Spot Forming Units
Spot Forming Units - Related Videos
06:37
Quantification of Colony-Forming Units of Gut-Associated Bacteria in Drosophila Flies
0 Views •
2025
Source: Dodge, R., et al. Fast Colony Forming Unit Counting in 96-Well Plate Format Applied to the Drosophila Microbiome. J. Vis. Exp. (2023)This video demonstrates the quantification of colony-forming units (CFUs) of gut-associated bacteria in Drosophila flies using a serial dilution and plating approach. Homogenized fly samples containing gut bacteria are serially diluted, plated on agar, and incubated to allow colony growth. Images of the plates are then analyzed using software to align,...
08:31
Identification and Isolation of Burst-Forming Unit and Colony-Forming Unit Erythroid Progenitors from Mouse Tissue by Flow Cytometry
0 Views •
Cited by 13 •
2022
Here, we describe a novel flow cytometric method for prospective isolation of early burst-forming unit erythroid (BFU-e) and colony-forming unit erythroid (CFU-e) progenitors directly from fresh mouse bone marrow and spleen. This protocol, developed based on single-cell transcriptomic data, is the first to isolate all the tissue's erythroid progenitors with high purity.
03:55
Counting Colony Forming Units (CFUs): Quantifying Bacteria from Fly Bodies
0 Views •
2023
Drosophila microbiota impacts the animal's development, immunity and physiology. This video describes a method to quantify bacteria from flies by determining the colony forming units from whole body preparations. The featured protocol demonstrates the technique with flies, reared under gnotobiotic conditions using four bacterial species.
03:33
Quantification of Bacterial Infection in Host Cells by the Colony-Forming Unit Assay
0 Views •
2025
This video demonstrates an in vitro quantification technique to determine Listeria monocytogenes infection of macrophages by the colony-forming unit assay. The bacterial colonies on the agar plate represent the intracellular bacterial population that escapes the host-defense mechanism and survives within the macrophages.
12:15
Growth Curves: Generating Growth Curves Using Colony Forming Units and Optical Density Measurements
0 Views •
2023
Source: Andrew J. Van Alst1, Rhiannon M. LeVeque1, Natalia Martin1, and Victor J. DiRita1 1 Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America Growth curves provide valuable information on bacterial growth kinetics and cell physiology. They allow us to determine how bacteria respond in variable growth conditions as well as to define optimal growth parameters for a given bacterium. An archetypal growth curve progresses...
FAQs
The assay first immobilizes secreted cytokines or antibodies by allowing them to bind capture antibodies on a membrane. Labeled detection antibodies then recognize the captured molecules, producing localized signals that appear as spots. This sequence links a cell’s secretion to a spatially confined readout, enabling researchers to count responding cells rather than measuring only the total molecule in a sample.
Normalizing Spot Forming Units to a defined cell number makes responses more comparable between samples with different input sizes. The resulting value reflects the frequency of cells releasing the measured cytokine or antibody, rather than simply the amount produced by the entire culture. This supports comparisons of antigen-specific responses and immune activation across experimental groups.
SFU measurements provide a functional readout because they capture secretion by individual responding cells. They can therefore reveal antigen-specific T-cell or B-cell activity even when only a relatively small sample is available. This combination of functional information and sample efficiency helps investigators assess immune responsiveness in studies of infection, vaccination, and immunotherapy.
An ELISpot workflow places cells in contact with a membrane carrying capture antibodies, allowing secreted cytokines or antibodies to bind locally. Labeled detection antibodies are then applied to identify the captured products and produce visible spots. Investigators count those spots and report the result relative to the defined number of cells used in the assay.
Researchers can measure responses from samples exposed to a relevant antigen and compare the normalized Spot Forming Units between experimental conditions or groups. Differences in spot frequency indicate differences in the number of cells releasing the measured cytokine or antibody. This makes the assay useful for examining immune activation associated with infection, vaccination, or immunotherapy.
The measured secreted product determines the immune activity being assessed. Cytokine-focused measurements can examine antigen-specific T-cell responses, whereas antibody-focused measurements can evaluate B-cell secretion. Because the assay records these activities as localized cellular responses, SFU data can connect infection or immune intervention with changes in functional cellular immunity.