2.1 The Prokaryotes Eubacteria and Archaea. Characteristics

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