I)  Measurement of cell growth -
       A)  Growth of bacterial cultures
            1)  Bacterial division - binary fission
                    a)  Generation time - time required for a cell to divide (and its population to double)

II)  Requirements for growth - Physical and nutritional
     A)  Physical - temperature, oxygen, pH, osmotic pressure
          1)  Temperature -
               a)  optimal temperature - preferred; grows best.
               b)  temperature range - range of temps that support growth.
               c)  Four groups of bacterial based on temperature ranges
                         Psychrophiles
                         Mesophiles
                         Thermophiles
                         Extreme thermophiles

          2)  Oxygen requirements -
                       a)  obligate aerobe -
                       b)  Obligate anaerobe -
                       c)  Facultative aerobe/anaerobe
                        d)  Microaerophilic -
                        e)  Aerotolerant -

          3)  pH - measure of concentration of hydrogen ions.
               a)  Most prefer pH ~ 7 (neutral); range 5-8.
               b)  fungi and yeast prefer lower pHs (~5-6).
               c)  Acidophiles -
 
        4)  Osmotic pressure -

     B)  Nutritional - molecular components required for metabolism.
          1)  Cells need a source of energy, carbon, various minerals, vitamins.
                  Some cells also require growth factors.
          2)  Elements required :  CHNOPS

          3)  Energy sources - light or chemical
          4)  Carbon sources - organic molecules or CO2.

          5)  Mineral requirements
                    Nitrogen , Sulfur, Phosphorus, Magnesium, Potassium, Iron, Trace elements.

           6)  Trace elements and growth factors -

III)  Growing bacteria in the lab
Create optimal conditions (physical, nutritional) for growing bacterial strains in the lab.
 
       A)  Media - material used for growing bacteria.  Several types.
          1)  Synthetic - chemically defined
          2)  Complex - chemically undefined

     B)  Special media for cultivation of specific bacteria in a mixed population -
            1)  Enrichment cultures -
            2)  Selective media -
            3)  Differential media -

    C)  Liquid or solid (agar - polysaccharide from seaweed).

    D)  Phases of growth - bacterial growth curve
            a)  Lag phase
            b)  Log phase
            c)  Stationary phase
            d)  Death phase

    E)  Direct measurement of Microbial growth
        1)  Plate counts
            a) Pour plates and spread plates

        2)  Most Probable Number
            a)  Statistical estimate of the number of bacteria
 
        3) Direct microscopic count
            a) Petroff-Hauser counting chamber

    F)  Indirect measurment of Microbial Numbers
        1)  Turbididty
        2)  Metabolic activity
        3)  Dry weight