Researchers studying the human gut microbiome can measure vastly different levels of microbial genetic material, proteins, and lipids because of technical or methodological differences. To make microbiome studies more standardized and reproducible, NIST is making a stable, homogeneous human stool reference material.

Modified from ©, drogatnev, ai_yoshi, mountainbrothers, fairywong
NIST hired a contractor to recruit two groups of people to provide the stool samples. For their current reference material: vegetarians and omnivores (1). Each participant provided stool samples over the course of multiple days; the samples were frozen and stored. They also kept track of their food intake so that researchers knew what types of molecules to expect in the stool (2). The frozen stool samples were thawed, and each groups samples blended together with some water to dilute the mixture (3). Researchers poured the mixture into one milliliter tubes. The blending process produces homogeneous contents, so each tube containeds the same mixture of molecules and other bacterial products. The tubes were frozen and packaged in boxes that each contained a few tubes from each group (4).

          Illustration shows how researchers can use NIST reference samples in their metabolomics experiments.
Soon, researchers will be able to purchase these reference materials from NIST. This will allow scientists to standardize their measurements across time, lab equipment, and methodologies. When each lab runs an experiment, they can include one of the NIST reference materials—either vegetarian or omnivore—in their experiments alongside their own collected stool samples as a baseline for other measurements (5,7).

Different teams may measure the same molecule at different levels due to technical discrepancies. Including the same NIST reference material provides a common point of reference for comparing results across tests (6,8).

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