Liquid Overlay
Liquid Overlay - Related Videos
04:33
Evaluation of a Liquid Overlay System for Viral Plaque Assays
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2026
Source: Baer, A. and Kehn-Hall, K. Viral Concentration Determination Through Plaque Assays: Using Traditional and Novel Overlay Systems. J. Vis. Exp. (2014).This video demonstrates the use of a liquid microcrystalline cellulose-based overlay in a plaque-based assay by comparing its effectiveness in viral plaque formation with that of a traditional semi-solid agarose overlay.
09:28
Viral Concentration Determination Through Plaque Assays: Using Traditional and Novel Overlay Systems
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Cited by 466 •
2014
Plaque assays are the gold standard for viral quantification, utilizing entrapping overlays on host cellular monolayers to determine viral titers. While various semisolid overlays have traditionally been used, here we demonstrate plaque techniques comparing semisolid overlays to a novel liquid microcrystalline cellulose among several families of viruses.
06:38
Use of the Soft-agar Overlay Technique to Screen for Bacterially Produced Inhibitory Compounds
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Cited by 141 •
2017
We describe a simple method for screening bacterial cultures for the production of compounds inhibitory towards other bacteria.
09:21
Efficiency of Liquid-liquid Extraction
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2023
Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA Liquid-liquid extraction (LLE) is a separation technique used instead of distillation when either: (a) the relative volatilities of the compounds to be separated are very similar; (b) one or more of the mixture components are temperature sensitive even near ambient conditions; (c) the distillation would require a very low pressure or a very high distillate/feed...
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.
FAQs
Diffusion allows soluble nutrients, signaling molecules, infectious particles, and antimicrobial compounds to move between the overlay and the biological sample. This exchange determines which factors remain available to cells or microorganisms during incubation. Measuring resulting changes in growth, viability, or infection can therefore connect a biological response to components that were present in the surrounding medium.
The medium determines which soluble factors contact the sample and remain available throughout incubation. Depending on its components, the overlay can support microbial survival, expose cells to antimicrobial compounds, or permit interaction with signaling and infectious factors. Comparing defined media helps investigators associate differences in biological responses with specific components rather than with the sample alone.
Growth, viability, and infection provide distinct measurable outcomes after incubation. A change in growth may indicate altered microbial support or inhibition, whereas viability reflects whether cells or microorganisms remain alive. Infection-related changes can show how surrounding soluble factors influence host–pathogen interactions. Together, these readouts help link visible or measurable effects to experimental conditions.
A typical workflow places a defined liquid medium over cells, microorganisms, or another biological sample, followed by incubation that permits continued contact and soluble-factor exchange. Investigators then assess changes in growth, viability, or infection under the selected condition. When secreted products are relevant, the surrounding liquid can also be recovered for further comparison or analysis.
This approach is useful when researchers need controlled contact between a sample and soluble immune, microbial, therapeutic, or signaling factors. It can support studies of host–pathogen interactions, microbial survival, and responses to antimicrobial compounds. By comparing experimental conditions, investigators can examine how defined surrounding factors alter infection-related or cellular outcomes.
Researchers can vary the defined components of the surrounding medium and compare the resulting growth, viability, or infection responses. This design helps identify whether a particular soluble factor contributes to support, inhibition, or another biological effect. Recovering secreted products from the overlay adds another comparison point, linking environmental conditions with released material and observed outcomes.