Shark Bay, Western Australia is a World Heritage area with extensive microbial mats and stromatolites. Microbial communities that comprise these mats have developed a range of mitigation strategies against changing levels of photosynthetically active and ultraviolet radiation, including the ability to biosynthesise the UV-absorbing natural products scytonemin and mycosporine-like amino acids (MAAs). To this end, the distribution of photoprotective pigments within Shark Bay microbial mats was delineated in the present study. This involved amplicon sequencing of bacterial 16S rDNA from communities at the surface and subsurface in three distinct mat types (smooth, pustular and tufted), and correlating this data with the chemical and molecular distribution of scytonemin and MAAs. Employing UV spectroscopy and MS/MS fragmentation, mycosporine-glycine, asterina and an unknown MAA were identified based on typical fragmentation patterns. Marker genes for scytonemin and MAA production (scyC and mysC) were amplified from microbial mat DNA and placed into phylogenetic context against a broad screen throughout 363 cyanobacterial genomes. Results indicate that occurrence of UV screening compounds is associated with the upper layer of Shark Bay microbial mats, and the occurrence of scytonemin is closely dependent on the abundance of cyanobacteria.

Bioanalytical Mass Spectrometry Facility Mark Wainwright Analytical Centre University of New South Wales Sydney New South Wales Australia

Biosystems Chemistry Department of Chemistry and Center for Integrated Protein Science Munich Technische Universität München Garching Germany

Department of Experimental Limnology Leibniz Institute of Freshwater Ecology and Inland Fisheries Stechlin Germany

Research Centre for Toxic Compounds in the Environment Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic

School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore

School of Biotechnology and Biomolecular Sciences University of New South Wales Sydney New South Wales Australia

School of Environmental and Life Sciences University of Newcastle Newcastle New South Wales Australia

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