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2.4 Bacteria

2.4 Bacteria. p. 108-112. Prior knowledge. What do you already know about bacteria? Tell a partner What do you want to know about bacteria? -tell a partner. Characteristics of all bacteria. All are unicellular All are prokaryotic (lack membrane bound organelles, no organized nucleus)

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2.4 Bacteria

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  1. 2.4 Bacteria p. 108-112

  2. Prior knowledge • What do you already know about bacteria? • Tell a partner What do you want to know about bacteria? -tell a partner

  3. Characteristics of all bacteria • All are unicellular • All are prokaryotic (lack membrane bound organelles, no organized nucleus) • Usually have a single chromosome in form of DNA loop called plasmid • Cells reproduce asexually by binary fission • Cells thrive only in moist environments and become inactive in dry environment

  4. Eukaryotic vs Prokaryotic Cells • Which kingdoms have eukaryotic cells? • Plants, animals, fungi and protists • Which kingdoms have prokarytic cells? • Bacterial kingdoms: Eubacteria and Archaebacteria

  5. Chart comparing prokaryotes and eukaryotes Revised from Table 1 on p. 108 in Nelson Biology 11 Textbook

  6. Archaebacteria -name means “ancient” or “primitive” bacteria -thought to be first living organisms on Earth -live in extreme environments -three groups of Archaebacteria: thermophiles, methanogens and halophiles

  7. Group of Archaebacteria: Thermophiles • Thermophiles means “heat-loving” • As name suggests, these organisms live in extremely hot environments

  8. Video showing thermophiles • http://www.youtube.com/watch?v=4LoiInUoRMQ&feature=fvw

  9. Methanogens • this group grows on carbon dioxide and hydrogen gas to produce methane • they live in environments such as volcanic deep-sea vents and mammals’ intestine • they are used to help digest sewage and oil spills; the methane they produce can be used as an alternative fuel source

  10. Halophiles • literally means “salt-loving” • live in extremely saline (salty) environments, such as salt flats and evaporation ponds (give these areas purplish-red colour) • used in cancer research

  11. Eubacteria • the majority of bacteria belong to the kingdom Eubacteria • bacteria within the kingdom are classified according to the following characteristics: • Composition of cell wall • Shape • Configuration • Type of respiration • Type of nutrition

  12. Characteristics of bacteria: cell wall composition • Can be gram-positive or gram-negative • gram-positive bacteria contain more peptidoglycan in their walls • A stain called crystal violet dye can be used to tell types apart: gram-positive will keep purple colour, gram-negative will appear pinkish-red

  13. Characteristics of bacteria: shape • 3 shapes: • Rod-shaped (bacillus, bacilli) • Spiral-shaped (spirillum, spirilla) • Spherical-shaped (coccus, cocci)

  14. Characteristics of bacteria: configuration • Bacteria form pairs, cluster colonies or chains of cells

  15. Characteristics of bacteria: type of respiration • Some bacteria are aerobic and therefore, must have oxygen to survive • Ex. Those that cause tuberculosis • Some bacteria are anaerobic and can only grow without oxygen • Ex. Those that cause tetanus • Many bacteria can grow with or without oxygen • Ex. E. coli

  16. Characteristics of bacteria: type of nutrition • Can be autotrophs • Chemosynthetic (making food by using chemical reactions) or photosynthetic (making food by using light energy) • Most are heterotrophs • They obtain energy by feeding on dead or decaying matter, or as parasites feeding on living tissue

  17. Reproduction and Growth of Eubacteria and Archaebacteria • Most bacteria reproduce asexually by binary fission -single strand of DNA replicates, identical genetic info gets transferred to each cell, and the cell is divided into two identical bacteria.

  18. More on reproduction and growth of bacteria • Some bacteria (but not many) use a form of sexual reproduction called conjugation. • Conjugation involves transfer of genetic material from donor to recipient via a sex pilus

  19. Bacterial growth: endospores • Endospores are dormant or resting cells formed during unfavourable environmental conditions • An endospore is a thickened cell wall that forms around the genetic material and cytoplasm

  20. Video on bacteria • http://www.youtube.com/watch?v=N-EYTtxsL8g

  21. Questions to assess your understanding • What are two kingdoms that contain bacteria? • Which kingdoms contain prokaryotes? • Which kingdoms contain eukaryotes?

  22. More questions • Name 3 characteristics of all bacteria. • What are three groups of Archaebacteria? • In which type of environment does each group of Archaebacteria live? • How are Eubacteria classified? • What are the 3 basic shapes of bacteria? • What are the types of nutrition used by bacteria?

  23. More questions • What is the name for asexual reproduction carried out by bacteria? • What is the name of sexual reproduction carried out by bacteria? • What is the purpose of endospores?

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