Section 18.2 Summary – pages 484-495

1. Section 18.2 Summary – pages 484-495 Archaebacteria: The extremists • Three types: • Methanogens live in anoxic habitats (swamps, lake sediments, digestive tracts of some mammals) and produce methane. • Halophiles live in bodies of water with high concentrations of salt (like the Dead Sea). • Thermophiles live in hot springs and near deep ocean thermal vents

2. Section 18.2 Summary – pages 484-495 Eubacteria: The heterotrophs • Heterotrophic eubacteria live almost everywhere and use organic molecules as their food source. • Some are parasites • Some are saprophytes (feed on dead organisms or organic wastes).

3. Section 18.2 Summary – pages 484-495 Eubacteria: Photosynthetic autotrophs • Cyanobacteria – photosynthetic bacteria. • Found in ponds, streams,and damp areas on land. • Were formerly known as blue-green algae. Cyanobacteria

4. Section 18.2 Summary – pages 484-495 Eubacteria: Chemosynthetic autotrophs • Chemosynthetic bacteria do not obtain the energy they need to make food from sunlight. • Chemosynthesis - energy comes from inorganic compounds containing sulfur and nitrogen.

5. Section 18.2 Summary – pages 484-495 The structure of bacteria • Prokaryotic cells have ribosomes. • But their ribosomes are smaller than those of eukaryotes. • Bacteria have a single circular chromosome.

6. Section 18.2 Summary – pages 484-495 The structure of bacteria Ribosome Cytoplasm Chromosome Flagellum Cell Membrane Gelatin-like capsule Cell Wall

7. Section 18.2 Summary – pages 484-495 The structure of bacteria • Penicillin interferes with the ability of some bacteria to make cell walls. • When bacteria are exposed to penicillin, holes develop in their cell walls, water enters their cells, and they rupture and die.

8. Section 18.2 Summary – pages 484-495 Reproduction by binary fission • Bacteria reproduce asexually by binary fission.

9. Section 18.2 Summary – pages 484-495 Sexual reproduction • Conjugation – a form of sexual reproduction in some bacteria. • During conjugation one bacterium transfers plasmid DNA or all or part of its chromosome to another through a needle-like structure called a pillus.

10. Section 18.2 Summary – pages 484-495 Aerobic and Anaerobic Bacteria • Obligate aerobes require oxygen for respiration. • Obligate anaerobes are killed by exposure to oxygen. • Some bacteria (facultative aerobes) can live either with or without oxygen.

11. Section 18.2 Summary – pages 484-495 A survival mechanism • Some bacteria produce endospores under unfavorable environmental conditions. • Endospore –DNA and a little cytoplasm are encased by a tough outer covering. • Endospores are resistant to drying out, temperature extremes, and harsh chemicals.

12. Section 18.2 Summary – pages 484-495 A survival mechanism • As an endospore, the bacterium is dormant and does not reproduce. • When environmental conditions improve, the endospore germinates (begins to grow and reproduce.) • Some endospores have germinated after more than a million years in the resting state.

13. Section 18.2 Summary – pages 484-495 A survival mechanism • To kill endospores, items must be sterilized (high heat and pressure). • Endospores of Clostridium botulinum can germinate in improperly sterilized canned food. • The anaerobic C. botulinumgrow and produce a deadly toxin which causes botulism.

14. Section 18.2 Summary – pages 484-495 The Importance of Bacteria • Nitrogen fixation • Recycling of nutrients • Production of foods and medicines • Bacteria also inhabit your intestines and produce vitamins and enzymes that help digest food.

15. Section 18.2 Summary – pages 484-495 Bacteria cause disease Bacterial diseases harm people in two ways: Growth of bacteria can interfere with the normal function of body tissues. Bacteria can release a toxin that attacks the host’s cells directly. Example: strep throat (streptococcus)

16. Section 18.2 Summary – pages 484-495 Bacteria cause disease Diseases Caused by Bacteria Treatment Transmission Symptoms Disease Fever, sore throat, swollen neck glands Antibiotic Inhale or ingest through mouth Strep throat (Streptococcus) Antibiotic Inhale Fatigue, fever, night sweats, cough, weight loss, chest pain Tuberculosis Puncture wound Stiff jaw, muscle spasms, paralysis Tetanus Open and clean wound, antibiotic; give antitoxin Rash at site of bite, chills, body aches, joint swelling Antibiotic Lyme disease Bite of infected tick Remove and fill the destroyed area of tooth Bacteria in mouth Destruction of tooth enamel, toothache Dental cavities (caries) Vaccination to prevent, antibiotics Sore throat, fever, heart or breathing failure Inhale or close contact Diptheria