Raman spectroscopic analysis of a desert cyanobacterium Nostoc sp. in response to UVB radiation.

Cyanobacteria are capable of tolerating environmental extremes. To survive in extreme environments, cyanobacteria have developed the capability to adapt to a variety of stresses. For example, cyanobacteria have adopted a number of strategies with which to survive UV stress, including expression of UV-screening pigments and antioxidant systems. We have previously shown that several antioxidants are significantly expressed in Nostoc sp. by UVB irradiation. We report here that the content of UV-responsive biomarkers such as β-carotene and scytonemin can be easily detected by Fourier transform Raman spectroscopy with use of a small sample size and that the content of β-carotene is dependant on the UVB intensity and exposure time. Our results indicate that Raman spectroscopy may be a helpful tool to analyze UV-protective molecules of cyanobacterium in astrobiological studies without access to large sample sizes and complicated extractions, which are needed by other analytical techniques such as high-performance liquid chromatography and mass spectrometry.