Nature’s 3D printer: bristle worms form bristles piece by piece

A new interdisciplinary study by the group led by molecular biologist Florian Raible from the Max Perutz Labs at the University of Vienna provides exciting insights into the bristles of the marine annelid Platynereis dumerilii. Specialized cells, so-called chaetoblasts, control the formation of the bristles. Their mode of operation is astonishingly similar to that of a technical 3D printer.

The project was carried out in collaboration with researchers from the University of Helsinki, Vienna University of Technology and Masaryk University in Brno and was recently published in the journal Nature Communications.

Chitin and its importance

Chitin is the primary building material for both the exoskeleton of insects and the bristles of bristle worms. Of particular interest is the softer beta chitin of bristle worms, which could be used for biomedical applications.

Florian Raible explains: “The process starts with the tip of the bristles, followed by the middle section and finally the base of the bristles. The finished parts are pushed further and further out of the body. During this development process, the important functional units are created piece by piece one after the other, which is similar to 3D printing.”

Chaetoblasts are specialized cells with long microvilli that contain a specific enzyme that produces chitin. These microvilli act like the nozzles of a 3D printer and eject chitin, which forms the bristles.

Florian Raible explains: “Our analysis suggests that the chitin is ejected by the individual microvilli of the chaetoblast cell. The precise change in the number and shape of these microvilli over time is therefore the key to shaping the geometric structures of the individual bristles, such as individual teeth on the bristle tip, which are precise down to the micrometer range.”

Cooperation and technologies

The study benefited from collaboration with the Vienna University of Technology and the University of Brno. Particularly valuable was the cooperation with the Jokitalo laboratory at the University of Helsinki, which used serial block face scanning electron microscopy (SBF-SEM) to investigate the arrangement of the microvilli.

First author Kyojiro Ikeda from the University of Vienna explains: “Standard electron tomography is very labor-intensive, as the cutting of the samples and their examination in the electron microscope must be done manually. With this approach, however, we can reliably automate the analysis of thousands of layers.”

The Raible lab plans to further improve the resolution of the observations to gain even more detailed insights into bristle formation. This research could open up new avenues for biomedical applications and sustainable material development.