Thesis (Ph. D.)--University of Maryland, College Park, 2006. / Includes bibliographical references (p. 125-133). Also available online via the University of Maryland website (https://drum.umd.edu/).

Stable carbon isotope fractionation during methanogenesis is affected by the availability of substrates. The effects of different substrates on methanogen biomass, total lipid extract, biomarkers and methane under both abundant and limiting substrate conditions were studied. Methanosarcina barkeri was grown with methanol, acetate, trimethylamine (TMA) and H2/CO2, and carbon isotope fractionation in methane production was greatest with methanol, followed by H2/CO2, TMA and acetate. In contrast, biomass was isotopically lightest in M.barkeri grown on methanol, followed by TMA, H2/CO2 and acetate. Generally, fractionation was greater in cultures grown with abundant substrate availability as compared to those supplied with limiting substrate. During autotrophic growth, fractionation was greatest during slower growth for both methane and biomass production. The results of these fractionation studies under controlled laboratory conditions can be applied to the interpretation of isotopic signatures for methane and methanogen biomarkers, and ecological processes, in marine environments. Several hypersaline springs off the western shore of Lake Winnipegosis, MB support unique microbial mat communities. These low temperature springs contain water with a mean salinity as high as 6.1%. Studies were undertaken to contrast the anaerobic microbial communities of these springs, specifically the methanogens and sulphate-reducing bacteria (SRB), and their contributions to biogeochemical cycling in these mats. Comparisons of lipid profiles revealed changes in the proportions of the dominant fatty acids related to the amount of mat growth. Cultures of SRB and methanogens were established with six different substrates. Methanogenic cultures grew best on TMA and methanol, but could use formate, H2/CO2 and glycine betaine as well. In contrast, H2/CO2 was the preferred substrate of the SRB enrichment cultures, which were also able to use formate, but not TMA, the breakdown product of the compatible solute glycine betaine. Maximum methane production occurred at 5% salinity. The lipid composition of the mats, including methanogen biomarkers, and the results of the enrichments on different substrates and at different salinities, suggest that methanogenesis in these springs is supported by compatible solutes whereas sulphate reduction is linked to availability of hydrogen and formate. / February 2005

The seasonal population fluctuation of anoxygenic phototrophs and the diversity of cyanobacteria at the Sulphur Mountain thermal springs of Banff, Canada were investigated and compared to the drastic population changes of the endangered snail Physella johnsoni. A new species and two strains of Rhodomicrobium were taxonomically characterized in addition to new species of Rhodobacter and Erythromicrobium. Major mat-forming organisms included Thiothrix-like species, oxygenic phototrophs of genera Spirulina, Oscillatoria, and Phormidium and purple nonsulfur bacteria Rhodobacter, Rhodopseudomonas and Rhodomicrobium. Aerobic anoxygenic phototrophs comprised upwards of 9.6 x 104 CFU/cm2 of mat or 18.9% of total aerobic heterotrophic bacterial isolates at certain sites, while maximal purple nonsulfur and purple sulfur bacteria were quantified at 3.2 x 105 and 2.0 x 106 CFU/cm2 of mat, respectively. Photosynthetic activity measurements revealed incredibly productive carbon fixation rates averaging 40.5 mg C/cm2/24 h. A temporal mismatch was observed for mat area and prokaryote-based organics to P. johnsoni population flux in a “tracking inertia” manner.

Stable carbon isotope fractionation during methanogenesis is affected by the availability of substrates. The effects of different substrates on methanogen biomass, total lipid extract, biomarkers and methane under both abundant and limiting substrate conditions were studied. Methanosarcina barkeri was grown with methanol, acetate, trimethylamine (TMA) and H2/CO2, and carbon isotope fractionation in methane production was greatest with methanol, followed by H2/CO2, TMA and acetate. In contrast, biomass was isotopically lightest in M.barkeri grown on methanol, followed by TMA, H2/CO2 and acetate. Generally, fractionation was greater in cultures grown with abundant substrate availability as compared to those supplied with limiting substrate. During autotrophic growth, fractionation was greatest during slower growth for both methane and biomass production. The results of these fractionation studies under controlled laboratory conditions can be applied to the interpretation of isotopic signatures for methane and methanogen biomarkers, and ecological processes, in marine environments. Several hypersaline springs off the western shore of Lake Winnipegosis, MB support unique microbial mat communities. These low temperature springs contain water with a mean salinity as high as 6.1%. Studies were undertaken to contrast the anaerobic microbial communities of these springs, specifically the methanogens and sulphate-reducing bacteria (SRB), and their contributions to biogeochemical cycling in these mats. Comparisons of lipid profiles revealed changes in the proportions of the dominant fatty acids related to the amount of mat growth. Cultures of SRB and methanogens were established with six different substrates. Methanogenic cultures grew best on TMA and methanol, but could use formate, H2/CO2 and glycine betaine as well. In contrast, H2/CO2 was the preferred substrate of the SRB enrichment cultures, which were also able to use formate, but not TMA, the breakdown product of the compatible solute glycine betaine. Maximum methane production occurred at 5% salinity. The lipid composition of the mats, including methanogen biomarkers, and the results of the enrichments on different substrates and at different salinities, suggest that methanogenesis in these springs is supported by compatible solutes whereas sulphate reduction is linked to availability of hydrogen and formate.

The seasonal population fluctuation of anoxygenic phototrophs and the diversity of cyanobacteria at the Sulphur Mountain thermal springs of Banff, Canada were investigated and compared to the drastic population changes of the endangered snail Physella johnsoni. A new species and two strains of Rhodomicrobium were taxonomically characterized in addition to new species of Rhodobacter and Erythromicrobium. Major mat-forming organisms included Thiothrix-like species, oxygenic phototrophs of genera Spirulina, Oscillatoria, and Phormidium and purple nonsulfur bacteria Rhodobacter, Rhodopseudomonas and Rhodomicrobium. Aerobic anoxygenic phototrophs comprised upwards of 9.6 x 104 CFU/cm2 of mat or 18.9% of total aerobic heterotrophic bacterial isolates at certain sites, while maximal purple nonsulfur and purple sulfur bacteria were quantified at 3.2 x 105 and 2.0 x 106 CFU/cm2 of mat, respectively. Photosynthetic activity measurements revealed incredibly productive carbon fixation rates averaging 40.5 mg C/cm2/24 h. A temporal mismatch was observed for mat area and prokaryote-based organics to P. johnsoni population flux in a “tracking inertia” manner.

Stable carbon isotope fractionation during methanogenesis is affected by the availability of substrates. The effects of different substrates on methanogen biomass, total lipid extract, biomarkers and methane under both abundant and limiting substrate conditions were studied. Methanosarcina barkeri was grown with methanol, acetate, trimethylamine (TMA) and H2/CO2, and carbon isotope fractionation in methane production was greatest with methanol, followed by H2/CO2, TMA and acetate. In contrast, biomass was isotopically lightest in M.barkeri grown on methanol, followed by TMA, H2/CO2 and acetate. Generally, fractionation was greater in cultures grown with abundant substrate availability as compared to those supplied with limiting substrate. During autotrophic growth, fractionation was greatest during slower growth for both methane and biomass production. The results of these fractionation studies under controlled laboratory conditions can be applied to the interpretation of isotopic signatures for methane and methanogen biomarkers, and ecological processes, in marine environments. Several hypersaline springs off the western shore of Lake Winnipegosis, MB support unique microbial mat communities. These low temperature springs contain water with a mean salinity as high as 6.1%. Studies were undertaken to contrast the anaerobic microbial communities of these springs, specifically the methanogens and sulphate-reducing bacteria (SRB), and their contributions to biogeochemical cycling in these mats. Comparisons of lipid profiles revealed changes in the proportions of the dominant fatty acids related to the amount of mat growth. Cultures of SRB and methanogens were established with six different substrates. Methanogenic cultures grew best on TMA and methanol, but could use formate, H2/CO2 and glycine betaine as well. In contrast, H2/CO2 was the preferred substrate of the SRB enrichment cultures, which were also able to use formate, but not TMA, the breakdown product of the compatible solute glycine betaine. Maximum methane production occurred at 5% salinity. The lipid composition of the mats, including methanogen biomarkers, and the results of the enrichments on different substrates and at different salinities, suggest that methanogenesis in these springs is supported by compatible solutes whereas sulphate reduction is linked to availability of hydrogen and formate.

No description available.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 1, 2007) Includes bibliographical references.

Carboxylated macromolecules such as alginate and glycoproteins are abundant components of modern shallow marine sediments where they are secreted by bacteria and marine infauna. Both organic compounds are proton and metal reactive; hence, they have the potential to facilitate metal sorption and biomineralization reactions. In this study, lab experiments were coupled to field-based sampling to assess the role that these compounds play in microbial mats, with particular emphasis on the hypersaline lagoons of Los Roques, Venezuela. Here I applied a surface complexation approach to model proton and Cd adsorption behaviour of both uronic acid-rich alginate and mucin. Measured total site concentrations, available for metal adsorption, demonstrate that these compounds have the potential to induce metal partitioning in early diagenetic microenvironments. Field results from Venezuela are consistent with Mg- and trace metal- enrichment that follows a likely correlation with the degradation states of microbial biomass trapped during accretion of modern microbialites.

No description available.