prokaryotes by lanyuehua

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									Prokaryotes
                       Prokaryotes
• Classification of prokaryotes has
  dramatically changed due to analysis of
  the genomes of various types of cells:
• The description of these organisms as
  members of Kingdom Monera, has been
  abandoned and replaced with a three
  domain system. These Domains are as
  follows:
   – Domain Bacteria
   – Domain Archaea
   – Domain Eukarya
• The domains bacteria and archaea
  contain the prokaryotic organisms.
• Domain Eukarya include the protists and
  the other multicellular kingdoms.
General Bacterial Structure
           General Characteristics
•Bacteria are the smallest "living" organisms
•Are prokaryotic cells
   •Lack Nucleus
   •DNA is naked. - a single loop - not bound into a
   chromosome.
   •May contain plasmids (small circular fragments of
   DNA)
   •Lack membrane-bound organelles
•Usually have an outer Cell Wall.
•Sometimes have an Outer Capsule - These stain red in a
Gram Stain test and are called Gram Negative bacteria.
•Those without an outer capsule stain blue in the gram stain
test and are called Gram Positive Bacteria
BACTERIAL CLASSIFICATION:

•   Bacteria are classified generally by 3
    characteristics
    –   The bacterial cell shape
    –   The bacterial cell arrangements
    –   Ability to accept a Gram stain
            Bacterial Shape:
• Bacteria have 4
  basic shapes:
  – Spherical - cocci
  – Rod-shaped –
    bacilli
  – Bent rod shaped
    - Vibrios
  – Spiral – spirilli
              Bacterial Arrangement:

• Bacteria have 3 basic
  arrangements:
  – Occurring singly =
    “Mono” arrangement
  – Occurring in pairs =
    “Diplo” arrangement
  – Occurring in long
    chains = “Strepto”
    arrangement
  – Occurring in clusters =
    “Staphlo” arrangement
                   Gram Staining:
• Bacteria can be
  categorized by their ability
  to accept a gram stain.
  – Bacteria are exposed to
    several staining agents;
    Crystal Violet, Gram’s Iodine,
    and safranine.                        Gram Negative Bacteria
     • If the bacteria possesses a cell
       capsule, it will retain a pink
       color. This is referred as to a
       “Gram Negative” bacteria
     • If the bacteria lacks a cell
       capsule it will retain a blue
       color. This is referred to as a
       “Gram Positive” bacteria

                                          Gram Positive Bacteria
   How Bacteria obtain energy:

• Two major categories:
  – Autotrophs - Make their own energy - 2 types
     • Phototrophic autotrophs - Get energy from sunlight
     • Chemotrophic autotrophs - Get energy from inorganic
       molecules (eg. Sulfides)
  – Heterotrophs - Energy obtained from other
    organisms
     • Chemotrophic heterotrophs - obtain energy by
       dissolving/absorbing organic material
     • Phototrophic heterotrophs - meet some energy needs
       from photosynthesis, but must absorb organic compounds.
      Bacterial Respiration
3 major categories

• Obligate aerobes. - Must have O2 in
  order to live
• Obligate anaerobes - Must live in an O2
  free environment
• Facultative anaerobes - Can live with or
  without O2.
       Bacterial Reproduction:

• Bacteria reproduce through binary fission.
• Can engage in primitive sexual reproduction
  called conjugation.
  – A bridge is formed between 2 bacteria
  – Plasmids are shared across bridge, thus
    exchanging genetic information.
  – In times of harsh conditions, bacteria can form
    endospores, to encapsulate themselves in a
    dormant state, until conditions improve.
                   Motility
• Some
  bacteria are
  motile - can
  move by
  either
  thrashing,
  secreting
  lubricating
  secretions or
  through use
  of a flagellum
                  Archaea
Evolutionary
  Relationships
• Analysis of
  molecules found
  within the cells
  suggests that
  eukaryotes are more
  closely related to
  archaea than to
  bacteria.
            Major Groups of Archaea


• Three major groups of archaea are found in
  extreme habitats.
  – Methanogens are found in anaerobic
    environments.such as marshes and in the intestinal
    tracts of animals. They produce methane as a
    result of cellular respiration.
  – Halophiles are found in environments with high salt
    concentration such as the great salt lake or soil
    with a high salt concentration.
  – Thermoacidophiles live in hot, acidic environments
    such as hot springs and hydrothermal vents.

								
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