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Microbiome of Living Trees

48:57 recording · AUTO · 4 speakers

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Brief overview

Two new papers show living tree wood hosts a distinct microbiome, and Cretan bacteria kill mosquito larvae.

  1. Wood is an unexplored microbial worldThe wood of living trees is the largest biomass reservoir on the planet, yet almost all prior sampling looked at roots, leaves and bark.
  2. Heartwood and sapwood are separate habitatsOxygen and carbon availability split the communities: anaerobic fermenters and methanogens inside, aerobic chemoheterotrophs and methanotrophs outside, with only about 19% prokaryotic transfer between
  3. Island bacteria as a biopesticide sourceScreening 788 Cretan isolates yielded 37 fast-acting larvicidal strains, some losing activity after 48 hours, which may be the safest for field use.
Executive Summary AI
  • Vincent Racaniello opens with a Nature paper, A Diverse and Distinct Microbiome Inside Living Trees, noting trees store more than 300 gigatons of carbon and the average tree carries 1 trillion prokaryotic cells in its woody tissues, one prokaryotic cell for every 20 plant cells.4:15
  • The team surveyed wood-associated microbiomes of over 150 living trees across 16 species in the northeastern United States, comparing the innermost five centimeters of heartwood with the outermost five centimeters of sapwood by 16S sequencing, with maples highest at 10 to the 7.3 cells per dry gram and black cherry and eastern hemlock lowest at 10 to the 4.8.6:12
  • Heartwood is anoxic and nutrient poor and holds Clostridia, Bacilli and methanobacteria plus higher nitrous oxide and methane, while sapwood is aerobic with obligate aerobes such as actinobacteria; only 3-5% of mineral soil and 6-13% of organic soil communities turned up in the trees, so soil plays a minor role.16:12
  • Michelle Swanson then presents a paper from Crete on biopesticides, motivated by the 700,000 people who die each year of mosquito-borne infection and by 80% of synthetic insecticides being withdrawn over the last 20 years for safety and environmental concerns.30:53
  • From 788 isolates sampled at 65 locations, 108 caused 100% mortality in common house mosquito larvae within a week and 37 from 20 genera killed within three days, about 10% of isolates, most of them extracellular nonpolar compounds from plants or the rhizosphere.39:08
Key Quote
“Can you imagine your surgeon being an airline pilot or your airline pilot being a surgeon?”
— Vincent Racaniello2:54
Key Quote
“The average tree has 1 trillion prokaryotic cells in its woody tissues.”
— Vincent Racaniello4:51
Key Quote
“They also point out that the wood of living trees is the largest reservoir of biomass on the planet.”
— Vincent Racaniello5:40