Combination of different microscopy techniques for the integrated study of extremophile endolithic microorganisms and their habitats

Some micro-organisms are able to withstand extreme environments and form communities within rocks. To characterise these endolithic micro-ecosystems, several microscopy and microanalytical approaches need to be combined, including scanning electron microscopy with back scattered electron imaging (SEM-BSE), low temperature scanning electron microscopy (LTSEM), confocal scanning laser microscopy (CSLM), and the X-ray energy dispersive spectroscopy (EDS) microanalytical system. These techniques have allowed the simultaneous observation of these micro-organisms and their habitats. SEM-BSE and LTSEM serve to evaluate the biodiversity of the rock from a morphological and ultrastructural perspective. LTSEM also permits water localisation in the cells and their microhabitats. Information on the spatial distribution of the micro-organisms inside the rock is provided by CSLM. Lithobiontic communities have been shown to interact with their substrate. The EDS technique coupled to SEM-BSE permits the chemical characterisation of mineral features, the detection of biomobilisation and biomineralisation processes, and yields information on the chemical environment. These techniques are also applicable in the search for fossilised micro-organisms.