The document discusses classification systems for viruses, bacteria, protists, and fungi. It describes the current three domain system which classifies organisms into Archaea, Bacteria, and Eukarya domains based on rRNA structure. Viruses are described as non-living particles that invade and multiply within host cells. They have a protein coat, genetic material, and surface proteins. Bacteria are classified according to characteristics like shape, staining, metabolism. Gram staining distinguishes between Gram positive and Gram negative bacteria based on cell wall thickness.

1. Viruses, Bacteria,
Protists and Fungi
DR C MWANDO
BSC HB, MBCHB (UNZA)

2. THE THREE DOMAIN
CLASSSIFICATION
As scientists learn more about organisms, classification
systems change. Genetic sequencing has given researchers a
whole new way of analyzing relationships between organisms.
The current system, the Three Domain System, groups
organisms primarily based on differences in ribosomal RNA
(rRNA) structure. Ribosomal RNA is a molecular building block
for ribosomes.
Under this system, organisms are classified into three
domains and six kingdoms. The domains are Archaea, Bacteria,
and Eukarya. The kingdoms are Archaebacteria (ancient
bacteria), Eubacteria (true bacteria), Protista, Fungi, Plantae,
and Animalia

4. Viruses
A virus is a tiny non-living particle that invades and
then multiples inside a living cell.

5. Viruses
Viruses act like parasites, organisms that live in or on another
organism and cause it harm.
The living organism that a virus attaches to and uses as a
source of energy is called the host.
Once the host is carrying and transmitting a virus it is
referred to as a vector.

6. Viruses are smaller than
cells, but can vary greatly in
size and shape.
BUT, ALL viruses have
three things in common.
1. A protein coat that
protects them, and
2. An inner core that
contains genetic material
(direction for making new
viruses)
3. Surface proteins that
allow it to attach to
certain cells in the host.
Virus Structure

7. Viruses are smaller than
cells, but can vary greatly in
size and shape.
BUT, ALL viruses have
three things in common.
1. A protein coat that
protects them, and
2. An inner core that
contains genetic material
(direction for making new
viruses)
3. Surface proteins that
allow it to attach to
certain cells in the host.
Some viruses are also surrounded by an additional outer membrane or
envelope.
Virus Structure

8. The proteins on the
surface of a virus play
an important role
during the invasion of a
host cell.
The shape of the
surface proteins allow
the virus to attach to
the proteins on the
surface of a host’s
cells.
Virus Structure

9. How Viruses Multiply
Once inside a cell, a viruses genetic material takes
over many of the cells functions. It instructs the
cell to produce the virus’s proteins and genetic
material. These proteins and genetic material
assemble into new viruses which go on to infect
more cells.

10. Active Virus

11. Hidden Virus

13. VIRAL REPLICATION
Attachment.
Penetration.
Uncoating (disassembly).
Transcription and Translation.
Assembly and
Release.

14. Common Viruses
Some viruses are very mild such as the common
cold, while others, such as HIV have severe
consequences for the host.

15. Common Viruses
Bacteriophage are robot like viruses that infect bacteria

16. Common VirusesCommon Cold -
Rhinovirus
The Flu –
Influenza
Virus

17. Common Viruses
Chicken Pox Measles

18. Common Viruses
HIV SARS

19. Viral Transmission
Viruses can be spread in many ways:
Contact with a contaminated object
Bite of an infected animal.
In sneezes and coughs
Contact with body fluids such as blood.

20. Viral Treatment
There are currently no cures for viral diseases, however, many
over the counter medications may help treat the symptoms.
Resting, plenty of fluids, and well balanced meals may be all
you can do to help your immune system fight a virus.

21. Preventing Viral Diseases
A vaccine is a substance introduced into the body to trigger
the bodies natural defenses.
A weakened or altered version of the virus puts the body on
“alert”. The immune system fights it off and makes antibodies
so that if the virus ever infects the body it can be destroyed
before it becomes harmful.

22. Virus

23. VIRUS CLASSIFICATION
Viruses are mainly classified by phenotypic
characteristics, such as morphology, nucleic
acid type, mode of replication, host
organisms, and the type of disease they
cause.

