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3. Microbes
A microorganism, or microbe,is
a microscopic organism which may exist
in its single-celled form or in a colony of
cells.

4. Microorganisms include all unicellular
organisms and so are extremely diverse. Of
the three domains of life identified by Carl
Woese, all of the Archaea and Bacteria are
microorganisms.

5. Microbes
Bacteria
Archaea
Fungi
Protists
Viruses
Microscopic Animals

6. Phylogenetic tree

7. Discovery
Louis Pasteur (1822–1895) (Father of
Medical Microbiology)
Pasteur proved the theory of spontaneous
generation and supported the germ theory of
disease.
In 1876, Robert Koch (1843–1910)
established that microorganisms can cause
disease.

8. Lord Joseph Lister (1827-1912) (Father of
antiseptic surgery):
He concluded that wound infections where due
to microorganisms.
Robert Kosh (1893-1910):
Demonstrated the role of bacteria in causing
disease.
Alexender flemming
He discovered the penicillin.

9. Bacteria
A member of a large group of
unicellular microorganisms which
have cell walls but lack organelles
and an organized nucleus, including
some which can cause disease.

10. Bacteria are microscopic, single-celled
organisms that have no nucleus and a
cell wall made of peptidoglycan.
Bacteria are the direct descendents of
the first organisms that lived on Earth,
with fossil evidence going back about
3.5 billion years.

11. Shape
Bacteria are a huge and diverse group. Its members
have many shapes, sizes, and functions, and they
live in just about every environment on the planet.
Various shapes of bacteria are as follows:
 Cocci (Round)
Diplococci
Staphylococci
 Bacilli (Rods)
 Spirochetes (Spiral)
 Pleomorphic (Many shapes)

12. Size
Most bacteria are much
smaller than our own
cells, though a few are
much larger and some are as small as viruses.
Average size: 0.2-5µm
Smallest bacteria: Mycoplasma
Largest virus: Poxvirus

13. Characteristics of Bacteria

14. Structure of Bacteria
Bacteria usually do not have any membrane-wrapped
organelles (e.g., nucleus, mitochondria, endoplasmic
reticulum), but they do have an outer membrane.
Most bacteria are also surrounded by at least one
layer of cell wall (peptidoglycane).

16. Archae
Archaea are microscopic, single-celled organisms
that have no nucleus and an outer membrane
containing unique lipids. On the surface, archae look
a lot like bacteria. They can have a similar size and
shape, their genetic material forms a circle, they lack
organelles, and they live in similar environments. But
biochemically, archaea are as different from bacteria
as they are from us.

17. Archae are surrounded by a membrane made
up of a type of lipid that isn’t found in any
other organism. Most archae also have a cell
wall, but theirs is very different from the
peptidoglycan cell wall of bacteria.

20. Archaea are best known for living
in extreme environments, but they
also live in non-extreme
environments, including the human
gut and skin.

21. Types of Archae
Thermoacidophiles
Thermoacidophiles, or thermophiles, inhabit hot
environments. They thrive in extremely
acidic, hot and moist regions, such as those in
and near sulfur hot springs. If they are in
temperatures below 131 degrees F (55
degrees C), they die.

22. Halophiles
Another type of archaebacteria are halophiles.
They thrive in extremely salty environments.
They make their home in water and soil, as
long as there is a very high amount of salt.

23. Methanogens
Methanogens can be found in environments that
are anaerobic (no oxygen). Types of
environments methanogens are found in are
swamps and marshes, or intestinal tracts of
animals and some humans. As their name
suggests, methanogens produce methane gas.

24. Viruses
MEANING:
Derived from latin word venome meaning poisonous
fluid.
DEFINITION:
It can be defined as non cellular infectious entities which
contain either RNA or DNA. Normally encased in
proteinaceous coat, and reproduce only in living cells.
Viruses utilize the biosynthetic machinery of the host for
its own synthesis and then transfer themselves
efficiently to other cells.

25. HISTORY
Louis Pasteur (1822-1895) and Robert Koch
(1843-1910) said, the word “virus” is referred
to as a poison associated with disease and
death.
Now viruses are recognized as particles of
nucleic acid often with a protein coat.

26. CHARACTERISTICS
 Obligate intracellular parasites
 20 to 300 nm in diameter
 10-1000 times smaller than most bacteria.
 Lake metabolic machinery for the synthesis of their
own nucleic acid and protein.
 Can pass through the pores of filters

27. STRUCTURE
 Virion:
The complete, mature and infectious particle is known
as virion. They are composed of a central core of nucleic
acid either DNA or RNA, which is also known as the
genome and is surrounded by a protein coat , the capsid.
Capsid gives definite shape to virion.
It is made up of protein subunits Known as capsomeres.
The number of capsomeres is characteristic of a
particular virus.

28. Virion of HIV-1

29. In some animal viruses the nucleocapsid
(nucleic acid and capsid) is covered by
another membrane derived from the host cell,
the envelope.
Animal and plant viruses may be polyhedron
(having many sides), helical (spiral),
enveloped or complex.

30. Classification
 Baltimore classification (first defined in 1971) is a
classification system that places viruses into one of
seven groups depending on a combination of
their nucleic acid (DNA or RNA), strandedness
(single-stranded or double-stranded), sense, and
method of replication. viral structures are often
difficult to determine under the microscope.
Classifying viruses according to their genome means
that those in a given category will all behave in a
similar fashion, offering some indication of how to
proceed with further research.

31. Viruses can be placed in one of the seven
following groups:
 I: dsDNA
viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses)
 II: ssDNA viruses (+ strand or "sense") DNA (e.g. Parvoviruses)
 III: dsRNA viruses (e.g. Reoviruses)
 IV: (+)ssRNA viruses (+ strand or sense) RNA
(e.g. Picornaviruses, Togaviruses)
 V: (−)ssRNA viruses (− strand or antisense) RNA
(e.g. Orthomyxoviruses, Rhabdoviruses)
 VI: ssRNA-RT (retro transcribing) viruses (+ strand or sense)
RNA with DNA intermediate in life-cycle (e.g. Retroviruses)
 VII: dsDNA-RT (retro transcribing) viruses DNA with RNA
intermediate in life-cycle (e.g. Hepadnaviruses)

33. Viral diseases
 Small pox
 Herpes simplex
 Influenza
 Mumps and measles
 Polio
 AIDS (acquired Immuno Deficiency Syndrome)
 Hepatitis A, B, C, D, E

34. Prevention and treatment
 Vaccines
Types:
• Live-attenuated
• Killed viruses
 Antiviral drugs
nucleoside analogues
Example:
• Aciclovir for Herpes simplex virus infections
• Lamivudine for HIV and Hepatitis B virus infection

35. Applications
Life sciences and medicine
Virotherapy
Materials science and nanotechnology