(From left to right). María José Gosalbes and Pilar Francino in the laboratories of the Genomics and Health Area of ​​the FISABIO Foundation.

A research team with the participation of the Institute of Integrative Systems Biology (I2SysBio) of the University of Valencia and the CSIC, together with FISABIO and CIBERESP, has carried out the first metatranscriptomic study of the intestinal microbiota of babies, which has allowed us to reveal the metabolism of the intestinal bacterial community during the first year of life, with a level of detail unknown until now.

Researchers from the Joint Unit in Genomics and Health of the Foundation for the Promotion of Health and Biomedical Research of the Valencian Community (FISABIO) and the Biomedical Research Consortium in the Epidemiology and Public Health Network (CIBERESP) have also participated in this work, dependent on the Carlos Health Institute III.

The environment is very important in the first years of life, both for the baby and for the bacteria in its intestinal microbiota. Bacteria and humans coexist in a harmonious symbiosis: people share with them the food they eat, which helps them metabolize (10% of the energy obtained from food is as a consequence of bacterial action). In addition, bacteria influence the development of the immune and nervous systems.

Thus, the study has examined the expression of all the bacterial genes that are part of the baby's intestinal flora from fecal samples obtained at 4 time points throughout the first year of life: 7 days after birth and at 3, 7 and 12 months of age. The analysis was also carried out on samples from the mothers obtained a week before delivery and a year later.

“In this study we have explored how the environment influences the gene expression of the community of bacteria in the baby's intestine, in particular the type of diet (which changes drastically during the first year of life mainly with the introduction of solid food),” explains María José Gosalbes, CIBEResp researcher at FISABIO and first author of the study.

“For the intestine bacteria,” she adds. the researcher – it is not the same to feed on carbohydrates from cereals in porridge than on human breast milk. In both cases, the biochemical pathways of metabolism are different and that requires the expression of different genes.” FISABIO.

The most surprising finding of the study is the signs of activity of bacteria that produce butyrate in the baby's intestine before the solid diet is introduced. This fatty acid with anti-inflammatory properties and which serves as food for the cells of the intestinal wall is of recognized importance for health in adults, but until now it was thought that it was not so relevant in babies.

The curious thing is that, in adults, bacteria synthesize butyrate from fiber and other complex carbohydrates ingested in the diet that are not found in breast milk. Subsequent studies will have to elucidate what substrates bacteria are using to produce butyrate in infants and whether this compound has the same functions in babies and adults.

Metatranscriptomics of bacteria

In this study, an omics technique has been used, metatranscriptomics, which consists of the global analysis of the genes that are being expressed in a bacterial community. Depending on the functional state or environmental stimuli, bacteria express some genes or others; Hence, metatranscriptomics provides essential information about the functional capacity of intestinal bacteria at all times.

Due to its technical difficulty, few laboratories in the world are capable of performing metatranscriptomics analysis of the human microbiome. However, these studies are necessary to fully understand microbial biology. “The great challenge for the future is to integrate all the data: genomics, metatranscriptomics, etc.,” says Francino.

Article:

M. J. Gosalbes, J. Compte, S. Moriano-Gutierrez, et al., «Metabolic adaptation in the human gut microbiota during pregnancy and the first year of life», EBioMedicine, https://doi.org/10.1016/j.ebiom.2018.10.071