Study reveals how snot facilitates infection

Sniffles, snorts and runny noses are hallmarks of cold and flu season – and this increase in mucus is exactly what bacteria use to launch a coordinated attack on the immune system, according to a new study. study conducted by researchers at Penn State. The team discovered that the thicker the mucus, the more bacteria are able to swarm. The findings could have implications for treatments that reduce the ability of bacteria to spread.

The study, recently published in the journal Nexus PNAS, demonstrates how bacteria use mucus to enhance their ability to self-organize and eventually cause infection. The experiments, carried out with synthetic stomach mucus from pigs, natural cervical mucus from cows and a water-soluble polymer compound called povidone, revealed that bacteria coordinate their movements better in thick mucus than in watery substances.

The results provide insight into how bacteria colonize mucus and mucosal surfaces, the researchers said. The results also show how mucus enhances bacterial collective movement, or swarming, which can increase the resistance of bacterial colonies to antibiotics.

“To the best of our knowledge, our study is the first demonstration of bacteria swimming collectively in mucus,” said Igor Aronson, Huck Professor of Biomedical Engineering, Chemistry and Mathematics at Penn State and corresponding author of the paper. ‘article. “We showed that mucus, unlike liquids of similar consistency, improves collective behavior.”

Mucus is essential for many biological functions, Aronson explained. It lines the surfaces of cells and tissues and protects against pathogens such as bacteria, fungi and viruses. But it is also the host material for infections of bacterial origin, particularly sexually transmitted and gastric diseases. According to Aronson, a better understanding of how bacteria thrive in mucus could pave the way for new strategies to fight infections and the growing problem of antibiotic resistance.

“Our results demonstrate how mucus consistency affects the random movement of individual bacteria and influences their transition to coordinated collective movement of large bacterial groups,” Aronson said. “There are studies demonstrating that the collective movement or swarming of bacteria improves the ability of bacterial colonies to repel the effect of antibiotics. The appearance of the collective behavior studied in our work is directly linked to swarming.”

Mucus is a notoriously difficult substance to study because it exhibits both liquid and solid properties, Aronson explained. Liquids are generally described by their viscosity level, thickness, or fluidity, and solids are described by their elasticity, the force they can withstand before breaking. Mucus, a viscoelastic fluid, behaves like both a liquid and a solid.

To better understand how mucus becomes infected, the team used microscopic imaging techniques to observe the collective movement of concentrated bacteria Bacillus subtilis in synthetic pig stomach mucus and natural cow cervical mucus. They compared these results with observations of Bacillus subtilis moving through a water-soluble polymer povidone at a wide range of concentrations, from high to low levels of povidone. The researchers also compared their experimental results to a computer model of collective bacterial movement in viscoelastic fluids like mucus.

The team discovered that the consistency of mucus profoundly affects the collective behavior of bacteria. The results indicated that the thicker the mucus, the more likely the bacteria were to exhibit collective movement, forming a coordinated swarm.

“We were able to show how mucus viscoelasticity enhances bacterial organization, which leads to consistent movement of infection-causing bacterial groups,” Aronson said. “Our results reveal that mucus elasticity and viscosity levels are a major factor in how bacterial communities organize themselves, which may provide insight into how we can control and prevent bacterial invasion of the mucus.”

Aronson explained that the team expects human mucus to exhibit similar physical properties, meaning their findings are also relevant to human health.

“The onset of collective movement of bacteria and their interaction with mucus should be the same as in cow, pig or human mucus since these substances have similar mechanical properties,” Aronson said. “Our results have implications for human and animal health. We show that mucus viscoelasticity can enhance the large-scale collective movement of bacteria, which can accelerate how quickly bacteria penetrate the protective mucus barrier and infect internal tissues.”