Functional diversity of microboring Ostreobium algae isolated from corals

2020

Article référencé dans le Web of Science WOS:000576801200001

Massé A., Tribollet Aline, Meziane T., Bourguet-Kondracki M. L., Yepremian C., Seve C., Thiney N., Longeon A., Couté A., Domart-Coulon I.

Environmental Microbiology, 2020, 22 (11), 4825-4846 ISSN 1462-2912

The filamentous chlorophyteOstreobiumsp. dominates shallow marine carbonate microboring communities, and is one of the major agents of reef bioerosion. While its large genetic diversity has emerged, its physiology remains little known, with unexplored relationship between genotypes and phenotypes (endolithicversusfree-living growth forms). Here, we isolated nine strains affiliated to two lineages ofOstreobium(>8% sequence divergence of the plastid generbcL), one of which was assigned to the family Odoaceae, from the fast-growing coral hostPocillopora acutaLamarck 1816. Free-living isolates maintained their bioerosive potential, colonizing pre-bleached coral carbonate skeletons. We compared phenotypes, highlighting shifts in pigment and fatty acid compositions, carbon to nitrogen ratios and stable isotope compositions (delta C-13 and delta N-15). Our data show a pattern of higher chlorophyllband lower arachidonic acid (20:4 omega 6) content in endolithicversusfree-livingOstreobium. Photosynthetic carbon fixation and nitrate uptake, quantified via 8 h pulse-labeling with(13)C-bicarbonate and(15)N-nitrate, showed lower isotopic enrichment in endolithic compared to free-living filaments. Our results highlight the functional plasticity ofOstreobiumphenotypes. The isotope tracer approach opens the way to further study the biogeochemical cycling and trophic ecology of these cryptic algae at coral holobiont and reef scales.

Limnologie biologique / Océanographie biologique [034] ; Ecologie, systèmes aquatiques [036]

FRANCE ; ZONE TROPICALE

Fonds IRD [F B010079791]

fdi:010079791