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Pseudomonas Outcompetes Klebsiella via Toroidal Displacement

50:24 recording · AUTO · 4 speakers

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Brief overview

Two papers show microbes compete for food: Pseudomonas slides rivals away, while Vibrio kills prey to eat.

  1. Pseudomonas pushes rivals away instead of killing themCFU counts and live-dead staining showed no killing; the Klebsiella simply slid outward on secreted rhamnolipid.
  2. Iron scarcity is the trigger for the surfactantHigh iron abolished the migration, and chelating iron in rich media restored it, because making surfactant all the time would be too expensive.
  3. Type 6 secretion is a foraging tool, not just a weaponPredators with fewer alginate lyase genes kill neighbours and feed on what leaks out, a possible type 6 secretion shunt in nutrient cycling.
Executive Summary AI
  • Vincent Racaniello records TWIM 335 on June 26, 2025 with Michelle Swanson in Ann Arbor, Michael Schmidt in Charleston and Petra Levin in St. Louis, around a theme of competition for food.1:47
  • Michelle presents an open-access mBio paper from Diana Prodman and co-authors at the Indian Institute of Science in Bangalore, the University of Dundee and Imperial College, in which a spot of Pseudomonas on a Klebsiella lawn on minimal media pushes the Klebsiella outward into a donut, or toroid, with no loss of viability.2:08
  • A systematic screen of 202 Pseudomonas gene-deletion strains left only two hits, both enzymes for rhamnolipid biosynthesis, and dripping pure rhamnolipid onto a Klebsiella lawn mimicked the live Pseudomonas while water did not.7:45
  • Figure five showed the outward migration only when iron was low, and chelating iron in iron-rich media reproduced it, supporting the model in figure 7D that Pseudomonas makes the surfactant under quorum sensing and iron starvation to shove competitors off the limited iron.11:14
  • Petra covers the Science paper Antagonism as a Foraging Strategy in Microbial Communities by Astrid Stubusch and colleagues in Zurich, where type 6 secretion Vibrio ordalei turns alginate-eating targets into slowly leaking round zombies, with type 6 systems in about 60% of the operational taxonomic units examined and up to 30 percent in the rhizoplane.19:28
Key Quote
“I'm Vincent Racaniello, and you're listening to the podcast that explores unseen life on Earth.”
— Vincent Racaniello0:35
Key Quote
“The dawn detergent of the microbial world.”
— Michael Schmidt17:38
Key Quote
“Everyone eats at this table is what Pseudomonas is effectively doing.”
— Michael Schmidt17:04