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The Niches of Bacterial Populations in Productive Waters: Examples from Coastal Waters and Four Eutrophic Lakes
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recent research in microbial ecology has focused on how aquatic bacterial communities are assembled. Only a few of these studies follow a “Gleasonian” approach where the roles of single bacterial populations are in focus. In this thesis, novel molecular tools were used to describe the distribution and evolutionary relationships of microbes in productive aquatic environments. Many new phylogenetic groups of bacteria were identified, likely representing bacterial populations restricted to productive freshwaters. I also addressed the dynamics and functional role of individual bacterial populations in eutrophic lakes and brackish environments with a focus on either biogeochemically significant or potentially pathogenic representatives. Flavobacteria blooms were observed, on occasions characterized by high heterotrophic production. In addition to high temporal dynamics microbial community composition and function differed on the spatial scale, as exemplified by free-living and Cyanobacteria-associated habitats. At the community scale, microbial processes, such as biomass production and substrate uptake could be predicted from the presence and absence of individual bacterial populations. I also studied the niches of potentially pathogenic Vibrio populations in various coastal waters. Using a novel culture-independent method, a V. cholerae population was detected along the entire Swedish coastline. Results from an environmental survey and a laboratory mesocosm experiment reveal that phytoplankton-derived dissolved organic matter enhance the growth of V. cholerae and other Vibrio spp. and hence create a largely overlooked niche for these heterotrophic bacteria. This thesis and future work on the role of individual bacterial populations will facilitate predictions of biogeochemical cycles and the distribution of bacteria in the context of global climate change and local eutrophication.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2006. , p. 68
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 254
Keywords [en]
Ecology, diversity, 16S rRNA, phytoplankton, bloom, pathogen, carbon cycle
Keywords [sv]
Ekologi
National Category
Ecology
Identifiers
URN: urn:nbn:se:uu:diva-7419ISBN: 91-554-6760-1 (print)OAI: oai:DiVA.org:uu-7419DiVA, id: diva2:169435
Public defence
2007-01-19, Ekmansalen, EBC (Evolutionary Biology Center), Uppsala, 10:00
Opponent
Supervisors
Available from: 2006-12-20 Created: 2006-12-20 Last updated: 2016-04-28Bibliographically approved
List of papers
1. Composition of freshwater bacterial communities associated with cyanobacterial blooms in four Swedish lakes.
Open this publication in new window or tab >>Composition of freshwater bacterial communities associated with cyanobacterial blooms in four Swedish lakes.
2004 In: Environmental Microbiology, Vol. 6, no 12, p. 1228–1243-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-95272 (URN)
Available from: 2006-12-20 Created: 2006-12-20Bibliographically approved
2. Blooms of Flavobacteria in four productive lakes
Open this publication in new window or tab >>Blooms of Flavobacteria in four productive lakes
Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-95273 (URN)
Available from: 2006-12-20 Created: 2006-12-20Bibliographically approved
3. Links between bacterial production, amino acid utilization and community composition in productive lakes
Open this publication in new window or tab >>Links between bacterial production, amino acid utilization and community composition in productive lakes
2007 (English)In: ISME Journal, ISSN 1751-7362, Vol. 1, no 6, p. 532-544Article in journal (Refereed) Published
Abstract [en]

Influence of distribution and abundance of bacterial taxa on ecosystem function are poorly understood for natural microbial communities. We related 16S rRNA-based terminal restriction fragment length polymorphism to bacterial production and arginine uptake kinetics to test if functional features of bacterioplankton in four lakes could be predicted from community composition. Maximum arginine uptake rate (arginine Vmax) ranged from 10% to 100% of bacterial production. Owing to high growth efficiencies on arginine (63–77%), the bacterial community could potentially saturate its carbon demand using this single organic substrate, for example, during sudden surges of free amino acids. However, due to low in situ concentrations of arginine in these lakes (<0.9 g l-1), actual uptake rates at ambient concentrations rarely exceeded 10% of Vmax. Bacterial production and arginine Vmax could be predicted from a subset of bacterial ribotypes, tentatively affiliated with several bacterial divisions (Cyanobacteria, Actinobacteria, Bacteroidetes and Proteobacteria). Multivariate statistical analysis indicates that there were both highly important and less important ribotypes for the prediction of bacterial production and arginine Vmax. These populations were either negatively or positively related to the respective functional feature, indicating contrasting ecological roles. Our study provides a statistically robust demonstration that, apart from environmental conditions, patterns in bacterial community composition can also be used to predict lake ecosystem function.

