Final answer:
Isolation methods in microbiology are techniques to separate and quantifiably count bacteria from mixed sources. These methods, like streak plate, pour plate, and spread plate, are essential for obtaining pure bacterial cultures and estimating bacterial cell density in samples.
Step-by-step explanation:
The term "isolation methods" refers to techniques used in microbiology to separate a single type of bacteria from a mixed source, allowing for the quantification of bacteria by colony counting. One common method is the streak plate method, where bacterial cells are spread over an agar plate to form individual colonies after incubation, each representing a clone of the original bacterial cell. This yields a pure culture of the bacteria. Other methods include the pour plate method, which involves mixing the bacteria in liquid agar, and the spread plate method, where bacteria are spread over solid agar with a sterile spreader. For dilute samples such as drinking water, the membrane filtration technique is used; organisms are trapped on a membrane, transferred to an agar plate, and counted to estimate cell density. These methods are crucial for estimating bacterial numbers in samples and achieving pure cultures for further analysis.