| 1. |
- Larsson, Bengt, et al.
(författare)
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Molecular oxygen in the rho Ophiuchi cloud
- 2007
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 466:3, s. 5-
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Tidskriftsartikel (refereegranskat)abstract
- Context: Molecular oxygen, O2, has been expected historically to be an abundant component of the chemical species in molecular clouds and, as such, an important coolant of the dense interstellar medium. However, a number of attempts from both ground and from space have failed to detect O2 emission.Aims: The work described here uses heterodyne spectroscopy from space to search for molecular oxygen in the interstellar medium. Methods: The Odin satellite carries a 1.1 m sub-millimeter dish and a dedicated 119 GHz receiver for the ground state line of O2. Starting in 2002, the star forming molecular cloud core ρ Oph A was observed with Odin for 34 days during several observing runs.Results: We detect a spectral line at v_LSR =+3.5 km s-1 with Δ v_FWHM=1.5 km s-1, parameters which are also common to other species associated with ρ Oph A. This feature is identified as the O2 (NJ = 11 - 1_0) transition at 118 750.343 MHz.Conclusions: The abundance of molecular oxygen, relative to H{2} , is 5 × 10-8 averaged over the Odin beam. This abundance is consistently lower than previously reported upper limits.Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Étude Spatiale (CNES). The Swedish Space Corporation has been the industrial prime contractor and also is operating the satellite. Appendix A is only available in electronic form at http://www.aanda.org
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| 2. |
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| 3. |
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| 4. |
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| 5. |
- Andersson, Agneta, et al.
(författare)
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Release of aminoacids and inorganic nutrients by heterotrophic marine microflagellates
- 1985
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Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599. ; 23, s. 99-106
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Tidskriftsartikel (refereegranskat)abstract
- Heterotrophic microflagellates isolated from the Baltic Sea and grown under laboratoryconditions were shown to release dissolved free amino acids (DFAA) when grazing bacteria. Flagellatesreleased 3H-amino acids when fed 3H-leucine-labelled bacteria, and concentrations of aminoacids increased in the experimental medium. Serine showed a strong positive correlation withflagellate feeding. Aspartic acid, glutamic acid and ornithine also increased more than other aminoacids. During consumption of bacteria, the flagellates released 13% of the ingested nitrogen asammonia, and 30 % of the ingested phosphorus as phosphate. In a field experiment off Scripps Pier, wemeasured bacterial production, flagellate abundance, and concentration of DFAA over a 28 h period.The concentration of DFAA showed a covariation with the flagellate numbers. Results from our fieldand laboratory experiments suggest that flagellates may be a source of DFAA in the sea.
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| 6. |
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| 7. |
- Andersson, Agneta, et al.
(författare)
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Vertical transport of lipid in seawater
- 1993
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 98:1-2, s. 149-155
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Tidskriftsartikel (refereegranskat)abstract
- Lipids in seawater act as solvents and transporters of lipophilic organic pollutants. To investigate a possible transport route of lipophilic pollutants, the vertical flux of lipid was quantified during an annual cycle in the northern Baltic Sea. The lipid content in both sedimenting material and different size fractions of seawater was analyzed. During the year, 8 g lipid m-2 sedimented out from the photic zone to the benthic system. The sedimentation of lipid accounted for 300 to 400 % of the average standing stock of pelagic lipid and was concentrated in the spring bloom period (April-June) when 70 % of the total lipid sedimentation occurred. About 30 % of the produced pelagic lipid settled out from the system. In seawater the lipid maximum occurred at the end of the spring bloom, shortly after nutrient depletion, indicating a stress response in the algae. Since lipid sedimentation is concentrated in the spring bloom, removal of lipophilic organic pollutants may be important during this period.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Blackburn, Nicholas, et al.
