Is it possible to smell pathogens and fight them before an infection?

Have you ever wondered if the smell of deadly pathogens triggers a defensive response in organisms?

Research from the University of California, Berkeley, unveils an unforeseen interaction between the sense of smell and protective responses in one of the most extensively studied laboratory organisms, the nematode C. elegans.

The mighty nematode

This tiny roundworm is providing groundbreaking insights into our understanding of infection response. Like humans, nematodes find their intestinal cells a common target for infection by bacteria.

To protect themselves, these microscopic creatures engage in a fascinating battle of survival, destroying their own iron-containing organelles, the mitochondria (the powerhouse of cells), to keep it safe from bacteria that steal iron.

Smelling out the pathogen

The researchers found that C. elegans can sense the odor of pathogens and get its intestinal cells ready to withstand the impending attack.

This discovery raises an intriguing question – Is there actually a smell coming off of pathogens that we can pick up on and help us fight off an infection?

And if mammals also share this ability to smell a pathogen and subsequently protect themselves, it could open doors to novel infection-fighting methods like a “pathogen-protecting perfume.”

Power of smell in pathogen defense

According Julian Dishart, the first author of the study, the novelty is that C. elegans is getting ready for a pathogen before it even meets the pathogen.

“There’s also evidence that there’s probably a lot more going on in addition to this mitochondrial response, that there might be more of a generalized immune response just by smelling bacterial odors,” said Dishart.

“Because olfaction is conserved in animals, in terms of regulating physiology and metabolism, I think it’s totally possible that smell is doing something similar in mammals as it’s doing in C. elegans.”

While this reaction has so far only been found in C. elegans, it’s a notion worth exploring in mammals due to the conservation of olfaction in regulating physiology and metabolism.

Mitochondrial distress signal

Further delving into our body’s response to stress, the researchers explain how our nervous system picks up cues from the environment and creates homeostasis for the entire organism.

They highlight how smell neurons are identifying environmental cues and which types of odorants from the pathogens trigger this response.

The scientists have previously discovered the importance of smell in mammalian metabolism. For instance, mice deprived of smell gained less weight despite consuming the same amount of food as their counterparts.

A similar response could be happening when we smell food, triggering a protective response in our gut to prepare us for any potential harm caused by foreign substances and metabolic processes involved in converting food to fuel.

The team proposes that the mitochondria’s sensitivity to pathogenic odors might be a remnant from a time when mitochondria were autonomous bacteria, before being incorporated into other cells to function as energy generators.

A step towards prevention

The research indicates that the smell of pathogens triggers an inhibitory response, sending a signal to the rest of the body. This was clear when the researchers halted the functioning of olfactory neurons in the worm.

All peripheral cells, predominantly intestinal cells, displayed signs of mitochondrial stress response, typical of a threat.

The experts concluded that serotonin is a key neurotransmitter in transmitting this information across the body. This discovery offers promising implications for disease prevention and treatment.

“If there are earlier detection mechanisms to increase our chances of survival, I think that’s a huge evolutionary win. And if we could harness that biomedically, that would be pretty wild,” said study senior author Andrew Dillin, a professor of molecular and cell biology at UC Berkeley.

The role of scent in behavioral adaptation

Scent plays a crucial role in shaping organism behavior, guiding survival tactics such as food foraging, predator avoidance, and mate selection. For instance, nematodes utilize olfactory cues to enhance their survival in the presence of threats.

Research indicates that certain odors can trigger defensive strategies in C. elegans, exemplifying the interplay between scent perception and instinctual behavior.

This understanding of olfactory influence extends beyond survival; it holds promise for pest control and disease management.

By manipulating the olfactory responses of organisms, scientists can develop scents that repel pathogens or attract beneficial species.

As we explore these connections, the potential benefits for ecological balance and human health become increasingly evident, underscoring the importance of olfactory research in advancing innovative strategies for a healthier future.

The study is published in the journal Science Advances.

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