Download Chapter 28: Prokaryotes

Chapter 28: Prokaryotes
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Prokaryotes are cellular and therefore are living organisms.
Significance: oldest, simplest, and most abundant form of life
important for ecology (photosynthesis, recycling,
symbiotic relationships, nitrogen fixing, and
bioremediation)
can cause disease by either:
(a) destroying cells or (b) producing toxins
May be treated with antibiotics (Ex: penicillin)
Classification into two groups: Archaea and Bacteria (or
Eubacteria)
Basic cell shapes:
bacillus (rod-shaped)
coccus (spherical)
spirillum (spiral or helical)
*** Gram stain can be used to help identify bacteria and then also
help with the choice of antibiotics.
Size: about 1 micron (micron = 0.000001 m)
Structure of bacteria: See Fig. 28.3 (p. 542)
basic structures: cell wall
plasma membrane
cytoplasm containing ribosomes
DNA chromosome (circular) in a nucleoid
some also have: gelatinous capsule
flagella for movement
pili for attaching to surfaces
plasmids - extra pieces of DNA
Fig. 28.11.b
Presence of F plasmid (conjugative plasmid) allows conjugation in prokaryotes
Fig. 28.14(left)
Fig. 28.14(right)
Generalized transduction – Viruses pack host DNA and transfer it
upon subsequent infection.
Specialized transduction is shown by phage exhibiting lysogenic
life cycle
Fig. 28.15
Natural transformation- One cell dies and releases its contents
into environment.
Prokaryotic metabolism
• Autotrophs or heterotrophs obtain carbon and
energy through light and chemical reactions
• Photoautotrophs carry out photosynthesis and obtain
carbon from carbon dioxide
• Chemolithoautotrophs obtain energy by oxidizing
inorganic substances
• Photoheterotrophs use light for energy but obtain
carbon from organic molecules
• Chemoheterotrophs obtain carbon and energy from
organic molecules
Bacterial Diseases
• Transfer sources – Mucus or saliva droplets,
contaminated food and water and insect vectors
• Causes Tuberculosis
• Tooth decay
• Helicobacter pylori causes ulcers
• Causes sexually transmitted diseases gonorrhea,
syphilis and chlamydia
• Gram-negative bacteria (pseudomonads) – plant
diseases
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