(författare)
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Rapid determination of bacterial abundance, biovolume, morphology, and growth by neural network-based image analysis
- 1998
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 64:9, s. 3246-3255
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Tidskriftsartikel (refereegranskat)abstract
- Annual bacterial plankton dynamics at several depths and locations in the Baltic Sea were studied by image analysis. Individual bacteria were classified by using an artificial neural network which also effectively identified nonbacterial objects, Cell counts and frequencies of dividing cells were determined, and the data obtained agreed well with visual observations and previously published values. Cell volumes were measured accurately by comparison with bead standards. The survey included 690 images from a total of 138 samples. Each image contained approximately 200 bacteria. The images were analyzed automatically at a rate of 100 images per h, Bacterial abundance exhibited coherent patterns with time and depth, and there were distinct subsurface peaks in the summer months. Four distinct morphological classes were resolved by the image analyzer, and the dynamics of each could be visualized. The bacterial growth rates estimated from frequencies of dividing cells were different from the bacterial growth rates estimated by the thymidine incorporation method. With minor modifications, the image analysis technique described here can be used to analyze other planktonic classes.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Boström, Kjärstin H., 1966-
(författare)
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Nitrogen fixation among marine bacterioplankton
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- While bacterioplankton indisputably control vital biogeochemical paths in the cycling of carbon and nutrients in the world’s oceans, our knowledge about the functional and genetic diversity of bacterioplankton communities is negligible. In this thesis, molecular and more traditional microbiological methods were used to study the specific function of N2-fixation and in a general sense diversity of marine bacterioplankton species.Most oceans are nitrogen limited and, therefore, adaptive to bacterioplankton capable of N2-fixation. Recent studies have found nifH genes (coding for the nitrogenase enzyme) related to diverse heterotrophic bacteria in oceanic seawater samples indicating that, along with cyanobacteria, also heterotrophic bacteria benefit from N2-fixation. Here, molecular and cultivation methods were used to examine diazotrophic bacterioplankton in the Baltic Sea. We successfully isolated heterotrophic N2-fixing bacteria belonging to the γ-proteobacterial class by means of low-nitrogen plates and semi-solid diazotrophic medium tubes. The isolates required low-O2 conditions for N2-fixation. Using Real-time PCR it was found that heterotrophic bacterioplankton carrying the nifH gene was abundant (3 x 104 nifH gene copies L seawater-1) at locations in the Southwest Baltic proper.With the aim to identify the main N2-fixing organisms in Baltic Proper surface waters, a clone library of nifH gene transcripts (RNA) was generated. Clone inserts were exclusively related to Aphanizomenon sp. and Nodularia sp. Using quantitative real-time PCR it was found that the nifH gene expression from Nodularia sp. was highly variable between stations in the Baltic Proper but was 10-fold higher during mid summer relative to early summer and fall. A diel study showed a 4-fold increase in Nodularia transcript concentrations at early to mid day relative to rest of the day. Real-time PCR was found to be a powerful and highly sensitive method for measuring gene expression.Since nucleic acids are a prerequisite for molecular analyses of bacterioplankton dynamics a protocol to extract DNA from seawater samples was developed with the aim to maximize the yield of high-quality DNA. Each step in the protocol was important for the efficiency of extraction. The obtained extraction efficiencies were up to 92% for seawater samples and up to 96% for isolates. The protocol provides a guideline for DNA extraction from seawater samples for other studies.In a global sampling campaign (9 locations from polar, tropical and temperate regions) we sampled DNA from surface water and constructed 16S rRNA gene libraries to investigate diversity and biogeography of bacterioplankton. Approx. 80% of the sequences found were similar to sequences already deposited in GenBank, indicating that a large fraction of the marine bacterioplankton already has been sampled, which in turn suggests a limited global bacterioplankton diversity.This thesis have improved our knowledge about the composition and nifH gene expression of the diazotrophic bacterioplankton community in the Baltic Sea and contribute significantly to the discussion on global marine bacterioplankton diversity and biogeography.
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| 16. |
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| 17. |
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| 18. |
- Dahlbäck, B., et al.
(författare)
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Mikrobiologiska aspekter på musselodling
- 1983
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Ingår i: Odling av blåmusslor. - Lund : Signum. - 918533054X ; , s. 60-67
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 19. |
- Dupont, Chris L., et al.
