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  • 1. Andersson, A.
    et al.
    Falk, S.
    Samuelsson, G.
    Hagström, Åke
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Nutritional characteristics of a mixitropic nanoflagellate, Ochromonas sp.1989In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 17, p. 117-128Article in journal (Refereed)
  • 2. Azam, F.
    et al.
    Smith, D.C.
    Steward, G.F.
    Hagström, Åke
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Bacteria-organic-matter coupling and its significance for oceanic carboncycling.1993In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 28, p. 167-179Article in journal (Refereed)
  • 3.
    Baltar, Federico
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Universidad de Las Palmas de Gran Canaria, Spain.
    Arístegui, Javier
    Universidad de Las Palmas de Gran Canaria, Spain.
    Gasol, Josep M.
    Yokokawa, Taichi
    Royal Netherlands Institute for Sea Research, Netherlands.
    Herndl, Gerhard J.
    University of Vienna, Austria.
    Bacterial Versus Archaeal Origin of Extracellular Enzymatic Activity in the Northeast Atlantic Deep Waters2013In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 65, no 2, p. 277-288Article in journal (Refereed)
    Abstract [en]

    We determined the total and dissolved extracellularenzymatic activity (EEA) of α-glucosidase and β-glucosidase(AGase and BGase), alkaline phosphatase (APase) and leucineaminopeptidase (LAPase) activities in the epi-, meso- andbathypelagic waters of the subtropical Northeast Atlantic.EEA was also determined in treatments in which bacterialEEAwas inhibited by erythromycin. Additionally, EEA decayexperiments were performed with surface and deep waters todetermine EEA lifetimes in both water masses. The proportionof dissolved to total EEA (66–89 %, 44–88 %, 57–82 % and86–100 % for AGase, BGase, APase and LAPase, respectively)was generally higher than the cell-associated (i.e.,particulate) EEA. The percentage of dissolved to total EEAwas inversely proportional to the percentage of erythromycininhibitedto total EEA. Since erythromycin-inhibited plusdissolved EEA equaled total EEA, this tentatively suggeststhat cell-associated EEA in the open oceanic water column isalmost exclusively of bacterial origin. The decay constants ofdissolved EEAwere in the range of 0.002–0.048 h−1 dependingon the type of extracellular enzyme, temperature and depthin the water column. Although dissolved EEA can have differentorigins, the major contribution of Bacteria to cellassociatedEEA and the long life-time of dissolved EEAsuggest that Bacteria—and not mesophilic Archaea—areessentially the main producers of EEA in the open subtropicalNortheast Atlantic down to bathypelagic layers.

  • 4.
    Broman, Elias
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Li, Lingni
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Fridlund, Jimmy
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Svensson, Fredrik
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Legrand, Catherine
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Dopson, Mark
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Spring and Late Summer Phytoplankton Biomass Impact on the Coastal Sediment Microbial Community Structure2019In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, no 2, p. 288-303Article in journal (Refereed)
    Abstract [en]

    Two annual Baltic Sea phytoplankton blooms occur in spring and summer. The bloom intensity is determined by nutrient concentrations in the water, while the period depends on weather conditions. During the course of the bloom, dead cells sink to the sediment where their degradation consumes oxygen to create hypoxic zones (< 2 mg/L dissolved oxygen). These zones prevent the establishment of benthic communities and may result in fish mortality. The aim of the study was to determine how the spring and autumn sediment chemistry and microbial community composition changed due to degradation of diatom or cyanobacterial biomass, respectively. Results from incubation of sediment cores showed some typical anaerobic microbial processes after biomass addition such as a decrease in NO2 + NO3 in the sediment surface (0–1 cm) and iron in the underlying layer (1–2 cm). In addition, an increase in NO2 + NO3 was observed in the overlying benthic water in all amended and control incubations. The combination of NO2 + NO3 diffusion plus nitrification could not account for this increase. Based on 16S rRNA gene sequences, the addition of cyanobacterial biomass during autumn caused a large increase in ferrous iron-oxidizing archaea while diatom biomass amendment during spring caused minor changes in the microbial community. Considering that OTUs sharing lineages with acidophilic microorganisms had a high relative abundance during autumn, it was suggested that specific niches developed in sediment microenvironments. These findings highlight the importance of nitrogen cycling and early microbial community changes in the sediment due to sinking phytoplankton before potential hypoxia occurs.

