VIRUSES

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VIRUSES BACTERIA
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• Key Concepts
• What is the difference between a virus and a
  bacteria?
• How do virus/bacteria reproduce?
• Importance of virus/bacteria

• Vocabulary
• Virus
• Bacteriophage
• Capsid
• Lytic cycle
• Lysogenic cycle
• Retrovirus
• Binary fission
• Conjugation
• Obligate Anaerobe
• Obligate Aerobe
• Endospore

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What is a virus?

• viruses are non-cellular particles made up of
  genetic material (DNA or RNA not both) and
  protein that can invade living cells

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Are Viruses Alive?

• like living things, viruses have genetic material
  and they can pass this on to future generations
• BUT, unlike living things, viruses are not made
  of cells
• outside of a cell, they don't reproduce, feed, or
  grow
• Therefore, most biologists consider viruses
  nonliving

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What do viruses do?

• viruses can invade the cells of plants, animals,
  and bacteria
• viruses cause illness like colds, flus, chicken
  pox, herpes, AIDS, polio, rabies, measles, mumps

Chicken pox
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What do viruses look like?

• a virus is made of a core of genetic material
  surrounded by a protein coat (CAPSID)
• viruses are SMALL!! (20-400 nanometers)

DNA
Bar 100nm
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• viruses come in a variety shapes rod-shaped
  tadpole-shaped helical cubelike

Human Influenza virus particles
T-4 bacteriophage
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How do viruses reproduce?

• viruses insert their genetic material into a host
  cell
• The CAPSID (outside protein) tricks the cell
  into allowing it inside
• once inside, the viral genes take over
• The hijacked cell transcribes the viral genes
• Uses the host cells own enzymes (ex DNA
  Polymerase)
• one of the ways a virus takes over a cell is
  described as the LYTIC CYCLE

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LYTIC CYCLE

• The cells lyse (burst) when the concentration of
  new viral particles is high
• The lytic cycle has its name because the host
  cell lyses and allows viral particles to escape

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RETROVIRUSES

• contain RNA as their genetic material
• retroviruses infect a cell and produce a DNA copy
  of their RNA
• (retro backward RNA is copied in to DNA)
• this DNA is inserted into the host cell's DNA
• example of retroviruses
• HIV

RNA
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How Can You Protect Yourself From Viral
Infections?

• The best way use of vaccines
• Preparation of weakened or killed virus or viral
  proteins
• When injected, the vaccine stimulates the immune
  system
• Sometimes produces permanent immunity
• Protect yourself
• Stay away from known sick people
• Wash your hands often

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Bacteria
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How are Bacteria Different?

• Bacteria are different in that they
• Are much bigger
• Have a different structure (made of cells) ?
  therefore are considered LIVING
• Reproduce differently (asexual and sexual)
• Bacteria are prokaryotes (no nucleus)
• Bacteria Have 2 Kingdoms
• Kingdom Archaebacteria and Eubacteria

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Some bacteria you probably familiar with
Tongue Bacteria
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The Size of Bacteria

• Prokaryotes typically range in size from 1-5um
  (micrometers)

bioluminescent
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The Structure of Bacteria

• 3 basic shapes rod-shaped, spherical shaped,
  spiral-shaped
• they may form long chains, large clumps/clusters,
  or colonies
• cell wall
•  movement propelled by flagella or cilia

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Breathing (RESPIRATION) in Bacteria

• some are aerobic respiration involves oxygen
• obligate aerobes-cannot survive without oxygen
• some are anaerobic respiration without oxygen
• obligate anaerobes-cannot survive with oxygen

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How Do Bacteria Obtain Energy?

• some make their own food (like plants)
  AUTOTROPHS
• some obtain their food (like us)
  HETEROTROPHS

These bacteria eat the nutrients in the agar.
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Reproduction in Bacteria

• most reproduce through
• binary fission (asexual)
• clones

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• Other bacteria exchange genetic information
  through CONJUGATION (a.k.a. bacteria sex)
• A hollow bridge forms between the 2 bacterial
  cells and genes move from 1 bacterium to the
  other
• ADVANTAGE increases genetic diversity in the
  bacterial population

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• If food and space are not an issue, bacteria
  divide at astonishing rates!
• Some can divide every 20 minutes!!
• If this were to continue to happen, the bacteria
  would reach a mass of 4000x the mass of the Earth
  in 48 hours! YUCK!!!

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EXPONENTIAL GROWTH!!!
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How Bacteria Can Be Controlled

• sterilization
• heating/boiling OR use a disinfectant (alcohol,
  bleach? chemical)
• food processing
• boiling, frying, steaming, refrigeration, salt,
  vinegar

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As labeled by humans, there are both BAD
bacteria and GOOD bacteria.
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"Bad" Bacteria

• Bacteria that causes illness and disease
  (pathogenic)
• Bacterial diseases
• diptheria, tuberculosis, typhoid fever, tetanus,
  syphilis, cholera, bubonic plague
• How are the diseases caused?
• Bacteria damage the cells tissues of an
  organism directly by breaking down the tissues
  for food
• Or Bacteria release toxins (poisons) that travel
  through the organisms body

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WARNING Disturbing Picture!!
NEXT SLIDE
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Ocean warning!
Flesh-eating bacteria
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"Good" Bacteria

• Bacteria that humans use and need in their
  everyday lives.

Escherichia coli (Esh-er-ish-e-ah coal-eye) one
of many kinds of microbes that live in your gut.
Wanted for helping you digest your food every
day.
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Lactobacillus acidophilus (lack-toe-bah-sill-us
acid-off-ill-us) one of the bacteria gang wanted
for turning milk into yogurt.
Pseudomonas putida (sue-doe-moan-us poo-tea-dah)
one of many microbes wanted for cleaning wastes
from sewage water at water treatment plants.
Saccharomyces cerevisiae (sack-arrow-my-seas
sair-uh-vis-ee-ay) a.k.a. baker's yeast. Wanted
for making bread rise.
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Streptomyces (strep-toe-my-seas) soil bacteria
wanted for making streptomycin, an antibiotic
used to treat infections.
Arbuscular mycorrhizas (ar-bus-que-ler
my-kuh-rye-zuh) one of a soil-living fungus
family. Wanted for helping crops take up
nutrients from the soil.
Bacillus thuringiensis (bah-sill-us
ther-in-gee-in-sis) a.k.a "Bt", a common soil
bacterium. Wanted as a natural pest-killer in
gardens and on crops.
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Good Bacteria in Summary

• Nitrogen Fixation
• Most organisms need nitrogen for DNA, RNA,
  proteins, and ATP
• Few organisms can convert nitrogen gas into
  useable nitrogen so they need help of legumes
  (beans, etc)

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1. Recycling of Nutrients
2. Foods and Medicines

Antibiotics
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How Do You Treat a Bacterial Infection?

• If prevention fails, take antibiotics
• Antibiotics kill bacteria without harming the
  cells of humans or animals
• They interfere with the cellular processes of
  bacteria
• Many antibiotics are produced naturally by living
  organisms
• Ex penicillin
• Others are synthetic (man-made)