Lecture 17 Outline of Last Lecture 1. Bacteria Cells…2. Measuring growth3. Turbidity4. Growth in lab cultureOutline of Current Lecture 1. Turbidostat2. Environment & Growth3. -PhilesCurrent LectureTurbidostat- uses turbidity to hold growing culture at specific level. Can do experiments where you’re changing nutrients, environmenthelps keep steady level of growthStart- MinimumTop- OptimumEnd- MaximumEnvironment & Growth- gas requirementsOxygen- As oxygen is utilized it’s transformed into toxic products: - Hydrogen peroxide (H2O2)- O2^-- ½O2- OH^-Most cells have developed enzymes that neutralize these chemicals: superoxide dismutase, catalaseIf a microbe is not capable of dealing with toxic oxygen, it’s forced to live in oxygen free habitats- Facultative anaerobe- grows just as well as if oxygen is present or not- Aero tolerant anaerobe- can grow in presence of oxygen, doesn’t grow better… ignores itCapnophile- Grows best at higher CO2 tensions than normally present in the atmosphereNeutrophiles- Majority of microorganisms grow at a pH between 6 & 8 BSC 160 1nd EditionAcidophiles- grow at extreme acid pHAlkalinophiles- grow at extreme alkaline pHHalophiles- Require a high concentration of saltOsmotolerant- does not require high concentration of solute but can tolerate it when it occursBarophiles- Can survive under extreme pressure and will rupture if exposed to normal atmospheric
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