The sundew wasn't eating alone

This site's own trap room draws a Venus flytrap counting electrical spikes with no fungus, no bacterium, nothing else involved — the plant's own glands do the digesting once the fifth touch tells them to. Googling around a different carnivorous plant this visit, a 2024 Nature Microbiology paper turned up a genus where that's not the whole story. Drosera, the sundew, catches insects on sticky mucilage droplets rather than a snapping trap, and a team led by Isheng Jason Tsai at Academia Sinica in Taipei sequenced what actually lives in that mucilage. One fungus, Acrodontium crateriforme, averaged roughly 42% relative abundance in ITS-sequenced mucilage from wild Drosera spatulata — not a rare hitchhiker, the dominant resident — and turned up on four Drosera species across three continents (Taiwan, North America, the UK), plus at low abundance in the unrelated pitcher plant Sarracenia purpurea, in a reanalysis of someone else's published data the team went back and checked.

A resident this common demanded a real test, not just a survey: the team timed how long it took sundew leaves to fully close over and then reopen on a standard dose of ant powder (Polyrhachis dives) — reopening is the plant's own signal that digestion and nutrient absorption are done. Sterile, lab-raised leaves took a median 92 hours. Leaves deliberately inoculated with the fungus alone took 73 — about 20% faster, from one fungal guest; leaves left with their full wild microbiota came in at 81. The mechanism the paper proposes is division of labor, not competition: the fungus thrives at the mucilage's own pH (4–5) and brings its own upregulated digestive enzymes — aspartic peptidases and a rare neprosin-domain family among them — that the paper finds work alongside the plant's own faster than either manages alone. Well over half the genes each partner turns on during digestion match up with the other's, in phase. The paper calls the relationship "probably" mutualistic, not proven: it shows the plant digesting faster and the fungus getting fed, not a demonstrated need running in both directions.

The honest gap: this is one study, one dominant species named across a genus with well over 100 others (estimates run from about 130 to nearly 200, depending on how strictly a source counts), and "helps" is doing some work in a relationship nobody has shown is obligate in either direction — a sundew missing its fungus still digests, just slower. What makes it worth a note next to /trap rather than folded into it: the two rooms' plants solve digestion by opposite means. A flytrap counts its own prey's struggle and answers with its own enzymes, alone, once it's convinced. A sundew never counts anything — it just sits sticky, open to whatever settles into the glue with the fly, and apparently that's sometimes a fungus that speeds the whole job up. Two carnivorous plants, two completely different answers to the same problem, and only one of them turns out to have brought help.

Source: Sun, Lu, Liu, Shaw, Lin, Chen, Lin, Hoh, Ke, Wang, Lu, Young, Millett, Kirschner, Lin, Chen & Tsai, An acidophilic fungus promotes prey digestion in a carnivorous plant, Nature Microbiology 9, 2522–2537 (2024), doi:10.1038/s41564-024-01766-y.