Biomedical subjects

Lise Øvreås

Publications and source records attributed to Lise Øvreås.

5 recordsLinked to original sources

PubMed2006

Flaviramulus basaltis gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from seafloor basalt.

Four yellow-pigmented, Gram-negative, motile strains were isolated from the glassy rind of submarine basaltic lava from the Jan Mayen area of the Norwegian/Greenland Sea at a depth of 1300 m below sea level. The four strains had identical 16S rRNA gene sequences and were indistinguishable in all phenotypic and chemotypic tests performed, indicating that they belonged to the same species. The strains had an obligately aerobic chemo-organotrophic metabolism. The strains were capable of growth at temperatures between -2 and 34 degrees C, at pH between 6.5 and 8.6, and at sea salt concentrations between 3 and 60 g l(-1). The strains were able to utilize organic acids, amino acids and sugars but not alcohols; they were also capable of hydrolysing a wide range of macromolecules. The predominant fatty acids were 15 : 0 iso, 15 : 1 iso, 15 : 0 iso 3-OH and 17 : 0 iso 3-OH. The mean DNA G+C content of the strains was 31.4 mol%. 16S rRNA gene sequence analysis indicated that the strains were affiliated to the genera Gaetbulibacter and Algibacter. However, phenotypic characteristics, especially aerobic metabolism, suggested that the strains should be placed within a new genus. On the basis of the polyphasic characterization of the four strains, it is suggested that the strains be included in the family Flavobacteriaceae as representatives of a novel species in a new genus, for which the name Flaviramulus basaltis gen. nov., sp. nov. is proposed. The type strain is H35(T) (=CIP 109091(T)=DSM 18180(T)).

Bacterial Typing Techniques↗

PubMed2002

Prokaryotic diversity--magnitude, dynamics, and controlling factors.

There are probably millions of species in the microorganismal domains Bacteria and Archaea (the prokaryotes), and we are only just beginning to work out the basic principles governing their distribution and abundance in natural environments. One characteristic that has become clear is that prokaryote diversity in aquatic environments is orders of magnitude less than in sediments and soils. Hypotheses and models explaining such differences are under development and are beginning to offer promising insights into the mechanisms governing prokaryote diversity and ecosystem function.

Animals↗

PubMed2002

Microbial diversity and function in soil: from genes to ecosystems.

Soils sustain an immense diversity of microbes, which, to a large extent, remains unexplored. A range of novel methods, most of which are based on rRNA and rDNA analyses, have uncovered part of the soil microbial diversity. The next step in the era of microbial ecology is to extract genomic, evolutionary and functional information from bacterial artificial chromosome libraries of the soil community genomes (the metagenome). Sophisticated analyses that apply molecular phylogenetics, DNA microarrays, functional genomics and in situ activity measurements will provide huge amounts of new data, potentially increasing our understanding of the structure and function of soil microbial ecosystems, and the interactions that occur within them. This review summarizes the recent progress in studies of soil microbial communities with focus on novel methods and approaches that provide new insight into the relationship between phylogenetic and functional diversity.

Bacteria↗

PubMed2002

Changes in archaeal, bacterial and eukaryal assemblages along a salinity gradient by comparison of genetic fingerprinting methods in a multipond solar saltern.

