High-throughput detection and quantification of vitamin B₁₂in microbiome isolates usingEscherichia coli

Vitamin B₁₂is an essential micronutrient produced only by prokaryotes, and animals must acquire it from their diet. Vitamin B₁₂is critical for the synthesis of methionine and propionyl-CoA metabolism. In humans, vitamin B₁₂deficiency has been linked to many disorders, including infertility and developmental abnormalities. The growing trend towards plant-based diets and the ageing populations increase the risk of vitamin B₁₂deficiency, and therefore, there is an increasing interest in understanding vitamin B₁₂biology. Accurate approaches for detecting and quantifying vitamin B₁₂are essential in studying its complex biology, from its biogenesis in Bacteria and Archaea to its effects in complex organisms. Here, we present an approach using the commonly availableE. colimethionine auxotroph strain B834 (DE3) and a multi-well spectrophotometer to detect and quantify vitamin B₁₂from biological samples at picomolar concentrations. We further show that our quantification method for vitamin B₁₂is sufficient to reveal important differences in the production of vitamin B₁₂from vitamin B₁₂-synthesising bacteria commonly found in the microbiome of wildCaenorhabditis elegansisolates. Our results establish a high-throughput and simple assay platform for detecting and quantifying vitamin B₁₂using theE. coliB834 (DE3) strain.