bacteria and viruses -...
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Bacteria and VirusesBacteria and Viruses
Bacteria are very successful because of their rapid growth rates and their
metabolic versatility
Outline of TodayOutline of Today’’s lectures 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: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 lineages of organisms arose from
bacteria
Characteristics of BacteriaCharacteristics of Bacteria
� Metabolic Diversity
� Photoautotrophic
�Chemoautotrophic
�Heterotrophs
� Sizes and Shapes
� 1 - 10 micrometers
�Coccus
�Bacillus
� Spirillum
� Structures
�Cell walls
�Membrane
�Ribosomes
�DNA in cytoplasm
One circular DNA
� Flagella
�Capsule
A BacteriumA Bacterium
How Small Are Bacteria?How Small Are Bacteria?
Bacillus cells on the tip of a pin
Magnified
14,000 times
Bacterial Growth and ReproductionBacterial Growth and Reproduction
�Increase in number of cells
�Binary fission
Bacterial ClassificationBacterial Classification
� Taxonomy
� Gene sequencing and comparative biochemistry
ArchaebacteriaArchaebacteria
They can thrive in hot thermal vents where They can thrive in hot thermal vents where
temperatures are far too hot for the survival of other temperatures are far too hot for the survival of other
life forms.life forms.
They can tolerate the absence of oxygen and, not They can tolerate the absence of oxygen and, not
only survive, but flourish. Also, they can live in only survive, but flourish. Also, they can live in
acidic soils, hot springs, coalmines, salt lakes, etc.acidic soils, hot springs, coalmines, salt lakes, etc.
They can even process inorganic molecules asThey can even process inorganic molecules as
an energy source.an energy source.
These bacteria are capable of living in some These bacteria are capable of living in some
of the most extreme environments on earth.of the most extreme environments on earth.
EubacteriaEubacteria
� Photoautotrophic
�Cyanobacteria
� Ponds and freshwater
� Chemoautotrophic
� Environment
�Cycling of N2 , S2
� Chemoheterotrophic
�Most bacteria
�Pathogenic
�Endospores
Roles of Prokaryotic OrganismsRoles of Prokaryotic Organisms
� Photosynthesis - Cyanobacteria
� Decomposers - 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 (Viruses (Key Concepts):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
Viral Multiplication CyclesViral Multiplication Cycles
� 5 Steps
�Attachment
�Penetration
�Replication
�Assembly
�Release
� Lytic pathway
�Host cell lysis
� Lysogenic pathway
�Viral DNA integrates into
bacterial chromosome
HIV, a retrovirus
In ConclusionIn 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 ConclusionIn Conclusion
�Many bacteria have external structures
that increase their survival and
pathogenicity
�Bacteria reproduce by binary fission
In ConclusionIn 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 ConclusionIn Conclusion
�There are two pathways common in the
multiplication of bacteriophages: lytic and
lysogenic
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