Scientists find a natural sunscreen hidden in hot springs bacteria

Cyanobacteria are photosynthetic bacteria that produce oxygen and are known for their ability to survive in harsh environments. To cope with extreme stress, they generate a wide range of chemical compounds. Among these are mycosporine-like amino acids (MAAs), which are small, water-soluble molecules that absorb ultraviolet (UV) radiation. MAAs help protect cells from sun damage and act as antioxidants by neutralizing stress-induced reactive oxygen species (ROS). Although these molecules share a basic structural framework, their variations give rise to different biological activities and functions.

Growing Interest in Safer UV Protection

As concerns increase over UV exposure and rising skin cancer rates, scientists are searching for safer compounds that offer effective sun protection. Conventional chemical sunscreens can block UV rays, but they are also linked to allergic reactions and other unwanted side effects. MAAs stand out because they are biocompatible and considered safe for human use. These qualities make them promising candidates for sustainable biotechnology and large-scale production of natural sunscreen alternatives.

Discovery in Thailand's Hot Springs

In a new study, researchers led by Professor Hakuto Kageyama of Meijo University and Professor Rungaroon Waditee-Sirisattha of Chulalongkorn University identified a novel MAA produced by thermophilic cyanobacteria living in hot springs in Thailand. Beyond identifying a new molecule, the research sheds light on how these organisms adapt to extreme environments. "Understanding stress-responsive biosynthesis in extremophilic cyanobacteria may accelerate industrial biotechnology for natural pigment and antioxidant production," says Prof. Kageyama when describing the motivation behind the work. The study was made available online on December 01, 2025, and later published in Volume 1009 of Science of The Total Environment on December 20, 2025.

A Unique Molecule With Rare Chemical Features

The research team isolated eight strains of heat-tolerant cyanobacteria from the Bo Khlueng hot spring in Ratchaburi Province, Thailand. During laboratory experiments, one strain known as Gloeocapsa species BRSZ produced a previously unknown UV-absorbing compound when exposed to UV-A and UV-B light. The compound, identified as β-glucose-bound hydroxy mycosporine-sarcosine (GlcHMS326), was then examined in detail to understand its structure and function.

GlcHMS326 is notable for undergoing three distinct chemical modifications: glycosylation, hydroxylation, and methylation. These modifications have not been previously reported in MAAs derived from cyanobacteria. Genetic analysis revealed that the cyanobacteria responsible for producing this compound contain a unique set of genes linked to these chemical changes.

Triggered by UV Light and Salt Stress

Production of GlcHMS326 increases significantly when the cyanobacteria are exposed to UV-A, UV-B, and high salt conditions. Although the organisms originate from hot springs, this specific compound is not triggered by heat stress. The chemical modifications found in GlcHMS326 contribute to its unusual structure and enhanced performance.

Methylation is known to improve the stability, UV absorption, and antioxidant activity of MAA compounds. Glycosylation is believed to further support stability, photoprotection, and antioxidant defense. Compared with more common MAAs, GlcHMS326 demonstrates stronger free-radical scavenging activity, indicating that its modified structure plays a key role in boosting its antioxidant potential.

Insights Into Evolution and Stress Tolerance

The study offers new insight into how cyanobacteria in extreme environments have evolved specialized metabolic pathways to produce effective natural UV-protective compounds. This unique MAA appears to play an important role in helping Gloeocapsa species tolerate environmental stress and likely serves several functions within these thermophilic cyanobacteria.

Emphasizing the broader importance of the research, Prof. Waditee-Sirisattha states, "Cyanobacteria are deemed unique among the microbial world. Our recent study underscores that extremophilic cyanobacteria are not only ecologically important but also represent a key area of research for multiple disciplines."

Potential for Eco-Friendly Sunscreens and Beyond

The newly identified compound stands out because of its versatility and potential for sustainable, large-scale production using cyanobacterial "biofactories." It could serve as an alternative to certain synthetic UV filters that raise environmental concerns, helping advance the development of more eco-friendly sunscreens. Its antioxidant properties also suggest possible uses in anti-aging products, skincare formulations, and pharmaceuticals.

"This discovery reminds us that nature still holds many chemical surprises. Extremophilic cyanobacteria reveal uncommon molecules that can inspire new directions in basic science and sustainable biotechnology," concludes Prof. Kageyama.

About Professor Hakuto Kageyama from Meijo University

Dr. Hakuto Kageyama is a Professor in the Graduate School of Environmental and Human Sciences at Meijo University in Japan. He earned his PhD in 2006 from the Graduate School of Science at Nagoya University, where he studied the circadian clock in cyanobacteria. His research focuses on cyanobacteria-derived compounds and their biotechnological applications. He has published 70 research articles and authored or co-authored five books. In 2021, he received the KOSÉ Cosmetology Award from the KOSÉ Cosmetology Research Foundation.

About Professor Rungaroon Waditee-Sirisattha from Chulalongkorn University

Dr. Rungaroon Waditee-Sirisattha is a Professor in the Department of Microbiology, Faculty of Science, at Chulalongkorn University in Thailand. She earned her Ph.D. from Chulalongkorn University in 2001 and later completed postdoctoral research with the Japan Society for the Promotion of Science, JAPAN. Her work focuses on how extremophiles adapt to harsh environments, the discovery of new compounds produced by these organisms, and metabolic engineering for biotechnological applications. She has contributed to 100 published research articles.

Funding Information

This research was supported by Thailand Science research and Innovation fund Chulalongkorn University (FOOD_FF_68_121_2300_022) (to Rungaroon Waditee-Sirisattha), The Singapore Ministry of Education MOE-T2EP30123-0007 (to Rungaroon Waditee-Sirisattha & Stephen B. Pointing), a research grant from Hibi Science Foundation (to Hakuto Kageyama), Japan Society for the Promotion of Science KAKENHI Grants 24K08623 (to Hakuto Kageyama), and the Postdoctoral Fellowship, the Second Century Fund (C2F), Chulalongkorn University (to Sasiprapa Samsri).