Keywords
amino-acid utilization, bacteria, community composition, lakes, production
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-95274 (URN)10.1038/ismej.2007.64 (DOI)000250232700007 ()18043654 (PubMedID)
Available from: 2006-12-20 Created: 2006-12-20 Last updated: 2011-01-20Bibliographically approved
4. Diurnal variations in the auto- and heterotrophic activity of cyanobacterial phycospheres (Gloeotrichia echinulata) and the identity of attached bacteria
Open this publication in new window or tab >>Diurnal variations in the auto- and heterotrophic activity of cyanobacterial phycospheres (Gloeotrichia echinulata) and the identity of attached bacteria
2005 In: Freshwater Biology, Vol. 51, p. 298-311Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-95275 (URN)
Available from: 2006-12-20 Created: 2006-12-20Bibliographically approved
5. Environmental influences on Vibrio populations in northern temperate and boreal coastal waters (Baltic and Skagerrak Seas)
Open this publication in new window or tab >>Environmental influences on Vibrio populations in northern temperate and boreal coastal waters (Baltic and Skagerrak Seas)
2006 (English)In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 72, no 9, p. 6004-6011Article in journal (Refereed) Published
Abstract [en]

Even if many Vibrio spp. are endemic to coastal waters, their distribution in northern temperate and boreal waters is poorly studied. To identify environmental factors regulating Vibrio populations in a salinity gradient along the Swedish coastline, we combined Vibrio-specific quantitative competitive PCR with denaturant gradient gel electrophoresis-based genotyping. The total Vibrio abundance ranged from 4 X 10(3) to 9.6 X 10(4) cells liter(-1), with the highest abundances in the more saline waters of the Skagerrak Sea. Several Vibrio populations were present throughout the salinity gradient, with abundances of single populations ranging from 5 X 10(4) to 7 X 10(4) cells liter(-1). Clear differences were observed along the salinity gradient, where three populations dominated the more saline waters of the Skagerrak Sea and two populations containing mainly representatives of V anguillarum and V. aestuarianus genotypes were abundant in the brackish waters of the Baltic Sea. Our results suggest that this apparent niche separation within the genus Vibrio may also be influenced by alternate factors such as nutrient levels and high abundances of dinoflagellates. A V. choleraelV. mimicus population was detected in more than 50% of the samples, with abundances exceeding 10(3) cells liter(-1), even in the cold (annual average water temperature of around 5 degrees C) and low-salinity (2 to 4 parts per thousand) samples from the Bothnian Bay (latitude, 65 degrees N). The unsuspected and widespread occurrence of this population in temperate and boreal coastal waters suggests that potential Vibrio pathogens may also be endemic to cold and brackish waters and hence may represent a previously overlooked health hazard.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-95276 (URN)10.1128/AEM.00917-06 (DOI)000240474000041 ()16957222 (PubMedID)
Available from: 2006-12-20 Created: 2006-12-20 Last updated: 2017-12-14Bibliographically approved
6. Growth response of Vibrio cholerae and other Vibrio spp. to cyanobacterial dissolved organic matter and temperature in Brackish Water
Open this publication in new window or tab >>Growth response of Vibrio cholerae and other Vibrio spp. to cyanobacterial dissolved organic matter and temperature in Brackish Water
2007 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 60, no 3, p. 411-418Article in journal (Refereed) Published
Abstract [en]

Environmental control of growth and persistence of vibrios in aquatic environments is poorly understood even though members of the genus Vibrio are globally important pathogens. To study how algal-derived organic matter and temperature influenced the abundance of different Vibrio spp., Baltic Sea microcosms inoculated with Vibrio cholerae, Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio alginolyticus and native bacterioplankton, were exposed to different temperatures (12–25°C) and amended with dissolved organic matter from Nodularia spumigena (0–4.2 mg C L−1). Vibrio abundance was monitored by culture-dependent and molecular methods. Results suggested that Vibrio populations entered a viable but nonculturable state during the incubations. Abundance of Vibrio spp. and total bacterioplankton were orders of magnitude higher in microcosms amended with organic matter compared with reference microcosms. Vibrio cholerae abundances ranged from 0.9 to 1.9 × 105 cells mL−1 in treatments amended with 4.2 mg C L−1. Vibrio cholerae abundance relative to total bacterioplankton and other Vibrio spp. also increased >10-fold. In addition, V. vulnificus abundance increased in mesocosms with the highest organic matter addition (0.9–1.8 × 104 cells mL−1). Temperature alone did not significantly affect abundances of total bacterioplankton, total Vibrio spp. or individual Vibrio populations. By contrast, cyanobacterial-derived organic matter represented an important factor regulating growth and abundance of V. cholerae and V. vulnificus in brackish waters.

Keywords
Vibrio cholerae, Vibrio spp., Cyanobacteria, DOM, brackish water, growth
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-95277 (URN)10.1111/j.1574-6941.2007.00303.x (DOI)000246708800007 ()17386033 (PubMedID)
Available from: 2006-12-20 Created: 2006-12-20 Last updated: 2017-12-14Bibliographically approved

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