Microbial mediators of the sulfur-, nitrogen-, and iron-cycles in freshwater ecosystems

Contains fulltext : 30036.pdf (publisher's version ) (Open Access)Human activities and concominant sulfur and nitrogen pollution endanger freshwater ecosystem quality. Improved knowledge on wetland biogeochemistry is a necessity to protect these valuable and fragile ecosystems. Effects of increased nitrate concentrations (stimulation of sulfide mineral oxidation, inhibition of sulfate reduction) and sulfate concentrations (internal eutrophication, sulfide toxicity, formation sulfide minerals) are known, but data on the associated microbiology are scarce. Therefore, freshwater microbial mediators of sulfur oxidation, iron reduction and iron oxidation were studied with culture-dependent and culture-independent methods with major emphasis on nitrate-dependent iron sulfide mineral oxidation. A bioreactor study with soil from the freshwater nature reserve Het Zwart Water showed that amorphous iron sulfide did stimulate denitrification whereas crystalline pyrite did not. The type of iron sulfide mineral seems an important determinant in the occurrence of anoxic iron sulfide mineral oxidation. Denitrifying sulfur-oxidizing Thiobacilli were shown to be likely promotors of anoxic iron sulfide mineral dissolution, based on integral molecular and chemical analyses of soil and groundwater samples from Het Zwart Water combined with enrichment and pure culture studies. Acidovorax sp., associated with nitrate-dependent iron oxidation, were detected in an enrichment culture on iron sulfide and nitrate and were abundant in Het Zwart Water groundwater. These bacteria may also contribute to anoxic iron sulfide mineral dissolution. Findings from an enrichment culture of Het Zwart Water ground water and molecular analyses of iron seep material from the nature reserve De Bruuk showed that iron reduction by Geobacter may not be restricted to atmospheric-oxygen-free conditions. Simultaneous detection of iron oxidizers and reducers indicated tight coupling of iron conversions in De Bruuk. The detection and abundance of bacteria that promote anoxic iron sulfide dissolution in our studies indicates that anoxic conditions alone do not suffice to protect freshwater ecosystems from adverse processes such internal eutrophication and release of potentially toxic metals.Radboud Universiteit Nijmegen, 25 april 2007Promotor : Jetten, M.S.M. Co-promotor : Camp, H.J.M. op den126 p

Competition and coexistence of aerobic ammonium- and nitrite-oxidizing bacteria at low oxygen concentrations

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A novel marine nitrite-oxidizing Nitrospira species from Dutch coastal North Sea Water

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Iron Sulfide and Pyrite as Potential Electron Donors for Microbial Nitrate Reduction in Freshwater Wetlands

Contains fulltext : 34570.pdf (publisher's version ) (Closed access

Induced cooperation between marine nitrifiers and anaerobic ammonium-oxidizing bacteria by incremental exposure to oxygen

Contains fulltext : 84337.pdf (publisher's version ) (Closed access)9 p

Nitrification and Anammox with urea as the energy source

Contains fulltext : 60347.pdf (publisher's version ) (Closed access)Urea is present in many ecosystems and can be used as an energy source by chemolithotrophic aerobic ammonia oxidizing bacteria (AOB). Thus the utilization of urea in comparison to ammonia, by AOB as well as anaerobic ammonia oxidizing (Anammox) bacteria was investigated, using enrichments cultures, inoculated with activated sludge, and molecular ecological methods. In batch enrichment cultures grown with ammonia a population established in 2 weeks, which was dominated by halophilic and halotolerant AOB as determined by fluorescence in situ hybridization (FISH) experiments, with the 16S rRNA targeting oligonucleotide probe NEU. In other batch enrichment cultures using urea, the AOB population was assessed by PCR amplification, cloning and phylogenetic analysis of amoA and ribosomal 16S rRNA genes. While only one of the 48 16S rRNA gene clones could be identified as AOB (Nitrosomonas oligotropha), the amoA approach revealed two more AOB, Nitrosomonas europaea and Nitrosomonas nitrosa to be present in the enrichment. FISH analysis of the enrichment with probe NEU and newly designed probes for a specific detection of N. oligotropba and N. nitrosa related organisms, respectively, showed that N. oligotropha-like AOB formed about 50% of the total bacterial population. Also N. nitrosa (about 15% of the total population) and N. europaea (about 5%) of the total population) were relatively abundant. Additionally, continuous enrichments were performed under oxygen limitation. When ammonia was the energy source, the community in this reactor consisted of Anammox bacteria and AOB hybridizing with probe NEU. As the substrate was changed to urea, AOB related to N. oligotropha became the dominant AOB in this oxygen limited consortium. This resulted in a direct conversion of urea to dinitrogen gas, without the addition of organic carbon

Mimicking the oxygen minimum zones: Stimulating interaction of aerobic archaeal and anaerobic bacterial ammonia oxidizers in a laboratory‐scale model system

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Essays presented to Dr. Kazuhiro Hayashida Dr. Kanesaburo Gushima in Honour of Their Sixtieth Birthday

具島兼三郎教授著書および主要論文目

Global impact and application of the anaerobic ammonium-oxidizing (anammox) bacteria

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