Nc. Russell et al., FT-RAMAN SPECTROSCOPIC ANALYSIS OF ENDOLITHIC MICROBIAL COMMUNITIES FROM BEACON SANDSTONE IN VICTORIA-LAND, ANTARCTICA, Antarctic science, 10(1), 1998, pp. 63-74
Laser-based Fourier-Transform Raman spectroscopy (FTRS) has been used
to identify in situ compounds of ecophysiological significance in dive
rse field-fresh Antarctic cryptoendolithic microbial communities. FTRS
does not disrupt the community and permits characterization of visibl
e and invisible compounds in their natural configuration within cells
and their current or former microhabitat. The small ''footprint'' of t
he microscopic laser beam permits accurate analysis of discrete zones
of compounds produced by extant or degraded micro-organisms with minim
um destruction of the biota. This spatial chemical analysis is applica
ble to any translucent or exposed habitat or biotic assemblage. Two hy
drated forms of biodegradative calcium oxalate were differentiated in
black-pigmented and hyaline lichen zones of endolithic communities. Th
e oxalate was restricted to zones containing fungi. Communities domina
ted by cyanobacteria at Battleship Promontory (77 degrees S) and a new
ly discovered site at Timber Peak (74 degrees S) contrasted chemically
with those dominated by eukaryotic algae at East Beacon (78 degrees S
). FTRS also showed the zonation of pigments including chlorophyll and
UV-protective carotenoids in situ. At extreme sites on the polar plat
eau, it revealed the presence of ''fossil'' endolithics where detrimen
tal climatic changes had made the microbes non-viable or amorphous, be
ing represented solely by their residual bio-molecules. The technique
has potential for past or present life-detection anywhere in the world
without destruction of the microniche.