EVERYTHING YOU NEED TO KNOW ABOUT PURE CULTURE

PURE CULTURE TECHNIQUE

Isolating a culture from a single bacterial strain or spore of fungus having no contamination of other bacterial strains or spores of other fungi is called pure culture.

MIX CULTURE

When a culture contains two or more different strains of bacteria is called a mixed culture.

HISTORY

From the 1800s to 1900s (this era is called the Golden Age of Microbiology) involved isolating pure cultures by creating artificial environments for the purpose of studies.

Was Edwin Klebs (1873) the first to give the concept of the dilution method?

Edwin Klebs was the first to give the concept of the fractional method which was a letter called the dilution method it involved the subculturing of a small volume from one liquid medium into another.

Then comes the Lister (1878) who added a loopful of spoiled milk into sterile water and observed the one bacterium into the glass slide. He then inoculated the milk sample with the previously inoculated boiled water but as it was quite obvious due to the lack of pure culture technique different morphological differences were observed.

WHAT WERE THE OBSTACLES IN PREPARING SOLID CULTURE MEDIA:

1) It was very costly method.

2) It was very difficult to maintain the consistency in the environment of the lab to prevent the variation in growth from one lab to another.

3) Lack of qualified staff.

4) It was very difficult to increase the shelf life of media and media were constantly getting spoiled.

In 1908 Prof R. Doerr poured nutrient agar on a petri plate and let the petri plate dry.

KOSCH AND POTATO

Kosch used potatoes and put them in glass vessels motile bacteria grew over them but it was investigated then potatoes were not a good substrate for every type of bacteria to grow. Then Kosch investigated Kleb's concept and thought that it would be better to solidify liquid medium to get isolated colonies

 Kosch in the 19th century used agar-agar as a solidifying agent for isolated pure colonies of Bacillus anthracis which was responsible for anthrax.

Kosch then represented his "Kosch postulates" which represented a criterion to establish a relationship between an organism and a disease.

Later in the 20th century, two microbiologists Julius Petri and Richard Julius Petri created a diagnostic tool for cultivating microorganisms which is called now a petri dish. The discovery of the petri dish revolutionized the whole microbiology field.

 Most of the strains which are isolating are heterotrophic which means they require organic compounds for their growth in a medium. The nutrient supplements that are added are extracts of proteins, inorganic salts, and sometimes carbohydrates. For fastidious organisms vitamins and other growth factors are also added.

When a pure culture is grown in a medium it utilizes all the nutrients and excrete toxic metabolites which eventually makes the culture die so periodic subculturing is necessary into a new medium.

WHY IT IS IMPORTANT TO HAVE A PURE CULTURE?

1) It helps to test antibiotic susceptibility test.

2) Genomic sequence could be done.

3) Proteomic studies could be done which helps to analyse the antigenicity of these proteins which facilitates the production of these proteins for serological tests.

PURE CULTURE IS A FAILURE IN TWO IMPORTANT PROCESSES:

1)      Fermentation

Fermentation involves the conversion of lactose of milk into lactic acid which settles milk solid into curd by different Lactic Acid Bacteria (LAB) although this could be done by pre-culture involving only one species of LAB the typical taste of curd could be lost.

2)      Waste Water Treatment

In this treatment by aerobic/microaerophilic bacteria complex organic compounds are converted into simpler compounds and then by anaerobic bacteria these simpler compounds are converted into different biogases, so pure culture fails to produce these biogases.

METHODS OF OBTAINING PURE CULTURE:

1) By serial dilution

The sample is taken and it is serially diluted then a small volume is taken and it is poured or spread on a medium after incubation isolated colonies are obtained.

2) By streak plate technique

A small volume of culture is taken in a wire loop and then spread over the surface of the agar after incubation isolated colonies are obtained.

3) By selective medium

This medium selects only the desired colonies.

4) By differential medium

This medium differentiates between the desired and undesired colonies

PURE CULTURE AND ITS FUTURE PERSPECTIVE

1) In medicine

Pure CULTURE isolation led to more advanced drug development and will help in understanding the host-pathogen relationship

2) In Biotechnology

More amino acids, antibiotics, and enzymes will be synthesized artificially by pure culture isolation.

3) In agriculture

Plant health can be improved by microorganisms which is possible only by pure culture isolation.

4) In Research

As research is advancing more and more day by day need for pure culture is increasing for this purpose as it provides a controlled environment.

5) In Bioremediation

Microorganisms help degrading pollutants and help in cleaning the environment

ALL THE CLONES ARE PURE CULTURES BUT ALL THE PURE CULTURES ARE NOT CLONES.

This statement can be explained as all the pure culture containing different strains of the same species but doesn't contain strains of different species so it is a clone but the strains of the same species are not genetically similar as for the clones, they should be genetically similar so they are not clones.