New tools for isolation and identification of micro-organisms.
Résumé
The microbial world contains a highly heterogeneous group of organisms sharing only one common characteristic, their small sizes. These organisms make up two (out of three) entire Domains of life on earth, the prokaryotic Bacteria and Archaea (Woese, 1987). Within the third Domain Eukarya, the majority of the phylogenetic diversity is contained within eukaryotic micro-organisms such as protozoa, algae, and fungi. Micro-organisms are estimated to make up more than a third of Earth's biomass (Whitman, et al., 1998). Because culturing provided the platform for building the depth and detail of modern microbiological knowledge, for a long time microbiologists ignored the challenge to identify and characterize uncultured organisms. One of the indicators that cultured micro-organisms did not represent much of the microbial world was the oft-observed "great plate count anomaly" (Staley and Konopka, 1985). The discrepancy between the sizes of populations estimated by dilution plating and by microscopy is particularly dramatic in some aquatic environments, in which plate counts and viable cells estimated by acridine orange staining can differ by four to six orders of magnitude, and in soil, in which 0.1 to 1% of bacteria are readily culturable on common media under standard conditions (Torsvik and Ovreas, 2002). Understanding the extend and importance of the genetic and biochemical diversity among strains of the same or very closely related species is a cornerstone issue for many microbiological disciplines such as biotechnology, taxonomy, diagnosis, diversity surveys, etc. We are only at the beginning of the history of the discovery of the amazing microbial diversity.