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

PhotoreactivationDeinococcus radiodurans

Pressure Piezophile Barophile

Obligate barophiles

Pseudomonas bathecetes

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

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

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

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 BacteriaBacteria Genus

Sulfur Indole Lactose Citrate Urease

Escherichia - + + - -Edwardsiella + + - - +/-Salmonella + - +/- + -Enterobacter - - + + +