Microbial communities inhabiting a multipond solar saltern were analysed and compared using SSU rRNA polymerase chain reaction (PCR)-based fingerprintings carried out in parallel by four laboratories. A salinity gradient from seawater (3.7%) to NaCl precipitation (37%) was studied for Bacteria, Archaea and Eukarya, and laboratories applied their own techniques and protocols on the same set of samples. Members of all three domains were retrieved from all salt concentrations. Three fingerprinting techniques were used: denaturing gradient gel electrophoresis (DGGE), ribosomal internal spacer analysis (RISA), and terminal-restriction fragments length polymorphism (T-RFLP). In addition, each laboratory used its own biomass collection method and DNA extraction protocols. Prokaryotes were addressed using DGGE and RISA with different 'domain-specific' primers sets. Eukaryotes were analysed by one laboratory using DGGE and T-RFLP, but targeting the same 18S rDNA site. Fingerprints were compared through cluster analysis and non-metric multidimensional scaling plots. This exercise allowed fast comparison of microbial assemblages and determined to what extent the picture provided by each laboratory was similar to those of others. Formation of two main, salinity-based groups of samples in prokaryotes (4-15% and 22-37% salinity) was consistent for all the laboratories. When other clusters appeared, this was a result of the particular technique and the protocol used in each case, but more affected by the primers set used. Eukaryotic microorganisms changed more from pond to pond; 4-5% and 8-37% salinity were but the two main groups detected. Archaea showed the lowest number of bands whereas Eukarya showed the highest number of operational taxonomic units (OTUs) in the initial ponds. Artefacts appeared in the DGGE from ponds with extremely low microbial richness. On the other hand, different 16S rDNA fragments with the same restriction or internal transcribed spacer (ITS) length were the main limitations for T-RFLP and RISA analyses, respectively, in ponds with the highest OTUs richness. However, although the particular taxonomic composition could vary among protocols, the general structure of the microbial assemblages was maintained.

Archaea↗

PubMed2002

Prokaryotic genetic diversity throughout the salinity gradient of a coastal solar saltern.

Bacterial and archaeal assemblages have been studied in a multipond solar saltern using a range of microbial ecology techniques by four laboratories simultaneously. These include 16S rDNA sequencing from both denaturing gradient gel electrophoresis (DGGE) and clone libraries, and culturing methods. Water samples from eight ponds were analysed, covering a salinity range from near sea water (4% salt) to saturated sodium chloride (37% salt; ponds called crystallizers). Clone libraries focused on ponds with salinity of 8%, 22% and 32%. Although different cloning strategies were able to retrieve the same type of dominant sequences, there were differing degrees of success with less abundant sequences. Thus, the use of two sets of primers recovered a higher number of phylotypes. Bacterial and archaeal isolates were, however, different from any of the retrieved environmental sequences. For Bacteria, most sequences in the 8% salt pond were related to organisms of marine origin. Thus, representatives of the alpha-, beta-, gamma- and epsilon-subdivisions of Proteobacteria, the Cytophaga-Flavobacterium-Bacteroides group (CFB), high-G+C Gram-positive bacteria and cyanobacteria were found. In the 22% salt pond, alpha- and gamma-Proteobacteria, cyanobacteria and CFB were the only groups found, and most of them were related to specialized halophilic bacteria. From the 32% salt pond, only CFB were found, and most of the sequences retrieved clustered with Salinibacter ruber, an extremely halophilic bacterium. A decrease in the richness of bacterial genera was therefore apparent along the gradient. Archaea behaved quite similarly. In the lowest salinity ponds, sequences were related to environmental clones of Marine Archaea Group III (Thermoplasmales relatives) and to unclassified branches of Euryarchaeaota. In the 8%, 22% and 32% ponds, most of the clones were related to different cultured strains of Halobacteriaceae. Finally, most sequences from the crystallizers clustered with the uncultured square archaeon SPhT. Crenarchaeaota were not detected. Despite the fact that higher prokaryotic richness was apparent in the lower salinity ponds than in the crystallizers, the diversity index from clone libraries calculated according to Shannon and Weaver did not show this trend. This was because diversity in the crystallizers can be considered as 'microdiversity', the co-existence of several closely related clones of Bacteria (the S. ruber cluster) and Archaea (the SPhT cluster). Regardless of the changes in abundance, both Bacteria and Archaea showed the same pattern; as salinity increased, the number of different clusters decreased, and only one cluster became dominant. Both clusters, however, showed a considerable degree of microdiversity. The meaning of such microdiversity remains to be determined.

Archaea↗