  • 5.
    Dar, Shabir A
    et al.
    Umeå University.
    Bijmans, Martijn F M
    Univ Wageningen & Res Ctr, Wageningen, Netherlands.
    Dinkla, Inez J T
    Bioclear BV, NL-9704 CG Groningen, Netherlands.
    Geurkink, Bert
    Bioclear BV, NL-9704 CG Groningen, Netherlands.
    Lens, Piet N L
    Univ Wageningen & Res Ctr, Wageningen, Netherlands.
    Dopson, Mark
    Umeå University.
    Population dynamics of a single-stage sulfidogenic bioreactor treating synthetic zinc-containing waste streams.2009In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 58, no 3, p. 529-537Article in journal (Refereed)
    Abstract [en]

    Waste streams from industrial processes such as metal smelting or mining contain high concentrations of sulfate and metals with low pH. Dissimilatory sulfate reduction carried out by sulfate-reducing bacteria (SRB) at low pH can combine sulfate reduction with metal-sulfide precipitation and thus open possibilities for selective metal recovery. This study investigates the microbial diversity and population changes of a single-stage sulfidogenic gas-lift bioreactor treating synthetic zinc-rich waste water at pH 5.5 by denaturing gradient gel electrophoresis of 16S rRNA gene fragments and quantitative polymerase chain reaction. The results indicate the presence of a diverse range of phylogenetic groups with the predominant microbial populations belonging to the Desulfovibrionaceae from delta-Proteobacteria. Desulfovibrio desulfuricans-like populations were the most abundant among the SRB during the three stable phases of varying sulfide and zinc concentrations and increased from 13% to 54% of the total bacterial populations over time. The second largest group was Desulfovibrio marrakechensis-like SRB that increased from 1% to about 10% with decreasing sulfide concentrations. Desulfovibrio aminophilus-like populations were the only SRB to decrease in numbers with decreasing sulfide concentrations. However, their population was <1% of the total bacterial population in the reactor at all analyzed time points. The number of dissimilatory sulfate reductase (DsrA) gene copies per number of SRB cells decreased from 3.5 to 2 DsrA copies when the sulfide concentration was reduced, suggesting that the cells' sulfate-reducing capacity was also lowered. This study has identified the species present in a single-stage sulfidogenic bioreactor treating zinc-rich wastewater at low pH and provides insights into the microbial ecology of this biotechnological process.

  • 6.
    Dopson, Mark
    et al.
    Umeå University.
    Lindström, E B
    Umeå University.
    Analysis of community composition during moderately thermophilic bioleaching of pyrite, arsenical pyrite, and chalcopyrite.2004In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 48, no 1, p. 19-28Article in journal (Refereed)
    Abstract [en]

    An analysis of the community composition of three previously undefined mixed cultures of moderately thermophilic bioleaching bacteria grown at 45 degrees C on pyrite, arsenical pyrite, and chalcopyrite has been carried out. The bacterial species present were identified by comparative sequence analysis of the 16S rRNA gene isolated from the bioleaching vessels and analyzed by denaturing gradient gel electrophoresis, cloning, and sequencing. The mixed cultures leached all three minerals, as shown by the increase in iron released from the mineral concentrates. The species identified from the mixed cultures during bioleaching of pyrite, arsenical pyrite, and chalcopyrite were clones closely related to Acidithiobacillus caldus C-SH12, Sulfobacillus thermosulfidooxidans AT-1, " Sulfobacillus montserratensis" L15, and an uncultured thermal soil bacterium YNP. It was also found that the same mixed culture maintained for over a year on chalcopyrite mineral selected approximately the same consortia of bacteria as the original mixed culture grown on chalcopyrite.

