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Baltar, Federico
Publications (10 of 30) Show all publications
Bunse, C., Israelsson, S., Baltar, F., Bertos-Fortis, M., Fridolfsson, E., Legrand, C., . . . Pinhassi, J. (2019). High Frequency Multi-Year Variability in Baltic Sea Microbial Plankton Stocks and Activities. Frontiers in Microbiology, 9, Article ID 3296.
Open this publication in new window or tab >>High Frequency Multi-Year Variability in Baltic Sea Microbial Plankton Stocks and Activities
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2019 (English)In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 9, article id 3296Article in journal (Refereed) Published
Abstract [en]

Marine bacterioplankton are essential in global nutrient cycling and organic matter turnover. Time-series analyses, often at monthly sampling frequencies, have established the paramount role of abiotic and biotic variables in structuring bacterioplankton communities and productivities. However, fine-scale seasonal microbial activities, and underlying biological principles, are not fully understood. We report results from four consecutive years of high-frequency time-series sampling in the Baltic Proper. Pronounced temporal dynamics in most investigated microbial variables were observed, including bacterial heterotrophic production, plankton biomass, extracellular enzyme activities, substrate uptake rate constants of glucose, pyruvate, acetate, amino acids, and leucine, as well as nutrient limitation bioassays. Spring blooms consisting of diatoms and dinoflagellates were followed by elevated bacterial heterotrophic production and abundances. During summer, bacterial productivity estimates increased even further, coinciding with an initial cyanobacterial bloom in early July. However, bacterial abundances only increased following a second cyanobacterial bloom, peaking in August. Uptake rate constants for the different measured carbon compounds varied seasonally and inter-annually and were highly correlated to bacterial productivity estimates, temperature, and cyanobacterial abundances. Further, we detected nutrient limitation in response to environmental conditions in a multitude of microbial variables, such as elevated productivities in nutrient bioassays, changes in enzymatic activities, or substrate preferences. Variations among biotic variables often occurred on time scales of days to a few weeks, yet often spanning several sampling occasions. Such dynamics might not have been captured by sampling at monthly intervals, as compared to more predictable transitions in abiotic variables such as temperature or nutrient concentrations. Our study indicates that high resolution analyses of microbial biomass and productivity parameters can help out in the development of biogeochemical and food web models disentangling the microbial black box.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
marine bacteria, phytoplankton, cyanobacteria, production, substrate uptake, enzyme activity, biogeochemistry
National Category
Microbiology Ecology
Research subject
Ecology, Microbiology; Ecology, Microbiology
Identifiers
urn:nbn:se:lnu:diva-80150 (URN)10.3389/fmicb.2018.03296 (DOI)000455948100001 ()2-s2.0-85064405301 (Scopus ID)
Available from: 2019-02-05 Created: 2019-02-05 Last updated: 2019-08-29Bibliographically approved
Muthusamy, S. D., Lundin, D., Branca, R. M., Baltar, F., Gonzalez, J. M., Lehtio, J. & Pinhassi, J. (2017). Comparative proteomics reveals signature metabolisms of exponentially growing and stationary phase marine bacteria. Environmental Microbiology, 19(6), 2301-2319
Open this publication in new window or tab >>Comparative proteomics reveals signature metabolisms of exponentially growing and stationary phase marine bacteria
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2017 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 19, no 6, p. 2301-2319Article, review/survey (Refereed) Published
Abstract [en]

