Difference Between Selective and Differential Media

Main Difference – Selective vs Differential Media

Selective and differential media are two types of media used to isolate and identify microorganisms. The main difference between selective and differential media is that selective media are used to isolate a particular strain of microorganisms whereas differential media are used to identify and differentiate a closely-related group of microorganisms. Selective media use specific growth characteristics of a microorganism to selectively grow that microorganism in the growth medium. Differential media allow the characterization of several microorganisms based on the growth patterns of them.

Key Areas Covered

1. What is Selective Media
– Definition, Role, Examples
2. What is Differential Media
– Definition, Role, Examples
3. What are the Similarities Between Selective and Differential Media
– Outline of Common Features
4. What is the Difference Between Selective and Differential Media
– Comparison of Key Differences

Key Terms: Antibiotic Resistance, Biochemical Characteristics, Differential Media, Indicators, Marker, Microorganisms, Selective Media

What is Selective Media

Selective media refer to a type of growth media that allows the growth of selected microorganisms in the medium. For example, if a particular microorganism is resistant to a particular antibiotic such as tetracycline or ampicillin, that antibiotic can be added to the medium, prohibiting the growth of other microorganisms in that medium. Selective growth media also ensures the survival and proliferation of microorganisms with certain properties. The gene that gives the ability to grow in the selective medium is known as the marker. Eukaryotic cells can also be grown in selective media. The selective media for eukaryotic cells commonly contain neomycin. A microorganism that grows on a selective agar medium is shown in figure 1.

Main Difference - Selective vs Differential Media

Figure 1: Trichophyton tonsurans

Some examples of selective media are shown in the table below.

Types of Selective Media

Selective Media	Type of Organisms
Eosin methylene blue (EMB)	Gram-negative bacteria
YM	Yeast and mold
MacConkey agar	Gram-negative bacteria
Hektoen enteric agar (HE)	Gram-negative bacteria
Mannitol salt agar (MSA)	Gram-positive bacteria
Terrific Broth (TB)	Recombinant strains of E.coli
Xylose lysine desoxycholate (XLD)	Gram-negative bacteria

What is Differential Media

Differential media refer to a type of growth media that allows the differentiation of closely-related microorganisms. Differential media is also known as indicator media. The biochemical characteristics of a microorganism are used in the differentiation and identification of the microorganism among other microorganisms. Specific nutrients or indicators are used in the differential media. The indicators can be either eosin y, neutral red, phenol red or methylene blue. They are added to the medium to indicate the above-mentioned characteristics visible in the medium. Selective and differential media are shown in figure 2.

Difference Between Selective and Differential Media

Figure 2: Selective (right) and Differential (left) Media

Types of Differential Media

Differential Media	Significance
Blood agar	Contains bovine heart blood that becomes transparent in the presence of hemolytic
Streptococcuseosin methylene blue (EMB)	Differential for lactose and sucrose fermentation
MacConkey (MCK)	Differential for lactose fermentation
Mannitol salt agar (MSA)	Differential for mannitol fermentation
X-gal plates	Differential for lac operon mutants

Similarities Between Selective and Differential Media

Selective and differential media are two types of growth media used to grow microorganisms.
Both selective and differential media are used to isolate and identify microorganisms.

Definition

Selective Media: Selective media refer to a type of growth media that allows the growth of selected microorganisms in the medium.

Differential Media: Differential media refer to a type of growth media that allows the differentiation of closely-related microorganisms.

Purpose

Selective Media: Selective media are used to isolate a particular strain of microorganisms.

Differential Media: Differential media are used to identify and differentiate closely-related microorganisms.

Types of Characteristics

Selective Media: Selective media use specific growth characteristics of a particular microorganism to select it from the others.

Differential Media: Differential media use unique growth patterns of microorganisms to differentiate them from others.

Number of Microorganisms

Selective Media: Selective media only allow the growth of a single microorganism in the medium.

Differential Media: Differential media allow several closely-related microorganisms to grow in the medium.

Indicators

Selective Media: Selective media do not use indicators.

Differential Media: Differential media use indicators.

Conclusion

Selective and differential media are two types of growth media used to isolate and identify microorganisms. Selective media are used to isolate a particular type of microorganism by giving a specific condition for the growth of that particular microorganism. Differential media are used to identify and differentiate microorganisms from a closely-related group with the help of unique growth patterns. The main difference between selective and differential media is their role in the identification of microorganisms.

Reference:

1. “Culturing Media.” Boundless Microbiology, Available here.

Image Courtesy:

1. “Trichophyton tonsurans on Dermatophyte Selective Agar” By Nathan Reading from Halesowen, UK – Trichophyton tonsurans on Dermatophyte Selective Agar (CC BY 2.0) via Commons Wikimedia
2. “Neisseria gonorrhoeae 01” (Public Domain) via Commons Wikimedia