Download Overview of the cell

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Blue Green Algae
Diagram of Bacteria
BACTERIA
Biology 20
Salmonella Bacteria
Common Bacteria
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Belong to the Domain Bacteria and Kingdom
Eubacteria
They are microscopic prokaryotes. Organisms are
classified as bacteria by one characteristic: the lack
of a cell nucleus.
They are the most numerous organisms on Earth.
There are more bacteria on or in your body than
there are people in the world!
Bacteria
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Relatively few species
of bacteria cause
infection.
Hundreds of species of
bacteria live on the
human body and within
the gastrointestinal
tract (critical to human
well-being).
Bacteria
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They have evolved into many different forms and
are part of every environment on Earth. For
example, there are:
• Aerobic organisms that need oxygen to survive.
• Anaerobic organisms that die in the presence of
oxygen.
• Autotrophic organisms that produce their own
food.
• Heterotrophic organisms that get their nutrition
from other organisms.
Kinds of Bacteria
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Currently identified
using DNA but
historically the shape
and arrangement of
bacteria identified
them
Shape
Spherical (coccus)
Rod-shaped (bacillus)
Spiral (spirillum)
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Three basic shapes:
round, rod-shaped, or
spiral
Kinds of Bacteria
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Spirillum only live as
single cells.
Arrangement
Diplo – paired
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Some coccus form pairs
and chains while others
grow in grape like
bunches.
Some bacilli also form
pairs or chains but they
do not grow in bunches.
Staph – in clusters
Strep – in chains
Characteristics
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Prokaryotic cell
Singular circular
chromosome
Cell wall containing
peptidoglycan
Lacking nuclear
envelope
Lacking organelles
and cytoskeleton
Structure
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Structures that help bacteria survive in
hostile environments
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Capsules (slime layers) – protects the
cell from drying out, helps evade
immune system and adhere to surfaces
Pilli – hair-like projections that help
cells attach to surfaces
Endospores – bacteria become
dormant until conditions become
favourable
Structure
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Structures that help bacteria
move
 Flagella – one or more taillike structures
Reproduction
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Occurs most often by an
asexual process called
binary fission
One cell splits into two cells;
offspring are genetically
identical to parents
Can occur in under 20
minutes; producing 1 billion
bacteria in under 10 hours
Reproduction
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Can also occur through
bacterial conjugation
Two cells attach to each
other and exchange genetic
information; offspring have
new genes and new traits
Only between bacteria in
the same or closely related
species
Photosynthetic Bacteria
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Cyanobacteria
 commonly
called bluegreen algae
 the
oldest known fossil
(>3.5 billion years old!)
 responsible for many
Proterozoic oil deposits
 cyanobacterial blooms
common on prairie sloughs
– can harm livestock, pets,
and humans
Gram-negative bacteria
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Few organisms have the
ability to utilize
atmospheric nitrogen.
Nitrogen-fixing bacteria
within the root nodules of
certain plants provide a
usable source of nitrogen
to plants. E.g. Rhizobium,
Pseudomonas
Bacteria & Health
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Only a small percentage of
bacteria cause disease in
humans.
Bacterial diseases include:
gonorrhea, chlamydia, strep
throat, pneumonia, acne,
botulism, food poisoning,
Lyme disease.
Bacteria can also cause
disease in plants and
animals.
Eubacteria & Archaebacteria
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Archaebacteria
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Classified in Domain and Kingdom Archaea
Thought to be more ancient than bacteria and yet
more closely relate to eukaryotes
Their cell walls do not contain peptidoglycan and
they have some of the same proteins as eukaryotes.
Archaebacteria
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There are diverse in shape and nutrition. Some are
autrophic, but most are heterotrophic.
They are referred to as “extremophiles” because
they can live in extreme environments: boiling hot
springs, salty lakes, thermal vents on the ocean
floor, and marsh mud where there is no oxygen.
Characteristics
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Prokaryotic cell
Singular circular
chromosome
Cell wall without
peptidoglycan
Membrane lipids
Lacking nuclear
envelope
With organelles and
cytoskeleton
Methanogens
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 Typically
found in
swamps and marshes
 Produce
methane gas
as a by-product of
metabolism
Thermoacidophiles
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 Resistant
to hot
temperatures and
high acid conditions
 Found
in acid hot
springs, acidic soil,
and deep ocean
volcanic vents