Class notes
Class Notes: Lecture 1 of M118L at UCI
- Institution
- University Of California - Irvine
Notes cover lecture 1A and 1B videos of M118L course at UCI. Includes lecture's practice problems.
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Lecture 1 (covers videos A & B) Abbreviations:Tuesday, January 5, 2021 8:36 PM Ex. = for example,
b/w = between
b/c = because
w/ = with
1. Explain the enrichment process that will be used to obtain bacterial isolates. Lab Walkthrough – Bacterial Isolation
2. Classify a given type of media based on its ingredients. • In this class, students will perform 2 different bacteria isolations:
3. State the importance of sterile technique and be able to follow these rules in lab. 1. Anal isolation: get intestinal bacteria.
4. Describe significance of various steps of Gram Staining. 2. Soil isolation: to get bacteria that secrete a fluorescent pigment.
• Culture media: medium used to grow microorganisms on/in. Ex. Agar plates, liquid • For successful isolation, a good sterile technique is needed.
media. • Quadrant streaking technique: section 4 areas on an agar plate (draw 3 lines in a
○ Essential nutrients present: carbon and nitrogen source, vitamins, amino acids. checkered pattern).
○ Defined media: composition of media is known. (What component, how much, ○ Sterile stick: for every quadrant, use a new stick. Rub some of the bacteria onto
etc.) the stick and then smear on one section of the plate. Using a new stick, touch the
○ Complex media: at least one component is unknown within the composition. bacteria in the corner a Q1 and spread it over Q2. Repeat for Q3 and Q4. For Q4,
○ Selective media: media that contains something that inhibits a particular do not use overlapping strokes.
organism's growth. Ex. High-salt media -> Osmotic pressure -> media is ○ Sterile loop: Rub some of the bacteria onto the sterile loop and then smear on one
selecting for organisms that can survive the osmotic stress! quadrant of the plate. Re-sterilize the loop w/ heat; wait for loop to cool down!
○ Enriched media: media that contains growth factor, or something essential for a Using the newly sterilized loop, touch the bacteria in the corner a Q1 and spread it
certain organism to grow. Ex. Media w/ sheep's blood -> excess nutrients over Q2. Repeat for Q3 and Q4. For Q4, do not use overlapping strokes.
○ Differential media: media that contains something that allows you to distinguish • To get a pure culture, student needs to get individual colonies. ->
b/w 2 or more types of bacteria. Ex. Media w/ pH indicator -> can indicate a • To get single colonies on a plate, student needs to dilute a culture b/c colony formation
certain bacteria on a non-buffered(can resist pH changes) media. requires cells to be far apart.
• Both organisms are surviving, and we can observe a difference b/w them. • Once bacterial colony is isolated, student must identify bacteria using Gram Stains.
• Gram stains: differentiate b/w gram positive(purple) and gram negative(pink).
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