Much of the phenotype of a microorganism consists of its repertoire of metabolisms and how and when its proteins are deployed under different growth conditions. Hence, analyses of protein expression could provide important understanding of how bacteria adapt to different environmental settings. To characterize the flexibility of proteomes of marine bacteria, we investigated protein profiles of three important marine bacterial lineages - Oceanospirillaceae (Neptuniibacter caesariensis strain MED92), Roseobacter (Phaeobacter sp. MED193) and Flavobacteria (Dokdonia sp. MED134) - during transition from exponential to stationary phase. As much as 59-80% of each species' total proteome was expressed. Moreover, all three bacteria profoundly altered their expressed proteomes during growth phase transition, from a dominance of proteins involved in translation to more diverse proteomes, with a striking appearance of enzymes involved in different nutrient-scavenging metabolisms. Whereas the three bacteria shared several overarching metabolic strategies, they differed in important details, including distinct expression patterns of membrane transporters and proteins in carbon and phosphorous metabolism and storage compounds. These differences can be seen as signature metabolisms - metabolisms specific for lineages. These findings suggest that quantitative proteomics can inform about the divergent ecological strategies of marine bacteria in adapting to changes in environmental conditions.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2017
National Category
Microbiology
Research subject
Ecology, Microbiology
Identifiers
urn:nbn:se:lnu:diva-66909 (URN)10.1111/1462-2920.13725 (DOI)000404007700018 ()2-s2.0-85017121020 (Scopus ID)
Available from: 2017-07-13 Created: 2017-07-13 Last updated: 2019-08-29Bibliographically approved
Baltar, F., Legrand, C. & Pinhassi, J. (2016). Cell-free extracellular enzymatic activity is linked to seasonal temperature changes: a case study in the Baltic Sea. Biogeosciences, 13(9), 2815-2821
Open this publication in new window or tab >>Cell-free extracellular enzymatic activity is linked to seasonal temperature changes: a case study in the Baltic Sea
2016 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 9, p. 2815-2821Article in journal (Refereed) Published
Abstract [en]

Extracellular enzymatic activities (EEA) are a crucial step on the degradation of organic matter. Dissolved (cell-free) extracellular enzymes in seawater can make up a significant contribution of the bulk EEA. However, the factors controlling the proportion of dissolved EEA in the marine environment remain unknown. Here we studied the seasonal changes in the proportion of dissolved relative to total EEA (of alkaline phosphatase [APase], β-glucosidase, [BGase], and leucine aminopeptidase, [LAPase]), in the Baltic Sea for 18 months. The proportio n of dissolved EEA ranged between 37-100%, 0-100%, 34-100% for APase, BGase and LAPase, respectively. A consistent seasonal pattern in the proportion of dissolved EEA was found among all the studied enzymes, with values up to 100% during winter and <40% du ring summer. A significant negative relation was found between the 21proportion of dissolved EEA and temperature, indicating that temperature might be a critical factor controlling the proportion of dissolved relative to total EEA in marine environments. Our results suggest a strong decoupling of hydrolysis rates from mi crobial dynamics in cold waters. This implies that under cold conditions, cell-free enzymes can contribute to substrate availability at large distances from the producing cell, increasing the dissociation between the hydrolysis of organic compounds and the actual microbes producing the enzymes. This also indicates that global warming could come to affect the hydrolysis of organic matter by reducing the hydrolytic activity of cell-free enzymes.

Place, publisher, year, edition, pages
Copernicus Publications, 2016
National Category
Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-49774 (URN)10.5194/bg-13-2815-2016 (DOI)000377277300014 ()2-s2.0-84969760880 (Scopus ID)
Projects
EcoChange
Available from: 2016-02-15 Created: 2016-02-15 Last updated: 2018-11-15Bibliographically approved
Baltar, F., Palovaara, J., Unrein, F., Catala, P., Hornak, K., Simek, K., . . . Pinhassi, J. (2016). Marine bacterial community structure resilience to changes in protist predation under phytoplankton bloom conditions. The ISME Journal, 10(3), 568-581
Open this publication in new window or tab >>Marine bacterial community structure resilience to changes in protist predation under phytoplankton bloom conditions
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2016 (English)In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, no 3, p. 568-581Article in journal (Refereed) Published
Abstract [en]

