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The Archaea Group
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The Archaea Group

Rolf Bernander Professor Department of Molecular Evolution Evolutionary Biology Center Uppsala University Norbyvägen 18C SE-752 36 Uppsala Sweden Phone: + 46-18-4714698 Fax: + 46-18-4716404 E-mail: Rolf.Bernander@ebc.uu.se

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• Discovery of new Cdv cell division machinery (commenting articles in PNAS and CIB)
• Global transcription map of an archaeal cell cycle
• Sulfolobus species contain three chromosome replication origins

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Archaea Life on Earth is divided into three main evolutionary lineages: the Archaea, Bacteria and Eukarya domains. Archaeal organisms display a fascinating mixture of features from the other two domains. In particular, the replication, transcription and translation proteins are homologous to those of eukaryotes, despite the fact that the archaea are prokaryotes. The archaea also display unique features, including distinct rRNA motifs, ether-linked membrane lipids, and the ability of certain genera to produce methane.

Evolution In the universal Tree of Life, the shortest and deepest branches consist of hyperthermophiles (high-temperature organisms). This suggests that the last common ancestor of all life on Earth may have been a hyperthermophile, and most hyperthermophiles are archaea. Thus, by studying the archaea, it may be possible to deduce properties of the earliest cellular organisms. It has also been suggested that the eukaryotic lineage originated from cellular fusions between different bacteria and archaea. Archaea may therefore provide insights into the origin of the eukaryotes, and act as simple model systems for complex eukaryal processes.

Extremophiles and applied science Many archaea are extremophiles that thrive under conditions of extreme heat, acidity, salinity and/or pressure, and there is intense industrial interest in archaea as sources of thermostable enzymes and other biomolecules of unusual properties. Archaea may also be used as cell factories in biotechnological processes that are carried out under extreme conditions. In addition, proteins from thermophiles are often easier to crystallize than counterparts from lower-temperature organisms. Thus, a range of important structures, including the Cdc6 replication initiation protein and the entire ribosome, have been solved with thermophiles as protein sources.

Ecology and diversity Although many archaea are extremophiles, rDNA amplification from environmental samples has made it clear that the archaea are widespread also in non-extreme biotopes. Thus, they have ecological significance for large-scale circulation of energy, nutrients and biomass, as well as for global warming, since methanogenic archaea annually release several hundred million tons of methane, an efficient greenhouse gas. We are members of the Microbiomics network, a research initiative aimed at development of novel tools for detection and functional studies of microorganisms in natural communities.

Exobiology All planets and moons in our solar system, except Earth, display environmental conditions that only extremophilic organisms could endure. Thus, knowledge about the biology of extremophiles is increasingly becoming releveant in searches for extraterrestrial life. We belong to the Swedish Astrobiology Network which deals with astrobiology and exobiology issues.

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We are interested in evolutionary, regulatory and mechanistic aspects of the main cell cycle processes, i. e. chromosome replication, genome segregation and cell division. We investigate cell cycle features of a wide range of archaea, as well as of several bacteria and eukaryotes. The work has shown that several archaeal cell cycle features are eukaryotic in nature. Archaea may, consequently, help to increase our understanding also of the eukaryotic cell cycle.

We use flow cytometry to characterize the cell cycle, to study replication and cell mass in exponential and stationary phase cultures, and to investigate the effects of drug treatments and mutations. In most of the studies, we also use epifluorescence microscopy in combination with computer-aided image analysis to study cell- and nucleoid structure. In addition, we have established several procedures for cell cycle synchronization of Sulfolobus species.

In collaboration with Dr. Dennis Grogan at the University of Cincinnati, we have isolated and characterized a set of conditional-lethal Sulfolobus acidocaldarius mutants that affect cell cycle progression. Also, we have discovered that in several euryarchaeal species, including Methanocaldococcus jannaschii, the cells contain multiple chromosome copies. In an extension of our work to include halophilic archaea, the ftsZ cell division protein of Haloferax mediterranei has been characterized. We have also studied chromosome replication patterns in Archaeoglobus fulgidus and M. jannaschii using marker frequency analysis.

In collaboration with Dr. Peter Nilsson at the Royal Institute of Technology (KTH), we have developed whole-genome DNA microarrays for Sulfolobus solfataricus and S. acidocaldarius, and used these for a variety of functional genomics studies. We also use the arrays for comparative genome hybridizations, relevant for our association with the Uppsala Center for Comparative Genomics. In a pioneering study, the arrays were used to demonstrate the first instance of multiple chromosome replication origins in prokaryotic organisms.

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Student projects available
We are looking for project students. For current projects, see UGSBR. Download project catalogue and look up Uppsala University Faculty of Science and Technology / Department of Evolution, Genomics and Systematics (p. 105-106).

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