GVA is a high throughput cell viability assay for microbiology. Akin to the classic CFU assay, GVA measures the number of viable microbes in a sample based on counting discrete colonies. The classic CFU assay uses a dilution series to measure viable cell concentrations across the many orders of magnitude that exist in nature; but this comes at the expense of time and resources. In contrast, GVA leverages the geometry of a cone to allow nature to run the dilution series for you at 30X the speed! Fortunately, you likely have a cone sitting on your bench in the form of a pipette tip.
How to set up a GVA assay
While there are several approaches to counting your cells, the protocol always begins with embedding cells within a hydrogel (e.g., agarose) in a pipette tip. Start with a sample containing microbes, mix it with a liquid gel, then allow the gel to solidify inside the pipette tip. After incubating the pipette tips until each bacterium forms a colony, measure the colony positions using one of the three approaches detailed below. Happy counting!
Preparing your Samples