Bacterial Physiology and genetics

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Bacterial Physiology and genetics

  1. 1. <ul><li>Bacterial Physiology and Genetics </li></ul>
  2. 2. <ul><li>Understand the meaning of the growth. </li></ul><ul><li>Important factors for growth. </li></ul><ul><li>How genetic variation occur in bacteria? </li></ul>
  3. 3. <ul><li>Meaning of Bacterial physiology ? </li></ul><ul><li>The biochemical reactions that together enable bacteria to live, grow and reproduce. </li></ul>
  4. 4. Microbial Growth
  5. 5. Microbial Growth - refers to the number of cells <ul><li>Requirements for Growth </li></ul><ul><ul><li>Physical </li></ul></ul><ul><ul><li>Chemical </li></ul></ul>
  6. 6. Nutritional Requirements Physical Requirements Autotrophs Heterotrophs Organic and Inorganic substances
  7. 7. Physical Requirements <ul><li>Temperature </li></ul><ul><ul><li>psychrophiles (cold loving microbes ) </li></ul></ul><ul><ul><ul><li>range 0 0 C - 20 0 C </li></ul></ul></ul><ul><ul><li>mesophiles (moderate temp. loving microbes) </li></ul></ul><ul><ul><ul><li>range 25 0 C - 40 0 C </li></ul></ul></ul><ul><ul><li>thermophiles (heat loving microbes) </li></ul></ul><ul><ul><ul><li>range 55 0 C - 88 0 C </li></ul></ul></ul>
  8. 8. pH <ul><li>Most bacteria grow between pH 7.2 - pH 7.4 </li></ul><ul><li>Very few can grow at below pH 5 </li></ul><ul><ul><li>many foods, like cheeses are preserved from spoilage by acids produced during fermentation </li></ul></ul>
  9. 9. Oxygen <ul><li>Bacteria can be classified base on their oxygen requirements </li></ul>
  10. 10. 1. Obligate Aerobes
  11. 11. 2. Obligate Anaerobes
  12. 12. 3. Facultative Aerobes Facultative Anaerobes
  13. 13. 4. Microaerophilic
  14. 14. Oxygen is lethal to some organisms <ul><li>All organisms produce superoxide ( O 2 -) </li></ul><ul><li>Superoxide is toxic to cells </li></ul><ul><li>Superoxide must be neutralized </li></ul>
  15. 15. Superoxide dismutase <ul><li>O 2 - + O 2 - + 2 H + -------> H 2 O 2 + O 2 </li></ul><ul><li>Hydrogen peroxide is also toxic to cells and it must be neutralized </li></ul>
  16. 16. Catalase <ul><li>2 H 2 O 2 --------> 2 H 2 O + O 2 </li></ul><ul><li>Obligate Anaerobes lack: </li></ul><ul><ul><li>Superoxide dismutase ( SOD ) </li></ul></ul><ul><ul><li>Catalase </li></ul></ul>
  17. 17. Phases of Growth <ul><li>4 Phases </li></ul><ul><li>1. Lag Phase </li></ul><ul><li>2. Log Phase </li></ul><ul><li>3. Stationary Phase </li></ul><ul><li>4. Death Phase </li></ul>
  18. 18. 1. Lag Phase <ul><li>Bacteria are first introduced into an environment or media </li></ul><ul><li>Bacteria are “checking out” their surroundings </li></ul><ul><li>cells are very active metabolically </li></ul><ul><li># of cells changes very little </li></ul>
  19. 19. 2. Log Phase <ul><li>Rapid cell growth (exponential growth) </li></ul><ul><li>population doubles every generation </li></ul><ul><li>microbes are sensitive to adverse conditions </li></ul><ul><ul><li>antibiotics </li></ul></ul>
  20. 20. 3. Stationary Phase <ul><li>Death rate = rate of reproduction </li></ul><ul><li>cells begin to encounter environmental stress </li></ul><ul><ul><li>lack of nutrients </li></ul></ul><ul><ul><li>lack of water </li></ul></ul><ul><ul><li>not enough space </li></ul></ul><ul><ul><li>metabolic wastes </li></ul></ul><ul><ul><li>oxygen </li></ul></ul><ul><ul><li>pH </li></ul></ul>Endospores would form now
