Saltwater intrusion due to global change is expected to have a detrimental effect on the biogeochemistry of tidal freshwater wetlands. Of particular concern is that fact that salinization can alter the role of these ecosystems in the global carbon cycling by causing shifts in microbial metabolism that alter greenhouse gas emissions and increase carbon mineralization rates. However, our understanding of how wetland microbial community dynamics will respond to saltwater intrusion is limited. To address this knowledge gap and increase our understanding of how microbial communities in tidal freshwater wetlands change over time (1, 3, 12, and 49 weeks) under elevated salinity conditions, an in situ soil transplant was conducted. Throughout the 49 weeks of saltwater exposure, salinity had no effect on soil quality (organic matter content and C:N ratio). In contrast, the concentration of porewater ion species (SO4-2, NO3-, and NH4+) considerably increased. The activity of hydrolytic enzymes, (ß-1,4-glucosidase and 1,4-ß-cellobiohydrolase) gradually decreased with prolonged exposure to saline conditions; by the final sampling event (49 weeks), activity was reduced by ~70% in comparison to the freshwater controls. Short term exposure to salinity (3 and 12 weeks) had a greater effect on phenol oxidase, decreasing activity by 10-20%. Saltwater exposure had an immediate (1 week) effect on potential rates of carbon mineralization; overall, carbon dioxide production doubled and methane production decreased by ~20-fold. These changes in gas production were correlated to increased salinity and to changes in the abundance of methanogens and sulfate reducing bacteria, suggesting a shift in the terminal step in organic matter degradation from methanogenesis to sulfate reduction. Principal component analysis revealed distinct changes in soil environmental conditions and carbon metabolism within weeks, but the response of the microbial community was slower (months to a year). Taken together, results from this study indicate that the response of tidal freshwater wetlands to salinization is driven by complex interactions of microbial related processes and environmental changes that are dependent on the duration of exposure. Assessing the impact of environmental perturbation on ecosystem function may be better achieved by complementary analysis of both microbial community structure and function.

The aim of this thesis is the utilization of phospholipid fatty acids (PLFA) analysis to determine groups of microorganisms present during the biodrying of sewage sludge and their description in relation to the temperature regime of the biodrying. Four experimental cycles A, B, C, D were followed. Cycles A, B and C, D differred from each other in the sewage sludge collected from two waste water treatment plants. The cycles A, B, C and D were each performed in two reactors with different aeration regimes to compare the mesophilic (max. temperature ±50 řC) and thermophilic (max. temperature ±70 řC) regimes of biodrying. PLFA analysis was used to determine the microbial groups. Concentrations of individual PLFA were subjected to principal component analysis (PCA). The total PLFA concentration corresponding to total microbial biomass was decreasing during both temperature regimes of cycles B, C, D, while the total PLFA concentration increased towards the end of both temperature regimes of cycle A. The total PLFA concentration reached statistically higher values at the end of the mesophilic regime of cycles B, C and D. The development of fungi to bacteria ratio showed that fungi applied more with the progression of both temperature regimes of cycles A, B and the thermophilic regime of cycle C. Based on...

La digestion anaérobie est un procédé biologique effectué par un réseau complexe et synergique de communautés microbiennes permettant la dégradation de matière organiques comme les déchets agricoles ou les effluents de station d’épuration en biogaz, un gaz valorisable en énergie. Les mécanismes influençant les communautés microbiennes au cœur de ce procédé mais aussi dans la nature restent incompris du fait de la faible compréhension de leur dynamique. Les objectifs de ce projet visent à donc développer un système de digestion anaérobie permettant de mieux comprendre la dynamique de l’assemblage des communautés microbiennes. Ainsi un nouveau procédé de réacteurs en continu dont les fonctions d’alimentation de soutirage et de dégazage sont automatisées a été développé. L’automatisation et le multiplexage des réacteurs permettent la manipulation de 30 réacteurs en continu en parallèle. Outre l’automatisation ce système, de nombreux paramètres sont flexibles comme le taux de charge (une fois par minute jusqu’à une condition batch), le volume de réacteur (50 à 200mL), la température (pièce – 55°C), mais aussi l’utilisation du système en aérobie ou l’implémentation d’autres outils comme des LEDs pour les cultures phototrophes. Capable de quantifier précisément la performance d’un écosystème méthanogène, ce système nous a permis de tester la structure et la performance d’écosystèmes méthanogènes mis en mélanges et testés de façon individuelle. En mélangeant des écosystèmes méthanogènes différents, la diversité des Archées a augmenté transitoirement. Une corrélation est d’ailleurs observée entre la diversité de ces communautés mélangées et leur performance méthanogène, seulement à même diversité les communautés individuelles ont un meilleur fonctionnement. L’assemblage de certaines communautés mélangées a pourtant permis une meilleure production de méthane que les communautés individuelles, ce qui suggère le développement d’interactions spécifiques de ces communautés. De façon nouvelle par rapport à la littérature, la majorité des communautés bactériennes individuelles sont retrouvées dans les communautés mélangées. Soit contrairement à l’idée d’une sélection d’une communauté plus adaptée ou plus fonctionnelle, ici la majorité des communautés se sont implantées. Ces expériences suggèrent qu’un paramètre tel que la fonctionnalité d’un bioprocédé peut-être amélioré par bioaugmentation. / Anaerobic digestion is a biological process carried out by a complex and synergistic network of microbial communities allowing the degradation of organic matter such as agricultural waste or effluents from wastewater treatment plants, into biogas, a gas recoverable into energy. The mechanisms influencing microbial communities at the heart of this process but also in nature remain misunderstood because of a low understanding of their dynamics. The objectives of this project are therefore to develop an anaerobic digestion system to better understand the dynamics of microbial community assembly. Thus, a new continuous reactor process has been developed with automated feeding, biomass wasting and degassing functions. Automation and multiplexing of reactors allows for the continuous parallel manipulation of 30 reactors in parallel. In addition to the automation, many parameters are versatile, such as the substrate loading (once a minute up to batch conditions), the reactor volume (50 to 200 mL), the temperature (room to 55°C), but also the use of the aerobic system or the implementation of other tools such as LEDs for phototrophic cultures. Capable of accurately quantifying the performance of a methanogenic ecosystem, this system has enabled us to test the structure and the performance of five different methanogenic ecosystems that have been mixed and tested individually. By mixing different methanogenic ecosystems the Archaea diversity has increased transiently. Besides, a correlation is observed between the diversity of mixed communities and their methanogenic performance; yet the individual communities have a better functioning at the same level of diversity. Interestingly, the mixture of some communities has allowed for better methane production than individual communities, suggesting the development of specific interactions in these communities. In a novel way compared to the literature and that the majority of individual bacterial communities are found in mixed communities. Contrary to the idea of selecting a more adapted or functional community, here the majority of communities have settled. These experiments suggest that a parameter such as the functionality of a bioprocess can be improved by bioaugmentation.

