Prokaryotes

1
Prokaryotes
2
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.

3
General Bacterial Structure
4
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

5
BACTERIAL CLASSIFICATION

• Bacteria are classified generally by 3
  characteristics
• The bacterial cell shape
• The bacterial cell arrangements
• Ability to accept a Gram stain

6
Bacterial Shape

• Bacteria have 4 basic shapes
• Spherical - cocci
• Rod-shaped bacilli
• Bent rod shaped - Vibrios
• Spiral spirilli

7
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

8
Gram Staining

• Bacteria can be categorized by their ability to
  accept a gram stain.
• Bacteria are exposed to several staining agents
  Crystal Violet, Grams Iodine, and safranine.
• 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 Negative Bacteria
Gram Positive Bacteria
9
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.

10
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.

11
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.

12
Motility

• Some bacteria are motile - can move by either
  thrashing, secreting lubricating secretions or
  through use of a flagellum

13
Archaea

• Evolutionary Relationships
• Analysis of molecules found within the cells
  suggests that eukaryotes are more closely related
  to archaea than to bacteria.

14
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.