Reacción a "Reactions: Mother's microbiota may pass genes to baby's microbiota by horizontal transfer"

This is a novel study in which the researchers put forward an interesting hypothesis: could bacteria that are not transmitted from mother to baby (i.e. not transmitted vertically) still influence the baby's microbiome through the transmission of specific genes to other bacteria (horizontal gene transfer)? 

Demonstrating horizontal gene transfer is complicated. What the authors did is to compare the DNA sequences of the genes they detected in 70 mothers and their babies and, in cases where the sequences are identical, transfer is inferred. 

The transmission of bacteria from mother to baby is very important for the formation of our microbiome, which is a great ally for our health: apart from aiding digestion, it protects us from pathogens and influences the development of the immune system. The first bacteria that reach our gut come from our mothers during and shortly after birth. Thus, babies born by caesarean section receive fewer bacteria from their mothers, and it is thought that this may be related to the development of allergies and autoimmune diseases. The transfer of genes from one bacterium to other bacteria of different species provides a new indirect mechanism that would complement the transmission of bacteria from mother to baby. 

Metagenomics is a very new and developing field, and there are variant methods for inferring the transmission of the microbiome from one person to another. Once these methods are consolidated and the results replicated in independent data, the interesting results of this study can be confirmed.