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Response of Coastal Shewanella and Duganella Bacteria to Planktonic and Terrestrial Food Substrates
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). (EcoChange; UMFpub)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). (EcoChange; UMFpub)ORCID iD: 0000-0002-1298-3839
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). (EcoChange)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). (EcoChange; UMFpub)ORCID iD: 0000-0001-7819-9038
2022 (English)In: Frontiers in Microbiology, E-ISSN 1664-302X, Vol. 12, article id 726844Article in journal (Refereed) Published
Abstract [en]

Global warming scenarios indicate that in subarctic regions, the precipitation will increase in the future. Coastal bacteria will thus receive increasing organic carbon sources from land runoff. How such changes will affect the function and taxonomic composition of coastal bacteria is poorly known. We performed a 10-day experiment with two isolated bacteria: Shewanella baltica from a seaside location and Duganella sp. from a river mouth, and provided them with a plankton and a river extract as food substrate. The bacterial growth and carbon consumption were monitored over the experimental period. Shewanella and Duganella consumed 40% and 30% of the plankton extract, respectively, while the consumption of the river extract was low for both bacteria, ∌1%. Shewanella showed the highest bacterial growth efficiency (BGE) (12%) when grown on plankton extract, while when grown on river extract, the BGE was only 1%. Duganella showed low BGE when grown on plankton extract (< 1%) and slightly higher BGE when grown on river extract (2%). The cell growth yield of Duganella was higher than that of Shewanella when grown on river extract. These results indicate that Duganella is more adapted to terrestrial organic substrates with low nutritional availability, while Shewanella is adapted to eutrophied conditions. The different growth performance of the bacteria could be traced to genomic variations. A closely related genome of Shewanella was shown to harbor genes for the sequestration of autochthonously produced carbon substrates, while Duganella contained genes for the degradation of relatively refractive terrestrial organic matter. The results may reflect the influence of environmental drivers on bacterial community composition in natural aquatic environments. Elevated inflows of terrestrial organic matter to coastal areas in subarctic regions would lead to increased occurrence of bacteria adapted to the degradation of complex terrestrial compounds with a low bioavailability.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2022. Vol. 12, article id 726844
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-192537DOI: 10.3389/fmicb.2021.726844ISI: 000767972200001Scopus ID: 2-s2.0-85125652797OAI: oai:DiVA.org:umu-192537DiVA, id: diva2:1638198
Funder
Swedish Research Council FormasAvailable from: 2022-02-16 Created: 2022-02-16 Last updated: 2024-01-17Bibliographically approved
In thesis
1. Microbial communities: descriptors of environmental change in marine ecosystems
Open this publication in new window or tab >>Microbial communities: descriptors of environmental change in marine ecosystems
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Mikrobiella samhällen : indikatorer på miljöförändringar i marina ekosystem
Abstract [en]

In northern marginal seas, like the northern Baltic Sea, climate change will lead to many alterations, for example increased inflows of nutrients and dissolved organic matter (DOM). Nutrients and DOM are fundamental drivers shaping marine microbial communities, including both bacterial and phytoplankton populations. Potentially microbial communities and their functions can be used as descriptors of environmental change in marine systems. 

Changed nutrient availability will affect the phytoplankton communities, which is widely used as descriptor of environmental state in aquatic systems. Traditionally phytoplankton is analyzed using microscopy in monitoring, while molecular methods holds a great potential for future development. I performed a comparative study between metabarcoding and microscopy. Metabarcoding and microscopy displayed relatively similar distribution pattern at the group level. The results showed that the relative abundances of the 18S rRNA amplicon at the group level best fitted the microscopy carbon biomass metric. The results are promising for implementing DNA metabarcoding as a complement to microscopy in phytoplankton monitoring, especially if databases would be improved and group level indexes could be applied to classify environmental state of water bodies.

Bacterioplankton are the main DOM processors in the marine food web. A shift in the quality and quantity of the DOM pool could affect the microbial community structure and alter their functioning. Presently it is poorly known how coastal bacteria respond compositionally and functionally to quality and quantity changes in DOM supply. To comprehensively address this question, there is a critical need for microcosm experimental studies as well as field studies. Thus, I used approaches from single species laboratory experiment to community levels in situ incubation experiments and community levels spatiotemporal field surveys to evaluate the impacts of climate shifts on microbial community. Intricate relationships between environmental factors and microbial communities, for example, links between key microbial functional genes and DOM conditions were identified. Results showed that bacteria isolated from coastal area harbor genes for the sequestration of autochthonously produced carbon substrates, while bacteria isolated from a river contained genes for the degradation of relatively refractive terrestrial organic matter. A field experiment showed that Gammaproteobacteria was promoted by plankton extract addition and the genes for chitin and cellulose catabolism are enriched by addition of autochthonous carbon sources. The field survey with comprehensive metagenomic investigation of microbial community composition indicated that the temporal variation is larger compare to spatial changes. Bacteroidia, Actinomycetia, Gammaproteobacteria, Acidimicrobiia, and Alphaproteobacteria were the dominant bacterial classes, with Bacteroidia being more abundant in inshore stations compared to offshore locations. The seasonal shift in the relative abundance of these bacterial classes suggests that environmental factors and ecological processes drive changes in the abundance of different bacterial classes over time. Overall, these studies strengthen our understanding of the relationships between microbial composition and biogeochemical processes in coastal areas.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2023. p. 23
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:umu:diva-207755 (URN)978-91-8070-087-0 (ISBN)978-91-8070-088-7 (ISBN)
Public defence
2023-05-26, KB.E3.01, KBC-huset, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2023-05-05 Created: 2023-05-02 Last updated: 2023-08-14Bibliographically approved

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Zhao, LiBrugel, SoniaRamasamy, Kesava PriyanAndersson, Agneta

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