lnu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Different gene expression responses in two Baltic Sea heterotrophic model bacteria to dinoflagellate dissolved organic matter
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. (Ctr Ecol & Evolut Microbial Model Syst EEMiS)
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. (Ctr Ecol & Evolut Microbial Model Syst EEMiS)ORCID iD: 0000-0002-8779-6464
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. (Ctr Ecol & Evolut Microbial Model Syst EEMiS)
University of Helsinki, Finland.
Show others and affiliations
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Phytoplankton release massive amounts of dissolved organic matter (DOM) into the water column during recurring blooms in coastal waters and inland seas. The released DOM includes dissolved organic carbon, nitrogen and phosphorus, in a complex mixture of both known and unknown compounds, and is a rich nutrient source for heterotrophic bacteria. The metabolic activity of heterotrophic bacteria during and after phytoplankton blooms can hence be expected to reflect the characteristics of the released DOM. With this in mind, we wanted to investigate if bacterioplankton could be used as “living sensors” of phytoplankton DOM quantity and quality, and to trace the flow of nutrients in the ecosystem. We used transcriptional activity from Baltic Sea bacterial isolates (Polaribacter sp. BAL334 (Flavobacteriia) and Brevundimonas sp. BAL450 (Alphaproteobacteria)) exposed to DOM derived from the dinoflagellate Prorocentrum minimum in exponential and stationary growth phases respectively. We observed strong responses both in terms of physiology – bacterial abundance – and the expressed metabolic pathways – e.g. Membrane Transport, Fatty Acids, Lipids and Isoprenoids – of the populations in samples exposed to dinoflagellate DOM compared with controls. Particularly striking was the increased expression of Ton and Tol transport systems, commonly associated with uptake of complex molecules, in both isolates. Equally important were the differences in metabolic responses between the two isolates, caused by differences in gene repertoire between them, emphasizing the importance of separating the responses of different taxa in analyses of community sequence data. Differences in response to DOM sourced from exponentially and stationary growing dinoflagellates were less pronounced, although not absent, than differences between the bacterial isolates. This suggests that shifts in metabolism during the different phases of a phytoplankton bloom might be detectable in individual bacterial populations. To conclude, our work opened a door to the future use of bacterioplankton as living sensors of environmental status, particularly with respect to phytoplankton blooms.

Keywords [en]
Alphaproteobacteria, Brevundimonas sp., Flavobacteria, mRNA, phytoplankton exudation, Polaribacter sp., Prorocentrum minimum
National Category
Microbiology
Research subject
Ecology, Microbiology
Identifiers
URN: urn:nbn:se:lnu:diva-90255OAI: oai:DiVA.org:lnu-90255DiVA, id: diva2:1372671
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2019-11-29Bibliographically approved
In thesis
1. Exploring gene expression responses of marine bacteria to environmental factors
Open this publication in new window or tab >>Exploring gene expression responses of marine bacteria to environmental factors
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacterioplankton are abundant in marine ecosystems, where they as “masters of transformation” of dissolved organic matter (DOM) are important for energy fluxes and biogeochemical cycles. However, the performance of bacteria in a changing marine environment influenced by anthropogenic activities is poorly understood. In this thesis, I did experiments with model bacteria and natural assemblages of bacteria, using microbiology methods combined with modern molecular tools, to investigate responses of marine bacteria to changes in environmental conditions like ocean acidification, organic pollution and organic matter released by phytoplankton. Experiments with a model gammaproteobacterium demonstrated that bacteria in stationary phase showed little responses to organic pollutants, whereas pollutants caused decreased bacterial growth and had a broad physiological impact on actively growing bacteria (as deduced from gene expression analysis). In an experiment with two distantly related marine model bacteria, we identified several important bacterial mechanisms, such as uptake of macromolecules and phosphonates, by which bacteria respond when exposed to DOM produced by photosynthetic dinoflagellates. Using natural bacterial communities in a Baltic Sea mesocosm experiment with the addition of river water from a forested or an agriculture influenced catchment area, we showed important interactions between river water type and the development of phytoplankton blooms that caused different bacterial gene expression activities. In the fourth set of experiments, marine bacterial communities were subjected to elevated CO2, to mimic ocean acidification, under high and low nutrient conditions in a mesocosm study. We found increased bacterial gene expression activity focused on maintaining pH homeostasis, but only under low nutrient conditions, indicating that bacteria focus on cell maintenance instead of growth when challenged by lowered pH. Finally, in a computational analysis, we compared genomes from yet uncultivated prokaryotes by two different strategies: metagenome assembled and single amplified genomes. Importantly, the analysis showed that both methods selected abundant taxa and generated nearly identical sequences in overlapping regions. To conclude, this thesis presents discoveries that will help form a better understanding of marine bacterial responses to present and future anthropogenic disturbances of marine ecosystems.

