1. Prokaryotes and Viruses
7/6/2018 9:09 AM
Prokaryotes and Viruses
Chapters 23 and 24
2013
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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. prokaryotic , unicellular
2. cell wall
Living organisms have been categorized into three main groups based on ribosomal RNA analysis.

4. Archaea Different from bacteria Three groups
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.