To test whether protist grazing selectively affects the composition of aquatic bacterial communities, we combined high-throughput sequencing to determine bacterial community composition with analyses of grazing rates, protist and bacterial abundances and bacterial cell sizes and physiological states in a mesocosm experiment in which nutrients were added to stimulate a phytoplankton bloom. A large variability was observed in the abundances of bacteria (from 0.7 to 2.4 x 10(6) cells per ml), heterotrophic nanoflagellates (from 0.063 to 2.7 x 10(4) cells per ml) and ciliates (from 100 to 3000 cells per l) during the experiment (similar to 3-, 45- and 30-fold, respectively), as well as in bulk grazing rates (from 1 to 13 x 10(6) bacteria per ml per day) and bacterial production (from 3 to 379 mu g per Cl per day) (1 and 2 orders of magnitude, respectively). However, these strong changes in predation pressure did not induce comparable responses in bacterial community composition, indicating that bacterial community structure was resilient to changes in protist predation pressure. Overall, our results indicate that peaks in protist predation (at least those associated with phytoplankton blooms) do not necessarily trigger substantial changes in the composition of coastal marine bacterioplankton communities.

National Category
Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-51064 (URN)10.1038/ismej.2015.135 (DOI)000370472500004 ()26262814 (PubMedID)2-s2.0-84939141929 (Scopus ID)
Available from: 2016-03-18 Created: 2016-03-18 Last updated: 2018-11-15Bibliographically approved
Baltar, F., Lundin, D., Palovaara, J., Lekunberri, I., Reinthaler, T., Herndl, G. J. & Pinhassi, J. (2016). Prokaryotic Responses to Ammonium and Organic Carbon Reveal Alternative CO2 Fixation Pathways and Importance of Alkaline Phosphatase in the Mesopelagic North Atlantic. Frontiers in Microbiology, 7, Article ID 1670.
Open this publication in new window or tab >>Prokaryotic Responses to Ammonium and Organic Carbon Reveal Alternative CO2 Fixation Pathways and Importance of Alkaline Phosphatase in the Mesopelagic North Atlantic
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2016 (English)In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 7, article id 1670Article in journal (Refereed) Published
Abstract [en]

To decipher the response of mesopelagic prokaryotic communities to input of nutrients, we tracked changes in prokaryotic abundance, extracellular enzymatic activities, heterotrophic production, dark dissolved inorganic carbon (DIC) fixation, community composition (16S rRNA sequencing) and community gene expression (metatranscriptomics) in 3 microcosm experiments with water from the mesopelagic North Atlantic. Responses in 3 different treatments amended with thiosulfate, ammonium or organic matter (i.e., pyruvate plus acetate) were compared to unamended controls. The strongest stimulation was found in the organic matter enrichments, where all measured rates increased >10-fold. Strikingly, in the organic matter treatment, the dark DIC fixation rates-assumed to be related to autotrophic metabolisms-were equally stimulated as all the other heterotrophic-related parameters. This increase in DIC fixation rates was paralleled by an up-regulation of genes involved in DIC assimilation via anaplerotic pathways. Alkaline phosphatase was the metabolic rate most strongly stimulated and its activity seemed to be related to cross-activation by nonpartner histidine kinases, and/or the activation of genes involved in the regulation of elemental balance during catabolic processes. These findings suggest that episodic events such as strong sedimentation of organic matter into the mesopelagic might trigger rapid increases of originally rare members of the prokaryotic community, enhancing heterotrophic and autotrophic carbon uptake rates, ultimately affecting carbon cycling. Our experiments highlight a number of fairly unstudied microbial processes of potential importance in mesopelagic waters that require future attention.

