Specific genes of infant gut bacterium determine its symbiotic function in the infant's gut

Reviewed by Emily Henderson, B.Sc.Oct 28 2020

While an infant's genes distinguish her from other newborns, a new peer-reviewed study reports that specific genes of a particular infant gut bacterium determine its symbiotic function in the infant's gut.

The study provides important guidance for clinicians when selecting a probiotic for use in infants to maximize impact on both short- and long-term health outcomes.

In the first study to provide genetic analysis of various strains of the infant probiotic bacteria Bifidobacterium longum subsp. infantis (B. infantis), researchers report that one particular strain of probiotic B. infantis, EVC001, possesses the genetic make-up that enables full metabolism of the nutritional components of human breast milk, the first step in providing important health benefits to the infant. The paper was published in the peer-reviewed journal Nutrients.

Gut bacteria are living organisms, and thus have different genes that determine how they function. What we've revealed in this paper is a truly elegant mechanism of action that is unique to EVC001 among the probiotic strains that were studied; it's a striking distinction that defines clear genetic differences that make some B. infantis strains far more beneficial to the health of infants than others."

Rebbeca Duar, PhD, Study Lead Author and Senior Scientist, Evolve BioSystems, Inc

B. infantis EVC001 has been documented for its critical role in restoring function and resolving dysbiosis by suppressing potentially pathogenic bacteria in newborns, supporting immune and gastrointestinal system development, and reducing intestinal inflammation. Infant gut dysbiosis has been linked to the development of necrotizing enterocolitis (NEC), asthma, eczema, food allergies, and Type-1 diabetes.

B. infantis EVC001 provides health benefits to infants by optimally metabolizing components of breast milk called human milk oligosaccharides (HMO) into lactate and acetate, which in turn lowers the pH of the infant's gut to a protective range.

As a result, EVC001 has been shown to effectively suppress the abundance of pathogenic bacteria in the infant's gut, reducing intestinal inflammation and lowering antibiotic resistance in both term and pre-term infants.

The researchers studied 14 different strains of B. infantis sourced from commercially available infant probiotic products as well as bacterial culture banks.

Each bacterial strain underwent DNA sequencing based on the presence or absence of the H5 gene cluster, which contains key genes involved in the transport of HMOs into the bacterial cell, where it then undergoes deconstruction and metabolism.

Researchers then measured the growth rates of each strain on HMO(s), correlating the growth rates to the H5 genetic profiles of each bacterial strain to determine the ability to metabolize and utilize all HMOs as a fuel source.

Of the 12 commercial probiotic strains of B. infantis studied, one strain, in particular, known as EVC001, showed twice as much growth than the other strains, and within one day had outgrown all other strains analyzed. Study authors note that growth and colonization of this bacteria correlate to optimal infant gut health.

"The importance of the infant gut microbiome for the health of babies has been widely documented, and the use of infant probiotics in the therapeutic portfolio is growing," said Dr. Duar. "This research represents a critical step forward by demonstrating that there are clear genetic and functional differences among different strains of B. infantis. In short, strain matters, since the choice of a particular strain will significantly impact the clinical and health benefits B. infantis will bring to the baby."