  21. 21. 4. Death Phase <ul><li>Death rate > rate of reproduction </li></ul><ul><li>Due to limiting factors in the environment </li></ul>
  22. 22. Bacterial Growth - increase in the # of cells <ul><li>Binary Fission </li></ul><ul><li>Generation Time (Doubling Time) </li></ul><ul><ul><li>time required for a cell to divide </li></ul></ul><ul><ul><li>most about 1 Hr. To 3 Hrs. </li></ul></ul><ul><ul><ul><li>E. coli - 20 minutes </li></ul></ul></ul><ul><ul><ul><li>Mycobacterium tuberculosis - 24 Hrs. </li></ul></ul></ul>
  23. 23. Binary Fission - unchecked <ul><li>E. coli - generation time of 20 min. </li></ul><ul><li>20 generations (about 7 hrs.) </li></ul><ul><ul><li>1 million cells </li></ul></ul><ul><li>30 generations ( about 10 hrs.) </li></ul><ul><ul><li>1 billion cells </li></ul></ul><ul><li>72 generations ( about 24 hrs.) </li></ul><ul><ul><li>1 x 10 21 </li></ul></ul><ul><ul><ul><li>1,000,000,000,000,000,000,000 cells </li></ul></ul></ul>
  24. 24. Limiting factors in the environment <ul><li>Lack of food, water or nutrients </li></ul><ul><li>space </li></ul><ul><li>accumulation of metabolic wastes </li></ul><ul><li>lack of oxygen </li></ul><ul><li>changes in pH </li></ul><ul><li>temperature </li></ul>
  25. 25. Bacterial Genetics <ul><li>Genetics is the study of heredity and variation. </li></ul><ul><li>Bacterial genetics is used as a model to understand DNA replication, genetic characters, their changes & transfer to next generations. </li></ul>
  26. 26. Double helical structure of DNA Replication
  27. 27. Important enzymes involved in Replication: <ul><li>DNA-dependent DNA polymerase. </li></ul><ul><li>if Error: nuclease enzyme </li></ul><ul><li>Restriction enzymes </li></ul>
  28. 28. Genetic Information In Bacteria Carries properties like virulence, pathogenicity & resistance Extrachromosomal genetic material in the cytoplasm Replicate independently Virus infecting bacteria Chromosome Plasmid Bacteriophage
  29. 29. PLASMIDS <ul><li>Circular DNA molecules </li></ul><ul><li>Important vectors in genetic engineering </li></ul><ul><li>EPISOME </li></ul><ul><ul><li>Plasmid DNA integrated with chromosomal DNA. </li></ul></ul><ul><ul><li>…………………………………………………… . </li></ul></ul><ul><ul><li>Transmissible and non-transmissible Plasmids </li></ul></ul>
  30. 30. Mechanisms Of Genetic Variations <ul><li>Mutation </li></ul><ul><li>Transfer or exchange of genetic material </li></ul><ul><ul><li>Transformation </li></ul></ul><ul><ul><li>Transduction </li></ul></ul><ul><ul><li>Conjugation </li></ul></ul><ul><ul><li>Transposition </li></ul></ul>
  31. 31. 1. Base substitution <ul><li>Results of mutation - </li></ul><ul><ul><li>Missense mutation – triplet code is altered so that a different amino acid is present at a particular position in the protein. </li></ul></ul><ul><ul><li>Nonsense mutation – converts a codon that specifies an amino acid into a termination codon.    </li></ul></ul>
  32. 32. 2. Frame Shift Mutation <ul><li>Cause - Deletion or insertion of a base - changes all of the codons downstream from the change </li></ul>
  33. 33. 3- Insertion <ul><li>Additional pieces of DNA </li></ul>
  34. 34. Gene Transfer in bacteria: <ul><li>Conjugation. </li></ul><ul><li>Transduction. </li></ul><ul><li>Transformation. </li></ul><ul><li>Transposition. </li></ul>
  35. 35. Process of Conjugation
  36. 36. Process of Transduction
  37. 38. Process of Transformation
  38. 39. 4- Tranposition. <ul><li>By Transposone </li></ul>
  39. 40. <ul><li>Thank you </li></ul>

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