Keywords
prokaryotic community structure, functional diversity, CO2 fixation, alkaline phosphatase, mesopelagic
National Category
Microbiology Ecology
Research subject
Ecology, Microbiology
Identifiers
urn:nbn:se:lnu:diva-59471 (URN)10.3389/fmicb.2016.01670 (DOI)000388562800001 ()27818655 (PubMedID)2-s2.0-84996605697 (Scopus ID)
Available from: 2016-12-23 Created: 2016-12-23 Last updated: 2018-10-24Bibliographically approved
Lindh, M. V., Sjöstedt, J., Andersson, A. F., Baltar, F., Hugerth, L., Lundin, D., . . . Pinhassi, J. (2015). Disentangling seasonal bacterioplankton population dynamics by high-frequency sampling. Environmental Microbiology, 17(7), 2459-2476
Open this publication in new window or tab >>Disentangling seasonal bacterioplankton population dynamics by high-frequency sampling
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2015 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 17, no 7, p. 2459-2476Article in journal (Refereed) Published
Abstract [en]

Multiyear comparisons of bacterioplankton succession reveal that environmental conditions drive community shifts with repeatable patterns between years. However, corresponding insight into bacterioplankton dynamics at a temporal resolution relevant for detailed examination of variation and characteristics of specific populations within years is essentially lacking. During 1 year, we collected 46 samples in the Baltic Sea for assessing bacterial community composition by 16S rRNA gene pyrosequencing (nearly twice weekly during productive season). Beta-diversity analysis showed distinct clustering of samples, attributable to seemingly synchronous temporal transitions among populations (populations defined by 97% 16S rRNA gene sequence identity). A wide spectrum of bacterioplankton dynamics was evident, where divergent temporal patterns resulted both from pronounced differences in relative abundance and presence/absence of populations. Rates of change in relative abundance calculated for individual populations ranged from 0.23 to 1.79 day(-1). Populations that were persistently dominant, transiently abundant or generally rare were found in several major bacterial groups, implying evolution has favoured a similar variety of life strategies within these groups. These findings suggest that high temporal resolution sampling allows constraining the timescales and frequencies at which distinct populations transition between being abundant or rare, thus potentially providing clues about physical, chemical or biological forcing on bacterioplankton community structure.

Place, publisher, year, edition, pages
Society for Applied Microbiology and John Wiley & Sons Ltd, 2015
National Category
Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-45558 (URN)10.1111/1462-2920.12720 (DOI)000358114300023 ()2-s2.0-84937073236 (Scopus ID)
Projects
EcoChange
Funder
Swedish Research Council FormasSwedish Research CouncilEcosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGE
Available from: 2015-07-25 Created: 2015-07-25 Last updated: 2019-02-27Bibliographically approved
Baltar, F., Palovaara, J., Vila-Costa, M., Salazar, G., Calvo, E., Pelejero, C., . . . Pinhassi, J. (2015). Response of rare, common and abundant bacterioplankton to anthropogenic perturbations in a Mediterranean coastal site. FEMS Microbiology Ecology, 91(6), Article ID UNSP fiv058.
Open this publication in new window or tab >>Response of rare, common and abundant bacterioplankton to anthropogenic perturbations in a Mediterranean coastal site
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2015 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 91, no 6, article id UNSP fiv058Article in journal (Refereed) Published
Abstract [en]

Bacterioplankton communities are made up of a small set of abundant taxa and a large number of low-abundant organisms (i.e. 'rare biosphere'). Despite the critical role played by bacteria in marine ecosystems, it remains unknown how this large diversity of organisms are affected by human-induced perturbations, or what controls the responsiveness of rare compared to abundant bacteria. We studied the response of a Mediterranean bacterioplankton community to two anthropogenic perturbations (i.e. nutrient enrichment and/or acidification) in two mesocosm experiments (in winter and summer). Nutrient enrichment increased the relative abundance of some operational taxonomic units (OTUs), e.g. Polaribacter, Tenacibaculum, Rhodobacteraceae and caused a relative decrease in others (e.g. Croceibacter). Interestingly, a synergistic effect of acidification and nutrient enrichment was observed on specific OTUs (e.g. SAR86). We analyzed the OTUs that became abundant at the end of the experiments and whether they belonged to the rare (<0.1% of relative abundance), the common (0.1-1.0% of relative abundance) or the abundant (>1% relative abundance) fractions. Most of the abundant OTUs at the end of the experiments were abundant, or at least common, in the original community of both experiments, suggesting that ecosystem alterations do not necessarily call for rare members to grow.

