PLOS: Breast Milk Has Been Fighting Microbes for 160 Million Years
16:50 20 October, 2026Scientists at the University of Oregon have found that breast milk’s ability to fight bacteria dates back approximately 160 million years, when a precursor protein to lactoferrin acquired a short fragment capable of damaging microbial membranes. The findings were published in the journal PLOS Biology.
Lactoferrin is found in breast milk, tears, and saliva and also plays a role in immune function. The protein contains a short fragment called lactoferricin, which can damage bacterial membranes and cause the bacteria to die. The researchers set out to investigate how this protective function evolved and how it changed over time.
The scientists reconstructed likely ancient versions of the protein using genetic data from different vertebrate species. They synthesized fragments of these proteins and tested their activity against four bacterial species, including Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.
The results showed that the original precursor protein had virtually no effect on bacteria. Following a gene duplication event approximately 160 million years ago, lactoferrin emerged, and its fragment was already capable of damaging bacterial membranes.
“Some modern variants were more potent than ancient ones, but evolution did not always enhance their protective properties. For example, human lactoferricin proved less effective against several bacteria than some variants found in other great apes,” the researchers explained.
The scientists also identified changes in specific amino acids that affected the peptide’s ability to kill particular bacterial species.
The authors believe that ancient versions of lactoferricin could serve as a starting point for developing new antibacterial agents amid growing microbial resistance to antibiotics. However, the findings are based on laboratory experiments, and the safety and effectiveness of these substances in the human body have yet to be established.