1. Chapter 6: Microbial Growth

2. Requirements for Growth Physical Requirements –Temperature –pH –Osmotic Pressure Chemical Requirements –Carbon –Nitrogen,Sulfur, Phosphorus –Oxygen

3. Temperature Psychrophiles: cold-loving –Mostly in ocean’s depths (not common) –Can grow 0°, optimal at 15° Psychrotrophs –Low temperature food spoilage bacteria –Can grow 0°, optimal 20-30° Mesophiles : moderate-temp-loving –Optimal 25-40° –Most common microbes, spoilage and disease Artic Sea bacteria: Strain34h, stained fluorescent blue for better viewing. E. coil

4. Temperature Thermophiles: heat-loving –Optimal 50-60° –Important in compost piles Hyperthermals: extreme thermophiles –Optimal 80°+ –Hot springs, volcanoes How do they tolerate the high temperatures? special enzymes fold their DNA into special heat-stable coils enzymes themselves are heat stable with extra bonds between amino acids. SEM of a thermophilic Bacillus species isolated from a compost pile at 55° Grand Prismatic Spring, Yellowstone National Park

6. Effects of Temperature on Growth Most of our plates are incubated at 32-35 o C

8. pH Most grow best between 6.5 and 7.5 Acidophiles: tolerant to acid Able to pump out poisonous H+ fast enough not to damage the DNA Inside the cell stays at 6.5 Acidic mud pot in Yellowstone Park – home to the acidophile Sulfolobus acidocaldarius. Credit: US National Park Service

9. Osmotic Pressure Need WATER for growth Many bacteria can be plasmolyzed by high concentrations of solutes.

10. Osmotic Pressure Obligate Halophiles: require high salt concentrations –If placed in fresh water they will burst and die Facultative Halophiles: do not require high salt, but can grow in concentrations up to 2% Vibrio parahaemolyticus - halophilic, facultative rod bacterium that causes a food-borne illness known as seafood poisoning. Usually transmitted through eating raw or undercooked seafood such as oysters. Less commonly, this organism can cause an infection in the skin when an open wound is exposed to warm seawater.

11. Chemical Requirements CARBON: Half the dry weight of a bacterium NITROGEN: (14%) Protein, Nucleic Acids SULFUR: Amino acids, vitamins PHOSPHORUS: Nucleic acids, ATP, phospholipids TRACE ELEMENTS: iron, copper, zinc Used as cofactors

12. Aerobes: Microbes that use O 2 Obligate aerobes: Require O 2 Anaerobes: Do not use O 2 Facultative anaerobes: can use O 2 when present, but can still live without Obligate anaerobes: Unable to use O 2, harmed from O 2 Aerotolerant anaerobes: cannot use O 2 for growth, but they tolerate it fairly well Microaerophiles: Aerobic, but only grow in conditions lower than those in air

14. Culture Media Agar Media: polysaccharide from a marine algae –Used as a thickener in foods (jelly) –Petri dishes, slants, test tubes Nutrient Broth/Agar –vitamins and other organic growth factors provided by meat extracts or yeast extracts –peptone

15. Tryptic Soy Agar (TSA) Contains enzymatic digests of casein and soybean meal –Provides amino acids and nitrogen glucose is the energy source Agar used as the gelling agent

16. Streaking Plates

17. http://www.sumanasinc.com/webcontent/animations/content/streakplate.html

18. Phases of Growth