National Category
Microbiology Ecology
Research subject
Natural Science, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-43485 (URN)10.1093/femsec/fiv058 (DOI)000359690000012 ()2-s2.0-84944171729 (Scopus ID)
Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2017-12-04Bibliographically approved
Lindh, M. V., Figueroa, D., Sjöstedt, J., Baltar, F., Lundin, D., Andersson, A., . . . Pinhassi, J. (2015). Transplant experiments uncover Baltic Sea basin-specific responses in bacterioplankton community composition and metabolic activities. Frontiers in Microbiology, 6, Article ID 223.
Open this publication in new window or tab >>Transplant experiments uncover Baltic Sea basin-specific responses in bacterioplankton community composition and metabolic activities
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2015 (English)In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 6, article id 223Article in journal (Refereed) Published
Abstract [en]

Anthropogenically induced changes in precipitation are projected to generate increased river runoff to semi-enclosed seas, increasing loads of terrestrial dissolved organic matter and decreasing salinity. To determine how bacterial community structure and functioning adjust to such changes, we designed microcosm transplant experiments with Baltic Proper (salinity 7.2) and Bothnian Sea (salinity 3.6) water. Baltic Proper bacteria generally reached higher abundances than Bothnian Sea bacteria in both Baltic Proper and Bothnian Sea water, indicating higher adaptability. Moreover, Baltic Proper bacteria growing in Bothnian Sea water consistently showed highest bacterial production and beta-glucosidase activity. These metabolic responses were accompanied by basin-specific changes in bacterial community structure. For example, Baltic Proper Pseudomonas and Limnobacter populations increased markedly in relative abundance in Bothnian Sea water, indicating a replacement effect. In contrast, Roseobacter and Rheinheimera populations were stable or increased in abundance when challenged by either of the waters, indicating an adjustment effect. Transplants to Bothnian Sea water triggered the initial emergence of particular Burkholderiaceae populations, and transplants to Baltic Proper water triggered Alteromonadaceae populations. Notably, in the subsequent re-transplant experiment, a priming effect resulted in further increases to dominance of these populations. Correlated changes in community composition and metabolic activity were observed only in the transplant experiment and only at relatively high phylogenetic resolution. This suggested an importance of successional progression for interpreting relationships between bacterial community composition and functioning. We infer that priming effects on bacterial community structure by natural episodic events or climate change induced forcing could translate into long-term changes in bacterial ecosystem process rates.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2015
National Category
Microbiology Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-44349 (URN)10.3389/fmicb.2015.00223 (DOI)000352541600001 ()25883589 (PubMedID)2-s2.0-84930943030 (Scopus ID)
Projects
EcoChange
Available from: 2015-06-15 Created: 2015-06-15 Last updated: 2019-02-27Bibliographically approved
Muthusamy, S. D., Baltar, F., González, J. M. & Pinhassi, J. (2014). Dynamics of metabolic activities and gene expression in the Roseobacter clade bacterium Phaeobacter sp. MED193 during growth with thiosulfate. Applied and Environmental Microbiology, 80(22), 6933-6942
Open this publication in new window or tab >>Dynamics of metabolic activities and gene expression in the Roseobacter clade bacterium Phaeobacter sp. MED193 during growth with thiosulfate
2014 (English)In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 80, no 22, p. 6933-6942Article in journal (Refereed) Published
Abstract [en]

