Microbe Control Environmental Controls Temperature Radiation Pressure pH Moisture Control Methods
Dec 18, 2015
pH Most Marine Molds vs. Bacteria
Molds like lower pH than bacteria
Acidophiles
http://www.brooklyn.cuny.edu/bc/ahp/CellBio/Growth/MGpH.html
Acidic mud pot in Yellowstone Park – home to the acidophile Sulfolobus acidocaldarius. Credit:
US National Park Service
Moisture Bacteria vs Molds
Bacteria like more moisture than molds
Food Preparation Dried Foods Freeze-Dried Foods “Cured” Foods
Microbe Control Methods TERMS:
Sterilize Kill or remove all life present
Disinfect Kill pathogens present Germicide Antiseptic
Sanitize Make safe to use or eat from
Ways to Sterilize & DisinfectSTERILIZE Burning Boiling Autoclave (pressure
cook) Filtration Irradiation Chemicals
Iodine Chlorine
DISINFECT Detergents/Soaps Acids & Bases Alcohols Mercury Cresols Hydrogen peroxide Formalin Antibiotics
Metabolic Diversity Two fundamental nutritional needs: Acquiring chemical energy in the form of ATP
Pump ions, move cargo, undergo chemical reactions in the cell
Obtaining carbon Used to synthesize fatty acids, DNA, RNA, and
other molecules
Growth (Culture) of Microbes Natural media
Extracts Infusions
Synthetic media Nutrient broth Nutrient agar
Broth Solidifiers Gelatin Animal protein Melts @ 20°C
Digested by microbes
Agar Plant carbohydrate Melts @ ~100°C,
solidifies @ ~42°C NOT digested by
(terrestrial) microbes
Which is useful for incubation at human body temperature?
Culturing Techniques Researchers use specific compounds and
substrates in the culture medium and observe what grows!
MacConkey agar Isolates enteric, Gram-negative, bacteria based on
their ability to ferment lactose
Simmons Citrate Test Tests the ability of certain organisms to utilize
citrate as a carbon source.
pH indicator = Bromthymol blue pH > 7.5 turns royal blue Neutral pH green (just like uninoculated media)
Christensen Urea Test Some bacteria utilize urea, which results in
the formation of ammonia. Alkaline
Produces a red-pink/red-violet color A negative reaction will have no color change and
the agar medium will remain pale yellow.