24. Baltimore 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),
1. strandedness (single-stranded or double-
stranded),
2. sense, and
3. method of replication

25. Baltimore classification
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)

26. Baltimore classification
V: (−)ssRNA viruses (− strand or antisense) RNA
(e.g. Orthomyxoviruses, Rhabdoviruses)
VI: ssRNA-RT viruses (+ strand or sense) RNA with
DNA intermediate in life-cycle (e.g. Retroviruses)
VII: dsDNA-RT viruses DNA with RNA
intermediate in life-cycle (e.g. Hepadnaviruses)

27. Baltimore classification

28. OTHER
CLASSIFICATION
Holmes classification
Holmes (1948) used Carl Linnaeus's system of
binomial nomenclature to classify viruses into 3
groups under one order, Virales. They are placed as
follows:
Group I: Phaginae (attacks bacteria)
Group II: Phytophaginae (attacks plants)
Group III: Zoophaginae (attacks animals)

29. LHT System of Virus
Classification
The LHT System of Virus Classification is
based on chemical and physical characters
like nucleic acid (DNA or RNA), symmetry
(helical or icosahedral or complex),
presence of envelope, diameter of capsid,
number of capsomers.
This classification was approved by the
Provisional Committee on Nomenclature of
Virus (PNVC) of the International
Association of Microbiological Societies
(1962

30. 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.
There are more bacteria organisms in your mouth
right now than there are people on the entire
planet!!

31. MAIN GROUPS OF BACTERIA
Proteobacteria: This phylum contains the largest group of
bacteria and includes E.coli, Salmonella, Heliobacter pylori,
and Vibrio. bacteria.
Cyanobacteria: These bacteria are capable of photosynthesis.
They are also known as blue-green algae because of their
color.
Firmicutes: These gram-positive bacteria include Clostridium,
Bacillus, and mycoplasmas (bacteria without cell walls).

32. MAIN GROUPS OF BACTERIA
Chlamydiae: These parasitic bacteria reproduce inside their
host's cells. Organisms include Chlamydia trachomatis (causes
chlamydia STD) and Chlamydophila pneumoniae (causes
pneumonia).
Spirochetes: These corkscrew-shaped bacteria exhibit a
unique twisting motion. Examples include Borrelia burgdorferi
(cause Lyme disease) and Treponema pallidum (cause syphilis).

33. Classification
Classification is based on 10 characteristics of bacteria
These help to provide data for identification and classification
1. Morphology
2. Staining
3. Motility
4. Growth
5. Atmospheric requirements
6. Nutritional requirements
7. Biochemical and metabolic activities
8. Pathogenicity
9. Amino acid sequencing of proteins and
10. Genetic composition

34. Morphology
Includes varying sizes, shapes, and cell arrangements of the bacteria
There are 3 basic shapes of bacteria:
A. Cocci (singular = coccus) or spherical shape
Can be:
-In chains of two (diplococci) e.g. Streptococcus pneumoniae
-Batches of grapes e.g. Staphylococcus aureus
B. Bacilli (singular = bacillus), also called rod-shaped
- Examples: Haemophilus influenza type B, Salmonella typhi, Yersinia
sp
C. Spiral
-Example: Treponema pallidum
-Vibrio cholerae is curved instead
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36. Staining
Various staining techniques are used to observe bacteria morphology
Some of the things observed include: shape, type of cell wall, nuclear
material, capsules, flagella, endospores, fat globules and granules
In 1884, Dr. Hans Christian Gram developed the famous Gram
staining procedure
He was Dutch (1853-1938)
It basically differentiates Gram positive and Gram negative bacteria
The colour of the bacteria at the end of the gram-staining procedure
(either purple or red) depends on the thickness and chemical
composition of the cell wall
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37. Gram Positives vs
Gram Negatives
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38. Procedure
Is one of the most useful procedures in microbiology
Has 4 steps:
Step1: Flood the heat fixed smear with CRYSTAL VIOLET (PURPLE DYE) for 30 min
- Result: All cells turn PURPLE
Step 2: Rinse gently with water and cover with GRAM’S IODINE SOLUTION
- Result: All cells PURPLE
Step 3: Wash of the iodine with water and decolourize with ALCOHOL (ETHANOL)
-Result: Gram positives remain PURPLE
Gram negatives turn COLOURLESS
Step 4: Counterstain with SAFRANIN (bright red dye)
-Result: Gram positives remain PURPLE
Gram negatives turn PINK OR BRIGHT RED
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39. The Gram Staining
Procedure
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41. Gram Positives vs Gram
Negatives
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42. Bacteria
Bacteria were discovered by accident in the late 1600’s by a
Dutch merchant named Anton van Leeuwenhoek.

