Scientists from the London Centre for Nanotechnology and the National Physics Laboratory have discovered a potential new way of killing harmful bacteria: by peeling them.
Their innovative method can kill bacteria within minutes, making it an exciting discovery in the race to find new antibiotics.
However, the underlying principle is not anything new. The body has many built-in defences against microbial intruders, including tiny molecules called antimicrobial peptides (AMPs).
These peptides attach to bacterial surfaces and fold themselves up into structures that can pierce through the protective layers, forming pores.
The pores let the contents of a bacterial cell flow out, or let antibacterial molecules flow in. At high concentrations of AMPs, this can kill the bacteria, but at low concentrations, it only makes small, temporary pores without much effect.
Inspired by the body’s own natural defences, the team of researchers designed a new peptide, called Tilamin, which is based on an existing AMP.
Instead of forming a hole through the membrane, Tilamin makes it thinner and effectively peels off the bacterial surface.
The surface of a bacterial cell is covered with molecules that protect it from our immune system and help it keep its shape.
Its surface has an inner layer called a cytoplasmic membrane, and an outer one called a cell wall.
The (inner) cytoplasmic membrane is made of two layers of a molecule called a phospholipid, which has a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail.
Since both the inside of a bacterium and its outside environment are full of water, the two layers of phospholipids are arranged with the heads pointing outwards and the tails inside.
AMPs usually form a pore straight through the membrane, but Tilamin attacks at an angle, forming a hole through one layer of phospholipids. This exposes the hydrophobic tails in the inner layer to water.
As more pores form, they expand and merge together, making the membrane quickly disintegrate. The membrane ruptures and the bacterium can no longer exist.
Tilamin seems to be non-specific, affecting different kinds of bacteria regardless of what their cell envelopes are made of.
That means this mechanism has the potential to be used to design more broad-spectrum antibiotics, which make up the first line of defence against bacterial infections.
Many bacteria are rapidly evolving ways to counter common antibiotics.
By using the body’s own defences as inspiration, researchers can engineer entirely new molecules that physically attack bacterial membranes.
Although we have a long way to go before we see this behind pharmacy counters, the design of Tilamin is definitely another step forward in our race against antibiotic resistance.
Image: Global Panorama