Combined fluorescence in situ hybridization and microautoradiography (FISH-MAR)

Cultivation independent studies have revealed, that due to the complexity of natural ecosystems such as activated sludge, rhizosphere, rumen etc., the pure cultivation of all related micro-organisms in these diverse ecosystems is quite unsuccessful [2]. Accordingly, the small subunit ribosomal RNA (SSU rRNA, i.e. 16S and 18S rRNA) or genes, obtained from these ecosystems without cultivation has become a widely accepted approach to describe the phylogenetic diversity of microbial communities present in these ecosystems [1, 6]. The rapid growth of the rRNA gene (rDNA) sequence data bank, accessible via the Internet (http://www.ncbi.nlm.nih.gov/BLAST/) has enabled us to compare microbial diversities across the globe without cultivation. However, these rRNA gene sequences provide very few direct clues regarding the interactions and the metabolic capabilities of the identified micro-organisms [9]. Accordingly, the knowledge available on the in situ physiology of the inhabitants of most microbial ecosystems is quite remote and the availability of such knowledge will enable our ability to manipulate ecosystems (e.g. activated sludge) to achieve better process performances with the aid of improved mathematical models