Abstract [sv]

Marina bakterier är abundanta och återfinns i alla marina ekosystem, där de som nedbrytare av organiskt material spelar en avgörande roll i att reglera flödet av energi och näringsämnenas kretslopp. Dock saknar vi kunskap om hur bakterieplankton reagerar på miljöförändringar i haven. Därtill är de molekylära mekanismerna för omsättningen av löst organiskt material från olika källor ofullständigt kända. I denna avhandling har jag med hjälp av bakterieisolat och naturliga bakteriesamhällen undersökt hur marina bakterier svarar på miljöförändringar genom att kombinera metoder inom klassisk mikrobiologi och moderna molekylärbiologiska verktyg. Det övergripande syftet med denna avhandling var att få en bättre förståelse för hur bakterier svarar på havsförsurning, organiska föroreningar och löst organisk kol utsöndrat av växtplankton. Under ett experiment med ett bakterieisolat inom klassen Gammaproteobacteria, uppvisade bakterierna svagare respons för organiska föroreningar då de befann sig i stationär fas än i en aktiv tillväxtfas. Detta märktes både genom minskad tillväxt och fysiologiska ändringar uppmätta genom genuttryck i bakterien. Vidare experiment med två skilda modellbakterier kunde vi identifiera viktiga processer såsom upptag av makromolekyler och fosfonater, som svar på tillsats av löst organiskt material producerat av dinoflagellater. I ett annat experiment använde vi naturliga bakteriesamhällen i vatten från Östersjön i ett storskaligt experiment, där vatten från floder i avrinningsområden dominerade antingen av skog eller jordbruk tillsattes. I detta experiment kunde vi visa hur vattnets ursprung påverkade utvecklingen av algblomningarna som i sin tur orsakade olika aktivitet i bakteriernas genuttryck. Vidare så undersöktes hur marina bakteriesamhällen påverkas av förhöjda CO2-halter under låg och hög näringstillgång. Det visade sig att bakterierna ökade sin aktivitet för att bibehålla pH-homeostasen, men bara under låg koncentration av näringsämnen. Detta innebar att bakterierna behövde ställa om sin ämnesomsättning från tillväxt till att lägga energi på att hantera syran i oligotrofa miljöer. Slutligen genomfördes dataanalyser där två metoder för att studera arvsmassan i bakterier tagna direkt från haven jämfördes. Vår studie visade att de två metoderna i viss mån kompletterade varandra men framför allt kunde vi bekräfta att ingen av de två uppvisade några systematiska fel. Sammanfattningsvis presenterar denna avhandling upptäcker som ger oss en bättre förståelse för hur marina bakterier i marina ekosystem svarar på nutida och framtida miljöförändringar orsakade av människor.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2019
Series
Linnaeus University Dissertations ; 371/2019
Keywords
Baltic Sea, dissolved organic matter, model bacteria, ocean acidification, organic pollutants, river loadings, transcriptomics
National Category
Ecology
Research subject
Ecology, Microbiology
Identifiers
urn:nbn:se:lnu:diva-90261 (URN)978-91-89081-19-2 (ISBN)978-91-89081-20-8 (ISBN)
Public defence
2019-12-18, Fregatten Ma117 campus Kalmar, Kalmar, 09:30 (English)
Opponent
Supervisors
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2019-12-03Bibliographically approved

Open Access in DiVA

No full text in DiVA

Authority records BETA

Karlsson, Christofer M. G.Lundin, DanielKarlsson, CamillaPinhassi, Jarone

Search in DiVA

By author/editor
Karlsson, Christofer M. G.Lundin, DanielKarlsson, CamillaPinhassi, Jarone
By organisation
Department of Biology and Environmental Science
Microbiology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 93 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf