Bacteria and Archaea

1. Bacteria and Archaea Chapter 27

2. Types of Bacteria and Archaebacteria

3. Bacteria and Archaea • Diverse, abundant, and ubiquitous • Most of the microbes (microscopic organisms) are bacteria or archaea • Virtually all are unnamed and undescribed • The total number of individual bacteria and archaea alive today at ~5  1030 • As much carbon in these cells as there is in all of the plants on Earth

4. Bacteria and Archaea • Bacteria and Archaea form two of the three domains of the tree of life

5. Bacteria • Prokaryotic • Cell walls made of peptidoglycan • Plasma membranes • Distinct ribosomes • RNA polymerase • Can cause human disease

6. Archaebacteria • Prokaryotic and unicellular • Call walls made of polysaccharides • Unique plasma membranes • Ribosomes and RNA polymerase similar to those of eukaryotes • No Known to cause human disease

7. Extremophiles • Bacteria or archaea that live in high-salt, high-temperature, low-temperature, or high-pressure habitats • Archaea are abundant forms of life in hot springs at the bottom of the ocean • Water at 300°C emerges and mixes with 4°C seawater • Enzymes that function at low temperature or high temperature are of commercial use

8. Cyanobacteria • No free molecular oxygen existed for the first 2.3 billion years of Earth's history • Cyanobacteria, were the first organisms to perform oxygenic photosynthesis

9. Cyanobacteria • Responsible for a fundamental change in Earth’s atmosphere • From an atmosphere dominated by nitrogen gas and carbon dioxide to one dominated by nitrogen gas and oxygen • Certain species of cyanobacteria can fix nitrogen • Form close association with plant roots • Symbiotic relationship

10. Classification and Study of Bacteria

11. Studying Bacteria and Archaebacteria • Biologists use several research strategies to answer questions about these species • Nutrient enriched agar • Based on establishing a specific set of growing conditions per bacteria • Used to isolate new types of bacteria and archaea

14. Studying Bacteria and Archaebacteria • Direct sequencing - strategy for documenting the presence of bacteria and archaea that cannot be grown in culture and studied in the laboratory

16. Evaluating Molecular Phylogenies • A tree of life based on morphology had only two divisions: prokaryotes and eukaryotes

17. Evaluating Molecular Phylogenies • The tree of life based on ribosomal RNA sequences shows three domains—Archaea, Bacteria, and Eukarya—and is now accepted as correct • The first lineage to diverge from the common ancestor was the Bacteria • Archaea and Eukarya are more closely related to each other than to the Bacteria

18. Evaluating Molecular Phylogenies

19. Major Clades of Bacteria

20. Classifying Bacteria

21. Diversity of Bacteria • Bacteria and Archaea have diversified into hundreds of thousands of distinct species • Overall patterns and themes help biologists make sense of the diversity • The sizes, shapes, and motility of Bacteria and Archaea can vary greatly

22. Diversity of Bacteria and Archaea

24. Gram Staining • Gram staining distinguishes bacteria by the type of cell wall

26. Bacterial Reproduction • Bacteria and archaea reproduce by fission • Splitting of cells • Bacterial cells can transfer copies of plasmids – extra-nuclear loops of DNA • During conjugation, a copy of a plasmid moves from one cell to a recipient cell • Conjugation tube is a morphological trait that is unique to bacteria and archaea

27. F factor (plasmid) Male (donor) cell Bacterial chromosome F factor startsreplication andtransfer Plasmids Plasmid completestransfer andcircularizes Cell now male Conjugation

28. Metabolic Diversity • Bacteria and Archaea produce ATP in three ways: • Phototrophs can use light energy. ATP is produced by cellular respiration. • Organotrophs oxidize reduced organic molecules. ATP is produced by cellular respiration or fermentation

29. Metabolic Diversity • Lithotrophs oxidize inorganic molecules. ATP is produced by cellular respiration with the inorganic compound serving as the electron donor • Autotrophs manufacture their own carbon-containing compounds heterotrophs live by consuming them

31. Cellular Respiration Variation in Bacteria • In cellular respiration • a molecule with high potential energy serves as an electron donor and is oxidized • a molecule with low potential energy serves as a final electron acceptor and is reduced • The potential energy difference is converted into ATP • Bacteria and archaea can exploit a wide variety of electron donors and acceptors

32. Cellular Respiration Variation in Bacteria

33. Cellular Respiration Variation in Bacteria

34. Cellular Respiration Variation in Bacteria • Fermentation is a strategy for making ATP without using electron transport chains • No electron acceptor is used; redox reactions are internally balanced • Lactic acid fermentation • Alcoholic fermentation

35. Key Lineages of Bacteria and Archaea

36. Lineages of Bacteria • There are at least 14 major lineages (phyla) of bacteria • Spirochetes have a corkscrew shape and unusual flagella • Chlamydiales are spherical and very tiny • Live as parasites inside animal cells

37. Lineages of Bacteria • High-GC (guanine and cytosine) Gram-positive bacteria have various shapes • Many soil-dwelling species form mycelia (branched filaments)

38. Lineages of Bacteria • Cyanobacteria are autotrophic • Produce an abundance of oxygen and nitroge • Also produce many organic compounds, that feed other organisms in freshwater and marine environments

39. Lineages of Bacteria • Low-GC Gram-positive bacteria cause a variety of diseases including anthrax, botulism, tetanus, gangrene, and strep throat • Lactobacillus is used to make yogurt

40. Lineages of Bacteria • Proteobacteria cause Legionnaire’s disease, cholera, dysentery, and gonorrhea • Certain species can produce vinegars. Rhizobium can fix nitrogen

41. Archaea Lineages • Archaea live in virtually every habitat, including extreme environments • Crenarchaeota are the only life-forms present in certain extreme environments, such as high-pressure, very hot, very cold, or very acidic environments

42. Archaea Lineages • Euryarchaeota live in high-salt, high-pH, and low-pH environments • Include the methanogens, which contribute about 2 billion tons of methane to the atmosphere each year