Agar Diffusion Assay
Agar Diffusion Assay - Related Videos
03:37
Assessing the Antimicrobial Activity of Nisin Variants Using an Agar Well Diffusion Assay
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2025
Source: Nickling, J. H., et.al. Antimicrobial Peptides Produced by Selective Pressure Incorporation of Non-canonical Amino Acids. J. Vis. Exp. (2018)This video demonstrates an agar well diffusion assay used to evaluate the antimicrobial activity of nisin variants. It shows how Lactococcus lactis expressing the membrane-bound peptidase NisP activates nisin precursors produced in E. coli, resulting in growth inhibition halos. The size of these halos reflects the bioactivity of each nisin variant.
04:36
Assay for Adhesion and Agar Invasion in S. cerevisiae
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Cited by 17 •
2006
We describe a qualitative assay for yeast adhesion and agar invasion as a measure of invasive and pseudohyphal differentiation. This simple assay can be used to assess the invasive phenotype of various mutants as well as the effects environmental cues and signaling pathways on yeast differentiation.
06:08
A Charcoal Agar Resazurin Assay to Evaluate Test Compound Activity Against Mycobacteria
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2025
This video showcases the Charcoal Agar Resazurin Assay (CARA) for evaluating the activity of antimicrobial compounds against Mycobacterium tuberculosis. CARA aids in assessing the efficacy of these compounds by gauging their impact on bacterial growth and distinguishing between bactericidal and bacteriostatic effects.
03:17
Soft Agar Overlay Assay for Detecting Bacteriocin-Mediated Killing in Pseudomonas syringae
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2025
Source: Hockett, K. L., and Baltrus, D. A. Use of the Soft-agar Overlay Technique to Screen for Bacterially Produced Inhibitory Compounds. J. Vis. Exp. (2017)This video demonstrates the procedure for detecting bacteriocin-mediated killing by spotting supernatant from an antibiotic-induced donor strain onto a soft agar overlay containing a test strain. Clear zones formed after incubation indicate bacterial inhibition.
08:18
Diffusion and Osmosis - Student Protocol
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2019
Diffusion in Agar ExpandNOTE: In this exercise, you will be given agar containing an indicator chemical called phenolphthalein. When phenolphthalein is exposed to the normal alkaline conditions in the agar, it will look pink. But when it is exposed to neutral or acidic conditions, it changes from pink to clear. You will make different size and shaped agar cubes as a model for cells to study the impact of cell size and shape on diffusion rate. To make the first set of cells, measure out and cut...
FAQs
Diffusion spreads the applied compound outward from a well or paper disk through the agar. If the agent inhibits the microorganism occupying the surrounding medium, growth is reduced in the area reached effectively, producing a clear region. Measuring that region converts a spatial growth response into a zone diameter for comparative evaluation under defined conditions.
The diameter reflects the outcome of antimicrobial activity as the sample moves through the agar, so it provides a basis for comparing agents or formulations tested under the same defined conditions. Its value is therefore evaluative and comparative, supporting assessment within the assay context rather than an unrestricted claim about performance in every setting.
Wells and paper disks provide two ways to position a sample directly on the agar surface. The surrounding microorganism-containing medium then allows the compound to diffuse from that application site. This flexibility enables investigators to evaluate antimicrobial samples in a format suited to the material being examined while retaining the same zone-based readout.
A basic workflow spreads the microorganism across an agar medium, places the antimicrobial sample in a well or on a paper disk, and allows the compound to diffuse through the gel. Investigators then examine the surrounding growth pattern and measure the clear zone diameter, using the result for comparison under defined conditions.
In bioengineering, the assay supports early screening and performance evaluation of antibiotics, antimicrobial biomaterials, coatings, and drug delivery systems. By measuring the inhibition zone produced by each sample, researchers can compare candidate designs or formulations and identify materials that warrant further development or quality evaluation.
The inhibition-zone diameter provides a comparative indication of how effectively a tested sample suppresses microbial growth under the assay conditions. This outcome helps distinguish performance among antibiotics, biomaterials, coatings, or delivery-system formulations. Because the result is tied to defined testing conditions, it is most useful for structured comparison during screening and product evaluation.