Chapt'24

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Chapt.24

• BACTERIA

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I. Bacteria

• microscopic prokaryotes
• have existed for 3.5 billion yrs.
• Found in every environment on earth
• Bacteria on pin

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II. 2 kingdoms based on ribosomal RNA sequences

• A. Archaebacteria (more ancient)
• 1. Cell walls contain unusual lipids and
  introns are found in DNA
• 2. Cell walls do NOT have peptidoglycan

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3. Types of Archaebacteria a.
Methanogens 1) can change H2 and CO2 into
methane gas 2) can only live in anaerobic
environments (found in swamps, sewage and
intestinal tracts)
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b. Extreme halophiles 1) LOVE salt! 2)
Use the salt to generate ATP 3) Found in the
Dead Sea and Great Salt Lake c.
Thermoacidophiles 1) LOVE high acidity and
temps! 2) Found in hot springs and
volcanic vents
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B. Eubacteria (true bacteria a.k.a.
germs) 1. Shapes a) Coccus (pl. - cocci) -
round
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b) Bacillus (pl. - bacilli) - rod-shaped
Ex. - E. coli
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c) Spirillum (pl. - spirilla) - spiral
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2. Types a) Diplo- (prefix meaning 2) b)
Strepto- (prefix meaning chains) c) Staphlo-
(prefix meaning clusters)
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Tuberculosis bacillus
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Staph infection
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Streptococcus A
Flesh eating bacteria
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3. Gram Stain a) Gram-positive- thicker layer
of peptidoglycan in cell wall will be
purple b) Gram-negative- thinner layer of
peptidoglycan outer membrane will be
pink
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Some Phyla of Eubacteria (Table 24-1 pg. 470)
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4. Eubacteria Phyla a) Cyanobacteria 1)
photosynthetic 2) Used to be classified with
algae! a) moved b/c they do NOT have
chloroplasts or nucleus 3) Encased in a
jellylike substance 4) Form heterocysts 5)
eutrophication/population bloom
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b) Spirochetes 1) gram-negative and
spiral 2) aerobic or anaerobic 3) move like
a cork-screw 4) can be parasitic a) ex
Treponema pallidum (syphilis) c)
Gram-Positive Bacteria 1) actinomycetes grow
in soil and produce antibiotics 2) ex
Strepococci, Lactobacilli
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d) Proteobacteria 1) Enteric bacteria-
gram-negative, heterotrophic, and inhabit
intestinal tracts a) ex E. coli
Salmonella 2) Chemoautotrophs- oxidize
chemicals to make food a) ex
nitrogen-fixing bacteria like Rhizobium
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III. Bacterial structure

• A. Cell wall
• eubacterial cell walls made of peptidoglycan
• archaebacterial cell walls contain other
  compounds

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B. Cell membrane

• made of lipid bilayer
• cell respiration takes place in cell membrane
  (no mitochondria)
• photosynthetic bacterial membranes have internal
  foldings called thylakoids (homologous to those
  found in chloroplasts)

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C. Cytoplasm

• bacteria have no organelles
• made up of a thick solution of ribosomes DNA
• bacterial DNA is arranged in a single,
  closed-loop type chromosome
• some bacteria have plasmids (self-replicating
  loops of DNA)

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D. Capsules

• outer covering produced by some bacteria
• made of polysaccharides which cling to cell
  surfaces
• protects bacteria from drying or harsh chemicals
• protects invading bacteria from hosts white
  blood cells
• glycocalyx
• fuzzy capsule made of sticky sugars
• lets bacteria attach to host cells

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E. Pili

• short, hairlike structures made of protein in
  some bacterial species
• help bacteria adhere to host cells
• transfer DNA or RNA from one bacterium to
  another

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Pilli
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F. Endospores

• dormant structure formed by some bacteria when
  placed in harsh conditions (ex. heat, dryness,
  chemicals, radiation)
• thick outer covering which surrounds DNA
• survives even if original cell is destroyed
• opens when conditions become favorable again -
  bacterium begins to reproduce
• found in Bacillus Clostridium

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Endospores
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Anthrax endospores
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G. Structures for movement

• flagella (s. - flagellum)
• propel bacteria in a tumble-like movement
• some bacteria have 2 or more
• protein tails
• some bacteria produce slime layer glide
  through it
• some spiral-shaped bacteria have flexible cell
  walls containing filaments that move cell like a
  corkscrew

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Flagella examples
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IV. Nutrition and Growth A. Autotrophic -
obtain energy from light or minerals B.
Heterotrophic - use organic matter for energy
1. Saprophytes- feed on dead and decaying
material
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C. O2 requirements 1. obligate anaerobes-
cannot survive in O2 a) ex. Clostridium
tetanus 2. facultative anaerobes- live with or
w/out O2 a) ex. E. coli 3. obligate aerobes-
cannot survive w/out O2 a) ex. Mycobacterium
tuberculosis
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V. Bacteria and Disease
A. Pathology 1.Scientific study of
disease 2. Bacteria cause disease by producing
toxins a. Exotoxins-made of protein
produced by Gram-positive bacteria
secreted into environment 1) Ex Tetanus
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• b. Endotoxins- made of lipids and carbs produced
  by Gram-negative bacteria not released until
  bacteria die
• 1) Cause fever, body aches, weakness, damage
  vessels in circulatory system
• 3. Can also cause disease by destroying body
  tissue
• a. Attach to host and secrete digestive enzymes
• b. Ex some Streptococci bacteria

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VI. Antibiotics -Drugs that combat with bacteria
by interfering with various cellular
functions -Ex -Penicillin- interferes with
cell wall synthesis -Tetracycline-
interferes with protein synthesis -Sulfa
drugs- man-made interferes with cell metabolism
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VII. Useful Bacteria
-Break down remains of organic matter in plant
and animal waste in sewage treatment -Producing
and processing food Ex Ferment lactose in milk
to produce buttermilk, yogurt, and sour
cream -Produce sauerkraut and pickles -Used
in industrial chemical production Ex petroleum
recovery, insecticides
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VIII. 3 ways of genetic recombination
A. Transformation 1. bacterium takes in DNA
from external environment 2. new DNA is
substituted for DNA fragment in bacterial
chromosome
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B. Conjugation 1. 2 bacteria join together to
exchange genetic material 2. bacterium w/ a
specialized pilus plasmid forms a conjugation
bridge w/ bacterium w/out pilus plasmid 3.
plasmid passes through bridge to acceptor
bacterium
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Conjugatingbacteria
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C. Transduction 1. virus obtains DNA fragment
from host bacterium 2. when viruses replicate,
they make copies of host DNA 3. new viruses
carry host DNA to a new bacterium which
expresses it