  • 7.
    Figueroa, Daniela
    et al.
    Umeå University ; Umeå Marine Sciences Centre.
    Rowe, O. F.
    Umeå University ; University of Helsinki, Finland.
    Paczkowska, Joanna
    Umeå University.
    Legrand, Catherine
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Andersson, Agneta
    Umeå University ; Umeå Marine Sciences Centre.
    Allochthonous Carbon-a Major Driver of Bacterioplankton Production in the Subarctic Northern Baltic Sea2016In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 71, no 4, p. 789-801Article in journal (Refereed)
    Abstract [en]

    Heterotrophic bacteria are, in many aquatic systems, reliant on autochthonous organic carbon as their energy source. One exception is low-productive humic lakes, where allochthonous dissolved organic matter (ADOM) is the major driver. We hypothesized that bacterial production (BP) is similarly regulated in subarctic estuaries that receive large amounts of riverine material. BP and potential explanatory factors were measured during May-August 2011 in the subarctic Råne Estuary, northern Sweden. The highest BP was observed in spring, concomitant with the spring river-flush and the lowest rates occurred during summer when primary production (PP) peaked. PLS correlations showed that ∼60 % of the BP variation was explained by different ADOM components, measured as humic substances, dissolved organic carbon (DOC) and coloured dissolved organic matter (CDOM). On average, BP was threefold higher than PP. The bioavailability of allochthonous dissolved organic carbon (ADOC) exhibited large spatial and temporal variation; however, the average value was low, ∼2 %. Bioassay analysis showed that BP in the near-shore area was potentially carbon limited early in the season, while BP at seaward stations was more commonly limited by nitrogen-phosphorus. Nevertheless, the bioassay indicated that ADOC could contribute significantly to the in situ BP, ∼60 %. We conclude that ADOM is a regulator of BP in the studied estuary. Thus, projected climate-induced increases in river discharge suggest that BP will increase in subarctic coastal areas during the coming century.

  • 8.
    Holmfeldt, Karin
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Titelman, Josefin
    University of Gothenburg ; University of Oslo.
    Riemann, Lasse
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Virus production and lysate recycling in different sub-basins of the northern Baltic Sea.2010In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 60, no 3, p. 572-580Article in journal (Refereed)
    Abstract [en]

    In the Gulf of Bothnia, northern Baltic Sea, a large freshwater inflow creates north-southerly gradients in physico-chemical and biological factors across the two sub-basins, the Bothnian Bay (BB) and the Bothnian Sea. In particular, the sub-basins differ in nutrient limitation (nitrogen vs. phosphorus; P). Since viruses are rich in P, and virus production is commonly connected with bacterial abundance and growth, we hypothesized that the role of viral lysis differs between the sub-basins. Thus, we examined virus production and the potential importance of lysate recycling in surface waters along a transect in the Gulf of Bothnia. Surprisingly, virus production and total P were negatively correlated. In the BB, virus production rates were double those elsewhere in the system, although bacterial abundance and production were the lowest. In the BB, virus-mediated cell lysates could account for 70-180% and 100-250% of the bacterial carbon and P demand, respectively, while only 4-15% and 8-21% at the other stations. Low concentrations of dissolved DNA (D-DNA) with a high proportion of encapsulated DNA (viruses) in the BB suggested rapid turnover and high uptake of free DNA. The correlation of D-DNA and total P indicates that D-DNA is a particularly important nutrient source in the P-limited BB. Our study demonstrates large and counterintuitive differences in virus-mediated recycling of carbon and nutrients in two basins of the Gulf of Bothnia, which differ in microbial community composition and nutrient limitation.

