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Association between Legionella species and humic substances during early summer in the northern Baltic Sea
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)
Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Umeå, Sweden.
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, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (EcoChange)ORCID iD: 0000-0001-7819-9038
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2023 (English)In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 9, article id 1070341Article in journal (Refereed) Published
Abstract [en]

Climate change is projected to cause alterations in northern coastal systems, including humification and intensified nutrient loads, which can lead to ecosystem imbalances and establishment of new bacterial species. Several potential pathogens, such as different species of Legionella, hide in the environment between infections, some by living inside protozoan host cells. Knowledge about the occurrence of Legionella in natural waters is missing, which disable risk assessments of exposure. We performed a study of the species diversity of Legionella in the northern Baltic Sea (Gulf of Bothnia) during early summer to map their occurrence and to identify possible environmental drivers. We detected Legionella and potential protozoan hosts along gradients of the Gulf of Bothnia. We also for the first time present third generation full-length 16S rRNA amplicon sequencing (Nanopore) to resolve environmental species classification of Legionella, with a method suitable to study all bacteria. Our data show that full length 16S rRNA sequences is sufficient to resolve Legionella while the standard short Illumina sequences did not capture the entire diversity. For accurate species classification of Legionella, harmonization between the Nanopore classification methods is still needed and the bias toward the well-studied Legionella pneumophila need to be resolved. Different Legionella species occurred both in the Bothnian Sea and in the Bothnian Bay and their abundance were linked to humic substances and low salinity. The relative abundance of Legionella was higher in the humic-rich northern waters of the Bothnian Bay. The link between Legionella species and humic substances may be indirect via promotion of the heterotrophic microbial food web, allowing Legionella species and similar bacteria to establish. Humic substances are rich in iron, which has been shown crucial for growth of Legionella species and other pathogens. Considering climate change projections in this regional area, with increased humification and freshwater inflow, this bacterial niche containing potential pathogens might become more widespread in the future Baltic Sea. This study demonstrates the significance of DNA sequencing to monitor public health relevant bacteria like Legionella species in the environment. Including sequencing of bacteria and protozoa in the environmental monitoring programs could be used to identify ecosystem imbalances, which enable appropriate responses to emerging diseases.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2023. Vol. 9, article id 1070341
Keywords [en]
Legionella, protozoa, predation resistance, aquatic microbiology, climate change, ecology change, marginal seas, humification
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-203899DOI: 10.3389/fmars.2022.1070341ISI: 000924634400001Scopus ID: 2-s2.0-85147432283OAI: oai:DiVA.org:umu-203899DiVA, id: diva2:1729879
Funder
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGESwedish Research Council FormasSwedish Armed ForcesAvailable from: 2023-01-23 Created: 2023-01-23 Last updated: 2023-11-13Bibliographically approved
In thesis
1. Bacteria that escape predation: waterborne pathogens and their relatives
Open this publication in new window or tab >>Bacteria that escape predation: waterborne pathogens and their relatives
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Bakterier som undkommer predation : vattenlevande patogener och deras släktingar
Abstract [en]

The hidden presence of opportunistic bacterial pathogens in the environment evokes concerns about emerging diseases, especially in the light of climate change. The co-evolution of bacteria and their predators (protozoa) has led to bacterial defence strategies of which some contribute to the ability of bacteria to cause disease. To increase our understanding of the interplay between bacteria, protozoa, land use, and climate scenarios in Nordic brackish and freshwater, four studies were designed. The first study explored the co-occurrence patterns between predation resistant bacteria (PRB) and bacterivorous protozoa in a coastal area in the northern Baltic Sea. The results showed higher PRB diversity in the bays and freshwater inlets, than in the offshore waters. Further, genotype specific interactions between protozoa and bacteria were identified. The second study focused on Legionella species diversity and their association with humic substances and low salinity, potentially facilitated through the promotion of the heterotrophic microbial food web or by iron availability. The third study examined the impact of intensified land use on bacterial taxa abundance and community composition in lake inflows, demonstrating indirect downstream effects on water quality. Factors such as pastures, fields, farms, aluminium, iron, and humic substances were linked to increased Legionella abundance. The fourth study exposed aquatic organisms to climate change scenarios, causing eutrophication or brownification with elevated iron levels. Pseudomonas aeruginosa were found to be especially persistent to iron, likely linked to the same mechanism that enables survival in protozoan cells. This trait was shared with other observed intracellular pathogens and uncultured species, who showed elevated resilience to brownification and ability to survive outside host cells. These findings identified complex relationships, which improve our understanding of the intricate dynamics that shape aquatic ecosystems, and highlight the importance of considering multiple factors in managing water resources and maintaining ecosystem health. Human activities including intensified land use can have far-reaching consequences, jeopardizing the pristine nature of water bodies and escalate the presence of environmental and opportunistic bacterial pathogens.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2023. p. 62
Keywords
bacterial pathogens, protozoa, predation resistance, aquatic microbiology, climate change, opportunists, humification, iron
National Category
Oceanography, Hydrology and Water Resources
Research subject
environmental science; Microbiology
Identifiers
urn:nbn:se:umu:diva-216610 (URN)9789180702058 (ISBN)9789180702041 (ISBN)
Public defence
2023-12-08, SAM.A.280, Samhällsvetarhuset, Umeå, 09:00 (English)
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Supervisors
Available from: 2023-11-17 Created: 2023-11-13 Last updated: 2023-12-20Bibliographically approved

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Eriksson, Karolina Ida AnnaRamasamy, Kesava PriyanAndersson, AgnetaSjödin, Andreas

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Eriksson, Karolina Ida AnnaRamasamy, Kesava PriyanAndersson, AgnetaSjödin, Andreas
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