Prokaryotes and Viruses

1. Prokaryotes and Viruses Chapters 23 and 24 2013

2. Prokaryotes • The most numerous organisms on earth • Earliest fossils 3.5 Billion years old • Lived before other life evolved. • Two major domains: Archaea and Bacteria

3. What are the traits of prokaryotes? • 1. • 2. • Living organisms have been categorized into three main groups based on ribosomal RNA analysis.

4. Archaea • Different from bacteria • Makeup of cell walls different– no peptidoglycan • Different lipids in cell membranes • DNA has introns • Three groups • Methanogens: convert hydrogen gas and carbon dioxide to methane. Anaerobic, many live in intestinal tract of cows and termites.

5. Halophiles: salt loving • Thermoacidophiles: acidic environments that are high in temperature.

6. Domain Bacteria • Most prokaryotes are bacteria • Three common shapes • Bacilli • Cocci • Spirilla They may occur in chains (streptococci) or clusters (staphylococci) Work with your shoulder partner to complete the “Classifying Bacteria : Shapes of Bacteria” worksheet.

7. Important Bacterial Groups • Proteobacteria: live symbiotically with other organisms Example: nitrogen-fixing Rhizobium • Gram-Positive Bacteria: many cause disease such as streptocaccus, others are helpful such as Lactobacilli which makes yogurt • Cyanobacteria: use photosynthesis but lack membrane-bound nucleus and chloroplasts. • Spirochetes: move by a corkscrew-like motion. • Chlamydia: gram-negative, coccoid pathogens live only inside animal cells.

8. Biology of Prokaryotes • Cell Wall: protective, different composition in Bacteria compared to Archaea • Cell Membrane and Cytoplasm: lipid bilayer but different between Archaea and Bacteria • Important metabolic functions occur on the membrane such as respiration. • In photosynthetic bacteria, the membrane folds like a thylakoid • DNA: a single closed loop of double-stranded DNA. Additional DNA maybe found in plasmids which are small, circular and self-replicating.

9. Capsules and Pili • Capsule is made of polysaccharides and protects the cell against drying or harsh chemicals, or in the case of pathogens, the hosts white blood cells. • Pili: short, hair-like protein structures on the surface. Help bacteria connect to each other and to surfaces such as the host cell.

10. Endospores: a thick-coated, resistant structure formed by some bacteria when environmental conditions aren’t favorable. • Can resist high temp., chemicals, radiation, drying and other environmental extremes. • This allows the bacteria’s DNA to survive for a long time.

11. Nutrition and Metabolism • Prokaryotes obtain nutrients either from nonliving environment or by utilizing the products or bodies of living organisms. • Heterotrophs obtain carbon from other organisms • Autotrophs obtain their carbon from CO2

12. Prokaryotic Habitats • Live in habitats based on their biochemical abilities • Obligate anaerobes: ? • Facultative anaerobes:? • Obligate aerobes:? • Prokaryotes have various temperature requirements for growth • Most bacterial species grow best at a pH of 6.5 to 7.5

13. Reproduction and Recombination • Prokaryotes usually reproduce by binary fission which is a form of asexual reproduction.

14. Prokaryotes can exchange pieces of DNA through recombination • Three ways: • Transformation: takes in NDA from its outside environment. • Conjugation: two prokaryotes bind together and one transfers DNA to the other. • Transduction: a virus obtains a small part of DNA from a host prokaryote which gets copied with the viral DNA

15. Bacteria and Humans • How can bacteria cause disease in humans? • Exotoxins: toxic substances that bacteria secrete into their environment. • Clostridium tetani= tetanus • Endotoxins: not released until the bacteria dies. • E. coli = fever, body aches, diarrhea, hemorrhage and weakness • By destroying body tissues by releasing enzymes.

16. Bacteria Microviewers • Complete the activity with both the helpful and harmful bacteria and the microviewers.