Abstract
Microbial life in extreme environments is attracting broad scientific interest. Knowledge about it helps in defining the boundaries for life to exist, and organisms living under extreme conditions are also interesting sources for enzymes with unusual and desirable properties. The tremendous progress in DNA sequencing technologies now makes it relatively easy to gain a representative overview of the composition of such communities, and many community studies have in the last decade applied metagenomics to characterize habitats extreme in, for example, temperature, salt and acidity. The future challenges in the field are likely to become more and more related to the conversion of the expected massive amounts of sequence information into an understanding of the corresponding biological community functions.