Welcome to the next episode of the WOrM Podcast 🪱Today we’re talking about something unexpected.A bioplastic — something we usually think of as sustainable, useful, even beneficial —can kill a worm.⸻🧬 The central ideaSome bacteria produce a polymer called polyhydroxybutyrate (PHB).It’s a carbon storage material.A bioplastic.But when C. elegans eats bacteria packed with PHB —it dies. ⸻🔬 What’s actually going on?This is not classic toxicity.It’s not a signalling pathway.It’s physical and systemic failure.PHB accumulates inside the bacteria, and when ingested:• the pharynx becomes deformed• the intestine distends• the gut barrier breaks down• the defecation programme fails The worm can’t process what it’s eating.It gets blocked.⸻⚡ Metabolism drives the effectThe key twist is this:PHB is only produced under certain metabolic conditions —when bacteria have excess carbon (like lactate or pyruvate). So the same bacteria can be:• harmless• or lethaldepending on what they’re fed.This is not just host–pathogen.It’s host–microbe–metabolism.⸻🧠 Cause and effect, proven cleanlyThey show this properly:• knock out PHB production → worms survive• engineer E. coli to make PHB → worms dieSo PHB is not correlated.It is sufficient to kill. ⸻🧠 The mechanism is mechanicalInside the worm:• PHB granules accumulate• the gut becomes physically obstructed• calcium waves that drive defecation become irregular or stop• the system collapsesThis is behaviour and physiology breaking down from the inside.⸻🧠 A partial rescue — and a clueMutations in nuc-1 rescue about half the animals. This gene normally helps digest bacterial DNA.Without it:• worms process PHB-containing food differently• less blockage occurs• survival improvesSo digestion itself is part of the failure mode.⸻🌍 The bigger pictureThis matters because:• many bacteria in natural worm environments can produce PHB• PHB production depends on nutrient context• host survival depends on bacterial metabolism, not just speciesSo ecology is not static.It’s state-dependent chemistry interacting with biology.⸻🧠 The take-home messageThis is not about a toxin.It’s about material inside bacteria becoming lethal through ingestion.And more broadly:what microbes make — and when they make it — can reshape host physiology completely.⸻📄 Paper discussedGiese, G. E.; Richards, D. M.; Florman, J. T.; Starbard, A. N.; Xu, A. A.; Durning, D. J.; Alkema, M. J.; Walhout, A. J. M. (2026)Bacteria producing the bioplastic polyhydroxybutyrate kill the nematode Caenorhabditis elegansPLOS Biologyhttps://doi.org/10.1371/journal.pbio.3003748If you enjoyed this episode, please like, follow, and subscribe wherever you listen to the WOrM Podcast ⭐🎧 It really helps others in the community find the show.This podcast is generated with artificial intelligence and curated by Veeren. If you’d like your publication or product featured on the show, please get in touch.📩 More info:🔗 www.veerenchauhan.com📧 [email protected]

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