A mesophilic relative of common glacier algae, Ancylonema palustre sp. nov., provides insights into the induction of vacuolar pigments in zygnematophytes

• Published in: Environmental microbiology 2024-07, Vol.26 (8), p.e16680-n/a
• Main Authors: Busch, Anna, Slominski, Emilia, Remias, Daniel, Procházková, Lenka, Hess, Sebastian
• Format: Article
• Language: English
• Subjects: Abiotic factors; Algae; Algal blooms; Aquatic plants; Autecology; Biosynthesis; Chlorophyceae - genetics; Chlorophyceae - metabolism; Chlorophyta - genetics; Chlorophyta - metabolism; Colour; Gallic acid; genomics; genus; Glaciers; Introduced species; microbiology; Moorland; Natural environment; New species; Phylogeny; Physical characteristics; Pigmentation; Pigments; Pigments, Biological - metabolism; Psychrophiles; species; Sun screens; sunscreens; Ultraviolet radiation; vacuoles; Vacuoles - metabolism
• ISSN: 1462-2912; 1462-2920; 1462-2920
• DOI: 10.1111/1462-2920.16680

The green algae of the genus Ancylonema, which belong to the zygnematophytes, are prevalent colonizers of glaciers worldwide. They display a striking reddish‐brown pigmentation in their natural environment, due to vacuolar compounds related to gallic acid. This pigmentation causes glacier darkening when these algae bloom, leading to increased melting rates. The Ancylonema species known so far are true psychrophiles, which hinders experimental work and limits our understanding of these algae. For instance, the biosynthesis, triggering factors, and biological function of Ancylonema's secondary pigments remain unknown. In this study, we introduce a mesophilic Ancylonema species, A. palustre sp. nov., from temperate moorlands. This species forms the sister lineage to all known psychrophilic strains. Despite its morphological similarity to the latter, it exhibits unique autecological and photophysiological characteristics. It allows us to describe vegetative and sexual cellular processes in great detail. We also conducted experimental tests for abiotic factors that induce the secondary pigments of zygnematophytes. We found that low nutrient conditions combined with ultraviolet B radiation result in vacuolar pigmentation, suggesting a sunscreen function. Our thriving, bacteria‐free cultures of Ancylonema palustre will enable comparative genomic studies of mesophilic and extremophilic zygnematophytes. These studies may provide insights into how Ancylonema species colonized the world's glaciers. We introduce a new species of zygnematophytes, Ancylonema palustre sp. nov., discovered in moorlands. This species exhibits a reddish intracellular pigmentation, a characteristic shared with its glacier‐dwelling relatives. Utilizing bacteria‐free cultures, we provide detailed descriptions of both vegetative and sexual processes. Our study also demonstrates that secondary pigments in these organisms can be induced by exposure to ultraviolet radiation.