Download Small, smaller, smallest

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Small, smaller, smallest
• Science uses the metric system
– Each unit differs by 1000x (103)
– Length: meter, millimeter, micrometer, nanometer
– Molecules are too small to talk about length
• Units are molecular weight: grams/mol
• i.e. how much do 6.023 x 1023 molecules weigh?
• What sizes are we talking about?
– We can see things about 0.1 mm (100 µm)
– Bacteria are generally 1 – 5 µm (0.0001 mm)
– We need special microscopes to see smaller than that.
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Something can’t be smaller than
the parts it is made of!
Sand is used to make bricks, and bricks are assembled to
make a house. A house can’t be smaller than a brick; a
brick can’t be smaller than grains of sand.
Likewise, small molecules are combined to make polymers
and polymers are used to make cells.
cic.nist.gov/lipman/sciviz/scan/jun24_ptC1a.jpg; www.littleitalymd.com/images/BrickL
www.kevscartoons.com/images/illustration/chil... ayer.gif
In the world of small, what’s big?
• Cells of eukaryotic organisms are big
– Nerve cells can be quite long
– White blood cells are about 10 µm in diameter
– An amoeba may be around 20 µm
• Prokaryotes and cell organelles are smaller
– E. coli is about 1 µm long
– A mitochondrion is about the same size
• Particles are smaller
– Viruses range from 20 to 200 nm (0.02 – 0.2 µm)
– Ribosomes, found inside cells, are about 20 nm
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In the world of small, what’s smaller?
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• Ribosomes, viruses, cell walls are made of polymers
– Ribosomes and viruses are combinations of proteins and
nucleic acids
– Cell walls are made of large molecules like
peptidoglycan and lipopolysaccharide
• Polymers are larger than the monomers they are
made of
– Proteins range from 10,000 to 500,000 MW
– Bacterial DNA is over 1 mm long! (but very skinny)
– Polysaccharides can be > 100,000 MW (grams/mol)
In the world of small, what’s smallest?
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• These are all small molecules ranging from 18 g/mol
to 1,000 g/mol
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Water, oxygen gas, nitrogen gas
Sugars (glucose, sucrose, etc.)
Amino acids
Nucleotides
Fatty acids, cholesterol, (even phospholipids aren’t big)
Organic acids found in metabolism
Vitamins
Antibiotics and most other drugs
History of microbiology
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• Ancient times
– People understood contagion
• Exposure to sick people resulted in disease
• Something was being spread (didn’t know what)
• Lepers: had to wear a bell and live away from town
– People understood immunity
• Chinese exposed themselves to mild smallpox virus to
build up protection against the often fatal major
smallpox virus.
Can’t have a science of microbiology if
you don’t know the microbes are there
• Microbiology as a biological science
– Robert Hooke, 1665, discovery of cells
– Antony van Leeuwenhoek, father of microbiology
• Dutch amateur lens grinder
• First person to see microbes, late 1600s
– Mid 1800s, microbes taken more seriously and studied
using the scientific method
micro.magnet.fsu.edu/.../ introduction.html
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History: the Golden Age
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• From about 1850 to start of 20th century
– Pasteur lays to rest the idea of spontaneous generation
– Pasteur shows fermentation associated with life
• Prevents unwanted fermentation by Pasteurization
• Saves the French wine industry
• Saves the French silkworm industry
– Germ theory of disease: sicknesses caused by microbes
– Robert Koch: Germany
• lab techniques like agar, staining
• Koch’s postulates: how to link a microbe w/ a disease.
More history
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• Semmelweis and handwashing (1848)
– Medical students vs. midwives: students working on
cadavers killed 20x more new mothers than midwives.
– Handwashing in chlorinated water greatly reduced
incidence of fatal infection.
• Lister and aseptic surgery (late 1800s)
– Spraying phenol on, over patients, greatly reduced rate of
infections following surgery
• Ehrlich and antimicrobials
– Differential staining of bacteria instilled idea of
chemicals that would attack bacteria, not host.
– Minor success, but beginning of antimicrobial therapy.
20th
Century Microbiology
• Molecular biology
• Use of microbes as model systems for study
• Study of DNA, proteins synthesis
• Tools and processes for recombinant DNA
• Applied microbiology
• Food industry
• Water and sewage treatment
• Bioremediation
• Medicine
– Emerging diseases; antibiotic resistance
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