Schematic representation of Brink as a functional living coating designed to enhance coral settlement. A) Harvest and isolation of lipopolysaccharide-producing bacteria from the tissues of the coral Montipora capitata (Thalassotalea euphylliae H1) and marine biofilm (Cellulophaga lytica HI1). B) Optimization of biopolymer mixture for microbial cell viability and mechanical properties. Rapid light-assisted cross-linking of Brink on calcium carbonate (CaCO3) plugs, a common restoration material. C) Brink sustains living bacteria that act as biofactories, producing lipopolysaccharides to attract coral larvae from the surrounding environment. Credit: Levy et al.

A living ink containing bacteria attracts coral larvae and could help rebuild reefs. The paper is in the journal PNAS Nexus.

Corals are struggling with , as well as warming and acidification caused by . One way to support coral reef persistence is to encourage coral recruitment onto the reef. Coral larvae are free-swimming animals that eventually settle onto a surface and transform into a polyp with a hard, durable body. Certain bacteria secrete chemical cues that stimulate settlement and metamorphosis. Settled polyps may then reproduce asexually, expanding the size of the reef.

Daniel Wangpraseurt and colleagues created a living material that encourages to attach and settle down. Bacterial Reef Ink (BRINK) is a photopolymerized hydrogel hosting two native Hawaiian settlement-inducing bacterial strains, Cellulophaga lytica and Thalassotalea euphylliae.

In test tanks, coral settlement on surfaces coated with BRINK was fivefold higher than on surfaces without ink for one coral species and fourfold higher for a different coral species. According to the authors, the ink could be customized to support a range of settlement-inducing tailored to specific coral reef environments worldwide.

More information: Microbial living materials promote coral larval settlement, PNAS Nexus (2025).

Journal information: PNAS Nexus

Provided by PNAS Nexus