Showing papers by "Christa Schleper published in 2005"

Novel genes for nitrite reductase and Amo-related proteins indicate a role of uncultivated mesophilic crenarchaeota in nitrogen cycling.

Abstract: Mesophilic crenarchaeota are frequently found in terrestrial and marine habitats worldwide, but despite their considerable abundance the physiology of these as yet uncultivated archaea has remained unknown. From a 1.2 Gb large-insert environmental fosmid library of a calcareous grassland soil, a 43 kb genomic fragment was isolated with a ribosomal RNA that shows its affiliation to group 1.1b of crenarchaeota repeatedly found in soils. The insert encoded a homologue of a copper-containing nitrite reductase with an unusual C-terminus that encoded a potential amicyanin-like electron transfer domain as well as two proteins related to subunits of ammonia monooxygenases or particulate methane monooxygenases (AmoAB/PmoAB) respectively. Expression of nirK and the amoA-like gene was shown by reverse transcription polymerase chain reaction (PCR) analyses in soil samples, the latter being found at higher levels when the soil was incubated with ammonia (measured by quantitative PCR). Further variants of both genes were amplified from soil samples and were found in the environmental database from the Sargasso Sea plankton. Taken together, our findings suggest that mesophilic terrestrial and marine crenarchaeota might be capable of ammonia oxidation under aerobic and potentially also under anaerobic conditions.

Genomic studies of uncultivated archaea

Abstract: Archaea represent a considerable fraction of the prokaryotic world in marine and terrestrial ecosystems, indicating that organisms from this domain might have a large impact on global energy cycles. However, many novel archaeal lineages that have been detected by molecular phylogenetic approaches have remained elusive because no laboratory-cultivated strains are available. Environmental genomic analyses have recently provided clues about the potential metabolic strategies of several of the uncultivated and abundant archaeal species, including non-thermophilic terrestrial and marine crenarchaeota and methanotrophic euryarchaeota. These initial studies of natural archaeal populations also revealed an unexpected degree of genomic variation that indicates considerable heterogeneity among archaeal strains. Here, we review genomic studies of uncultivated archaea within a framework of the phylogenetic diversity and ecological distribution of this domain.