The microbes in our gut help us digest food, for example, whereas those on our tongue and skin can guard against invading pathogens.
After the human gut, it is time for the nose to shine.
Within the nasal region, researchers have discovered a treasure trove of beneficial bacteria. And they appear to promise good health.
Sarah Lebeer, a microbiologist at the University of Antwerp and one of the authors of the study, went searching for bacteria in the noses of 100 healthy people. Then, she along with other researchers compared the microbes they found with those from hundreds of patients with chronic nasal and sinus inflammation.
They discovered 30 common types of microbes.
But the one group stood out: antimicrobial and anti-inflammatory bacteria called Lactobacillus.
Their study has been published in Cell Reports.
Lactobacilli usually thrive in oxygen-poor areas.
Researchers were surprised to discover them in an organ flush with fresh air. But a closer look revealed that the particular strain her team found in human noses has special genes called catalases that safely neutralize oxygen—a rarity among other lactobacilli. “They seem to have adapted to that environment,” Lebeer says.
Under a microscope, the researchers could also see tiny, hairlike appendages called fimbriae that anchor the bacteria to the nose’s inner surface. Lebeer thinks the microbes may also use the hairs to bind to receptors on skin cells inside the nose, prompting the cells to close like a trap door. With fewer cells open, allergens and harmful bacteria have a harder time getting inside them.
Researchers investigated whether lactobacilli, which are important taxa in several habitats of the human body, could also be important for the URT.
They also started by sequencing and phylogenetic placement of the amplicon sequence variants (ASVs) of the 16S rRNA V4 gene region of URT samples taken from 100 healthy volunteers and 225 patients with CRS.
They then aimed to cultivate lactobacilli from different healthy URT samples and implemented a combination of genomic and functional in vitro and in vivo analyses to explore their habitat adaptation to the human URT and their potential as URT probiotic. The colonization capacity of one nasopharynx-isolated strain of the lactic acid bacteria (LAB), genetically and functionally shown to be adapted to several biotic and abiotic factors of this underexplored human body site, was then evaluated in healthy volunteers.
The Lactobacillus genus complex (LGC) includes important beneficial taxa in different human body niches The bacteria belonging to this genus are known to be rod shaped, fermentative bacteria producing lactic acid from sugar fermentation under anaerobic or micro-aerophilic conditions.
This lactic acid production is a hallmark of their beneficial functions, because it inhibits the growth of pathogens. In addition, also their long history of safe use and their beneficial immunomodulatory, metabolic, and epithelial cell interactions often underlie the beneficial roles of lactobacilli.
Highlights of the Report
- Lactic acid bacteria are enriched in the healthy human nose and nasopharynx
- Lactobacillus casei AMBR2 is functionally adapted to the upper respiratory tract
- L. casei AMBR2 has antimicrobial and immunomodulatory properties
- Live L. casei AMBR2 is safe for intranasal application in healthy humans