43. Bacteria
Structure
Bacteria are prokaryotes:
◦ No nucleus
◦ DNA in a loop in the cell
◦ Few organelles
◦ Usually have a cell wall
◦ Usually have a flagellum

44. Bacteria
Structure
Most bacteria cells have one of three basic shapes:

46. Bacteria
obtaining food and energy
Like all living things, bacteria need to have a sources of food and
a way to break that food down in order to survive.
Most bacteria need oxygen to break their food down, but a few
do not require oxygen for respiration.

47. Bacteria
reproduction
Bacteria can reproduce asexually (one parent) by
means of binary fission: one cell divides into two
identical cells.
or
Bacteria can reproduce sexually (two parents) by
means of conjugation: one bacteria transfers some
genetic material to another bacteria though a thread
like bridge.

48. Bacteria
endospore formationSome bacteria can survive harsh conditions like freezing, heating and drying by
forming an endospore.
An endospore is a small rounded, thick walled, resting cell that forms in a
bacteria cell and houses the bacterial DNA.

49. Transmission of
Bacterial Pathogens
In Sneezes, Coughs, Saliva:
(Pneumonia, Whooping Cough, Bacterial
Meningitis)
By Animal Vectors:
(bubonic plague, typhus)
In Contaminated Food or Water:
(typhoid, salmonella, e. coli)
ANTIBIOTICS HELP GET RID OF BACTERIAL
PATHOGENS

50. Protists
Section 3Protists are eukaryotes that can not be classified as animals, plants
or fungi.
Because protists are so diverse they are grouped according to the
characteristics they share with organisms in other kingdoms.

51. Animal-Like Protists
Animal-like protists are heterotrophs and most are
able to move from place to place to obtain food,
however, unlike animals they are unicellular.
Animal-like protists may be called protozoans.

52. Animal-Like Protists
1. Protozoans with Pseudopods (ex. Amoeba)
2. Protozoans with Cillia (ex. Paramecium)
3. Protozoans with Flagella (ex. Peranema)
4. Protozoans that are Parasites. (ex. Plasmodium)

53. Pseudopods (Amoeba)

54. Cilliates (Paramecium)

55. Giardia
Trichonympha
Plasmodium
Flagellates
Parasites

56. Plant-Like Protists
Plant-like protists are commonly called alage. They are grouped
together because, like plants, they are all autotrophs.
Diatoms Dinoflagellates Euglena

57. Plant-Like Protists
Plant like protists play an important role in ecosystems.
They provide a source of food for many other organisms
They make much of the oxygen that makes up the Earths
atmosphere.

58. Algae (Euglena)

59. Fungus-Like Protists
Like fungi, fungi-like protists are heterotrophs, have cell walls, and use
spores to reproduce.
Slime Mold Water MoldDowny Mold

60. Fungi
Fungi are eukaryotes that have cell walls, are heterotrophs
that feed by absorbing their food, and use spores to
reproduce.

61. Fungi
Cell Structure
Fungi may be unicellular, like yeast, or mulitcellular.
The cells of multicellular fungi are arranged into branching threadlike tubes
called hyphae.
What a fungus
looks like
depends on how
the hyphae are
arranged.

62. Fungi
Obtaining Food
First fungi grow hyphae into a food source.
Then digestive chemicals ooze from the hyphae into the food,
breaking it down into small substances that can be absorbed
by the hyphae.

63. Fungi
Reproduction
Fungi usually reproduce by making lightweight spores in
reproductive structures called fruiting bodies. The spores can
then be carried easily through the air or water to new sites.
Most fungi reproduce both sexually and asexually.

64. Fungi
Reproduction
Asexual Reproduction: Cells at the tips of the hyphae can
divide to form spores, which grow into fungi that are
genetically identical to the parent.
Sexual Reproduction: Hyphae of two fungi can grow together
and exchange genetic material, then grow a new spore
producing structure.

65. Asexual Reproduction

66. Budding

67. Sexual Reproduction

69. Fungi
role in nature
Fungi are food
Fungi are environmental recyclers
Fungi fight disease
Fungi cause disease
Fungi help plants grow

70. Symbiosis
Symbiosis is a close relationship between two different
species, in which at least one of the species benefits from the
partnership.
If both species benefit it is called symbiotic mutualism.

71. Symbiosis

72. Symbiosis
Lichen – Relationship Between Algae and Fungi

73. Parts of a Fungus

74. Yeast Budding