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Nutrient additions resulting in phage release and formation of non-nucleoid-containing bacteria
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
2006 (English)In: Aquatic Microbial Ecology, ISSN 0948-3055, Vol. 43, no 2, 107-112 p.Article in journal (Refereed) Published
Abstract [en]

The responses of aquatic bacteriophages to (1) P additions in P-limited batch cultures and (2) separate P and N additions in batch cultures that were both P- and N-limited were monitored. Possible connections between the abundance of non-nucleoid-containing cells (non-Nu CC) and viral abundance were also examined. The water used in the experiments was collected from the mesotrophic Lake Erken (Sweden) in late autumn. In both experiments, nutrient addition resulted in increases in viral abundance and non-nucleoid-containing bacterial cells. However, in the P- and N-limited cultures, P addition resulted in increases in viral abundance and non-nucleoid-containing bacterial cells, but no increase in bacterial abundance. In contrast, in the cultures to which N was added, increases in viral abundance were accompanied by increases in the abundance of both bacteria and non-nucleoid-containing cells. The results show that there is a connection between changes in the abundance of viruses and non-nucleoid-containing cells. However, there are indications that viral abundance can change in response to changes in the P status of the environment without any increase in bacterial abundance.

Place, publisher, year, edition, pages
2006. Vol. 43, no 2, 107-112 p.
Keyword [en]
Europe, Virus, Ecology, Microbiology, Environment, Sweden, Batchwise, Aquatic environment, Release, Bacteria, Phage
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97909OAI: oai:DiVA.org:uu-97909DiVA: diva2:173023
Available from: 2008-12-22 Created: 2008-12-22 Last updated: 2009-09-25Bibliographically approved
In thesis
1. Significance and Diversity of Lake Bacteriophages
Open this publication in new window or tab >>Significance and Diversity of Lake Bacteriophages
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Viruses has a relatively recently been discovered in high abundances in aquatic systems. Their possible importance has therefore been largely overlooked. In aquatic food webs there should be large differences in carbon and nutrient fluxes depending on whether the main cause of bacterial mortality is viral infection or grazing, where lysis following viral infection should result in a release of organic carbon and nutrients from the lysed bacteria and hence not reach higher trophic levels. Recent research on aquatic viruses has mainly focused on marine environments and the number of studies on freshwater viral ecology is limited. Hence, there is a need for more studies on the importance and functioning of viruses in freshwater systems.

The aims of this thesis were to explore the functioning and diversity of viruses that infects bacteria (phages) in freshwater systems. To effectively address this I conducted two experiments and three field studies in 23 lakes in different parts of Sweden. The results show that viral infection and subsequent lysis of the host cell can partly explain the formation of non-nucleoid-containing bacteria and further that viruses can respond to increases in phosphorus concentrations without any net increase in bacterial abundance. Generally, a larger part of bacterial production in lakes were grazed by flagellates than lysed by viruses, but a larger fraction of the total bacterial mortality can be attributed to viruses in hypolimnion compared to in epilimnion. Further, the largest impact of phages on bacterial production may be in humic lakes, which have a relatively high frequency of visibly infected bacterial cells, but low flagellate abundance. Community composition of bacteria and viruses were only weakly coupled in the studied systems. The most important factors for predicting viral community composition were temperature and concentrations of dissolved organic carbon, total phosphorus and soluble reactive phosphorus. The viral community composition changed over the season and temperate phages could be detected by incubations with mitomycin C showing that a large fraction of the viruses detected appeared to be temperate phages. The most important environmental factor co-varying with viral community composition was again concentrations of total phosphorus.

To summarize, bacteriophages, as a bacterial mortality factor, are important in freshwater microbial food webs and phosphorus supply has a potential central function in the regulation of the importance of bacteriophages and additionally for viral diversity.

Place, publisher, year, edition, pages
Uppsala: Universitetsbiblioteket, 2008. 52 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 585
Keyword
viral ecology, lake, bacteriophage, diversity, phosphorus
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-9499 (URN)978-91-554-7371-6 (ISBN)
Public defence
2009-01-09, Lindahlsalen, EBC, Uppsala, 13:15
Opponent
Supervisors
Available from: 2008-12-22 Created: 2008-12-22 Last updated: 2016-04-28Bibliographically approved

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