Potentially dangerous staphylococci compete with other bacteria for biotin in the human nasal cavity. This could offer a new point of attack in the fight against the harmful bacteria.
A community of microorganisms lives in our noses – some dangerous, others harmless. The bacterium Staphylococcus aureus is particularly notorious. Some strains have developed comprising resistance to antibiotics, and the severe infections they cause are, in some cases, no longer treatable. This makes the bacterium one of the dreaded ‘hospital bugs.’
Around one third of humans are host to S. aureus and thus carry a bacterium in their nose that is pathogenic and can cause infection. Whether it feels at home there, however, depends largely on its more harmless cohabitants, the so-called commensals. These non-pathogenic bacteria can have both growth-promoting and suppressing influences on S. aureus.
A recently published study in The ISME Journal reveals that competition plays a major role in the nutrient-poor habitat of the human nose. “There’s an active contest between S. aureus and nasal commensals for the vitamin biotin, which affects the fitness of S. aureus,” says Simon Heilbronner, Professor of Microbiology at LMU’s Biocenter and lead scientist of the study. The infection biologist and his team investigated which molecular mechanisms underlie interactions between S. aureus and its commensals.
Biotin is vitally important for all organisms, because it acts as a cofactor for enzymes. This makes it indispensable for various metabolic pathways, including gluconeogenesis, fatty acid synthesis, and the breakdown of amino acids. The human body cannot produce the vitamin itself and has to ingest it with food, entailing that its concentration in tissues remains generally low. “Our results show that biotin is available to a very limited extent in the nasal cavity and that deficiency impairs growth and functionality of the cell membrane of S. aureus,” explains Heilbronner.
Although the bacterium, like some of its commensals, can produce biotin itself, synthesis requires a lot of energy. Furthermore, certain quantities of the vitamin are constantly lost involuntarily through processes at the cell membrane. “All investigated nasal bacterial strains therefore possess very effective molecular mechanisms for absorption of the vitamin” – a decisive factor causing competition for this precious and strongly limited resource.
In addition, some bacteria – especially coagulase-negative staphylococci – are strongly reliant upon neighbors that can produce biotin, because they lack the capability of biosynthesis entirely. Accordingly, they feed on the production of others and reduce the amount of available biotin in the nasal habitat.
“We were able to demonstrate that biotin strongly influences the interactions between the species of the human nasal microbiome and promotes both competition and mutual dependencies,” says Heilbronner. “Despite its ability to produce biotin itself, S. aureus needs to ingest biotin from the environment for optimal growth and presence of commensals competing for the same resource do therefore slow growth of the pathogen”
This represents a possible point of attack in the fight against multi-resistant germs: “Scientists could specifically develop probiotics consisting of commensals that do not supply biotin for S. aureus with biotin, but compete for it. Alternatively, they could utilize new drugs that block the synthesis or intake of biotin. If successful, such strategies would drive S. aureus out of the nose and reduce the risk of infection.”