Microbe Control  Environmental Controls  Temperature  Radiation  Pressure  pH  Moisture  Control Methods

Temperature  Growth Temperature  Maximum  Optimum  Minimum  Heat  Cold Thermocrinis ruber

Radiation  Blue Light  UV  X-rays  Gamma Rays  Photoreactivation Deinococcus radiodurans

Pressure  Piezophile  Barophile  Obligate barophiles  Pseudomonas bathecetes

pH  Most  Marine  Molds vs. Bacteria  Molds like lower pH than bacteria  Acidophiles 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 & Disinfect STERILIZE  Burning  Boiling  Autoclave (pressure cook)  Filtration  Irradiation  Chemicals  Iodine  Chlorine DISINFECT  Detergents/Soaps  Acids & Bases  Alcohols  Mercury  Cresols  Hydrogen peroxide  Formalin  Antibiotics

Pasteurization  Louis Pasteur  Internal temperature  Batch (Vat)  HTST  UP

Growth (Culture) of Microbes  Natural media  Extracts  Infusions  Synthetic media  Nutrient broth  Nutrient agar

Broth Solidifiers  Gelatin  Animal protein  20°C  Digested by microbes  Agar  Plant carbohydrate  ~100°C, ~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

SIM Test  S = Sulfur reduction  I = Indole production  Kovac’s reagent  M = Motility

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.

Identifying Specific Bacteria Bacteria Genus SulfurIndoleLactoseCitrateUrease Escherichia-++-- Edwardsiella++--+/- Salmonella+-+/-+- Enterobacter--+++