Dreissenid mussels: the resilience and success of an invasive species

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Mussels with byssus threads: common mussel (Mytilus edulis) above, quagga mussel
Mussels with byssus threads: common mussel (Mytilus edulis) above, quagga mussel (Dreissena bugensis) below, and byssus threads in the middle. Photo: Miriam Simmons et al., PNAS, DOI: 10.1073/pnas.2311901120; licensed under CC BY-NC-ND 4.0

Scientists shed light on unique fibre structure, evolutionary history and combating invasive species

Zebra and quagga mussels, which belong to the Dreissenid family, are freshwater invasive species widespread throughout western Europe and North America. They present a significant danger to native ecosystems by competing for resources. Using a fibrous anchor called a byssus, Dreissenid mussels also cause biofouling by attaching persistently to underwater surfaces and for example block the intakes of power stations and water treatment plants. A research team led by McGill University in Canada and Göttingen University in Germany discovered that a rare genetic event, occurring over 12 million years ago, played an important role in shaping one of Europe and Canada’s most damaging invasive species. Their research also sheds light on how mussel fibres could inspire the development of sustainable materials in the future. Their findings were published in PNAS.

The researchers collected material from zebra and quagga mussels in Germany and Canada to investigate how these mussels stick to surfaces. Researchers at McGill used a variety of techniques to characterise some of the materials properties of the byssus thread to better understand how this biological material allows the animal to attach itself with such resilience to almost any underwater surface. Researchers in Göttingen identified and sequenced a gene that codes for a byssus thread protein that makes the distinctive silken fibres, performed the structural modelling of the protein and carried out analyses that clarified its evolution. During his involvement in the project Professor Daniel J. Jackson (University of Göttingen) observed Dreissenid mussels in Germany’s Northeimer Seenplatte lakes. He explains, -It was shocking to see how abundant they are there. This shows how invasive the quagga and zebra mussels are, and how they can completely dominate certain habitats.-

The researchers discovered that a previously undocumented evolutionary event contributed to Dreissenid mussels- resilience and success as an invasive species. Jackson explains, "More than 12 million years ago, it is likely that a single bacterium transferred foreign genetic material into a single mussel endowing its descendants with the ability to make these fibres. Given their crucial role in mussel attachment in freshwater habitats, this horizontal gene transfer event supported the harmful global expansion of these mussels.- This research, marking important progress in the understanding of invasive mussels and their attachment mechanisms, could offer potential solutions to mitigate their damaging environmental and economic impact.

In addition, the research advances understanding of the mechanisms of biofouling and sheds light on how mussel fibres could inspire the development of sustainable materials. The researchers found that the building blocks of the fibres were massive coiled-coil proteins, the largest ever found. These proteins, structurally similar to those found in human hair, were found to transform into silk-like beta crystallites through the simple application of stretching forces by the mussel during formation. This method of fibre fabrication is much simpler than spider silk formation, potentially offering an easier route toward biotechnological manufacture of sustainable fibres - an industry currently dominated by artificial spider silks. Professor Matthew Harrington, McGill University Department of Chemistry, explains: "Dreissenid byssus fibres, which resemble spider silk structurally, could inspire future development of tough polymer fibres, contributing to more durable and sustainable materials typically used in textiles and technical plastics.-

Original publication: -Invasive mussels fashion silk-like byssus via mechanical processing of massive horizontally acquired coiled coils- by Miriam Simmons et al., was published in PNAS. DOI: 10.1073/pnas.2311901120