Why Are Pure Cultures Essential in Biological Research?
The environment around us consists of a mixed population of microbes. Each of these groups of organisms contributes to the ecology. However, ever wondered how are the studies carried on such microbes? Is it feasible to study and experiment with all of these together? Well, no. It isn’t. To carry out the studies on these microbes, it is essential to dissect the mixed culture into a pure culture.
Now, what is a pure culture? What purpose does it serve? What is pure culture microbiology? What are the pure culture methods or pure culture techniques? Let us help you understand all these terms in detail.
Pure Culture Definition
Put down in simple terms, pure culture is defined as a laboratory culture that contains just one species of organisms in microbiology. Microbes are usually in mixed cultures. But, the pure culture can be derived from it through the transfer of a bit of its sample in the new and sterile growth medium.
The process of pure culture isolation usually takes place by the dispersion of cells across the surface medium. This mainly involves thinning of the sample before it is inoculated into a new medium. There are several pure culture techniques utilized by scientists to carry out the process of the creation of discrete colonies of pure microbes.
The techniques of isolation of the pure culture were primarily developed by Robert Koch during the mid-19th century. Microbiologists of those times readily adopted these methods for the production of a single strain of the organism.
The inculcation of such techniques of pure culture led to bacterias characterization that was responsible for causing anthrax, tuberculosis, and such major diseases. Following this, scientists developed similar procedures for protozoa, fungi, and algae.
Are you wondering that do pure culture organisms serve any commercial purposes? Well, yes, they do. It is mainly used for commercial fermentation purposes including yoghurt, alcohol, citric, lactic acid, and several other beverages for many years now. The pure culture technique has also contributed to the development of several vaccines and antibiotics.
Pure Culture Collections:
These are a resource and method of preserving the genetic resources of these organisms. The collection of pure culture organisms varies widely depending on size and some specializations as well. These have gained importance over the years due to their authenticity, reliability, and practical uses. For culture, several national federations are present across various countries, and detailed information is available about the same.
How is the Purity of Culture assessed?
The assessment of the purity of culture is carried out through different methods. These are as follows:
The same cultural characteristics are shown on the media obtained in the isolated colonies of pure culture organisms.
The same culture organisms look alike when observed under the microorganisms. This means that they get the same stain and have the same morphology.
Just like similar biochemical results the isolated colonies of pure culture perform identically, i.e., separately.
Biochemical Characteristics of Pure Culture
The mixed culture organisms show different results in the case of experiments.
The pure culture organisms show similar results in the case of experiments.
What is the Importance of Pure Culture in Microbiology?
The organisms of pure culture can be grown, tested, characterized, and identified.
It is feasible to study the clinical aspects and physiology of pure culture organisms.
Irrespective of the number of times the test is done, the same results will be obtained for a particular culture of organisms during any sort of test.
Spontaneous mutation occurs slowly in the case of pure culture, and the clone so formed is identical in all forms and aspects.
Pure Culture Techniques Microbiology
The various techniques used to obtain pure culture in microbiology are as follows:
Sterilization process for media and glassware
Dispersion of individual cells takes place across the medium
The thinning process of samples is carried out multiple times before the inoculation of fresh media takes place.
FAQs on Pure Culture: Key Concepts, Importance & Techniques
1. What is a pure culture in microbiology?
A pure culture is a laboratory culture that contains only a single species or strain of a microorganism, with no contaminants. It is essential for accurately studying the properties, behaviour, and characteristics of a specific microbe, such as its role in disease or its use in industrial processes.
2. Why is obtaining a pure culture so important in microbiology?
Obtaining a pure culture is crucial for several reasons:
- Accurate Identification: It allows scientists to identify a specific bacterium or fungus without confusion from other organisms.
- Disease Diagnosis: It helps in isolating and identifying the pathogen causing an infectious disease.
- Antibiotic Production: It is necessary for growing the specific microbes that produce antibiotics like penicillin.
- Research: It provides a reliable and consistent population of a single organism for scientific experiments.
3. What are the main methods used to isolate a pure culture?
The most common methods for isolating microorganisms to create a pure culture include:
- Streak Plate Method: A technique where a sample is streaked across the surface of an agar plate to separate individual cells.
- Pour Plate Method: The sample is mixed with molten agar and then poured into a petri dish, so colonies grow both on and within the medium.
- Spread Plate Method: A small volume of a diluted liquid sample is spread evenly over the surface of an agar plate.
- Enrichment Culture: Using a special medium that encourages the growth of a desired microbe while inhibiting others.
4. How is the streak plate method different from the pour plate method?
The main difference lies in where the microbial colonies grow. In the streak plate method, colonies grow only on the surface of the agar. In the pour plate method, the inoculum is mixed into the agar itself, so colonies develop both on the surface and embedded within the agar medium. The streak plate method is generally faster and more common for isolation.
5. What happens if sterile techniques are not used when preparing a pure culture?
If sterile (aseptic) techniques are not followed, the culture will become contaminated. This means unwanted microbes from the air, your hands, or non-sterile equipment will grow alongside your target organism. A contaminated culture is no longer 'pure' and can lead to incorrect experimental results, failed diagnostics, or spoiled industrial products.
6. What environmental conditions are crucial for growing a pure culture?
For successful growth, a pure culture requires a controlled environment with the right conditions. Key factors include:
- Nutrients: A suitable growth medium that provides all the necessary food for the microbe.
- Temperature: Each microbe has an optimal temperature for growth.
- Oxygen: Some microbes need oxygen (aerobes), while others are killed by it (anaerobes).
- pH Level: The acidity or alkalinity of the medium must be within the microbe's preferred range.
7. What is the real-world application of using an enrichment culture?
Enrichment cultures are very useful when you need to isolate a specific microbe that is rare in a natural sample, like soil or water. For example, if you want to find bacteria that can break down oil, you would create a medium where oil is the only source of carbon. This enriches the population by allowing only the oil-eating bacteria to grow, making them much easier to isolate.
8. How did Robert Koch's work contribute to pure culture techniques?
Robert Koch was a pioneer in microbiology who developed many of the foundational techniques we still use. His key contribution was developing methods to grow bacteria on solid media like agar. This allowed individual bacterial cells to grow into visible, isolated colonies. By picking a single colony, he could be sure he was growing a pure culture, a critical step in proving that specific microbes cause specific diseases (Koch's Postulates).
