Bacteria Review

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Bacteria Review
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Kingdoms

• Organisms are classified into six different
  kingdom.
• Two of the kingdoms, classify organisms that we
  know as bacteria.
• They are Eubacteria and Archaebacteria.

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Both Kingdoms have the following characteristics

• Unicellular
• Prokaryotes
• Cell walls
• Heterotrophs or Autotrophs

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Differences between the kingdomsEubacteria

• Cell walls contain a carbohydrate called
  peptidoglycan. It makes the wall strong and
  thick.
• Live almost everywhere!

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Archaebacteria

• Cell walls do not contain peptidoglycan.
• Live in environments that are harsh
• Methanogens produce methane gas
• Halophiles very salty
• Thermoacidophiles very hot and acidic

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Halophiles
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Thermophiles
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Methanogens Produce Methane Gas
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Bacteria are

• The smallest of all living organisms.
• A very diverse group.
• So how do we group or classify such a microscopic
  and vast group?

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Bacteria are classified by

• Shape
• bacilli rod-shaped
• cocci round
• spirilla spiral / corkscrew
• Materials in Cell Wall
• have thick peptidoglycan - Gram-positive
• have thin peptidoglycan Gram-negative
• have no peptidoglycan

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Bacteria are classified by

• Movement
• No movement
• Movement with flagella, spiral motion or slime
  layer
• How they obtain food and use energy
• Chemoheterotrophs take in food for energy and
  carbon.
• Photoheterotrophs is photosynthetic but needs
  organic compounds for carbon.
• Chemoautotrophs make carbon molecules from CO2
  using energy from chemical reactions
• Photoautotrophs use sunlight to change CO2 and
  water to carbon compounds

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Bacteria are classified by

• What sort of environment they need
• Rich in oxygen
• Obligate aerobes
• Without oxygen or lacks oxygen
  Obligate anaerobes
• OR they can live with or without oxygen
• Facultative anaerobes

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Gram Staining

• Scientists have developed a method of staining to
  determine what materials are in the cell wall.
• This procedure is called Gram Staining.
• Two different stains are applied to a cell. How
  each cell absorbs the stains tells us what type
  of materials are in the cell wall.

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Process of Gram Staining

• First, bacteria on a glass slide are stained with
  a violet stain.
• Then, the slide is washed with alcohol.
• Finally, the slide is stained with a red stain.

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Gram Positive Results

• If the cell wall absorbs the violet stain, the
  cell is classified as Gram .
• This means the cell wall contains peptidoglycan
  and is very strong and thick.

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Gram Absorbs violet stain.
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Typical Gram-positive bacteria

• Staphylococcus epidermidis and Staphylococcus
  aureus which is a common cause of boils
• Streptococcus pyogenes which causes many a sore
  throat and scarlet fever and Streptococcus
  pneumoniae which causes lobar pneumonia
• Clostridium tetani which cause tetanus (lockjaw)
• Actinomyces odontolyticus which is found in
  mouths
• Bacillus subtilis which are common microbes
  living in soil

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Gram Negative Results

• The violet stain is not absorbed.
• The alcohol wash DISSOLVES the lipids in the cell
  wall.
• Then, the cell absorbs the red stain.

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Gram - absorbs red dye.
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Typical Gram-negative bacteria

• whooping cough, Bordetella pertussis
• typhoid, Salmonella typhi
• cholera, Vibrio cholerae

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• Why do we need to know what is in the cell wall?

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• Some cell walls protect the bacteria from being
  affected by antibiotics.
• If a doctor knows what type of cell wall the
  bacteria has, he will prescribe medicine that
  will get through the cell wall!!

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SHAPES

• Bacilli

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Cocci
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• Spirilla

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• Strepto bacteria cluster in rows
• Staphylo bacteria cluster in grape-like clusters

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A bacterial model contains the following
structures

• A cell wall with or without peptidoglycan
• A cell membrane
• Cytoplasm
• Ribosomes
• A circle of DNA
• Structures for movement
• And Pili
• Structures that help connect 2 bacteria during
  the exchange of genetic material.

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Model of a Bacterium
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Reproduction Binary Fission

• Asexual
• One bacterium divides into two daughter bacteria.
• Each new daughter is IDENTICAL to the parent.

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Two daughter cells are about to separate by
cytokinesis.
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How do bacteria with in a species become diverse?

• Conjugation!
• Hollow structures, called pili, connect two
  bacteria.
• Genetic material is exchanged through this
  structure.

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Conjugation Model
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What is the result of conjugation?
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GENETIC DIVERSITY!

• After conjugation is complete, each bacterium has
  a new combination of base sequences
• This sequence is completely different then the
  sequences either bacterium had in the beginning.

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Why is diversity important?
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It ensures that the bacteria will

• Survive in a difficult environment.
• Reproduce and pass their genes to the next
  generation.

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Spore Formation

• In unfavorable conditions, endospores form
• Endospores are like tough shells enclosing the
  nucleus of bacterial DNA
• In favorable conditions, they germinate and grow

Clostridium botulinum
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We can not live without Bacteria!

• They are everywhere!
• They are in us!
• They are on us!
• They help us in millions of ways!

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Roles of Bacteria

• Clean the water in the mining of gold.
• Make artificial snow.
• Bleach wood pulp white.
• Give flavor to food.
• Decompose dead organic material.
• Produce antibiotics and medicines.
• Recycle nitrogen in the nitrogen cycle.
• Cause diseases.

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Bacteria causes disease two ways

• They actually eat the cell they affect.
• Example Tuberculosis in the lungs.
• They produce toxins that poison the cell they
  affect.
• Example Botulism (food poisoning caused by nerve
  toxin)