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CHAPTER 20 OUTLINE
VIRUSES AND BACTERIA
THE TRUE BACTERIA: Most ancient of organisms
TWO BACTERIAL KINGDOMS: Archaebacteria (ancient) and
Eubacteria (true)
 Prokaryotes (both): lack nuclear membrane, mitochondria, Golgi
apparatus, ER, lysosomes
 Divide by fission
SYSTEMATICS:
 Eubacterial evolution: no consensus…???
 See 20.7 diagram: Gram + and Gram - (react with Gram’s stain)
ANATOMY: see size chart overhead 20.8
 Size
 Cell Shape: should be review (look at pictures on p. 562)
 Cell Wall
 Different from plant cell walls (plant wall is made of
cellulose, eubacteria wall is made of murein
 Murein: polymer of polysaccharides cross linked with
amino acids( also called peptidoglycan)

 INTERESTING: Penicillin inhibits the formation of
exposed peptidoglycan, and therefore interferes with
reproduction of gram+ bacteria.
 Mycoplasmas
 Capsules:
 Endospores: mostly rod shaped form these resting cells.
HOW BACTERIA MOVE:
 Flagella UNLIKE eucaryotic cell flagella.
HOW BACTERIA REPRODUCE:
 Binary fission: 2 equal daughter cells essentially like the parent
cell.
 ENORMOUS reproductive potential
 Ie. division once every 20 minutes. This would result in
500,000 “offspring” in 6 hours…
 There is genetic variation…review chapter 10
a. Conjugation (DNA transferred from donor cells)
b. transformation (DNA from dead cells
c. transduction (DNA carried by viruses)
OBTAINING ENERGY AND RAW MATERIALS:
 most are heterotrophic (parasites/saprophytes)
 Many are aerobic, some anaerobic
 Obligate anaerobes:
 Facultative anaerobes
 Some perform both fermentation and the Krebs/Electron
Transport Chain, if oxygen is present.
 There are at least 10 other types of fermentation besides
lactic acid and alcoholic.
BACTERIAL PHOTOSYNTHESIS:
 Most are chemoheterotrophs
 Chemoautotrophs:
(in ch.40 we will discuss nitrifying bacteria in more depth)
 Photosynthetic bacteria: (photoheterotrophs),
 Example: Green and purple anaerobic photosynthetic
bacteria possess chromatophores, vesicles that contain
pigments/enzymes for the photosynthesis (only
photosystem I) Do NOT possess chlorophyll a
 Photoautotrophs:
 Example: Cyanobacteria: aerobic photosynthetic bacteria.
-cyanobacteria generate molecular oxygen as a by-product of
photosynthesis
-contain: phycocyanin (blue pigment).
-may contain: phycoerythrin (red pigment).
FIXING NITROGEN: cyanobacteria and other anaerobic bacteria
 Conversion of N2 into ammonia (NH3).
 LIMITED BY THE ENZYME, NITROGENASE, WHICH IS
INACTIVE IN PRESENCE OF OXYGEN…see below…
 HOW does cyanobacteria do it? They are oxygen-generating
photosynthesizers….
 Most are filamentous forms that produce heterocysts, where
the fixation takes place.
DISEASE CAUSING BACTERIA: many…STD, TB, tetanus…
 Can disease tissues, can interfere with normal functions of
organism, can produce toxins
 Exotoxins are produced by living bacterial cells.
BENEFICIAL BACTERIA: far outnumber harmful ones
 Ie. nitrogen fixing bacteria…vital to agriculture, decomposers,
human digestive system, industrial processes, food industry,
antibiotic production (read p. 572-573 for ideas)
ARCHAEBACTERIA:
Differ from eubacteria in a number of ways:
a. cell walls, if present have different chemical properties
b. lipids in their cell membranes are branched, not straight
c. “younger” kingdom than the eubacterial kingdom
Four groups: confined to EXTREME habitats
1. Methanogens
2. Halophiles
3. Sulfur Reducers:
4. Thermoacidophilic Bacteria