(författare)
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Functional Tradeoffs Underpin Salinity-Driven Divergence in Microbial Community Composition
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:2, s. e89549-
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial community composition and functional potential change subtly across gradients in the surface ocean. In contrast, while there are significant phylogenetic divergences between communities from freshwater and marine habitats, the underlying mechanisms to this phylogenetic structuring yet remain unknown. We hypothesized that the functional potential of natural bacterial communities is linked to this striking divide between microbiomes. To test this hypothesis, metagenomic sequencing of microbial communities along a 1,800 km transect in the Baltic Sea area, encompassing a continuous natural salinity gradient from limnic to fully marine conditions, was explored. Multivariate statistical analyses showed that salinity is the main determinant of dramatic changes in microbial community composition, but also of large scale changes in core metabolic functions of bacteria. Strikingly, genetically and metabolically different pathways for key metabolic processes, such as respiration, biosynthesis of quinones and isoprenoids, glycolysis and osmolyte transport, were differentially abundant at high and low salinities. These shifts in functional capacities were observed at multiple taxonomic levels and within dominant bacterial phyla, while bacteria, such as SAR11, were able to adapt to the entire salinity gradient. We propose that the large differences in central metabolism required at high and low salinities dictate the striking divide between freshwater and marine microbiomes, and that the ability to inhabit different salinity regimes evolved early during bacterial phylogenetic differentiation. These findings significantly advance our understanding of microbial distributions and stress the need to incorporate salinity in future climate change models that predict increased levels of precipitation and a reduction in salinity.
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| 20. |
- Fahlgren, Camilla, et al.
(författare)
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Annual Variations in the Diversity, Viability, and Origin of Airborne Bacteria
- 2010
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 76:9, s. 3015-3025
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Tidskriftsartikel (refereegranskat)abstract
- The presence of bacteria in aerosols has been known for centuries, but information on their identity and role in dispersing microbial traits is still limited. This study monitored the airborne bacterial community during an annual survey using samples collected from a 25-m tower near the Baltic Sea coast. The number of CFU was estimated using agar plates while the most probable number (MPN) of viable bacteria was estimated using dilution-to-extinction culturing assays (DCAs). The MPN and CFU values produced quantitatively similar results, displaying a pronounced seasonal pattern, with the highest numbers in winter. The most dominant bacteria growing in the DCAs all formed colonies on agar plates, were mostly pigmented (80%), and closely resembled (>97%) previously cultured bacteria based on their 16S rRNA gene sequences. 16S rRNA gene clone libraries were constructed on eight occasions during the survey; these revealed a highly diverse community with a few abundant operational taxonomic units (OTUs) and a long tail of rare OTUs. A majority of the cloned sequences (60%) were also most closely related to previously ""cultured"" bacteria. Thus, both culture-dependent and culture-independent techniques indicated that bacteria able to form colonies on agar plates predominate in the atmosphere. Both the DCAs and clone libraries indicated the dominance of bacteria belonging to the genera Sphingomonas sp. and Pseudomonas sp. on several sampling occasions. Potentially pathogenic strains as well as sequences closely resembling bacteria known to act as ice nuclei were found using both approaches. The origin of the sampled air mass was estimated using backward trajectories, indicating a predominant marine source.
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| 21. |
- Farnelid, Hanna, et al.
(författare)
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Nitrogenase Gene Amplicons from Global Marine Surface Waters Are Dominated by Genes of Non-Cyanobacteria
- 2011
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:4, s. e19223-
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Tidskriftsartikel (refereegranskat)abstract
- Cyanobacteria are thought to be the main N-2-fixing organisms (diazotrophs) in marine pelagic waters, but recent molecular analyses indicate that non-cyanobacterial diazotrophs are also present and active. Existing data are, however, restricted geographically and by limited sequencing depths. Our analysis of 79,090 nitrogenase (nifH) PCR amplicons encoding 7,468 unique proteins from surface samples (ten DNA samples and two RNA samples) collected at ten marine locations worldwide provides the first in-depth survey of a functional bacterial gene and yield insights into the composition and diversity of the nifH gene pool in marine waters. Great divergence in nifH composition was observed between sites. Cyanobacteria-like genes were most frequent among amplicons from the warmest waters, but overall the data set was dominated by nifH sequences most closely related to non-cyanobacteria. Clusters related to Alpha-, Beta-, Gamma-, and Delta-Proteobacteria were most common and showed distinct geographic distributions. Sequences related to anaerobic bacteria (nifH Cluster III) were generally rare, but preponderant in cold waters, especially in the Arctic. Although the two transcript samples were dominated by unicellular cyanobacteria, 42% of the identified non-cyanobacterial nifH clusters from the corresponding DNA samples were also detected in cDNA. The study indicates that non-cyanobacteria account for a substantial part of the nifH gene pool in marine surface waters and that these genes are at least occasionally expressed. The contribution of non-cyanobacterial diazotrophs to the global N-2 fixation budget cannot be inferred from sequence data alone, but the prevalence of non-cyanobacterial nifH genes and transcripts suggest that these bacteria are ecologically significant.
