Invasive mussels are a major threat to aquatic ecosystems and human infrastructure. They can attach to almost any surface with their protein-based fibers, called byssal threads.
But how do they make these strong and flexible fibers, and where did they get the genes for them?
The Mystery of the Mussel Silk
Kilian FICHOU/AFP via Getty Images
A team of researchers from McGill University has unraveled the secrets behind the mussel silk.
They found that invasive mussels, such as zebra and quagga mussels, use a unique mechanism to transform their protein precursors into silk-like fibers.
They also discovered that these proteins were acquired from another organism through horizontal gene transfer, a rare evolutionary event.
The researchers used various techniques to analyze the structure and function of the byssal thread proteins.
They found that the proteins are very large and rich in asparagine, an amino acid that forms coiled coils, a type of helical structure.
The coiled coils are then mechanically processed into beta-sheet crystals, a type of flat structure, during the formation of the byssal thread. This process results in a fiber that has both elasticity and strength, similar to spider silk.
The researchers also traced the origin of the byssal thread proteins. They found that the genes encoding these proteins are not present in other bivalves, but are closely related to a gene from a marine bacterium.
This suggests that the mussels acquired the gene through horizontal gene transfer, a process in which an organism transfers genetic material to another organism that is not its offspring.
The researchers estimated that this event occurred at least 12 million years ago, before the divergence of zebra and quagga mussels.
The study also provided insights into the molecular basis of mussel adhesion and the evolution of silk-like materials in nature.
Moreover, it suggested new ways to control invasive mussels and prevent their spread. One possibility is to target the coiled-coil proteins or the enzyme that converts them into beta-sheet crystals and disrupt their function.
Another possibility is to design surfaces that are resistant to mussel adhesion, by mimicking the properties of spider silk or other natural materials.
Invasive mussels are native to the Caspian Sea and the Black Sea, but they have spread to many parts of the world, including North America, Europe, and Asia, through ballast water discharge and recreational boating.
They can reproduce rapidly and form dense colonies that can clog water intake and discharge pipes, damage aquatic habitats and biodiversity, and alter water quality and chemistry. They are estimated to cause billions of dollars of damage every year.
