Why Microbial Diversity Is Hard to Reproduce in the Lab

Microbial ecosystems, such as those found in seawater, soil, or the human gut, are known for their remarkable diversity. However, scientists often face challenges when trying to replicate this diversity in laboratory settings, as many microorganisms fail to survive under these conditions. A recent study from the Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg, provides new understanding of this issue, indicating that microbial survival relies not only on individual needs but also on a complex network of relationships that can be easily disrupted. 

Published in PNAS, the research led by Dr. Thomas Clegg and Prof. Dr. Thilo Gross approaches microbial communities as networks based on cross-feeding, where species exchange metabolic by-products. Each species requires certain nutrients and releases substances that serve as food for others. Using network theory—an analytical method from physics—the researchers modeled these interactions to better understand the stability of microbial communities.

Their analysis showed that the loss of even a single population can cause the entire network to collapse, leading to a sudden drop in diversity. “These collapses act as tipping points, resembling blackouts in power grids or supply chain breakdowns seen during the COVID-19 pandemic,” said Clegg. Laboratory cultivation itself can trigger such disruptions, as missing members in a sample may result in the absence of essential metabolic products for other species.

The study is the first to demonstrate how these dependencies affect entire microbial communities. It reveals that even in resource-rich lab environments, communities may fail if their networks are disturbed, and recovery is difficult even after resources are restored. “It’s not just about what individual microbes need, but who they depend on,” Clegg noted, emphasizing that the fate of the community depends on these hidden relationships.