Microbial Growth P.2 Ch.6

Microbial Growth P.2 Ch.6

1. Requirements of Growth:

   • Culture Media:
     • Obtaining Pure Cultures:
       • Preserving Bacterial Cultures:
         • Deep Freezing: -50 to -95 C
           • Lyophilization(Freeze drying): Frozen -54 to -72/dehydrated in a vacuum
     • Measurement of Microbial Growth:
       • Plate Counts
         • Filtration
           • Most Probable Number (MPN)
             • Direct Microscopic Count
               • Indirect Methods:
                 • Turbity
                   • Metabolic Activity
                     • Dry weight
                 • Indirect: Metabolic activities: measure amount of metabolic such as acid
                   • Dry Weight: for mold
               • Direct Microscopic Advantages: No incubation Time
                 • Disadvantage: Motile microbes difficult to count
                   • Dead cells counted
                     • High cell concentration required to count
             • Multiple tube MPN test
               • Count positive tubes
                 • Useful for microbes that wont grow on solids
                   • Useful for using different medium to ID microbes
           • Membrane Filtration:
             • Advantages: Can study in diluted samples
               • Disadvantages:
                 • Breaks up cells
                   • Does not catch all cells
         • Advantages: Measures Viable # of cells
           • Disadvantages: Take time for incubation
             • Bacteria Grow in Clumps
               • CFU mesures
                 • Too many to count
   • Bacterial division/Binary Fission
     • Budding
       • Condispores(actinomycetes
         • Fragmentation of filaments

2. Growth of Bacterial Cultures: