Download Bacteria / Monerans

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.
• 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
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.