BACTERIA

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BACTERIA

• The Oldest Living Structures
• on The Earth

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CLASSIFICATION

• Living things can be grouped in THREE domains.
• Prokaryotes account for two of the domains.
• Eukaryota are all eukaryotic organisms

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DOMAIN ARCHAEA

• Most inhabit extreme environments on the earth.
  There are THREE main groupings.
• Methanogens are anaerobic and live in swamps,
  marshes, the gut of animals and sewage treatment
  ponds
• Extreme Halophiles live in high salt areas such
  as the Dead Sea and Great Salt Lake
• Extreme Thermophiles live in hot springs with
  temperatures of 60 to 80 celsius.

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DOMAIN BACTERIA

• Bacteria account for most prokaryotes.
• Includes the spirochetes, gram-positive bacteria
  and cyanobacteria.
• These are the bacteria that the Grade 11 course
  will concentrate upon.

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DOMAIN COMPARISON
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Size Relationships
Micron Virus (.05 1 micron) Bacteria (.5 1.5
microns) Red blood cell (5 microns) White blood
cell (5 8 microns) Sperm (60 microns)
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Bacterial Shapes

• Bacillus bacteria are rod shaped.
• Cocci bacteria are round.
• Spirillum are spiral shaped

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Identification
Gram Stain The Gram stain differentiates
bacteria on the basis of structure and
composition of the layers of the cell wall. Upon
completing the stain, Gram positive bacteria
appear purple and Gram negative bacteria appear
pink. Gram positive cell walls have a simpler
structure than Gram negative cell walls. Also
note the shapes of bacteria represented here.
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General Structure

• Nearly all prokaryotes have cell walls
• Bacteria have one major chromosome and rings of
  DNA called plasmids.
• Ribosomes are present to help in protein
  formation.
• Many disease causing bacteria have a thick outer
  slime capsule for protection.
• Many bacteria have small hair-like pili to attach
  to other cells.

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Bacterial Cell Structure

• The CELLS ALIVE site will teach you about
  bacterial cell structure. Click on the cell parts
  to learn more about each.

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Bacterial Motility
A motile E. coli propels itself from place to
place by rotating its flagella. To move
forward,the flagella rotate counterclockwise and
the organism "swims". But when flagellar rotation
abruptly changes to clockwise, the bacterium
"tumbles" in place and seems incapable of going
anywhere. Then the bacterium begins swimming
again in some new, random direction. Swimming is
more frequent as the bacterium approaches a
chemoattractant (food). Tumbling, hence
direction change, is more frequent as the
bacterium moves away from the chemoattractant. So
it is a complex combination of swimming and
tumbling that keeps them in areas of higher food
concentrations.
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Bacterial Reproduction

• Prokaryotes reproduce asexually by binary fission
  thus making new DNA almost continually .
• They can exchange genetic material in three ways
  transformation where genes are taken up from the
  surrounding environment, conjugation where genes
  are transferred from cell to cell and
  transduction where genes are transferred between
  prokaryotes by viruses.

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Bacterial Population Growth
Click on the Cells Alive! icon and when you reach
that page scroll down to DIVIDING BACTERIA. On
viewing the dividing bacteria take note of the
FOUR stages of the population growth curve.
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Bacterial Nutrition

• Photoautotrophs use the suns energy and
  manufacture sugars.
• Chemoautotrophs need only carbon dioxide to
  obtain energy from inorganic substances.

• Photoheterotrophs are unique and use light to
  generate energy but must obtain but must obtain
  carbon in organic forms.
• Chemoheterotrophs use organic molecules such as
  sugar for energy.

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Aerobic vs Anaerobic

• Obligate aerobes must live where there is oxygen
  present.

• Obligate anaerobes must live where there is no
  oxygen. They get there energy through
  fermentation.
• Facultative anaerobes can live where there is
  oxygen or no oxygen.

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Not all bacteria are bad!!

• Many bacteria aid in the decomposition dead
  organisms and waste.
• Bacteria control the nitrogen cycle.
• Bacteria is used to make cheese and yogurt.
• Bacteria can be used to make antibiotics.
• Bacteria are used to make sauerkraut.
• Bacteria are used to clean up oil spills.
• Bacteria are very useful in genetic engineering.

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Food Bourne Bacteria Can Harm You
Some of our more notorious food bourne bacteria
are botulinum, salmonella, staphylococcus and E.
coli. Clicking the icon above will lead you to a
site with information on these bacteria.
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Methods of Food Preservation

• Freezing
• Refrigeration
• Pasteruization
• Canning
• Salting
• Lactic acid (sauerkraut)
• Vinegar