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
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
Respiration vs. Fermentation Cellular respiration Cellular respiration Efficient way to produce ATP Fermentation Less efficient and does not involve the transport of electrons In many organisms, it is an alternative metabolic strategy In others, it’s the only way for cells to make ATP
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--+++