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Bacterial Growth and Reproduction

Bacterial Growth and Reproduction

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Bacterial Growth and Reproduction

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  1. Bacterial Growth and Reproduction

  2. If bacteria are capable of dividing every 20 minutes, and if environmental conditions are favorable, how many would we have after just 48 hours? Rate of Bacterial Growth and Reproduction

  3. If bacteria are capable of dividing every 20 minutes, and if environmental conditions are favorable, how many would we have after just 48 hours? • 4000 times the mass of the Earth! Rate of Bacterial Growth and Reproduction

  4. Thankfully this situation does not happen in real life. • What are two main factors that serve to keep the reproduction of bacteria in check? • 1. The availability of food. • 2. The production of waste products. Rate of Bacterial Growth and Reproduction

  5. Binary Fission: • Bacteria divide by binary fission when they (approximately) double in size. • Their surface area to volume ratio gets to be too low. Methods of Reproduction

  6. Binary fission is a form of asexual reproduction because: • It involves no recombination of genetic material, so daughter cells are clones of parent cells. • There is one parent only, no fusion of gametes to produce a daughter cell. Methods of Reproduction

  7. (Pinching) Methods of Reproduction

  8. Conjugation: • Some bacteria reproduce by a form of sexual reproduction called conjugation. • After conjugation is complete the bacteria will divide by binary fission as usual. • During conjugation: • Bacteria transfer genetic material from one cell to another along a protein bridge. • Donor  Recipient (F+  F-) Methods of Reproduction

  9. Methods of Reproduction

  10. Spore Formation: • This involves the formation of endospores. • This can happen when growth or environmental conditions become unfavorable. • An endospore has a thick internal wall that encloses the DNA and part of the cytoplasm. Methods of Reproduction

  11. Spore formation helps the species survive, but it is not actually a form of reproduction because the endospore does not reproduce, it just remains dormant for a certain period then opens up and the bacteria begin to grow again. • No reproduction takes place. Methods of Reproduction

  12. Foods: • Beverages, cheese, yogurt, buttermilk, sour cream, pickles, vinegar, sauerkraut… Importance of Bacteria

  13. Industrial Uses: • Clean up oil spills, mining of minerals from the ground, remove wastes and poisons from water… Importance of Bacteria

  14. A symbiotic relationship is one in which two organisms live together and one or both benefit from the partnership. • Bacteria and humans have a “win-win” symbiotic relationship: • With E. coli? Importance of Bacteria

  15. The E. coli bacteria live in the colon. • They are provided with warmth, shelter and food from the large intestine of humans. • Humans get the production of vitamins and the breakdown of waste material from the bacteria. Importance of Bacteria

  16. Cattle also have a symbiotic relationship with bacteria. • They do no produce the enzymes (neither do we) necessary to break down cellulose (the main carbohydrate) in grass and hay. • Bacteria in their intestines can make these enzymes allowing that digestion of the food! Importance of Bacteria

  17. Bacteria are essential to life on Earth. • Without them, plants and animals would use up all of the essential minerals needed for life. • Bacteria break down, decompose and recycle dead material and return usable minerals back into the ground and enrich the soil. Bacteria in the Environment

  18. Many bacteria are heterotrophic saprophytes: • These are bacteria that do not make their own food. • They get their nutrition from the molecules of once living things (a.k.a. dead organisms). Bacteria in the Environment

  19. So far we have seen a few different ways to identify different bacteria: • 1. Carbohydrates in cell walls: Gram+ = 1 layer, Gram- = 2 layers • 2. Shape: round, rod, spiral • 3. Grouping: chains (strepto), clusters (staphylo) • 4. Flagella: none, 1, 2, etc. • 5. Colony or colour on a streak plate Energy in Bacteria

  20. We can also identify bacteria by the lifestyle they lead: • Today we will look at how they obtain food. Energy in Bacteria

  21. Phototrophic Autotrophs: • They use photosynthesis to make food from sunlight. • i.e. blue/green algae or cyanobacteria Food for Bacteria: Autotrophs

  22. ChemotrophicAutotrophs: • They make food from inorganic molecules like sulfur, iron, oxygen and ammonia. • They live in harsh environments. • i.e. archaebacteria Food for Bacteria: Autotrophs

  23. Phototrophic Heterotrophs: • They use sunlight for energy, but they also need organic molecules for nutrition. Food for Bacteria: Heterotrophs

  24. ChemotrophicHeterotrophs: • They get their food from obtaining organic molecules then breaking them down and absorbing them. • Things that do this: • Salmonella, humans, animals… • They compete with us for food, but produce toxins that give us food poisoning. Food for Bacteria: Heterotrophs

  25. There are two ways that bacteria can get the energy out of the food: • Respiration • Fermentation Energy from Food

  26. Respiration • Uses oxygen to get energy from food. • This is the more efficient way compared to anaerobic. • Obligate Aerobes • These are strictly aerobes • They need to live in O2 • Most eubacteria fit here Energy from Food

  27. Fermentation • They get energy from food without using oxygen. • Obligate Anaerobes • They are strictly anaerobes • They must live in the absence of oxygen • They are poisoned by oxygen • They live in the soil or deep in the Earth • Ex. Botulism, tetanus and most arachaebacteria Energy from Food

  28. There are also Facultative Anaerobes: • They do not need air, but they can use it, and most actually prefer it. • They are not poisoned by oxygen • Ex. E. coli, Listeria Energy from Food

  29. Energy from Food