Bacteria

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Bacteria
Part 1History
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Bacteria

• Fossil evidence suggests bacteria have been
  around for over 3.5 billion years.
• In comparison humans have been around roughly 1
  million years.
• Most abundant form of life on Earth

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Time Machine

• Close your eyes and try to imagine travelling
  back in time 4 billion years.
• What does the world look like around you?
• What is the atmosphere like?
• Are there plants or animals?

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Ancient Earth

• At the time when the first bacteria would have
  been created the planet was highly acidic, very
  saline,extremely hot with an atmosphere
  containing mostly C02 and Nitrogen.
• There were no plants, animals, oceans or oxygen
  present.

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Bacterial Evolution

• Autotrophic bacteria carried out photosynthesis
  and converted CO2 into Oxygen.
• These bacteria are partially responsible for the
  current, oxygen rich atmosphere that we currently
  have.

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Bacteria
Part 2 Structure
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Introduction

• Members of the Monera kingdom are all bacteria.
• most abundant, most ancient, most simple of all
  organisms
• over 4500 different kinds of bacteria
• they are important constituents of the
  atmosphere, soil, water.

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Bacteria Structure

• Unicellular, procaryotes
• lack organelles
• DNA is free in the cytoplasm (no nuclear
  membrane)
• 1 ?m in size

capsule
flagella
ribosome
DNA
cell wall
cell membrane
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External Structures Capsule

• Gel like coating on the outside of the cell
• helps cells attach to their environment
• protection from being eaten by other microbes

capsule
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Streptococcus mutans

• Bacteria that causes tooth decay
• secretes the capsule in the presence of sugar and
  sticks to teeth
• this causes plaque to form on the teeth resulting
  in tooth decay

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Flagella

• Help bacteria to move
• spirrilum and rod shaped bacteria have flagella,
  spherical shaped bacteria lack flagella
• need flagella to move around to look for nutrients

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Cell Wall Peptidoglycan

• Chemically different than plant cell walls made
  up of cellulose
• A matrix of sugar crosslinked with amino acids
• function helps keep the shape of cell, and
  protects the cell from swelling or breaking.

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Cell Wall
Gram Positive Staphylococcus cells
Gram Negative E. coli cells

• 2 different types of cell walls
• Gram Positive - contain a thick layer of
  peptidoglycan that absorbs stain.
• Gram Negative - contains a thin layer of
  peptidoglycan that does not absorb stain.

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Cell Membrane

• Bi-lipid layer with protein channels
• retains the cytoplasm in the cell
• is the barrier between the internal and exterior
  environment
• important in the transport of molecules into and
  out of the cell

Protein channel
Lipids
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Ribosomes

• Ribosomes are the protein synthesizing factories
  of the cell.

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Endospore

• Endospores are highly resistant resting
  structures produced within cells
• Spores are resistant to heat, radiation,
  chemicals, and dessication
• Spores that were dormant for thousands of years
  in the great tomes of the Egyption Pharohs were
  able to germinate and grow when placed in
  appropriate medium.

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Bacteria
Part 3 Classification
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The Different Types of Bacteria

• Bacteria are extremely diverse and therefore live
  in many different environments and play many
  different roles.

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Shapes of Bacteria

• Shapes
• Round coccus
• Rod bacillus
• Spiral spirillus

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Metabolism based Classification

• Aerobic bacteria use oxygen to carry on
  respiration which produces energy. MOST bacteria
  are aerobic.
• Facultative Anaerobic bacteria bacteria that
  can produce energy with or without oxygen. This
  is called fermentation.
• Obligate Anaerobes bacteria can only produce
  their energy in an oxygen-free environment. This
  process is also called fermentation.

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Nutrition Based ClassificationAutotrophic
Bacteria

• Obtain energy from inorganic (non-living)
  sources. 2 types
• photosynthetic bacteria contain chlorophyll in
  the cell membrane (not held in a plastid).These
  are the blue-green or cyanobacteria.
• Chemoautotrophic bacteria energy comes from
  inorganic molecules such as nitrogen, sulfur,
  hydrogen and iron compounds.

Oscillatoria
Sulfur bacteria
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Heterotrophic Bacteria

• Obtain energy from organic (living) sources.
  These bacteria play a leading role in the
  breakdown and decomposition of organic molecules.
  Thus are key players in the biological recycling
  of nutrients.

Rhizobacterium on clover stem
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2 type of Heterotrophic bacteria

• Saprobes feed on dead plant and animal matter.
  They secrete digestive enzymes onto the organic
  matter which digest the food into small
  particles. This food can then be absorbed by
  the bacteria.
• Gives soil its characteristic smell
• Mutant bacteria able to breakdown inorganic
  material such as nylon, plastic, herbicides and
  pesticides.

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• Parasites These bacteria live on or in living
  organisms and may cause disease.
• Examples meningitis, pneumonia, tuberculosis.

Bacteria causing pneumonia and meningitis
Listeria bacteria which causes food poisoning
Staphylococcus cause toxic shock syndrome
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Tuberculosis
Lung tissue infected with pink, rod shaped
Mycobacterium tuberculosis
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Uses of Bacteria

• Lactobacillus used in dairy foods to change
  glucose into lactose.
• Used in making foods like sauerkraut,
  yogurt,cheeses, vinegar.
• Use bacteria to make food for cattle (silage)
  which helps increase milk production.
• Used as herbicides and pesticides.

Backgound image Lactobacillus
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Uses of Bacteria

• Some bacteria are used in industry to clean up
  wastes, chemical spills of PCBs, gas and oil. The
  bacteria can digest toxic chemicals and turn them
  into harmless products.
• As long as toxic materials remain, the bacteria
  will continue to digest them. Once the
  contaminate is gone the bacteria have no food
  source and will die. Perfect cleaning mechanism.

Backgound image Lactobacillus
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Reproduction

• Mostly by asexual reproduction
• Binary Fission- a form of asexual reproduction
  where a parent cell divides into two identical
  cells.
• Under ideal conditions, lots of food, proper
  temperature and lots of space, bacteria divide
  every 20 minutes and in 24 hours a single
  bacterial cell could produce 2 million kg of
  bacterial cells.

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Binary Fission
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Sexual Reproduction

• . Genetic recombination is responsible for
  generating diversity within bacterial
  populations. It is defined as the combining of
  genetic material from two individuals into the
  genome of a single individual. Three processes
  named transformation, transduction, and
  conjugation are responsible for bacterias
  genetic recombination( sexual reproduction).

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Transformation

• living cells take up DNA from their environment.
  A foreign allele is incorporated into a bacterial
  chromosome by replacing the native allele. Thus
  the transformed cell now has a chromosome
  containing DNA from two different cells.

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Transduction

• In transduction, viruses that infect bacteria or
  phages are responsible for this gene
  transfer.
• Bacterial DNA found in the phage is transferred
  to the new host and is incorporated into the host
  genome.

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Transduction
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Conjugation

• "Conjugation is the direct transfer of genetic
  material between two bacterial cells that are
  temporarily joined"(Biology Campbell 3rd edition
  1993). Animation
• Conjugation resembles sexual reproduction, in
  that the two bacteria join (mate) and exchange
  genes. Conjugation is a one way transfer of
  DNA. The DNA donor uses appendages called sex
  pili to attach to the recipient. This is followed
  by the formation of a cytoplasmic bridge for
  which DNA can be transferred through, and promote
  recombination.

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Conjugation
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Assignment

• Complete work sheet- both sides
• Clay Activity- model a bacterium and go through
  the steps of binary fission and conjugation.
• Book- Page 531, Think Creatively 28