Stress Test To Separate Gentle Bacteria From Sturdy Ones
By scooping the guts out of bacteria and refilling them with an expansive fluid, scientists can discover whether a microbe is structurally strong or weak, gaining insights that could help fight infectious diseases or aid studies of the beneficial bacterial communities known as microbiomes.
Bacteria. Sometimes we can’t live with ’em, but there’s a growing appreciation that we can’t live without ’em. Whether it’s disease-causing pathogens or beneficial species that live in communities known as microbiomes, scientists agree on one thing – we need to know more about bacteria, particularly how they are built and how they live together.
“Today we study a tiny subset of bacteria,” said Bo Wang, assistant professor of bioengineering at Stanford. “We need new ways to poke and prod these organisms to figure out what makes them tick, as well as novel methods to identify the vast number of species that still remain in the shadows.”
With this in mind, Wang’s lab has developed a clever way to strip out almost everything but the core exoskeleton of a bacterium, leaving behind an empty cell wall that is essential to maintaining the distinctive shape of any bacterial cell. The researchers then filled this shell with an expandable fluid to measure how much internal stress each species of microbe could withstand. Observing these hollowed-out bacteria under a microscope enabled them to determine which species became bloated by the outward pressure, and which resisted expansion and stayed the same size.
The researchers described this expansion microscopy technique in a paper in PLoS Biology. KC Huang, a professor of bioengineering and of microbiology and immunology and co-author of the paper, explained that there is a direct connection between the strength of a cell and how much it will expand under this treatment. The more expandable the cell, the weaker its wall, and vice versa, information critical for efforts to fight bacterial infections.
“A lot of research focuses on ways to get antibiotics through the cell wall so that they can take effect,” Huang said. “Any way to gain insight into a cell’s survival traits and weak points means that we can be more effective at eliminating invaders.”
Probing the microbiome
In addition to fighting disease, the researchers believe their technique will prove equally useful in microbiome research, an emerging field that studies not just a single bacterial species but how ecosystems of species work together. There is a diverse collection of species in every microbiome, and their environments can be hellish. Bacteria in the gut are packed tighter than passengers on a rush-hour subway, and in addition to pushing and shoving, they’re periodically doused with acids. Expansion microscopy provides new information on how these bacteria survive under pressure, enabling scientists to separate the tough cells from the tender in a crowd.
“This technique reveals something about the character or personality of bacteria that were previously hidden,” Wang said.
Cells within a community are often identified by their shape or color, so resistance to expansion provides the next dimension of understanding: firmness. “After someone tells you what an object looks like, the next thing you want to know is what it feels like,” Huang said. “Expansion microscopy makes this sense of touch something you can see.”
Source & Credit @ Stanford University, BY TOM ABATE.