Which of the following bacteria is correctly paired with its FISH probe?

• A. Lactobacillus spp. with Lacto999
• B. Clostridium spp. with Erec482
• C. Streptococcus spp. with Strep123
• D. Bifidobacterium spp. with Bifi789

Answer: (B)

FISH probes are short DNA sequences designed to bind specifically to ribosomal RNA of particular bacterial groups, so the probe name often reflects its target. Erec482 is a well-established probe that binds to 16S rRNA sequences characteristic of the Erec_482 group within the Clostridium coccoides–Eubacterium rectale cluster, a set of Firmicutes commonly grouped under Clostridium spp. This makes the pairing with Clostridium spp. a correct and widely used combination for detecting those gut bacteria in situ. The other proposed probe names do not correspond to standard, validated probes for those taxa, so they aren’t recognized as correct pairings in typical FISH panels. In practice, researchers rely on validated probes like Erec482 to quantify Clostridium-coccoides–Eubacterium rectale–related populations, while Lactobacillus and Bifidobacterium would use different, specifically validated probes (with different designations) if targeted.