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Publications (4 of 4) Show all publications
Holmfeldt, K., Titelman, J. & Riemann, L. (2010). Virus Production and Lysate Recycling in Different Sub-basins of the Northern Baltic Sea. Microbial Ecology, 60(3), 572-580
Open this publication in new window or tab >>Virus Production and Lysate Recycling in Different Sub-basins of the Northern Baltic Sea
2010 (English)In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 60, no 3, p. 572-580Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
SPRINGER, 2010
Identifiers
urn:nbn:se:umu:diva-140775 (URN)10.1007/s00248-010-9668-8 (DOI)000282971400010 ()20407893 (PubMedID)
Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2018-06-09
Holmfeldt, K., Dziallas, C., Titelman, J., Pohlmann, K., Grossart, H.-P. & Riemann, L. (2009). Diversity and abundance of freshwater Actinobacteria along environmental gradients in the brackish northern Baltic Sea. Environmental Microbiology, 11(8), 2042-2054
Open this publication in new window or tab >>Diversity and abundance of freshwater Actinobacteria along environmental gradients in the brackish northern Baltic Sea
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2009 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 11, no 8, p. 2042-2054Article in journal (Refereed) Published
Abstract [en]

P>Actinobacteria are highly abundant in pelagic freshwater habitats and also occur in estuarine environments such as the Baltic Sea. Because of gradients in salinity and other environmental variables estuaries offer natural systems for examining factors that determine Actinobacteria distribution. We studied abundance and community structure of Bacteria and Actinobacteria along two transects in the northern Baltic Sea. Quantitative (CARD-FISH) and qualitative (DGGE and clone libraries) analyses of community composition were compared with environmental parameters. Actinobacteria accounted for 22-27% of all bacteria and the abundance changed with temperature. Analysis of 549 actinobacterial 16S rRNA sequences from four clone libraries revealed a dominance of the freshwater clusters acI and acIV, and two new subclusters (acI-B scB-5 and acIV-E) were assigned. Whereas acI was present at all stations, occurrence of acII and acIV differed between stations and was related to dissolved organic carbon (DOC) and chlorophyll a (Chl a) respectively. The prevalence of the acI-A and acI-B subclusters changed in relation to total phosphorus (Tot-P) and Chl a respectively. Community structure of Bacteria and Actinobacteria differed between the river station and all other stations, responding to differences in DOC, Chl a and bacterial production. In contrast, the composition of active Actinobacteria (analysis based on reversely transcribed RNA) changed in relation to salinity and Tot-P. Our study suggests an important ecological role of Actinobacteria in the brackish northern Baltic Sea. It highlights the need to address dynamics at the cluster or subcluster phylogenetic levels to gain insights into the factors regulating distribution and composition of Actinobacteria in aquatic environments.

Place, publisher, year, edition, pages
WILEY-BLACKWELL PUBLISHING, INC, 2009
Identifiers
urn:nbn:se:umu:diva-140778 (URN)10.1111/j.1462-2920.2009.01925.x (DOI)000268655000011 ()19453610 (PubMedID)
Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2018-06-09
Riemann, L., Holmfeldt, K. & Titelman, J. (2009). Importance of Viral Lysis and Dissolved DNA for Bacterioplankton Activity in a P-Limited Estuary, Northern Baltic Sea. Microbial Ecology, 57(2), 286-294
Open this publication in new window or tab >>Importance of Viral Lysis and Dissolved DNA for Bacterioplankton Activity in a P-Limited Estuary, Northern Baltic Sea
2009 (English)In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 57, no 2, p. 286-294Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
SPRINGER, 2009
Identifiers
urn:nbn:se:umu:diva-140779 (URN)10.1007/s00248-008-9429-0 (DOI)000262829500008 ()18670729 (PubMedID)
Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2018-06-09
Titelman, J., Riemann, L., Holmfeldt, K. & Nilsen, T. (2008). Copepod feeding stimulates bacterioplankton activities in a low phosphorus system. Aquatic Biology, 2(2), 131-141
Open this publication in new window or tab >>Copepod feeding stimulates bacterioplankton activities in a low phosphorus system
2008 (English)In: Aquatic Biology, ISSN 1864-7782, E-ISSN 1864-7790, Vol. 2, no 2, p. 131-141Article in journal (Refereed) Published
Abstract [en]

Zooplankton sloppy feeding releases high-quality dissolved organic matter, which is readily used by microbes. We hypothesized that in phosphorus (P) limited environments, released dissolved DNA may be a particularly important source of P for bacteria. In an incubation experiment with water from the Bothnian Bay, Sweden, we investigated the short-term effect of copepod feeding activity on bacterial production, DNA uptake and phosphatase activity. Consistent patterns in bacterial activity measures suggested that copepod feeding activity stimulated phosphatase activity, DNA uptake and production. The P taken up as dissolved DNA exceeded cellular P requirements. We speculate that bacterioplankton cells in the Bothnian Bay store excess P intracellularly during times of extensive sloppy feeding, which may then subsequently be utilized to prevent P limitation of growth.

Place, publisher, year, edition, pages
INTER-RESEARCH, 2008
Keywords
bacteria, copepod, DNA uptake, phosphorus, alkaline phosphatase, dissolved DNA, Bothnian Bay
Identifiers
urn:nbn:se:umu:diva-140781 (URN)10.3354/ab00042 (DOI)000259452500004 ()
Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2018-06-09
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9207-2543

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