1. What are two methods used to obtain pure cultures of microbes from a mixed cu
ID: 188077 • Letter: 1
Question
1. What are two methods used to obtain pure cultures of microbes from a mixed culture?
Which of these methods also allows one to count how many cells were in the sample?
2. Fill in each cell in the table below with either "Yes" or "No", indicating the requirements/capabilities of
the microscopy method when viewing bacteria
3. Fill in the blanks.
The two prokaryotic domains of life, the ________________________ and the _______________________, do not
have nuclei.
The organisms that produced most of the oxygen in the atmosphere of the early earth are called
______________________.
The first person to microscopically observe and describe bacteria was _________________________________.
4.Fill in the blanks.
When __________________ carry out respiration, they transfer _________________ from organic compounds to
terminal electron acceptors.
Phototrophs use energy from _____________________ to move electrons and generate a ___________________
force.
Requires staining of the cells:? Allows visualization of live cells? Type of microscopy Bright-field Dark-field Phase-contrast Transmission electronExplanation / Answer
Answer to Question-1:
A mixed culture contains more than one type of microorganisms in it. However, in order to study a particular type of microorganism, we need to obtain pure culture. The two methods to obtain the pure culture of microbes from mixed culture are:
(i) dilution of the mixture is carried out so that the colonies can be separated far from each other on the agar surface, so that after the incubation colonies are distinctly visible from each other.
(ii) secondly, a desired colony is picked up by scrapping the plate gently, which is then tranferred to a sterile media. After the incubation, all the organisms grown in the culture will belong to the the same organism of our interest.
The first method to obtain pure culture is SPREAD PLATE METHOD. In this method, no dilution of mixed culture or microorganisms is done in the agar plates. Rather than this, serial dilution containing sterile medium is carried out. A small aliquot from the serially diluted solution is taken and poured on the agar plate and evenly spead with the help of spreader. After incubatimg, colonies appears. However, in some plates, well isolated colonies appears because of separation of individual microorganism by spreading the diluted drop on the media plate.
The second method is POUR PLATE METHOD. In this method,diluted samples are mixed with melted agar media. It is based on the principle that, the diluted samples in succesive tubes which permits the proper distribution of microbial cells in the medium. The content of the serially diluted tubes are poured on the agar media plates. Plates are incubated so that colonies can grow. Once the colonies develops, they can be seen on sub-surface as well as on the surface. An isolates colony of interest is picked up and cultured on the another plate so that the colonies appearing are of utmost purity.
Out of these two above methods, the second method that is POUR PLATE METHOD allows to count the cells present in the sample which can be either done by measuring the turbidity of the solution or by visualizing and counting the cells under the microscope.
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