1. GROWTH OF MICROORGANISMS

2. Nutritional Classification Based upon energy and carbon sources Energy source- electron donors –Phototrophs (light nourishment) –Photosynthesis

3. Electron Donors Chemotrophs Oxidation Reduction Breaking & forming bonds

5. Carbon Source Autotrophs (self) Heterotrophs ( different) Combination of terms

6. Photoautotrophs Energy(electrons) source-light Carbon source-CO 2 Green & purple Sulfur bacteria

7. Photoheterotrophs Energy source-light Carbon source –organic cpds Green & purple non Sulfur bacteria

8. Chemoautotrophs Energy source is oxidation -reduction reactions Carbon source Nitrifying bacteria

9. Chemoheterotrophs Energy & carbon source Remove electrons from H in organic cpds Final electron acceptor is oxygen Final electron acceptor is organic cpd

10. Physical Requirements for Growth Temperature-range –Psychrophiles –Psychrotrophs

11. Temperature Mesophiles-25-40C Thermophiles-50-60C Hyperthermophiles

12. Determination of Range Maximum temperature Minimum temperature Optimum temperature is closer to max

13. pH Measures acidity or alkalinity Bacteria grow best at slightly alkaline pH Add buffers to bacterial cultures Molds & yeasts lower pH

14. Osmotic Pressure Microbes need water to grow Use salt/sugar to preserve food Obligate halophiles Facultative halophiles

15. Chemical Requirements for Growth Carbon source-50% of dry weight of cell Nitrogen source-amino acids, nucleic acids

16. Minerals Trace elements –Small amounts of Fe, Zn, Cu, Co etc. –Macronutrients-S & P Water-medium for chemical reactions

17. Other Growth Requirements Growth factors-essential nutrients E. coli needs no growth factors

18. Other Growth Requirements Buffers A solidifying agent

19. Agar Advantages Few organisms degrade it Liquefies at 100 C Liquid until 40-50 C Lab-keep liquid at 50 C Once solidified, heat to 100 C Gelatin –Nutrient for some organisms –Liquefies at 35-37 C

20. Oxygen Requirements Aerobes –Use molecular oxygen for respiration –Superoxide free radicals (O. - ) –Superoxide dismutase- must have –H 2 O 2 is toxic

21. Oxygen Requirements Facultative anaerobes

22. Oxygen Requirements Obligate anaerobes

23. Oxygen Requirements Aerotolerants Microaerophiles

24. Growth of Bacterial Population Binary fission or budding Generation time-doubling time

25. Growth Curve Lag phase-preparing to grow Log phase Stationary phase-growth ceases Death Phase

26. Growth of a Colony Mass of cells –pure culture Some colonies are distinct Mixture of cells in different phases of growth

27. Growth of a Colony Location within colony determines access to oxygen Surface cells fully aerobic E. coli obtain energy aerobic respiration Embedded cells in center-anaerobic

28. Biofilms In nature, microbes in liquid environment Cells imbedded in extracellular slime –Excreted by cells Type of defense mechanism

29. Biofilms Quorum sensing Important role in infections Soaps & disinfectants