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| 22. |
- Frisk, U., et al.
(författare)
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The Odin satellite - I. Radiometer design and test
- 2003
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 402:3, s. L27-L34
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Tidskriftsartikel (refereegranskat)abstract
- The Sub-millimetre and Millimetre Radiometer (SMR) is the main instrument on the Swedish, Canadian, Finnish and French spacecraft Odin. It consists of a 1.1 metre diameter telescope with four tuneable heterodyne receivers covering the ranges 486-504 GHz and 541-581 GHz, and one fixed at 118.75 GHz together with backends that provide spectral resolution from 150 kHz to 1 MHz. This Letter describes the Odin radiometer, its operation and performance with the data processing and calibration described in Paper II.
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| 23. |
- Fuhrman, J.A., et al.
(författare)
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Diel variations in bacterioplankton, phytoplankton, and related parameters in the Southern California Bight.
- 1985
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Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599. ; 27, s. 9-20
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Tidskriftsartikel (refereegranskat)abstract
- The principal objectives of this study were (i) to determine the extent of coupling betweenphytoplankton and microheterotrophs on the shelf off Southern California. (ii) to compare differentmeasures of primary and bacterial secondary production, and (iii) to assess whether sampling timesshould be as strictly controlled for microheterotroph as for autotroph studies. Two diel cycles (May andOctober) were studied by sampling an isotherm as the ship followed paired submerged drogues. Wefound significant die1 changes of chlorophyll, 14C bicarbonate incorporation, bacterial abundance andthymidine incorporation, frequency of dividing bacterial cells (FDC), abundance of non-pigmentedflagellates, particulate organic carbon and nitrogen and their ratios, and dissolved oxygen. Theseparameters all had higher values dunng daylight hours than at night, showing close coupling betweenthe phytoplankton (light-forced) and the microheterotrophs. The ratio of in vivo to extractedchlorophyll a fluorescence, however, displayed a maximum at midnight and minimum at midday,suggesting an endogenous rhythm. Primary production measured by the 14C method was similar to netproduction inferred from in situ oxygen changes. Short-lived peaks in FDC values suggested partlysynchronized bacterial division.
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| 24. |
- Fuhrman, J.A., et al.
(författare)
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Extraction from natural planktonic microorganisms of DNA suitable for molecular biological studies
- 1988
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 54:6, s. 1426-1429
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Tidskriftsartikel (refereegranskat)abstract
- We developed a simple technique for the high-yield extraction of purified DNA from mixed populations ofnatural planktonic marine microbes (primarily bacteria). This is a necessary step for several molecularbiological approaches to the study of microbial communities in nature. The microorganisms from near-shoremarine and brackish water samples, ranging in volume from 8 to 40 liters, were collected on 0.22-,um-pore-sizefluorocarbon-based filters, after prefiltration through glass fiber filters, to remove most of the eucaryotes. DNAwas extracted directly from the filters in 1% sodium dodecyl sulfate that was heated to 95 to 100°C for 1.5 to2 min. This procedure lysed essentially all the bacteria and did not significantly denature the DNA. The DNAwas purified by phenol extraction, and precautions were taken to minimize shearing. Agarose gel electrophoresisshowed that most of the final preparation had a large molecular size (>23 kilobase pairs). The DNA wassufficiently pure to allow complete digestion by the restriction endonuclease Sau3AI and ligation to vector DNA.In a sample in which the extracted DNA was quantified by binding to the dye Hoechst H33258, DNA wasquantitatively extracted, and 45% of the initially extracted DNA was recovered after purification. Final yieldswere a few micrograms of DNA per liter of seawater and were roughly 25 to 50% of the total bacterial DNAin the sample. Alternatives to the initial harvest by filtration method, including continuous-flow centrifugationand thin-channel or hollow-fiber concentration followed by centrifugation, were less efficient than filtration interms of both time and yield, largely because of the difficulty of centrifuging the very small bacteria typical ofmarine plankton. These methods were judged to be less appropriate for studies of natural populations as theyimpose a strong selection for the larger bacteria.
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| 25. |
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