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Topic 3: Microbes in the Environment
- Microbes are everywhere
- found in water, air, and the earth
- live in and on our bodies
- occupy ecological niches on all forms of life and in most environments
- Most microbes are harmless
- When a medium is selected for culturing bacteria, macronutrients, an energy source, and any necessary growth factors must be provided.
- Chemically defined medium: a medium whose exact chemical composition is known.
- Most chemoheterotrophic bacteria are grown on complex media.
- Complex media: media for which the exact chemical composition varies slightly from batch to batch.
- Organic carbon, energy, and nitrogen sources are usually supplied by protein in the form of meat extracts and partially digested proteins called peptones.
- Nutrient broth: commonly used liquid complex medium.
- Nutrient agar: when agar is added to a nutrient broth medium and becomes a solid medium.
- Agar is an extract from marine red algae.
- Few microbes can degrade agar so it remains solid during microbial growth.
- Liquefies in 100 °C and remains in a liquid state until cooled to 40 °C.
- Once solidified, it can be incubated at temperatures of up to 100 °C and remain solid.
- Media must be sterilized after preparation.
- Most common method is steam sterilization or autoclaving → using steam under pressure.
- Material to be sterilized is placed in the autoclave and heated to 121 °C at 15 lbs of pressure (15 psi) for 15 minutes
- Petri plates, containing a solid media, provide a large surface area for examination of colonies
- Inoculated: intentionally introduced
- Bacteria that is inoculated on media will increase in number during an incubation period.
- Liquid media becomes turbid, cloudy, due to bacterial growth.
- On solid media, colonies will be visible
- Colony: population of cells that arises from a single bacterial cell,
- Colony-forming unit: a colony that may arise from a group of the same microbes attached to one another
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Explore Top NotesNoteStudied by 17 peopleNoteStudied by 12 peopleNoteStudied by 112 peopleNoteStudied by 21 peopleNoteStudied by 16 peopleNoteStudied by 26 people
4.15 Beethoven
NoteStudied by 17 peopleSoftball Study Guide
NoteStudied by 12 peopleChapter 1: The Comparative Method
NoteStudied by 112 peopleWhy is the rent so high? Final review
NoteStudied by 21 peopleClimate Change - Exploring Earth Climate, Prevailing Winds, and How Heat Traps In Our Atmosphere
NoteStudied by 16 peopleCOMPUTERS NOTES
NoteStudied by 26 people