easily
spread from one person to another.
Noncommunicable diseases are caused by
microorganisms that normally grow outside the
human body and are not transmitted from one host
Tetanus, Clostridium tetani
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Recombinant DNA Technology
microbes, plants, and animals
manipulated for practical
Production of human blood-
clotting factor by E. coli to
Inserting a missing gene or
repairing a defective one in
humans by inserting desired
gene into host cells
The Modern Age of Microbiology
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Discovery of Antimicrobial Agents
Alexander Fleming (1881 – 1955), a
Scottish biologist and
bacterial staphylococci colonies
disappearing on plates
contaminated with mold.
Fleming extracted the compound
from the mold responsible for
destruction of the bacterial
The product of the mold was
named penicillin, after the
Penicillium mold from which it
Nobel Prize in Physiology of
Medicine in 1945.
Images: Penicillium mold, PHIL #8396; Staphylococcus aureus on
antibiotic test plate, PHIL #2641; Poster attached to a mailbox
offering advice to World War II servicemen, 1944, NIHFrom the Virtual Microbiology Classroom on ScienceProfOnline.com
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The Modern Age of Microbiology
How Do We Defend Against Disease?
The study of blood serum
Von Behring and Kitasato – existence in the blood
of chemicals and cells that fight infection
The study of the body’s defense against specific
Fleming discovered penicillin
Domagk discovered sulfa drugs
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Picture on slide no: 1 taken from
Picture on slide no: 15 taken from;
HISTORY OF MICRO ORGANISMS AND PICTURES, DR PRABESH K CHOUDHARY
Definition of terms; Dr.T.V.Rao
microbiology-medical-graduates/ , 2014
Notes on classification and pictures, DR PRABESH K CHOUDHARY
Microbes diseases and pictures, R
introduction-of-microbiology-saravanan/ , 2010
NOTES BACTRIA AND VIRUS and pictures, vidhyakalai