Note Sheet 15

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Note Sheet 15 Bacteria Part 1 2
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What are bacteria?

• Bacteria single-celled organisms that do not
  have a nucleus
• A bacteria organism is one single prokaryotic
  cell thats the whole organism
• A bacterias only goal is to stay alive and make
  more bacteria
• Bacteria are the smallest living things and they
  cover nearly every centimeter of the Earth

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What is the structure of a bacteria cell?

• Most bacteria have the following structures a
  cell wall, a cell membrane, cytoplasm, DNA, and
  ribosomes

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What are the 3 main types of bacteria?
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What are the 3 main types of bacteria?

• Bacteria are identified by one of 3 shapes
• Bacilli rod-shaped bacteria (singular is
  bacillus)

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Color-enhanced scanning electron micrograph
showing Salmonella typhimurium (red) invading
cultured human cells
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What are the 3 main types of bacteria?

• Bacteria are identified by one of 3 shapes
• Cocci spherical-shaped (like a ball) bacteria
  (singular is coccus)

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methicillin-resistant Staphylococcus aureus (MRSA)
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What are the 3 main types of bacteria?

• Bacteria are identified by one of 3 shapes
• Spirilla spiral-shaped bacteria (singluar is
  spirillum)

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Do all bacteria make you sick?

• NO Bacteria are everywhere in nature, but only
  a few cause disease
• Many bacteria actually live inside of you and
  help you in different ways

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Escherichia coli in the human intestines

• E. coli normally colonizes an infant's intestines
  within 40 hours of birth, arriving with food or
  water or with the individuals handling the child
• Harmless strains of E. coli benefit the host by
  producing vitamin K (necessary for blood
  coagulation)
• They also prevent harmful bacteria from becoming
  established in the intestine

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What causes disease? - Germ Theory of Disease

• The germ theory of disease, also called the
  pathogenic theory of medicine, is a theory that
  proposes that microorganisms are the cause of
  many diseases
• Although highly controversial when first
  proposed, it is now a cornerstone of modern
  medicine and clinical microbiology, leading to
  such important innovations as antibiotics and
  hygienic practices

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How do bacteria make you sick?

• Some bacteria live in your body tissues
  disrupting their function symptoms are
  generally caused by the bodys defenses
• EX. The bacteria that causes tuberculosis
  colonize lung tissue disrupting lung function
• Some bacteria release poisons that harm the body
• EX. Tetanus is caused by a neurotoxin produced by
  Clostridium tetani bacteria

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Muscular spasms in a patient suffering from
tetanus. Painting by Sir Charles Bell, 1809.
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The discovery of antibiotics

• In 1928, Alexander Fleming was investigating
  staphylococci.
• In August 1928, Fleming went on vacation with his
  family. Before leaving he had stacked all his
  cultures of staphylococci on a bench in a corner
  of his laboratory.
• On returning, Fleming noticed that one that the
  colonies of staphylococci culture was
  contaminated with a fungus, and bacteria that had
  immediately surrounded it had been destroyed
• The fungus was from a group of fungi called
  Penicillum, and he called the bacteria-killing
  substance it produced penicillin

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Discovery of Penicillin
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How do bacteria make you sick?

• Antibiotics Substances that block the growth
  and reproduction of bacteria
• One of the major reasons for the increase in life
  expectancy over the last 100 years is the use of
  antibiotics to cure bacterial infections

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A test to see if a specific antibiotic will
affect a strain of staph bacteria
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Antibiotic Resistance Too much of a good thing?

• Many bacteria have developed resistance to
  certain antibiotics
• The more we use antibiotics, the more we risk the
  development of resistant bacteria strains
• Antibiotics are frequently prescribed
  unnecessarily, and taken irresponsibly
• Antibiotics are used extensively in agriculture
• In some cases, bacteria can be resistant to more
  than one type of antibiotic
• Resistance is determined by genes, and can be
  transferred from one bacteria to another via
  transformation or transduction
• Antibiotic resistance poses a significant problem
  for human health now and in the future

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Bacteria Part 2
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How do bacteria reproduce?

• Binary Fission process where a bacteria cell
  grows to double its normal size, copies its DNA,
  and divides into 2 identical cells
• Some bacteria can divide as often as every 20
  minutes

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How do bacteria get energy?

• Like you, most bacteria get energy by breaking
  down sugar
• Bacteria dont have mitochondria, so they dont
  perform respiration exactly the same way that
  eukaryotic cells do
• Glycolysis and fermentation the process where
  glucose is broken down into either lactic acid or
  alcohol/CO2 releasing 2 ATPs of energy
• Other bacteria have light-absorbing pigments and
  can make their own food in a process similar to
  photosynthesis

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How do humans control bad bacteria?

• Sterilization process of destroying bacteria
  using great heat or chemicals
• Most bacteria cannot survive high temperatures
  for a long time

• Cooking food to high enough temperature kills
  bacteria
• Foods can be preserved for a long time by killing
  all the bacteria with heat and then placing the
  foods into sterile glass jars or cans

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Canning Tomatoes250 lbs of tomatoes 10-12
hours 45 to 50 quarts of crushed tomatoes
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How do humans control bad bacteria?

• Bacteria grows more slowly at low temperatures,
  so refrigeration and freezing keeps food longer
• Salt and vinegar prevent the growth of bacteria
  as well

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Impact of Refrigeration

• The refrigerator allows the modern family to keep
  food fresh for much longer than before. This
  allows a vastly more varied diet and improved
  health resulting from improved nutrition. Dairy
  products, meats, fish, poultry and vegetables can
  be kept refrigerated in the same space within the
  kitchen.
• The refrigerator lets people eat more salads,
  fresh fruits and vegetables, without having to
  own a garden or an orchard.
• Exotic foodstuffs from far-off countries that
  have been imported by means of refrigeration can
  be enjoyed in the home because of domestic
  refrigeration.
• Freezers allow households to buy food in bulk it
  can be eaten at leisure, and bulk purchase saves
  money. Ice cream, a popular commodity of the 20th
  century, could previously only be obtained by
  traveling long distances to where the product was
  made fresh, and had to be eaten on the spot.

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Making Pickles

• 6 Kirby cucumbers, cleaned, stemmed and halved,
  lengthwise1/2 cup of white vinegar2 tablespoons
  of salt1 tablespoon of black peppercorns1
  tablespoon of coriander seeds3 cloves of garlic,
  minced1/2 cup of fresh dill
• Place salt, peppercorns, coriander seeds, garlic
  and dill in a sterilized 1-quart Mason jar
• Layer sliced cucumbers in jar, leaving 1/2 inch
  at the top
• Pour in vinegar
• Fill jar with water, seal with lid and shake for
  about a minute Refrigerate for six days, shaking
  daily

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How do humans control bad bacteria?

• Bacteria need a way into an organism to infect
  that organism

• Hand-washing prevents bacteria from getting in
  the mouth
• Nose hair and mucus prevent bacteria from getting
  into the airways through the nose
• Keeping cuts clean and bandaged prevents bacteria
  from entering the bloodstream