  • 9. Middelboe, M.
    et al.
    Hagström, Åke
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Blackburn, N.
    Sinn, B.
    Borch, N.H.
    Pinhassi, Jarone
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Simu, Karin
    Effects of bacteriophages on the population dynamics of four strains of pelagic marine bacteria.2001In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 42, p. 395-406Article in journal (Refereed)
  • 10.
    Riemann, Lasse
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Grossart, Hans-Peter
    Elevated lytic phage production as a consequence of particle colonization by a marine Flavobacterium (Cellulophaga sp.)2008In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 56, p. 505-512Article in journal (Refereed)
  • 11.
    Riemann, Lasse
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Holmfeldt, Karin
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Titelman, Josefin
    Importance of viral lysis and dissolved DNA for bacterioplankton activity in a P-limited estuary, northern Baltic Sea2009In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 57, no 2, p. 286-294Article in journal (Refereed)
    Abstract [en]

    Through lysis of bacterioplankton cells, viruses mediate an important, but poorly understood, pathway of carbon and nutrients from the particulate to the dissolved form. Via this activity, nutrient-rich cell lysates may become available to noninfected cells and support significant growth. However, the nutritional value of lysates for noninfected bacteria presumably depends on the prevailing nutrient limitation. In the present study, we examined dynamics of dissolved DNA (D-DNA) and viruses along a transect in the phosphorus (P)-limited A-re Estuary, northern Baltic Sea. We found that viruses were an important mortality factor for bacterioplankton and that their activity mediated a significant recycling of carbon and especially of P. Uptake of dissolved DNA accounted for up to 70% of the bacterioplankton P demand, and about a quarter of the D-DNA pool was supplied through viral lysis of bacterial cells. Generally, the importance of viral lysates and uptake of D-DNA was highest at the estuarine and offshore stations and was positively correlated with P limitation measured as alkaline phosphatase activity. Our results highlight the importance of viral activity for the internal recycling of principal nutrients and pinpoints D-DNA as a particularly relevant compound in microbial P dynamics.

  • 12.
    Riemann, Lasse
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Winding, A.
    Community dynamics of Free-living and Particle-associated Bacterial assemblages during a Freshwater Phytoplankton Bloom.2001In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 42, p. 274-285Article in journal (Refereed)
  • 13. Sjoqvist, C.
    et al.
    Kremp, A.
    Lindehoff, Elin
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Umeå Marine Sci Ctr.
    Bamstedt, U.
    Egardt, J.
    Gross, S.
    Jonsson, M.
    Larsson, H.
    Pohnert, G.
    Richter, H.
    Selander, E.
    Godhe, A.
    Effects of Grazer Presence on Genetic Structure of a Phenotypically Diverse Diatom Population2014In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 67, no 1, p. 83-95Article in journal (Refereed)
    Abstract [en]

    Studies of predator-prey systems in both aquatic and terrestrial environments have shown that grazers structure the intraspecific diversity of prey species, given that the prey populations are phenotypically variable. Populations of phytoplankton have traditionally considered comprising only low intraspecific variation, hence selective grazing as a potentially structuring factor of both genetic and phenotypic diversity has not been comprehensively studied. In this study, we compared strain specific growth rates, production of polyunsaturated aldehydes, and chain length of the marine diatom Skeletonema marinoi in both grazer and non-grazer conditions by conducting monoclonal experiments. Additionally, a mesocosm experiment was performed with multiclonal experimental S. marinoi populations exposed to grazers at different levels of copepod concentration to test effects of grazer presence on diatom diversity in close to natural conditions. Our results show that distinct genotypes of a geographically restricted population exhibit variable phenotypic traits relevant to grazing interactions such as chain length and growth rates. Grazer presence affected clonal richness and evenness of multiclonal Skeletonema populations in the mesocosms, likely in conjunction with intrinsic interactions among the diatom strains. Only the production of polyunsaturated aldehydes was not affected by grazer presence. Our findings suggest that grazing can be an important factor structuring diatom population diversity in the sea and emphasize the importance of considering clonal differences when characterizing species and their role in nature.

  • 14. Uronen, P
    et al.
    Kuuppo, P
    Legrand, Catherine
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Tamminen, T
    Allelopathic activity of toxic Prymnesium parvum leads to release of dissolved organic carbon and increase in bacterial biomass2007In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184XArticle in journal (Refereed)
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