Transcript Bacteria and Viruses

To Review: Archaebacteria
• Are prokaryotes
• Unicellular organisms
without nuclei
• No organelles
• Have Cell Walls
• Archaebacteria is the oldest
organism.
• Lacks peptidoglycan.
• DNA is more similar to
eukaryotes, denotes lineage.
• Live in extreme
environments
– No oxygen (anoxic)
– Hot Springs, deep ocean
• Energy: Chemosynthesis
To Review: Eubacteria
• Are Prokaryotes
• Unicellular organisms without
nuclei
• Are characterized by …
– Shape
– Chemical nature of cell walls
– The way they move
– The way they obtain energy
• No organelles
• Cell Walls thicker (peptidoglycan, a
carbohydrate)
• Live anywhere
– Freshwater, saltwater, on land,
in the human body
• Can be heterotrophic,
photosynthetic and chemosynthetic
Bacterial Feeding
• Heterotrophs – take in organic
molecules for energy and a supply
of Carbon.
• Chemoheterotrophs – use
chemicals for gaining energy.
• Autotrophs – create their own
energy.
– Photoautotrophs – gain energy
from light from the sun to convert
CO2 and water into energy
– Chemoautotrophs – make
organic carbon from CO2.
• Do not require light, but instead
use energy from chemical
reactions using Ammonia, HS,
nitrates, S, and Fe.
• Live in the deep ocean.
In bacterial infections, they harm the host by
either destroying cells for food or releasing
toxins (poisons) in the host’s body.
Bacterial Reproduction
• Binary Fission – asexual
reproduction
– Chromosomes are replicated and
move to the poles of the cell
– As the bacterium gets larger, it
pinches in between
– Genetically identical
– Very fast (every 20 mins)
• Conjugation – sexual
reproduction
– Through a pilus (pili) exchange
genetic information
– Not genetically identical
– Creates new genetic
compositions (genetic diversity)
– Allows for greater survival in a
changing environment
Survival Mechanisms
• Bacteria who need oxygen are
called obligate aerobes
• Bacteria who are killed by
oxygen are called obligate
anaerobes
• When conditions become
harsh, they can form an
endospore that contains DNA.
• When conditions improve, the
endospore germinates.
– Can take months
• Bacteria can be harmful to
people for these reasons.
Bacteria forming on food
creates toxins that can harm
humans.
Why Bacteria?
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• Bacteria are important in the supporting
roles of life.
– Some are producers that give off oxygen.
– Some are decomposers that break down
nutrients in dead matter and the atmosphere.
– Some help in nitrogen fixation so plants can
turn Nitrogen gas into a useable form.
• Human Uses for Bacteria
– Food, Beverages, mining, water treatment,
medicine, digestion in the human intestines.
• Viruses are non-living particles
of nucleic acid, protein and
some lipids that cause
influenza.
• Composed of DNA or RNA in a
protein coat called a capsid.
• Viruses that only infect bacteria
are called bacteriophages.
• Named after their disease or
discoverer.
• Likely evolved later since they
are dependent on living things.
• Why Non-Living?
– Cannot reproduce without
infecting a host cell
– Do not grow and develop
– Do not respond to the
environment.
Viruses
Viral “Reproduction”
• Lysogenic cycle
– Virus attaches to host cell
– Inserts viral nucleic acid and
inserts it into the host
cell’s chromosome
(prophage)
– Gets replicated as host cell
divides (through mitosis)
– Can remain inactive for a
long period of time.
Like Bacteria, Viruses produce disease by disrupting the body’s normal
equilibrium. They either directly attack cells or cause cells to change their
patterns of growth or influence their function in the body.
Lytic Cycle
• Lytic cycle
– Starts as the lysogenic
cycle until triggered.
– Takes over cell
machinery to make
virus only! (Chops up
cell’s DNA to shut
down all defenses.)
– Viruses are assembled
in the host cell
– Burst out of the host
cell releasing new
virus
• 30 min = 200 viruses
HIV virus
• Retroviruses
– Use RNA instead of DNA
– Reverse transcriptase
creates DNA from the RNA in
the host cell
• In Sub-Saharan Africa over
23 million living with
HIV/AIDS, 4 million
infected each year.
• HIV contact via
– Saliva/Sexual Contact
– Mucus Membranes
– Shared hypodermic
needles
– Blood transfusion (rare)
Tales of HIV and AIDS
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Preventing Disease
• Vaccine – preparation of weakened or killed
pathogens that is injected for the creation of
immunity against the pathogen.
• Control – Sterilization by Heat, Disinfectants,
Food Storage (Cans, etc)
• Antibiotics – Compounds that block the
growth and reproduction of bacteria.
– One of the major reasons the for dramatic
increase in life expectancy in the past 200 years.
– Not effective against viruses.