A groundbreaking study published in Nature on August 6, 2025, by scientists from the Yale School of the Environment has unveiled a hidden world within trees: trillions of bacteria residing within their woody tissues. This discovery illuminates the critical role these internal microbial communities play in forest ecosystems, offering new perspectives on tree health, nutrient cycling, and the broader implications for forest ecology.
Researchers meticulously examined 150 living trees across 16 species in the northeastern United States. Their findings revealed that each tree harbors approximately one trillion bacteria, with distinct microbial communities inhabiting the inner heartwood and outer sapwood. The heartwood, characterized by its oxygen-poor environment, is home to anaerobic microbes, while the sapwood, rich in oxygen, supports aerobic microbes. These microorganisms are not merely passive inhabitants; they are actively engaged in producing gases and cycling nutrients, underscoring their vital contribution to the tree's internal biological processes.
The study also highlighted significant variations in microbial communities among different tree species, suggesting a potential coevolutionary relationship. For instance, sugar maples host a different microbial consortium compared to pines, indicating that these internal ecosystems are finely tuned to specific tree physiologies and chemistries. This species-specific interaction is crucial for understanding the intricate dynamics of forest ecosystems.
This research opens a new frontier in environmental microbiology, with scientists like lead researcher Jonathan Gewirtzman emphasizing the vast, unexplored biodiversity within trees. "There is a massive reservoir of unexplored biodiversity—countless microbial species living inside the world's trees that we've never documented," Gewirtzman stated. Understanding these communities is paramount, especially as climate change could alter them. Some of these microbes may even hold keys to enhancing tree growth, bolstering disease resistance, or yielding valuable compounds. Further exploration into wood microbiomes globally is essential to fully grasp the factors influencing microbial diversity.
The findings by Yale scientists, including Mark Bradford and Peter Raymond, underscore the complex interdependence between trees and their internal microbial partners. This symbiotic relationship is increasingly recognized as fundamental to plant health and adaptation, with implications for how forests might respond to environmental shifts and contribute to global carbon cycling. The internal wood microbiome is now understood as a specialized ecological niche, contributing to the tree's resilience and overall vitality.