Bacteria and viruses share some characteristics: - They can both reproduce rapidly and mutate. However, bacteria are cellular and prokaryotic while viruses are non-cellular and require a host cell to reproduce. - Bacteria come in many types including autotrophs that produce their own food and heterotrophs that feed on organic material. They have cell walls and circular DNA. - Viruses have either DNA or RNA inside a protein coat and some have an additional envelope. They reproduce by taking over the machinery of living host cells. While viruses cause disease, some bacteria are useful in food webs, nitrogen fixation, and producing antibiotics.

1. GENERAL
CHARACTERISTICS OF
VIRUS & BACTERIA

2. BACTERIAL CHARACTERISTICS
Bacterial
Characteristics
Bacteria are of immense
importance because of
their rapid growth,
reproduction, and
mutation rates, as well as,
their ability to exist under
adverse conditions.
The oldest fossils known,
nearly 3.5 billion years
old, are fossils of bacterialike organisms.

3. • Those that are classified as autotrophs are either photosynthetic, obtaining energy from
sunlight or chemosynthetic, breaking down inorganic substances for energy .
• Bacteria classified as heterotrophs derive energy from breaking down complex organic
compounds in the environment.
• This includes saprobes, bacteria that feed on decaying material and organic
wastes.

4. BACTERIA STRUCTURE AND TYPES

5. BACTERIA
• Bacteria are often maligned as the causes of
human and animal disease. However, certain
bacteria, the actinomycetes, produce antibiotics
such as streptomycin and nocardicin.
• Bacteria live on the roots of certain
plants, converting nitrogen into a usable form.
• Bacteria make up the base of the food web in
many environments.

6. Bacteria can
be anaerobes
or aerobes.
Bacteria have
circular DNA
called
plasmids
Bacteria have
cell walls.
Bacteria are
prokaryotic
and unicellular.
Bacteria can
be heterotroph
or autotroph
About:Bacteria
Bacteria can
be useful as
well as
pernicious.

7. GENERAL CHARACTERISTICS OF VIRUS
 Viruses are infectious agents with both living and nonliving characteristics.
1. Living characteristics of viruses
 a. They reproduce at a fantastic rate, but only in living host cells.
b. They can mutate.
2. Nonliving characteristics of viruses
• They are a cellular, that is, they contain no cytoplasm or cellular organelles.
• They carry out no metabolism on their own and must replicate using the host cell's metabolic
machinery.

8. GENERAL STRUCTURE OF VIRUS

9. CHARACTERISTICS OF VIRUS
Virion (Virus particles)
size range is ~10-400
nm
All virions contain a
nucleocapsid which is
composed of nucleic
acid (DNA or RNA) and
a protein coat (capsid)
Some viruses consist
only of a
nucleocapsid, others
have additional
components
Envelopes
• virions having envelopes =
Enveloped viruses
• virions lacking envelopes =
Naked viruses

10. THE ENVELOPE
Many viruses that infect humans
and other animals are enveloped.
Envelopes form when viral
glycoproteins and oligosaccharides
associate with the plasma
membrane of the host cell.
All envelopes have a phospholipid
bilayer.

11. VIRUS CLASSIFICATION