| |
Kaeding, L. R. (2010). Relative contributions of climate variation, lake trout predation, and other factors to the decline of Yellowstone Lake cutthroat trout during the three recent decades. Ph.D. thesis, Montana State University, Bozeman, MT.
Abstract: The relative contributions of climate variation, lake trout Salvelinus namaycush predation, and other factors to the recent, three-decade decline of the lacustrine-adfluvial (i.e., a life-history form consisting of fish that mostly live in a lake but spawn in an inflowing tributary) Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri (YCT) population of Clear Creek, a Yellowstone Lake tributary, were evaluated. Strong growth of that population's storied spawning run between the early 1960s and 1978, when the run peaked at about 70,000 fish, had been considered key evidence of recovery of the lake's YCT population from formerly excessive angler harvest and other adverse factors. Thus the run's subsequent, almost continuous decline to about 500 fish in 2007 was perplexing. Gillnet catches of YCT at established lake locations likewise indicated a concurrent decline in the lake-wide YCT population. Prominent among the factors that may have importantly affected the YCT population during the recent decades was predation by the illegally introduced, reproducing, nonnative lake trout discovered in Yellowstone Lake in 1994. Data mainly taken from YCT in the spawning run ( n = 29 years) and gillnet catch ( n = 30 years) were examined for information useful to specifying the Leslie matrix of a dynamic, age-structured model that had climate as a covariate. The model, fitted to spawning run size and mean total length (TL) of YCT in the run during 1977-2007 ( n = 29 data years), explained 87% of variation in observed run size, 86% of variation in observed mean TL, and strongly suggested that climate (as indexed by total-annual air degree-days > 0°C measured on the lake's north shore) had an important effect on recruitment of age-0 YCT to subsequent spawning runs. Results also suggested that an effect of lake trout predation on survival of age-1 to age-5 YCT became apparent only during the recent decade. The important test of ongoing efforts to control lake trout in Yellowstone Lake and thereby limit their predation on YCT – on the basis of data for YCT – will occur when climatic conditions improve for YCT recruitment to the Clear Creek and other YCT spawning stocks of the lake.
Keywords: NRBIB_YELL;2011;animal studies;fish;Yellowstone cutthroat trout;Clear Creek;lake trout;climate
|
|
Xu, Y. (2010). Physiological, biochemical and molecular factors associated with heat tolerance in bentgrass (Agrostis spp.). Ph.D. thesis, Rutgers, .
Abstract: High temperature is a major factor limiting the growth of cool-season plant species during summer. Understanding mechanisms of plant tolerance to high temperature would help develop effective management practices and heat-tolerant cultivars through breeding or biotechnology. This dissertation research explored physiological, biochemical and molecular mechanisms for improving heat tolerance in two bentgrass species, creeping bentgrass ( Agrostis stolonifera L.), a widely used cool-season grass species on golf course tees and putting greens, and thermal rough bentgrass ( Agrostis scabra Willd.) adapted to geothermal areas in Yellowstone National Park.
The dissertation reports research in three main components. The first section compared differential heat-induced metabolism of hormones, proteins and metabolites between heat-sensitive creeping bentgrass and heat-tolerant A. scabra. Based on the findings that heat tolerance of bentgrass was associated with changes in stress-related hormone levels, the effects of foliar-applied hormone or hormone inhibitors on creeping bentgrass to enhance heat tolerance were further studied. Results from both growth chamber and field studies confirmed the effectiveness of applying hormones or hormone-based plant growth regulators on alleviating heat injuries in creeping bentgrass. In the last part of the dissertation, a few transgenic creeping bentgrass lines with improved heat tolerance were characterized. These transgenic lines carry a gene ( ipt ) controlling cytokinin synthesis. Increased ipt gene expression and cytokinin levels were confirmed and changes in morphological and physiological traits of the plants were examined. Genome-wide protein responses to the addition of the gene and their association with heat tolerance were discussed. The results indicated that transformation with the ipt gene induced protein changes involved in multiple functional groups, mainly in energy, protein destination and storage, and disease/defense categories in both leaves and roots of creeping bentgrass, thus cytokinins may have regulatory roles in multiple metabolic pathways for heat tolerance. Taken together, these studies suggest summer performance of creeping bentgrass may be improved by properly applying hormone-based plant growth regulators or biostimulants, and incorporating molecular markers developed from heat- and/or hormone-responsive proteins and metabolites may facilitate selection of heat-tolerant creeping bentgrass cultivars.
Keywords: NRBIB_YELL;2011;plant studies;Agrostis scabra;surface temperature
|
|
Windman, T. (2010). Organic compounds in hydrothermal systems. Ph.D. thesis, Arizona State University, .
Abstract: This study provides a link between thermodynamic calculations and observations of organic compounds in natural hydrothermal systems. Formate, acetate and succinate were quantified in hot spring fluids from Yellowstone National Park. Analytical concentrations of these molecules were used to evaluate their potential as energy sources for metabolisms of heterotrophic thermophilic microorganisms. The isotopic compositions of bulk dissolved organic and inorganic carbon were measured as a means to identify possible sources of carbon in hot spring fluids. These data are coupled to the isotopic composition of water samples collected simultaneously at the same springs to link carbon sources with the sources of the water that supplies the hydrothermal springs. Finally, a technique for estimating standard state thermodynamic properties of aqueous hydrocarbons was developed. The properties were then used in thermodynamic calculations to predict hydrocarbon solubilities, and to evaluate relative stabilities compared with naturally occurring redox buffering mineral assemblages.
Keywords: NRBIB_YELL;2011;geology;carbon;water chemistry
|
|
Garcia Costos, A. M. (2010). Isolation and characterization of Candidatus Chloracidobacterium thermophilum. Ph.D. thesis, Pennsylvania State University, .
Abstract: Historically, new microorganisms have been discovered either by setting up enrichment cultures in the laboratory that favor particular types of physiologies or by sequencing the amplified 16S ribosomal RNA gene from DNA extracted from environmental samples. These approaches have been successful in exposing the large variety of physiological capabilities (enrichment cultures) and vast phylogenetic diversity (16S rRNA surveys) of the microbial world. Yet they pose severe limitations to furthering our understanding of microbial diversity and to the discovery of microorganisms with novel physiologies. Another approach, metagenomics, has emerged as a powerful tool to study community composition, to define physiological capabilities of microbial communities and to discover novel microorganisms. A particularly fascinating group of microorganisms to study are the chlorophototrophs. Chlorophototrophs use membrane-embedded chlorophyll-protein complexes called reaction centers to harvest light energy and transform it into chemical energy. Prior to the work presented here, there were five known bacterial phyla that contained chlorophototrophs, including the Cyanobacteria, Chlorobi, Chloroflexi, Firmicutes and Proteobacteria. These distinct groups vary in their reaction centers, accessory pigments and carbon metabolism among other properties. Microbial mats in alkaline hot springs of Yellowstone National Park are dominated by chlorophototrophic microorganisms and provide an ideal setting for studying them. The mats from two particular springs, Octopus and Mushroom Springs, have been the subject of over three decades of research, and much is known about their geochemistry and microbial composition. Two phyla of chlorophototrophs, the Cyanobacteria and the Chloroflexi reside in these low-carbonate and low-sulfide mats. A metagenomic study conducted on these mats revealed the presence of a third type of chlorophototroph that had escaped detection by other approaches and that belongs to the phylum Acidobacteria, a phylum previously not known to contain chlorophototrophs. An analysis of the metagenome predicted this new chlorophototroph, Candidatus Chloracidobacterium thermophilum, to have Type-1 reaction centers, the Fenna Matthew Olson protein and chlorosomes as antenna structures, properties also found in the chlorophototrophic Chlorobi. Unlike the Chlorobiales, however, Cab. thermophilum was predicted to be an aerobe. The present work describes the isolation of this new chlorophototroph in culture and its initial characterization. An enriched culture of Cab. thermophilum has been generated from a cyanobacterial enrichment culture cultivated from the mats of Octopus Spring that contained Cab. thermophilum as a minor component. Like other Acidobacteria, Cab. thermophilum is difficult to culture and has long generation times and fastidious growth requirements. In addition, the culture contains heterotrophic microorganisms that seem to be providing unidentified, essential growth factor(s). Physiological studies of this culture have confirmed the metagenomic predictions that Cab. thermophilum is an aerobic chlorophototroph that synthesizes chlorosomes containing bacteriochlorophyll c as antenna pigments. In order to understand the physiology of Cab. thermophilum further, its genome has been completely sequenced. It consists of two chromosomes, both of which harbor essential genes. The genome contains all of the genes required for phototrophy with chlorosomes as antenna structures but lacks key genes of all known carbon fixation pathways, as well as genes for assimilatory nitrate and sulfate reduction. In addition, it lacks the biosynthetic pathways for the synthesis of the amino acids valine, isoleucine and leucine. These genomic analyses clearly define Cab. thermophilum as a chlorophotoheterotroph that is dependent on other members of the mat community for essential nutrients. The structure of the chlorosome antenna complex of Cab. thermophilum has been investigated and its protein, lipid, quinone and pigment composition elucidated. Although synthesized by an aerobe, the chlorosomes resemble those of other green bacteria in their general shape and by the presence of CsmA and CsmI-like proteins. However, they contain additional unique proteins and lipids. Moreover, the presence of the xanthophylls echinenone and canthaxanthin reflects the aerobic environment from which Cab. thermophilum was isolated. Like the chlorophototrophic Chlorobi, Cab. thermophilum synthesizes three types of chlorophylls, bacteriochlorophyll (BChl) c, chlorophyll (Chl) a and BChl a. High performance liquid chromatography analyses combined with mass spectrometry have revealed that Cab. thermophilum methylates its BChl c at the C-8 and C-12 positions and that its C-17 propionic group is esterified with a variety of isoprenoid and straight alkane moieties. The most abundant BChl c species, especially at high light intensities, has been found to be [8-iBu, 12-Et]-BChl c esterified with the unbranched C-18 alcohol, octadecanol. Interestingly, although Cab. thermophilum is an aerobe, its chlorosomes exhibit redox-dependent quenching of fluorescence emission. Lastly, carotenoid biosynthesis in Cab. thermophilum has been investigated. Three genes predicted to code for a lycopene cyclase, a ketolase, and a hydroxylase respectively have been expressed heterologously and their enzymatic activities confirmed.
Indexing (document details)
Keywords: NRBIB_YELL;2011;microbiology;Candidatus Chloracidobacterium thermophilum;Octopus Spring;Mushroom Spring
|
|
Alexander, J. D. (2010). Influence of environmental features on Tubifex tubifex and Myxobolus cerebralis infected Tubifex tubifex in Yellowstone National Park: Implications for whirling disease risk. Ph.D. thesis, Montana State University, Bozeman, MT.
Abstract: Whirling disease (WD) is an emerging parasitic disease of salmonids that is increasing in severity and geographic range. Whirling disease is caused by the myxosporean parasite, Myxobolus cerebralis, and can effect significant mortality in wild and cultured salmonid populations. Myxobolus cerebralis was recently detected in Yellowstone National Park (YNP) where it may be causing native Yellowstone cutthroat trout (YCT) to decline. Myxobolus cerebralis exploits the aquatic oligochaete, Tubifex tubifex, as its primary host and spores released by T. tubifex are infective to salmonid fish. The aim of this study was to assess WD risk for YCT populations in YNP by focusing on the disease source, T. tubifex, which had not previously been characterized. My objectives were to characterize T. tubifex populations and dynamics of M. cerebralis infections in T. tubifex and to establish factors associated with M. cerebralis infections in T. tubifex. In addition, I examined relationships between infection dynamics in T. tubifex and transmission to fish hosts (WD risk).
In Pelican Creek, T. tubifex and M. cerebralis infected T. tubifex were widely distributed and abundant. Infected T. tubifex were most abundant in reaches characterized by intermediate geothermal influence. However, WD risk was high in all reach types, which indicated that low parasite success in the oligochaete host in reaches with high or no geothermal influence did not translate into reduced WD risk in these reaches. In tributaries throughout YNP, susceptible T. tubifex were widely distributed but experimental and field data suggest M. cerebralis -infected T. tubifex may be unable to survive in all tributaries where uninfected T. tubifex were found. In particular, environmental factors influenced by confinement, including proportions of coarse and fine substrates, may preclude establishment of M. cerebralis in tributaries in YNP. Thus, environmental features, rather than oligochaete host factors, may be most influential for M. cerebralis dynamics in T. tubifex and WD risk to fish in YNP. While further research is needed to identify specific mechanisms, these results suggest environmental features related to confinement may be useful for assessing WD risk at broad scales when the oligochaete host is characterized by low genetic variability.
Keywords: NRBIB_YELL;2011;animal studies;fish;whirling disease;Tubifex tubifex;Pelican Creek;Myxobolus cerebralis
|
|
|
