Human fetal lungs contain bacterial microbiomas, The lungs and placenta of the fetus in the womb have shown the signatures of bacterial microbiomas 11 weeks after fertilization, which shows that bacteria can colonize the lungs long before birth.

This first finding deepens the puzzle of how germs or microbial products enter these organs before birth and what role they play in the normal development of the lungs and the immune system.

The team found that the signature of human microbiome DNA in the fetus was present in the lungs in the first trimester.

These lung microbiomas show changes in diversity during fetal development, indicating that microbiomas mature with gestational age. Finally, placental microbiomas are also present in human fetal tissue, and the signature of these microbiomas shows a taxonomic overlap with the corresponding human lung microbiomas and the Human fetal lungs contain bacterial microbiomas

We speculate that maternal-fetal DNA transfer and the possibility of other microbial products, as well as live or dead bacteria, are a realistic choice, researchers say. This can serve as a “primary” development of the innate immune system of the fetus and contribute to the formation of normal host connections. In addition, similar microbioma profiles were found after cesarean section or vaginal delivery, showing that microbes were able to reach the lungs before birth.

In the new study, 31 samples of lung, placenta and fetal tissue were taken between 11 and 20 weeks’ gestation.

Bacterial DNA was discovered by gene analysis of target genes for 16S ribosomal RNA, the standard method for distinguishing different microbial taxa.

The first analysis of 16S in Singapore revealed 48 unique taxa in lung samples, 11 unique taxa in placental samples and 24 common taxa. Analysis of 16S from the same sample in the UAB revealed two separate groups of lung microbiome based on fetal age, one group of pregnancy after 11 to 15 weeks and the other after 16 to 20 weeks. In addition, both gestational age groups showed significant changes in microbiome diversity over time.

The distribution and diversity of bacterial taxa shows some overlap in the combined fetal and placental signature microbiomas, the researchers said.