Metagenomic analyses of surface seawater reveal that genes for sulfur oxidation are widespread in bacterioplankton communities. However, little is known about the metabolic processes used to exploit the energy potentially gained from inorganic sulfur oxidation in oxic seawater. We therefore studied the sox gene system containing Roseobacter clade isolate Phaeobacter sp. strain MED193 in acetate minimal medium with and without thiosulfate. The addition of thiosulfate enhanced the bacterial growth yields up to 40% in this strain. Concomitantly, soxB and soxY gene expression increased about 8-fold with thiosulfate and remained 11-fold higher than that in controls through stationary phase. At stationary phase, thiosulfate stimulated protein synthesis and anaplerotic CO2 fixation rates up to 5- and 35-fold, respectively. Several genes involved in anaplerotic CO2 fixation (i.e., pyruvate carboxylase, propionyl coenzyme A [CoA], and crotonyl-CoA carboxylase) were highly expressed during active growth, coinciding with high CO2 fixation rates. The high expression of key genes in the ethylmalonyl-CoA pathway suggests that this is an important pathway for the utilization of two-carbon compounds in Phaeobacter sp. MED193. Overall, our findings imply that Roseobacter clade bacteria carrying sox genes can use their lithotrophic potential to gain additional energy from sulfur oxidation for both increasing their growth capacity and improving their long-term survival.

National Category
Microbiology
Research subject
Ecology, Microbiology
Identifiers
urn:nbn:se:lnu:diva-37307 (URN)10.1128/AEM.02038-14 (DOI)000344161700010 ()2-s2.0-84908269085 (Scopus ID)
Available from: 2014-09-27 Created: 2014-09-27 Last updated: 2018-05-17Bibliographically approved
Palovaara, J., Akram, N., Baltar, F., Bunse, C., Forsberg, J., Pedrós-Alió, C., . . . Pinhassi, J. (2014). Stimulation of growth by proteorhodopsin phototrophy involves regulation of central metabolic pathways in marine planktonic bacteria. Proceedings of the National Academy of Sciences of the United States of America, 111(35), E3650-E3658
Open this publication in new window or tab >>Stimulation of growth by proteorhodopsin phototrophy involves regulation of central metabolic pathways in marine planktonic bacteria
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2014 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, no 35, p. E3650-E3658Article in journal (Refereed) Published
Abstract [en]

Proteorhodopsin (PR) is present in half of surface ocean bacterioplankton, where its light-driven proton pumping provides energy to cells. Indeed, PR promotes growth or survival in different bacteria. However, the metabolic pathways mediating the light responses remain unknown. We analyzed growth of the PR-containing Dokdonia sp. MED134 (where light-stimulated growth had been found) in seawater with low concentrations of mixed [yeast extract and peptone (YEP)] or single (alanine, Ala) carbon compounds as models for rich and poor environments. We discovered changes in gene expression revealing a tightly regulated shift in central metabolic pathways between light and dark conditions. Bacteria showed relatively stronger light responses in Ala compared with YEP. Notably, carbon acquisition pathways shifted toward anaplerotic CO2 fixation in the light, contributing 31 +/- 8% and 24 +/- 6% of the carbon incorporated into biomass in Ala and YEP, respectively. Thus, MED134 was a facultative double mixotroph, i.e., photo- and chemotrophic for its energy source and using both bicarbonate and organic matter as carbon sources. Unexpectedly, relative expression of the glyoxylate shunt genes (isocitrate lyase and malate synthase) was >300-fold higher in the light-but only in Ala-contributing a more efficient use of carbon from organic compounds. We explored these findings in metagenomes and metatranscriptomes and observed similar prevalence of the glyoxylate shunt compared with PR genes and highest expression of the isocitrate lyase gene coinciding with highest solar irradiance. Thus, regulatory interactions between dissolved organic carbon quality and central metabolic pathways critically determine the fitness of surface ocean bacteria engaging in PR phototrophy.

National Category
Ecology
Research subject
Natural Science, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-37306 (URN)10.1073/pnas.1402617111 (DOI)000341230800012 ()2-s2.0-84907227908 (Scopus ID)
Available from: 2014-09-27 Created: 2014-09-27 Last updated: 2017-12-11Bibliographically approved
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