Graduation date: 1999

Antarctica provides some of the most extreme environments on earth. Low temperatures, low water availability and nutrient deficiency are contributing factors to the limited colonisation of Antarctic biotopes, particularly in the continental Dry Valleys. The survival of microorganisms in this harsh continent provides the basis for the significance of this study. This study aimed to explore microbial phylotypic diversity across a 500 m altitudinal transect in the Miers Dry Valley, Ross Desert, East Antarctica. The study also attempted to infer from phylogenetic data, the possible presence of indicative phenotypes which might contribute to a functional microbial community.

<p>Soil communities are regarded as among the most complex and diverse assemblages of microorganisms with estimated bacterial numbers in the order of 10â?¹ cells.gâ?»&sup1 / . Studies on extreme soils however, have reported lower cell densities, supporting the perception that the so-called extreme environments exhibit low species diversity. To assess the extent of microbial diversity within an extreme environment, the mineral soils of the Dry Valleys, Ross Dependency, Eastern Antarctica were investigated using 16S rDNA analysis.</p>

Thesis (Ph. D.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: John C. Priscu. Includes bibliographical references (leaves 181-201).

Philosophiae Doctor - PhD / Soil communities are regarded as among the most complex and diverse assemblages of microorganisms with estimated bacterial numbers in the order of 109-1 cells.g. Studies on extreme soils however, have reported lower cell densities, supporting the perception that the so-called extreme environments exhibit low species diversity. To assess the extent of microbial diversity within an extreme environment, the mineral soils of the Dry Valleys, Ross Dependency, Eastern Antarctica were investigated using 16S rDNA analysis. Three mineral soils designated MVG, PENP and BIS were analysed, each differing with respect to altitude, protein, lipid, water and DNA content. The mid-altitude sample, MVG, yielded the highest levels of DNA and the low altitude BIS soil contained the highest levels of protein, lipid and water. 16S clone libraries were constructed and 60 unique clones were identified and sequenced. BLASTn analysis revealed eight phylogenetic groups with Cyanobacteria, Actinobacteria and Acidobacteria representing the majority. The Cyanobacterial phylotypes were unique to the desiccated high-altitude soils of the PENP sample, suggesting a soil-borne Cyanobacterial population. 21% of the phylotypes identified were assigned as ‘uncultured’. DNA isolated from the Antarctic mineral soils was also used to construct a metagenomic clone library consisting of 90700 clones with an average insert size of 3.5 kb, representing an estimated 3.4% of the available metagenome. Activity-based screening of the library for genes conferring lipolytic activity yielded no positive clones. It is suggested that the failure to produce positive clones might be a result of insufficient nucleotide coverage of the metagenomic DNA. The metagenomic DNA extracted from the Dry Valley mineral soils was further analyzed using PCR. Two sets of degenerate primers based on conserved regions within lipolytic genes were used to target lipase and esterase genes. One set of primers was selected from a previous study. A second primer set was designed manually from amino acid alignments of true lipase genes from family I, sub-families I-VI. PCR analysis resulted in nine partial gene fragments varying between 240 bp and 300 bp. Bioinformatic analysis revealed that all nine partial gene fragments harboured α/β-hydrolase motifs, putatively identifying two esterases and three lipases from both bacterial and fungal origin. / South Africa

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Microplankton at five sites off South Georgia in January to February 1991 was dominated by a range of diatoms. The haptophyte Phaeocystis was present in three of the five sites but in low abundance only. Diatoms dominated at a more southerly site near the Antarctic Peninsula in March, whereas dinoflagellates dominated at a site near Deception Island. Multivariate analysis allowed the seven sites to be distinguished on the basis of microplankton species composition. Analysis of thirteen lipid classes present in total lipid extracted from the microplankton also demonstrated substantial differences from site to site. Multivariate analysis showed a different pattern of variation from the species ordination, with the South Georgia sites forming a distinct cluster. Outlier sites identified in the species and lipid ordinations confirmed the association between some taxonomic groups and lipid 'fingerprints'. Fatty acids extracted from total lipid in microplankton at five sites around South Georgia and two sites near the Antarctic Peninsula ranged from 37 to 195 J.Lg1-1, with a ratio of fatty acids in polar lipid: neutral lipid ranging from 4: 1 to 1:2. A further eleven particulate samples analysed from sites around the Antarctic Peninsula had slightly lower fatty acid content with a mean of 50 J.Lg1-1. Fatty acids in polar lipid were rich in (n-3) polyunsaturated fatty acids, chiefly 20:5(n-3). However, 22:6(n-3) could be as abundant as 20:5(n-3) in polar lipid from microplankton less than 20 J.1m, and also in dinoflagellate-rich microplankton. Neutral lipid was dominated by 16:0, 16:1(n-7) and 18:1(n-9) fatty acids and contained only low levels of (n-3) polyunsaturated fatty acids. The data reveal the high nutritional quality of microplankton lipids in the Southern Ocean for filter feeding animals, including krill. Samples of krill from eight sites around South Georgia consisted predominantly of immature animals, and females were entirely absent from samples from two of the eight sites studied. Animal wet mass varied from 0.16-1.72 g (median values of 0.47, 1.15 and 1.46 g for immatures, males and females respectively). Lipid amounts varied from 5-147 mg per animal (median values of 17.8, 21.0 and 73.3 mg for immatures, males and females respectively). Triacylglycerol (TAG) and phosphatidylcholine were the two most abundant lipid classes in all animals. Multivariate analysis of lipid composition indicated significant overlap between sex-maturity classes, although female krill tended to be distinguished from males by higher proportions of TAG and lower proportions of phosphatidylserine plus phosphatidylinositol. Reproductive investment is implicated in the overall variability in lipid content and composition, with females containing high lipid levels as reserves for egg production, whilst males showed apparent lipid deficits resulting from short-term mobilisation of storage material for spermatophore production and attachment. Significant and systematic site-to-site variability in lipid content and composition were evident in the samples and this could not be explained by the sex ratio or animal size. Such variability might have arisen from local patterns of krill distribution but could not be ascribed simply to temporal changes in lipid during the study. Immature Antarctic krill (length 40-45 mm) maintained in an aquarium for up to nine months were fed dense suspensions of cultures of two algal taxa, the haptophyte /sochrysis and the diatom Thalassiosira. Following acclimation to the experimental feeding regime, the animals were transferred to identical containers holding cultures of the same alga already labelled with [14C]bicarbonate. Faecal pellets collected after transfer showed detectable radioactivity after 30 minutes for /sochrysis and 55 minutes for Thalassiosira, providing an estimation of gut throughput time. With both algal cultures, radioactivity in faecal pellets increased over the 4-5 hour collection period. However, whilst faecal pellets derived from Isochrysis showed a rapid initial increase followed by an approach to a plateau value, the radioactivity in Thalassiosira-derived pellets increased steadily. A first-order kinetic model fitted to these data showed a more rapid turnover time for Isochrysis (k = 47 min) than for Thaiassiosira (k = 256 min). The assimilation efficiency based on the ratio of ingested radiolabelled lipid to that egested in faeces was 86% for /sochrysis and 63% for Thalassiosira, whereas corresponding efficiencies calculated from mass lipid budgets were 75% for /sochrysis and 77% for Thalassiosira. Analysis of fatty acid content and composition of total lipid from algae, krill and faecal pellets established that all dietary fatty acids were very efficiently ssimilated although there was a relatively preferential excretion of saturated fatty acids. All the assimilated fatty acids were extensively catabolised with the possible exceptions of saturated fatty acids and 18:4. Evidence was obtained for some biosynthesis of saturated fatty acids from non-lipid dietary precursors and for a limited conversion of 18:3 to 18:4 Collating the data presented in this thesis in a budget indicates that under suitable conditions, Euphausia superba is capable of acquiring the lipid necessary for growth and reproduction over time scales of only a few weeks and certainly within a single summer. Hence, krill appears to be an animal capable of high energy throughput and high reproductive output.

A phytoplankton bloom dominated by the pennate diatom Nitzschia curta (Van Heurck) Hasle was observed during January-February 1983 at a receding ice-edge in the Western Ross Sea, Antarctica. The core of the bloom was found between 100-150 Km from the ice-edge. Nitzschia curta cell densities up to 22 x 10⁶ cells/1 were observed. The nanoplankton contributed to 18% (average) of the total biomass. The contribution of another pennate diatom, Nitzschia closterium (Ehrenberg) W. Smith, was significant in two offshore stations (22% and 90%). Other diatom species, dinoflagellates and other phytoplankton groups were very few in number. A wind-driven upwelling event occurred along the ice-edge. The presence of off-shore species (e.g. Nitzschia kerguelensis) close to the ice suggests the existence of an eddy circulation. Results of elemental composition experiments with 10 Antarctic diatoms showed that the C:Si:N ratio for Antarctic diatoms, when compared to the Redfield-Richards ratio for diatoms of other environments, have less carbon and more silicon per unit nitrogen. Comparison of laboratory results with the field data confirms the anomalous elemental composition of the major bloom species observed in the Ross Sea. Blooms like the one observed in this study seem to be restricted to the Western part of the Ross Sea and appear to be produced in inshore waters late in the austral summer. / Graduation date: 1985

The objective of this research is to determine the influence of liquid water content on the toxicity of petroleum hydrocarbons (PHC) to soil microorganisms in frozen soil. This research was conducted on soil collected from an aged diesel fuel spill site at Casey Station, East Antarctica, as well as on spiked diesel contaminated soil from Macquarie Island, a sub-Antarctic island.<p> Suitable soil biogeochemical toxicity endpoints for PHC contamination were identified using sub-Antarctic soil from Macquarie Island spiked with diesel fuel. The sensitivity of nitrification, denitrification, carbohydrate utilization and total soil respiration to diesel fuel was assessed. Potential nitrification activity (PNA) was the most sensitive indicator of contamination assessed for nitrogen cycling, with a PHC concentration effecting microbial activity by 20% of the control response, EC₂₀, of 190 mg PHC kg^-1 soil.<p> Petroleum hydrocarbon toxicity in polar soil was assessed by sampling 32 locations at an aged diesel spill site at Casey Station, East Antarctica. Samples were taken nine times throughout an austral summer to encompass frozen, thaw and refreeze periods. Toxicity was assessed using potential activities of substrate induced respiration, total respiration, nitrification, denitrification, and metabolic quotient, as well as microbial community composition and bacterial biomass. The most sensitive indicator was community composition with an EC₂₅ of 800 mg kg^-1, followed by nitrification (2000 mg kg^-1), microbial biomass (2400 mg kg^-1) and soil respiration (3500 mg kg^-1). Despite changes in potential microbial activities and composition over the frozen/thaw/refreeze period, the sensitivity of these endpoints to PHC did not change with liquid water or temperature. <p> The influence of liquid water (è_liquid) on nutrient supply rate and gas diffusion, which are important factors in microbial degradation of PHC, was determined using contaminated soil from Casey Station. Freezing reduced nutrient supply rate of both NH₄⁺ and NO₃^-. However, an increase in è_liquid was linked to increases in nitrate and ammonia nutrient supply rates in frozen soil. Similarly for gas diffusion, decreases in D_s due to freezing were much more pronounced in soils with low è_liquid compared to soils with higher è_liquid contents. Further research is needed to determine whether bioremediation in cold regions could be enhanced during the period of time where the soil temperature is below 0^oC by controlling factors that increase the amount of liquid water.<p> The influence of liquid water content on the <i>in situ</i> toxicity of PHC to soil microorganisms was evaluated using stable isotope dilution technique to measure gross mineralization and nitrification, which was compared to the toxicity endpoints of potential microbial activities. Liquid water content did not have a significant effect on either gross mineralization or nitrification. Gross nitrification was sensitive to PHC contamination, with toxicity decreasing over time. The EC₂₅ value for gross nitrification was 400 mg kg^-1 for 1 month incubation period. In contrast, gross N mineralization was not sensitive to PHC contamination. Toxic response of gross nitrification to PHC contamination was comparable to PNA with similar EC₂₅ values determined by both measurement endpoints (400 mg kg^-1 for <i>in situ</i> nitrification compared to 200 mg kg^-1 for PNA), indicating that potential microbial activity assays are good surrogates for <i>in situ</i> toxicity of PHC contamination in Polar Regions.<p> Based on ecotoxicological data collected, the recommended soil quality guideline for on PHC contamination in polar soils would be 200 mg kg^-1.