1 / 32

Chapter 6: Microbial Growth

Chapter 6: Microbial Growth. How do bacteria grow?. Not in size Increase in population size One cell divides into 2 new cells – binary fission. Binary fission. Binary fission:. Attachment of chromosome to p.m.; replication of DNA; new p.m. and cell wall laid down between the 2 chromosomes

lucas
Télécharger la présentation

Chapter 6: Microbial Growth

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 6: Microbial Growth

  2. How do bacteria grow? • Not in size • Increase in population size • One cell divides into 2 new cells – binary fission

  3. Binary fission

  4. Binary fission: • Attachment of chromosome to p.m.; replication of DNA; new p.m. and cell wall laid down between the 2 chromosomes • This is the way that each new daughter cell gets one chromosome

  5. How can we describe growth? 2n = no. of cells in n generation Generation time Nt = N0 x 2n

  6. Growth problems If Staphylococcus aureus has a doubling time (generation time) of 30 minutes and 5 hours have passed, how many generations have been produced? a. How many 30 minute time chunks are in 5 hours? = 10 ANSWER: 10 generations

  7. Growth problems If Staphylococcus aureus has a generation time of 30 minutes and 5 hours have passed, how many bacteria will be present at the end of the time period? • We have already determined that 10 generations will occur. • 2n = # cells at n generation • 210 = # cells at the 10th generation ANSWER = 1024 cells

  8. Growth problems If Staphylococcus aureus has a generation time of 30 minutes and 5 hours have passed, how many bacteria will be present at the end of the time period if we start with 3,000 cells? Nt = N0 x 2n Nt= 3,000 x 210 = 3,072,000 cells at the end of 5 hours

  9. Growth curve: lag, log, stationary, and death phases • What occurs in each?

  10. How can population size be counted? (Advantages and disadvantages of each method) 1. Direct methods A. Microscopic count with hemacytometer/ Petroff Hauser counting chamber

  11. Petroff Hauser counting chamber

  12. B. Plate counts – dilution series and plates

  13. C. Filtration

  14. D. Coulter counter/flow cytometer/Fluorescence activated cell sorter (FACS)

  15. 2. Indirect methods A. Dry weight B. Metabolic activity C. Turbidity

  16. Turbidity

  17. Growth requirements of microbes A. Temperature: Thermophiles Mesophiles Psychrophiles

  18. B. pH: acidophiles C. Osmotic pressure (# of solutes in solution) Halophiles D. Oxygen: Types: Obligate aerobe Facultative anaerobe Obligate anaerobe Aerotolerant anaerobe Microaerophilic

  19. Enzymes needed to survive in presence of oxygen: Catalase Peroxidase Super oxide dismutase (SOD)

  20. E. Nutrients C, N, P, S elements needed Mg, Fe, etc. trace elements needed Media: Defined or complex Selective vs. differential Special

  21. Mannitol salt agar – selective medium

  22. Blood agar – differential medium

  23. The End

More Related