A new study suggests that bacteria passed from parents to their offspring play a crucial role in the health of animals, plants, and fungi.
Microorganisms are essential partners for many living organisms. They help their hosts absorb nutrients, support immune functions, and maintain overall health. Researchers at the University of Oxford’s Department of Zoology have now investigated why some bacteria appear to be more beneficial than others.
The study highlights the importance of how bacteria are transmitted between generations. Many microbes are inherited directly from parents—most often from the mother—when newborn organisms are exposed to microbes during birth, hatching from eggs, or germination in plants. These inherited microbes often form part of the host’s microbiome, including the gut flora.
According to the researchers, this vertical transmission—passing bacteria from parent to offspring—can strongly influence how hosts and microbes evolve together. When bacteria are inherited across generations, both the host and the microbes have more opportunities to adapt to one another, strengthening their symbiotic relationship.
“If a bacterium is passed on vertically, it has a vested interest in its host’s wellbeing,” explained Professor Stuart West, co-author of the study from Oxford’s Department of Zoology. “A healthy host will produce more offspring, and those offspring will also inherit the same bacteria. In contrast, microbes that are acquired from the environment have less incentive to support the host’s long-term health.”
The researchers also found that removing bacteria that assist with nutrient absorption tends to be more harmful to the host than removing bacteria that provide protection against parasites or disease. This may be because nutrient uptake is a constant requirement for survival, whereas protection against parasites is only occasionally necessary.
The study aimed to identify patterns that explain how cooperative relationships between microbes and their hosts evolved over time.
The findings were published in Nature Communications.
Reference:
Fischer, R. M. et al. “The evolution of host–symbiont dependence.” Nature Communications, July 4, 2017. DOI: 10.1038/ncomms15973.