Difference Between Colony and Plaque Hybridization

The main difference between colony and plaque hybridization is that the colony hybridization is the method used in the selection of bacterial colonies with the desired genes whereas the plaque hybridization is the selection method of phages with desired genes. Furthermore, colony hybridization can be used in the screening of plasmid– or cosmid-based libraries while plaque hybridization can be used in the screening of phage libraries.

Colony and plaque hybridization are two techniques used in the screening of genomic or cDNA libraries. They are also called colony lift and plaque lift respectively.

Key Areas Covered

1. What is Colony Hybridization
     – Definition, Type of Libraries, Screening Methods
2. What is Plaque Hybridization
     – Definition, Type of Libraries, Screening Methods
3. What are the Similarities Between Colony and Plaque Hybridization
     – Outline of Common Features
4. What is the Difference Between Colony and Plaque Hybridization
     – Comparison of Key Differences

Key Terms

Colony, Colony Hybridization, Library Screening, Plaque, Plaque Hybridization

What is Colony Hybridization

Colony hybridization is a screening method used in the selection of bacterial colonies with a desired DNA sequence. It is also called colony blot hybridization, colony lift or replica plating. It allows the screening of colonies plated with high density. The original procedure of colony hybridization was first developed by Grunstein and Hogness. First, the bacterial colonies can be transformed onto a membrane and the bacterial colonies are lysed, exposing the nucleic acids. Then, the exposed nucleic acids are fixed onto the membrane by denaturing them and are hybridized with the radioactive probes.

Figure 1: Colony Hybridization Method

A colony is a cluster of bacteria developed from a single bacterial cell through the asexual reproduction. Hence, all bacterial cells in a particular colony possess the same genetic makeup as well as the transformed genetic material. Generally, bacteria are transformed with the aid of plasmid or cosmid vectors.

What is Plaque Hybridization

Plaque hybridization is the screening method for recombinant phages. It is a modification of colony hybridization by Benton and Devis in 1977. The method is also called plaque lift. Plaque hybridization procedure is similar to the colony hybridization procedure and the plaques are lifted by contacting them to a nitrocellulose membrane. Nucleic acids are then exposed and fixed on to the membrane, hybridizing with desired probes.

Figure 2: Plaques on an Agar Plate

A plaque is a clear zone on an agar plate produced by a particular bacteriophage by the lysis of bacterial cells on that area. Due to the less amount of DNA transferred on to the nitrocellulose membrane, plaque hybridization produces fewer background signals.

Similarities Between Colony and Plaque Hybridization

• Colony and plaque hybridization are two techniques used in the screening of genomic or cDNA libraries.
• The main principle in both techniques is the nucleic acid hybridization.
• Both are filter hybridization methods, which allow the primary screening of libraries by in Situ replication on a nitrocellulose membrane.
• They allow high density screening.
• A single-stranded DNA molecule is used as a probe, which can hybridize to its complementary sequence in order to identify the specific sequences.
• Both hybridization techniques are quick and can handle a very large number of clones.
• They are used in the identification of incomplete gene sequences, which cannot be expressed.

Difference Between Colony and Plaque Hybridization

Definition

Colony hybridization refers to a method of selecting bacterial colonies with desired genes while plaque hybridization refers to a screening method used in the identification of recombinant phages.

Developed by

The colony hybridization was first developed by Grunstein and Hogness while the plaque hybridization was first developed by Benton and Devis in 1977.

Types of Libraries

Colony hybridization involves the identification of plasmid- or cosmid-based libraries while plaque hybridization involves the identification of phage libraries.

Number of Lifts

Colonies can be lifted for a single time while plaques can be lifted several times.

Background Signals

More background signals occur in the colony hybridization while the background signals are less in plaque hybridization.

Conclusion

The colony hybridization is a screening method of bacterial colonies in the libraries produced with plasmid or cosmid vectors. On the other hand, plaque hybridization is a screening method of bacteriophages in the phage libraries. The main difference between colony and plaque hybridization is the type of libraries screened in each method.

Reference:

1. Kaksonen, Anna. “Molecular Approaches for Microbial Community Analysis.” Leaching – BioMineWiki, 20 Apr. 2006, Available here
2. Dale, J W, and P J Greenaway. “Identification of Recombinant Phages by Plaque Hybridization.” Methods in Molecular Biology (Clifton, N.J.)., U.S. National Library of Medicine, Available Here

Image Courtesy:

1. “Blot Hybridization” By Kaksonen – http://wiki.biomine.skelleftea.se/biomine/molecular/index_22.htm (Public Domain) via Commons Wikimedia 
2. “M. smegmatis plaque” By Wazzzup7up – Own work (Public Domain) via Commons Wikimedia