Meningococcal bacterial aggregates form a thick honey-like liquid that flows through blood vessels

July 10, 2018, Pasteur Institute

The Inserm team led by Guillaume Duménil at the Institut Pasteur, in collaboration with several teams of physicists, has unraveled a key stage in infection by Neisseria meningitidis, a human pathogen responsible for meningitis in infants and young adults. Bacterial aggregates in blood vessels appear to facilitate the progression of the disease. Even if treatment is administered rapidly, the mortality rate due to meningococcal infections remains very high.

Human meningococcal meningitis is characterized by bacterial accumulation in blood vessels, which completely fill up with bacteria. But the mechanisms that govern the formation of these aggregates and the impact of the process are still unknown. A consortium of scientists, intrigued by this formation of intravascular aggregates, set out to understand this stage of , especially its underlying physical basis. "The bacterial aggregates formed by Neisseria meningitidis unexpectedly behave like a thick liquid, with a consistency similar to that of honey," explains Guillaume Duménil, head of the Pathogenesis of Vascular Infections Unit. "The bacteria multiply rapidly in blood vessels, forming aggregates which gradually adapt to the complex geometry of the vascular network, like a flowing liquid." The research shows that the formation of these aggregates and their viscous properties are vital for the progression of the infection. A bacterial mutant that forms solid rather than liquid aggregates is at a considerable disadvantage in colonizing .

A viscous liquid with original properties

The thick liquid nature of the aggregates depends on a virulence factor known as type IV pili. These long filaments, which have adhesive and dynamic properties, are constantly extending and retracting at the bacterial surface. The bacteria use type IV pili to find other bacteria, draw them in and temporarily establish contact. Aggregation is therefore based on an intermittent process of attraction between bacteria—in other words, a constant alternation between the presence and absence of attraction. In physical terms, this intermittent process of interaction gives the aggregates original properties that had not previously been described. For example, bacteria inside exhibit a higher level of motility than that observed in the diffusion of isolated . "As well as improving our understanding of a lethal human infection, our research reveals a new type of active matter—a bacterial aggregate with a viscous, honey-like consistency—based on the intermittent attractive forces between its component parts," concludes Guillaume Duménil.

This multidisciplinary study was the result of close collaboration between a laboratory specializing in meningococcal infections (Guillaume Duménil, Institut Pasteur and Inserm) and physicists. By working with the teams led by Nelly Henry (CNRS, UPMC), Raphael Voituriez (CNRS, UPMC) and Hugues Chaté (CEA, CNRS, Paris-Saclay University), the researchers were able to combine a quantitative experimental approach with a physics-based model of active matter.

Explore further: Bacterial conversations in cystic fibrosis

More information: Daria Bonazzi et al, Intermittent Pili-Mediated Forces Fluidize Neisseria meningitidis Aggregates Promoting Vascular Colonization, Cell (2018). DOI: 10.1016/j.cell.2018.04.010

Related Stories

Bacterial conversations in cystic fibrosis

June 5, 2018

"A large part of my research is thinking about how bacteria communicate," says Sophie Darch. The postdoctoral researcher works with School of Biological Sciences Professor Marvin Whiteley, studying the social lives of bacteria.

Recommended for you

Scientists study puncture performance of cactus spines

November 20, 2018

Beware the jumping cholla, Cylindropuntia fulgida. This shrubby, branching cactus will—if provoked by touching—anchor its splayed spines in the flesh of the offender. The barbed spines grip so tightly that a segment of ...

Traffic noise stresses out frogs, but some have adapted

November 20, 2018

Frogs from noisy ponds near highways have altered stress and immune profiles compared to frogs from more quiet ponds—changes that reduce the negative effects of traffic noise on the amphibians. According to a new study, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.