Scytonemin Production by Cyanobacteria: A Threat To Algal Stromatolites in Salkhan Fossil Park, India
摘要
The present study concerns protection of important stromatolites on boulders in the Salkhan Fossil Park, Sonebhadra, India. Unfortunately, the fossils are at risk of biodegradation by rock-encrustations dominated by cyanobacteria. Some cyanobacteria have yellow-brown, lipophilic extracellular polysaccharide sheath pigment scytonemin that absorbs UV radiation and helps them to survive. Scytonemin, an evolutionary significant pigment, was extracted and purified from the surface of the stromatolite boulders. Genera including Scytonema sp., Lyngbya sp., and Aphanocapsa sp. were the most prevalent in these encrustations. Scytonemin was identified and characterized using fourier transform infrared (FTIR) spectroscopy, electro spray ionization-mass spectrometry (ESI-MS/MS), high-performance liquid chromatography (HPLC), and UV-Vis spectroscopy. With an absorption peak at 386 nm and a retention time of 1.45 min, scytonemin was found to be significantly present in the samples. Additionally, absorption was also observed at 252, 278, and 300 nm. In the FTIR spectrum, absorption was detected at 3421, 2940, 1027, and 1000–1320 cm−1. This compound’s identity as scytonemin was further confirmed by the ESI-MS/MS spectrum, displaying significant peaks at m/z 489, 517, 529, and 544. Scytonemin is a way to identify the presence of cyanobacterial colonization and its production enable them to cope with the harsh environmental conditions to survive in the rock incrustations. This biological issue is significant since it is related to the regrettable neglect of an important geological site, which is also a social and political issue. The biodegradation of the fossils at this park may be significantly influenced by the biological crusts that are rich in scytonemin.