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2.1 The Prokaryotes
Eubacteria and Archaea
Characteristics
• One-celled• Lack membrane-bound organelles• 1m long
Diagram
• Plasmid (small loop of DNA)• Capsule (protection)• Flagellum (locomotion)• Pilli (attachment)
Habitat
lives anywhere…• Inside your body• Outside your body• Water• Soil• Hot springs• Ice
Prevalence
• 10 000 types• < 1% possible species
Roles
• Pathogens (cause disease)• Decomposers• Producers• Mutualistic roles (human intestines making
vitamins K and B12)• Commercial uses (yogurt, cheese, soy sauce)• Antibiotics• Geochemical cycles (N cycle)
6 Major GroupsGroup Key Features
Proteobacteria(Purple bacteria)
Photosynthetic Nitrogen-fixingDisease-causing
Green bacteria PhotosyntheticSalt water/hot springs
Cyanobacteria(blue-green algae)
PhotosyntheticAquatic producers/nitrogen fixers
Gram-positive bacteria Disease-causingFood productionLost cell wall, smallest
Spirochetes Flagellum, cork-screw motionDisease-causing, digests wood
Chlamydias ParasiticDisease-causing
Shapes
• Coccus (round)• Bacillus (rod-shaped)• Spirillum (spiral-shaped)
• Diplo-…found in pairs• Staphylo-…found in clumps• Strepto-…found in strings
Shapes
• Name these:
Answersdiplococcus, staphylococcus streptococcus
Metabolism
• Autotrophic or heterotrophic• Obligate aerobes…need O2
• Facultative aerobes…can switch to anaerobic fermentation in the absence of O2
• Obligate anaerobes…need zero O2
Reproduction
• Binary Fission
Conjugation
Transformation
• Cells pick up a loose fragment of DNA from its surroundings.
Horizontal Gene Transfer
• new DNA comes from a different species.
Endospore
Highly resistant structure forms around chromosome when cell is under stress.
Diseases
• Cholera• Diphtheria• Lyme disease• Pertussis• Scarlet fever• Tetanus• E. coli
Antibiotics
• Bacteria adapt and become resistant
ArchaeaSubgroup Key features
Methanogens Low oxygen environmentsConvert chemicals into methaneSwamps, lakes, marshes, sewage, digestive tracts
Halophiles Salt-lovingDead Sea, preserved foodsAerobic, organic food, some use light
Extreme thermophiles Hot places, 70°C to 90°CHotsprings, hydrothermal vents
Psychrophiles Cold places -10°C to -20°CAntarctic and Artic oceans