Archaebacteria and Eubacteria

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Archaebacteria and Eubacteria
Sunita Kaushik Department of Botany, DAVCG,
Yamunanagar.
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• 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 bacteria-like
  organisms.

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• Bacteria can be autotrophs or hetertrophs.
• Those that are classified as autotrophs are
  either photosynthetic, obtaining energy from
  sunlight or chemosynthetic, breaking down
  inorganic substances for energy .

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• 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, as well as those that live as
  parasites, absorbing nutrients from living
  organisms.

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• Depending on the species, bacteria can be aerobic
  which means they require oxygen to live
• or
• anaerobic which means oxygen is deadly to them.

Green patches are green sulfur bacteria.  The
rust patches are colonies of purple non sulfur
bacteria.  The red patches are purple sulfur
bacteria.
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Archaebacteria
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• Methanogens
• These Archebacteria are anaerobes. They make
  methane (natural gas) as a waste product. They
  are found in swamp sediments, sewage, and in
  buried landfills. In the future, they could be
  used to produce methane as a byproduct of sewage
  treatment or landfill operation.

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• Halophiles
• These are salt-loving Archaebacteria that grow
  in places like the Great Salt Lake of Utah or
  salt ponds on the edge of San Francisco Bay.
  Large numbers of certain halophiles can turn
  these waters a dark pink. Pink halophiles contain
  a pigment very similar to the rhodopsin in the
  human retina. They use this visual pigment for a
  type of photosynthesis that does not produce
  oxygen. Halophiles are aerobes, however, and
  perform aerobic respiration.

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Extreme halophiles can live in extremely salty
environments. Most are photosynthetic autotrophs.
The photosynthesizers in this category are purple
because instead of using chlorophyll to
photosynthesize, they use a similar pigment
called bacteriorhodopsin that uses all light
except for purple light, making the cells appear
purple.
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• Thermophiles
• These are Archaebacteria from hot springs and
  other high temperature environments. Some can
  grow above the boiling temperature of water. They
  are anaerobes, performing anaerobic respiration.
• Thermophiles are interesting because they contain
  genes for heat-stable enzymes that may be of
  great value in industry and medicine. An example
  is taq polymerase, the gene for which was
  isolated from a collection of Thermus aquaticus
  in a Yellowstone Park hot spring. Taq polymerase
  is used to make large numbers of copies of DNA
  sequences in a DNA sample. It is invaluable to
  medicine, biotechnology, and biological research.
  Annual sales of taq polymerase are roughly half a
  billion dollars.

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Eubacteria
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• Cyanobacteria
• This is a group of bacteria that includes some
  that are single cells and some that are chains of
  cells. You may have seen them as "green slime" in
  your aquarium or in a pond.
• Cyanobacteria can do "modern photosynthesis",
  which is the kind that makes oxygen from water.
  All plants do this kind of photosynthesis and
  inherited the ability from the cyanobacteria.

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Cyanobacteria were the first organisms on Earth
to do modern photosynthesis and they made the
first oxygen in the Earth's atmosphere.
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• Bacteria are often maligned as the causes of
  human and animal disease. However, certain
  bacteria, the actinomycetes, produce antibiotics
  such as streptomycin and nocardicin.

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• Other Bacteria live symbiotically in the guts of
  animals or elsewhere in their bodies.
• For example, bacteria in your gut produce vitamin
  K which is essential to blood clot formation.

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• Still other Bacteria live on the roots of certain
  plants, converting nitrogen into a usable form.

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• Bacteria put the tang in yogurt and the sour in
  sourdough bread.
• Saprobes help to break down dead organic matter.
• Bacteria make up the base of the food web in many
  environments.

Streptococcus thermophilus in yogurt
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• Bacteria are prokaryotic and unicellular.
• Bacteria have cell walls.
• Bacteria have circular DNA called plasmids
• Bacteria can be anaerobes or aerobes.
• Bacteria are heterotrophs or autotrophs.
• Bacteria are awesome!

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• Bacteria can reproduce sexually by conjugation or
  asexually by binary fission.

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Endospore

• Bacteria can survive unfavorable conditions by
  producing an endospore.

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Shapes of Bacteria
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Penicillin, an antibiotic, comes from molds of
the genus Penicillium Notice the area of
inhibition around the Penicillium.
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• Penicillin kills bacteria by making holes in
  their cell walls. Unfortunately, many bacteria
  have developed resistance to this antibiotic.

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• The Gram stain, which divides most clinically
  significant bacteria into two main groups, is the
  first step in bacterial identification. 
• Bacteria stained purple are Gram - their cell
  walls have thick petidoglycan and teichoic acid.
  
• Bacteria stained pink are Gram their cell walls
  have have thin peptidoglycan and
  lipopolysaccharides with no teichoic acid.

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In Gram-positive bacteria, the purple crystal
violet stain is trapped by the layer of
peptidoglycan which forms the outer layer of the
cell. In Gram-negative bacteria, the outer
membrane of lipopolysaccharides prevents the
stain from reaching the peptidoglycan layer. The
outer membrane is then permeabilized by acetone
treatment, and the pink safranin counterstain is
trapped by the peptidoglycan layer.
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• The Gram stain has four steps
• 1. crystal violet, the primary stain followed
  by
• 2. iodine, which acts as a mordant by forming a
  crystal violet-iodine complex, then
• 3. alcohol, which decolorizes, followed by
• 4. safranin, the counterstain.

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Is this gram stain positive or negative?
Identify the bacteria.
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Is this gram stain positive or negative?
Identify the bacteria.
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• Gram staining tests the bacterial cell wall's
  ability to retain crystal violet dye during
  solvent treatment.
• Safranin is added as a mordant to form the
  crystal violet/safranin complex in order to
  render the dye impossible to remove.
• Ethyl-alcohol solvent acts as a decolorizer and
  dissolves the lipid layer from gram-negative
  cells. This enhances leaching of the primary
  stain from the cells into the surrounding
  solvent.
• Ethyl-alcohol will dehydrate the thicker
  gram-positive cell walls, closing the pores as
  the cell wall shrinks. 
• For this reason, the diffusion of the crystal
  violet-safranin staining is inhibited, so the
  bacteria remain stained.