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Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/1216

Title: 
  • is Physiological and phylogentic studies of thermophilic hydrogen oxidizing bacteria from Icelandic hot-springs
Abstract: 
  • is

    Twenty seven thermophilic hydrogen oxidizing cultures (pure
    cultures or co-cultures) were obtained from various hot springs in
    Grensdalur, Hveragerði in SW-Iceland. The cultures were investigated in
    detail with respect to phylogenetics, physiology, hydrogen uptake rates and
    biomass yield.
    Enrichments under hydrogen oxidation conditions showed that 10%
    oxygen gave best results for obtaining stable pure- or co-cultures.
    Phylogenetic studies of the enrichments were done with partial- and
    full 16S rRNA analysis and DGGE analysis. Four main groups of hydrogen
    oxidizing bacteria were detected in the enrichment cultures obtained. The
    closest similarities were to species within the genera of Hydrogenophilus,
    Thiomonas (moderate thermophiles), Hydrogenobacter and
    Sulfurihydrogenibium (true thermophiles). Three enrichments revealed
    bacteria close to Hydrogenophilus denitrificans and H. thermoluteolus.
    Three enrichments resulted in bacteria closely related to several species of
    Thiomonas. Fourteen enrichments gave closest relationship to strict
    chemolithotrophs belonging to Hydrogenobacter and five enrichments
    showed the closest relationship to Sulfurihydrogenibium sp. Phylogenetic
    studies also showed that heterotrophic bacteria were very persistent. Among
    contaminants were Meiothermus, Anoxybacillus and Geobbacillus sp.
    Batch experiments on all enrichments showed great variation in
    hydrogen oxidation rate and biomass yield. The hydrogen oxidation rate
    varied from 0,16 to 1,64 mol H2L-1h-1 and the biomass yield from 0,21 – 3,18
    g DCW per mol H2 consumed. In general, the moderate thermophilic
    enrichments oxidized hydrogen faster as compared with the true
    thermophiles and produced more biomass.
    Cultivation in fed batch cultures of selected enrichments resulted in
    higher hydrogen uptake rates and biomass formation compared with batch
    cultures. The maximum hydrogen uptake rate and biomass yield for
    Ralstonia eutropha was 15,05 H2L-1h-1 and 4,9 g DCW per mol H2 utilized.
    Similar values for the moderate thermophilic enrichments (containing
    viii
    Hydrogenophilus and Thiomonas) 22 and 31 mmol H2L-1h-1; 4,5 and 3,4 g
    DWC per mol H2 utilized, respectively. The true thermophilic enrichments
    gave less biomass but similar hydrogen uptake rates as compared to the
    moderate thermophilic enrichments and the mesophilic control.
    Finally, four enrichment cultures were tested for oxidation of various
    sulphur compounds. Two thermophilic enrichments could utilize thiosulphate
    and produced sulphur or sulphuric acid. Enrichment containing Thiomonas
    sp. could oxidize thiosulphate to sulphuric acid and enrichment containing
    Hydrogenophilus sp. utilized sulphur.
    Keywords: Thermophilic; Hydrogen oxidizing; Aerobic; Biomass yield;
    Hydrogen uptake; Bacteria; Phylogeny

Description: 
  • is Verkefnið er opið nemendum og starfsfólki Háskólans á Akureyri frá og með 23.maí 2009.
Accepted: 
  • Jan 1, 2007
URI: 
  • http://hdl.handle.net/1946/1216


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Dagný Björk Reynisdóttir_heild.pdf3.55 MBMembersPhysiological - heildPDF
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