Gut bacteria subspecies compete by temperature
The bacteria in your gut look similar to those in other people at the species level. But within a single species, there can be important variants that the body treats very differently. New research shows that environmental temperature determines which variant of a bacterial species survives in the gut. That changes how we understand the gut-ageing connection.
Most microbiome studies focus on which species of bacteria are present. But within a species, subspecies (called clades) can differ significantly in genetics and function. Researchers tracked the gut microbiome of fruit flies over more than ten years at two different temperatures. They looked not just at which species were present, but at which variants of the bacterium Lactiplantibacillus plantarum survived.
Temperature decides which variant wins
The study, published in eLife, shows that the three identified variants of L. plantarum responded very differently to temperature differences. At higher temperatures, a different variant dominated compared to lower temperatures. In cell culture and in living animals, the researchers confirmed that the variants also differ functionally: they grow at different rates and have different effects on the host. Environmental selection thus operates at the subspecies level, not just at the species level.
This is a methodological finding with broad implications. Studies that only look at the species level may miss functionally important shifts that only become visible at a finer resolution.
Relevance for the gut-ageing link
As we age, the composition of the gut microbiome changes. Studies link those changes to systemic inflammation, reduced nutrient absorption, and metabolic decline. If functional diversity within bacterial species plays a role in that shift but is systematically missed in research, we may be underestimating the gut-ageing connection. Future research will need to determine whether this is also relevant in humans and in the context of ageing.
Search terms to explore further: intraspecific diversity gut microbiome, Lactiplantibacillus plantarum functional differentiation, microbiome subspecies selection