Freezing preserves food and stock cultures but it is

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Freezing preserves food and stock cultures but it is not effective at killing microbes. 6
UNIT I-Module 2-Ch4 & 5: Dynamics of Prokaryotic Cell Structure and Control ofProkaryotic GrowthExplain how aerobic, microaerophilic, and anaerobic conditions can be provided for bacterial cultivation. To determine an organism’s O2 requirement→ grow it in a shake tubeby boiling nutrient agar to drive off O2; cool to just above solidifying temp; inoculate and gently swirl. Based on their O2 requirements they can be separated into: Obligate aerobes→ organisms that require O2 for growth (i.e. Micrococcus luteus)Produces superoxide dismutase and catalase as protection means against reactive oxygen species. Most can be incubated in air (about 20% O2) Shaken broth cultures provide max aeration Many medically important bacteria (i.e Neisseria, Haemophilus) grow best with increased CO2 One method to incubate is to use a candle jar Some are capnophiles→ they require increased CO2 Facultative anaerobes→ organisms that grow best when O2 is available but can also grow in its absence (i.e E.coli)Produces superoxide dismutase and catalase as protection means against reactive oxygen species. Most can be incubated in air (about 20% O2) Shaken broth cultures provide max aeration Obligate anaerobes→ organisms that cannot grow in the presence of O2 (i.e Clostridium botulinum) Microaerophiles→ organisms that require small amounts of O2 (2%-10%) for growth and are inhibited at lower concentrations (i.e H. pylori). Produces superoxide dismutase and catalase as protection means against reactive oxygen species. Require lower O2 concentrations→ can incubate in gas-tight container with chemical packet Aerotolerant anaerobes→ organisms that are indifferent to O2. They can grow in its presence but do not use it to harvest energy. (i.e Streptococcus). Aka obligate fermenters→ because fermentation is their only metabolic option Produces superoxide dismutase but not catalase as protection means against reactive oxygen species. 7
UNIT I-Module 2-Ch4 & 5: Dynamics of Prokaryotic Cell Structure and Control ofProkaryotic GrowthAnaerobic containers→ a specialized container that can maintain anaerobic conditions; a chemical reaction in a packet generates those conditions Useful if microbe can tolerate brief O2 exposures Can also use semisolid culture medium containing a reducing agent Anaerobic chamber→ an enclosed compartment maintained in an anaerobic env; a special port is used to add or remove items. Provides a more stringent approach.

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