Bacteria and Viruses
Bacteria are very successful because of
their rapid growth rates and their
metabolic versatility
Outline of Today’
Today’s lecture
I.
Monera – Prokaryotic Organisms
* Key Concepts
• Characteristics
• Growth and reproduction
• Classification
• Archaebacteria
• Eubacteria
• Roles of Prokaryotic Organisms
II. Viruses
* Key Concepts
• Size
• Disease caused by viruses
Key Concepts:
The
simplest forms of life are bacteria
Bacteria
are the only prokaryotes
Bacteria
reproduce by binary fission
The
first living organisms on earth were
bacteria (4 billion years!)
Different
bacteria
lineages of organisms arose from
Characteristics of Bacteria
Metabolic
Diversity
Structures
Photoautotrophic
Cell
Chemoautotrophic
Membrane
Heterotrophs
Ribosomes
Sizes
1
and Shapes
walls
DNA
in cytoplasm
One circular DNA
- 10 micrometers
Coccus
Flagella
Bacillus
Capsule
Spirillum
A Bacterium
How Small Are Bacteria?
Magnified
14,000 times
Bacillus cells on the tip of a pin
Bacterial Growth and Reproduction
Increase
in number of cells
Binary fission
Bacterial Classification
Taxonomy
Gene
sequencing and comparative
biochemistry
Archaebacteria
These bacteria are capable of living in some
of the most extreme environments on earth.
They can thrive in hot thermal vents where
temperatures are far too hot for the survival of other
life forms.
They can tolerate the absence of oxygen and, not
only survive, but flourish. Also, they can live in
acidic soils, hot springs, coalmines, salt lakes, etc.
They can even process inorganic molecules as
an energy source.
Eubacteria
Photoautotrophic
Chemoheterotrophic
Cyanobacteria
Ponds
Most
and freshwater
Chemoautotrophic
bacteria
Pathogenic
Endospores
Environment
Cycling
of N2 , S2
Roles of Prokaryotic Organisms
Photosynthesis
Decomposers
- Cyanobacteria
- saprobes- feed on dead organisms
Nitrogen
fixation: N2 to NH3 - plants can use
ammonia (Atmosphere 78% N2 molecules)
Pathogenicity-be
able to cause disease : Clostridium
tetani Tetanus, Clostridium botulium Botulism,
Black Death – plague, Tuberculosis, Streptococcus
pneumonia
Produce
vitamins: Escherichia coli ( E. coli) V K
Commercial
uses: Beer and Wine (sugar to alcohol),
Cheese and Yogurt
Viruses (Key
(Key Concepts):
Viruses
are non-cellular
Viruses
are nonliving infectious agents
Viruses
consist of either DNA or RNA
surrounded by a protein coat
Some
may have an envelope and spikes
Viruses
cannot reproduce on their own but
must use a host cell’s machinery
Enveloped
or non-enveloped
Viruses Size: 0.05-0.2 µm
Viruses
Enveloped or non-enveloped
Spiked
Enveloped Virus
Viral Multiplication Cycles
Lytic
5
Steps
pathway
Host
cell lysis
Attachment
Lysogenic
Penetration
Viral
Replication
Assembly
Release
pathway
DNA integrates into
bacterial chromosome
Smallpox
Herpes simplex lesion of lower lip,
second day after onset
Measles
HIV, a retrovirus
In Conclusion
After
the origin of life, a divergence occurred
leading to Eubacteria and common ancestors of
Archaebacteria and Eukaryotic cells
All
bacteria are prokaryotes
Bacteria
have 3 basic shapes: cocci, bacilli, and
spirilla
In Conclusion
Many
bacteria have external structures
that increase their survival and
pathogenicity
Bacteria
reproduce by binary fission
In Conclusion
Viruses
are nonliving infectious agents
Viruses
consist of either DNA or RNA
surrounded by a protein coat
Some
may have an envelope and spikes
Viruses
cannot reproduce on their own but must
use a host cell’s machinery
There
are five steps in the multiplication cycle of
a virus
In Conclusion
There
are two pathways common in the
multiplication of bacteriophages: lytic and
lysogenic