Prokaryotic diversity in the Antarctic: the tip of the iceberg.

In contrast to the rather limited diversity of plants and animals to be found in the Antarctic, the microbial diversity of this continent has been shown to be "surprisingly" diverse. Apparently barren soil and rock landscapes, as well as the numerous and diverse lakes found at the edges of the continent, harbor a range of prokaryotes which indicate that the extremely low temperatures which prevail seasonally are no obstacle to microbial colonization. Both direct cultivation methods and modern molecular genetic methods have contributed to our understanding of the range of organisms to be found. Cultivation based studies are often hampered by constraints inherent in the methods selected for the isolation of organisms. Molecular-based approaches do not suffer from the same cultivation-based biases, but other problems need to be taken into consideration. It has rarely been possible to combine both techniques in a single study, nor has it usually been possible to take the results and conclusions drawn from the study of one environment and apply this knowledge to a further series of experiments on the same environment. The Antarctic may be considered to be a geographically well isolated area to study. Comparison with other environments that may also be "isolated" from their surroundings (i.e., hot springs or highly saline lakes) allows parallels to be drawn. The conclusions drawn provide important insights into the way the Antarctic may have been colonized and the microbiota diversified. Much work still needs to be done beyond the simple task of making an inventory. The functioning of complex communities, such as mat systems, requires an understanding of the ecology of the systems, not only at the level of the whole system, but also the role of localized environments within that system. Perhaps these ecosystems have, in the absence of plant and animal communities, a role to play in the monitoring of polar climate change. The information available at present clearly indicates that the Antarctic is deserving of further study at the microbial level.