Researchers measure biomass distribution in microbial communities to assess fairness in nature

On July 8, 2026, researchers from the University of Helsinki explored the fairness of biomass distribution in microbial communities. The study, led by Teemu Kuosmanen, was published in PLOS Biology and investigates whether these distributions are meritocratic, akin to economic principles.

Understanding Microbial Community Dynamics

Microbial communities consist of various species that interact in complex ways. The study examined 14 different microbial communities, each made up of four bacterial species, grown under both favorable conditions and three challenging environments involving antibiotics. The aim was to measure how biomass was allocated among these species as they reached equilibrium.

Researchers found that some communities displayed a highly meritocratic distribution of biomass, while others were systematically unfair. For instance, in environments with stronger antibiotics, biomass often concentrated in a single key species. This raises questions about the overall fairness of the natural distribution.

Measuring Fairness with the Shapley Value

The researchers employed the Shapley value, a concept from game theory, to quantify fairness in biomass distribution. This method assesses how shared outputs should be divided among community members based on their contributions. The results revealed that many ecological distributions were less equitable than those predicted by a fully meritocratic model.

• 14 microbial communities studied
• 4 bacterial species in each community
• 3 challenging environments tested
• Shapley value used for fairness measurement

Kuosmanen stated, "In economics, free competition, which natural selection embodies, is generally thought to lead to an efficient and meritocratic outcome. But we have practically no idea whether the state of nature is a fair and meritocratic place." This highlights the need for further exploration into ecological fairness.

The Role of Historical Dependencies in Fairness

Fairness in microbial communities is influenced by historical factors and the initial conditions of species. Differences in growth rates, known as the lag phase, can impact how resources are distributed. Species with shorter lag phases tend to receive a fairer share of biomass, while those with longer phases may struggle or benefit based on the growth of others.

Kuosmanen noted, "We noticed that species with a short lag phase generally received the fair share matching their contribution. Species with a longer lag phase, in turn, either suffered or benefited from the fact that some other species were able to grow before them." This suggests that past conditions can perpetuate unfairness within these communities.

Ultimately, the study offers a new perspective on ecological fairness through the lens of randomly assembled microbial communities. Kuosmanen concluded, "It is possible that nature's own communities are even fairer than this experiment suggests."