Why is null hypothesis testing critical for viable cell count comparisons?

Null hypothesis testing enables objective evaluation of whether observed differences in viable bacterial counts between wild-type and cellulose-deficient strains are statistically significant, supporting robust target validation decisions.

How does independent variable isolation improve root colonization assays?

Isolating variables such as cellulose production allows teams to attribute changes in root colonization directly to specific genetic or biochemical factors, increasing mechanistic clarity in the discovery pipeline.

What do quantitative dependent variable measurements enable in this protocol?

Quantitative measurement of viable cell counts provides reproducible data for comparing bacterial adhesion and colonization, enabling reliable assessment of intervention effects and supporting data-driven advancement decisions.

Why are replication requirements important for cross-functional collaboration?

Replication ensures that viable cell count results are consistent and reproducible across teams, facilitating cross-functional data integration and increasing confidence in portfolio-level decisions.

What statistical analysis capabilities are needed before implementing viable count assays?

Teams require statistical tools to analyze differences in viable counts, assess significance, and control for experimental variability, ensuring that assay outputs support rigorous R&D decision-making.

Assessing Root Colonization of Tomato Seedlings by a Pathogenic Bacterium Using Viable Cell Counts

JoVE Encyclopedia of Experiments

Microbiology

0 views • 2:30 min • February 26th, 2026

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Take containers holding tomato seedlings grown in sterile sand.

The seedling roots are inoculated with either a cellulose-producing wild-type or a cellulose-deficient mutant strain of a plant-pathogenic bacterium.

Remove the sealing material from one container, invert it on sterile paper, and tap to release the sand cylinder containing the plant.

Split the sand cylinder lengthwise to expose the root.

Then, dip the root into a sterile buffer and shake to dislodge loosely attached bacteria.

Repeat the process for the other root.

Transfer the washed roots to a fresh buffer. Sonicate them to release tightly adhered bacteria.

Use these sonicated suspensions to prepare serial dilutions, plate them on agar, and incubate to allow viable bacteria to form colonies.

Higher viable counts in the wild-type strain, compared to the cellulose-deficient mutant, highlight the critical role of cellulose fibrils in promoting bacterial adhesion to the root surface.

To determine the number of viable bacteria found to plants grown in sand, begin by removing the sealing material from the top and bottom of the container.

Place the container over a piece of sterile paper and gently knock the container against the surface to loosen the sand before gently lifting the sand with the plant from the container.

When the cylinder of sand and the plant are free on the paper, split the sand down the middle to reveal the plant root. If desired, take samples of the sand from near the edge of the container as well as near the root. This may be useful to determine the spread, accumulation, and growth of bacteria.

Pick up the root and remove the sand and bacteria that are loosely adhered by dipping the root in a measured volume of water or buffer and gently shaking. Determine the viable cell count of the bacteria in the resulting suspension by plating it on suitable medium such as Luria agar. This represents the number of bacteria loosely associated with the root. Finally, remove the tightly bound bacteria by sonication and determine their numbers.