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Ch. 7 - Fundamentals of Microbial Growth
Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition
Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook
All textbooksNorman-McKay 2nd EditionCh. 7 - Fundamentals of Microbial GrowthProblem 3
Chapter 7, Problem 3

After performing the streak plate method, what feature(s) would you look for on the agar plate to determine if you have a pure culture?

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1
Understand that a pure culture contains only one type of microorganism, which means all colonies should have the same characteristics.
Examine the agar plate for colony morphology, including size, shape, color, texture, and margin; in a pure culture, these features should be uniform across all colonies.
Look for isolated colonies that are well separated from others, indicating successful dilution and streaking.
Check for the absence of any colonies that differ in appearance, as the presence of different colony types suggests contamination or mixed culture.
Confirm that the growth pattern is consistent with the expected microorganism, reinforcing that the culture is pure.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Streak Plate Method

The streak plate method is a microbiological technique used to isolate individual bacterial colonies by spreading a diluted sample across an agar surface. This method helps separate different microorganisms so that single colonies can grow from individual cells, facilitating the identification of pure cultures.
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Colony Morphology

Colony morphology refers to the visible characteristics of microbial colonies on an agar plate, such as shape, size, color, texture, and margin. Observing uniform colony morphology across the plate suggests the presence of a pure culture, as all colonies originate from the same microorganism.
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Pure Culture Identification

A pure culture contains only one type of microorganism. To confirm purity after streaking, look for colonies that are consistent in appearance without contamination or mixed growth. The absence of differing colony types indicates successful isolation of a single species.
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Related Practice
Textbook Question

Match the term to the proper description(s). A term can have more than one description.

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Textbook Question

Which of the following pathogens would hyperbaric oxygen therapy, a treatment that increases the level of dissolved oxygen in tissues, most likely ward off? Select all that apply.

a. Anaerobic thermophile

b. Anaerobic mesophile

c. Facultative anaerobic thermophile

d. Facultative anaerobic mesophile

e. Microaerophilic mesophile

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Textbook Question

A Salmonella species is grown for 8 hours. In this time, each cell divides about four times. What is the generation time?

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Textbook Question

If a bacterium that normally lives in the gastrointestinal tract is plunged into a salty solution, what would occur?

a. Halophilic adjustment

b. Osmotic concentration

c. Lysis

d. Plasmolysis

e. Nothing

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Textbook Question

Choose the false statement about binary fission.

a. It generates genetically diverse daughter cells.

b. It is an asexual form of reproduction.

c. It is the most common way that prokaryotes divide.

d. It leads to exponential population growth.

e. If it occurs in a single plane, it could generate chains of bacteria.

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