Bacteria

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Bacteria

• The smallest and most common microorganisms are
  prokaryotes which are single-celled organisms
  that lack a nucleus.

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Prokaryotes

• Used to simply be called bacteria
• Used to be placed in the kingdom Monera
• Now classified into two kingdoms
• Eubacteria
• Archaebacteria

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Eubacteria
ribosome

• Larger of the two kingdoms
• Live almost
• anywhere
• Their cell wall contains peptidoglycan

peptidoglycan
cell wall
cell membrane
pili
DNA
flagellum
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Archaebacteria

• Cell wall lacks peptidoglycan
• Their DNA is more like that of eukaryotes than
  eubacteria
• They live in extremely harsh environments
• Very salty halophiles
• Very hot or very cold extremophiles
• Oxygen free environments
• (thick mud, digestive tract of
• animals) produce methane
• methanogens

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Bacteria
are classified into the kingdoms of
live in harsh environments such as
include a variety of lifestyles such as
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Identifying prokaryotes

• Prokaryotes are identified by their
• Shapes
• Chemical nature of
  their cell walls
• The way they move
• The way they obtain energy

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Bacilli (bacillus) Rod-shaped prokaryotes
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Cocci (coccus) Sphericalprokaryotes
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Spirilla (spirillum) Spiral and corkscrew
shaped prokaryotes
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Cell Walls

• A Gram stain is used to differentiate between
  cell wall composition.

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Gram positive

• Bacterial cells with one thick cell wall that
  contains peptidoglycan stain violet and are Gram
  positive

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Gram negative

• Bacterial cells with thinner walls with an outer
  layer of lipid stain pink or light red and are
  Gram negative

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Movement

• Flagella whip structures
• Lash, snake or spiral forward
• Glide along a layer of slime they secrete
• Do not move

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How prokaryotes obtain energy

• Prokaryotes that obtain energy in a similar
  manner to green plants are photoautotrophs. An
  example is cyanobacteria
• Prokaryotes that obtain energy directly from
  inorganic molecules are chemoautotrophs

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Energy continued

• Prokaryotes that make their own food are
  autotrophs
• Prokaryotes that obtain their food from an
  outside source are heterotrophs
• Some heterotrophs can release toxins that are
  responsible for food poisoning

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Heterotrophs

• Chemoheterotrophs take in organic molecules for
  both energy and a supply of carbon
• An interesting group are those that capture
  sunlight for energy but need organic compounds
  for their carbon source (nutrition). These are
  photoheterotrophs.

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How prokaryotes release energy from their food

• Obligate aerobes Require oxygen for cellular
  respiration
• Obligate anaerobes Oxygen is toxic release
  energy through fermentation
• Facultative anaerobes Do not need oxygen, but
  are not killed by it. Can switch back and forth
  between cellular respiration and fermentation

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Reproduction

• Prokaryotes reproduce asexually through binary
  fission

Prokaryotes exchange genetic material through
conjugation
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Endospore

• When growth conditions become unfavorable,
  bacteria can form spores called an endospores
  that allow them to stay dormant until conditions
  are favorable.

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Importance of bacteria

• Bacteria are important decomposers and help the
  ecosystem recycle nutrients
• All organisms rely on bacteria for nitrogen
  fixation
• However, bacteria are also pathogens and cause
  disease by either breaking down tissues or
  producing poisons

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Human uses of bacteria

• Food production (cheese, yogurt, sour cream,
  buttermilk, pickles, sauerkraut and vinegar).
• Industry digest petroleum (clean up oil
  spills), remove waste products and poisons from
  water, mine minerals, genetic engineering for
  medicines and hormones

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Methods of controlling bacteria

• Antibiotics drugs or natural compounds used to
  attack and destroy bacteria
• Sterilization destroy bacteria by heat or
  chemical action (disinfectants)
• Refrigeration cold temperature slows bacteria
  growth
• Canning heat food to a high temperature, place
  in sterile glass jars or metal cans
• Chemically preserving foods salt (salted meat),
  vinegar (pickled), sugar (jam)