O processo de domesticação e posterior melhoramento das plantas cultivadas foram essenciais para o sustento do crescimento populacional observado na recente história da humanidade. Porém, no processo de melhoramento das culturas não foi considerado o importante papel que o microbioma rizosférico desempenha nas plantas. Neste contexto, esta pesquisa foi direcionada ao estudo do microbioma rizosférico do feijoeiro, considerando um genótipo selvagem e outro cultivado, a fim de determinar a composição e funcionalidade do microbioma em cada rizosfera. Assim, para testar a hipótese de que materiais ancestrais têm maior capacidade de hospedar micro-organismos benéficos na rizosfera quando comparados a cultivares modernas, os genótipos de feijão cultivado IAC Alvorada e selvagem Wild Mex foram cultivados em Terra Preta da Amazônia (TPA), solo caracterizado por abrigar uma grande diversidade microbiana. O DNA total do solo rizosférico de cada genótipo de feijão e do bulk soil foi extraído para realizar o sequenciamento metagenômico usando a plataforma Illumina MiSeq. O solo rizosférico também foi usado para isolar e selecionar bactérias antagonistas a fungos radiculares patógenos do feijoeiro, Rhizoctonia solani e Fusarium oxysporum f. sp. phaseoli. A abordagem dependente de cultivo permitiu recuperar 11 bactérias que apresentaram atividade antagônica in vitro contra os patógenos avaliados, os isolados bacterianos foram identificados como pertencentes aos gêneros Streptomyces, Kitasatospora, Alcaligenes, Achromobacter, Pseudomonas, Stenotrophomonas, Brevibacillus e Paenibacillus. A abordagem independente de cultivo revelou que a composição da comunidade microbiana na rizosfera do feijão selvagem Wild Mex foi caracterizada pela maior abundância relativa dos filos bacterianos Acidobacteria, Verrucomicrobia, Gemmatimonadetes, e do filo fúngico Glomeromycota quando comparada com a composição da rizosfera do genótipo cultivado IAC Alvorada, a qual foi constituída em maior proporção pelos filos bacterianos Firmicutes, Planctomycetes, Deinococcus-Thermus e pelo filo fúngico Ascomycota. No nível taxonômico de gênero, a comunidade microbiana da rizosfera do feijão selvagem Wild Mex apresentou maior frequência relativa de gêneros fixadores do nitrogênio, nitrificadores, antagonistas e promotores do crescimento vegetal. A rizosfera do feijão selvagem Wild Mex apresentou maior abundância relativa de funções relacionadas à fixação do nitrogênio, produção de sideróforos e de ácido indol acético (AIA), quando comparada com o genótipo cultivado IAC Alvorada. O padrão de distribuição observado na análise de ordenação das funções no microbioma da rizosfera do feijão selvagem Wild Mex foi diferente do padrão encontrado no bulk soil e na rizosfera do feijão cultivado IAC Alvorada. Os resultados indicaram que o genótipo selvagem é mais seletivo no recrutamento de micro-organismos e funções na rizosfera quando comparado com o cultivar moderno. Em conclusão, os resultados revelaram que o processo de domesticação e melhoramento genético das plantas cultivadas potencialmente debilitou a capacidade do hospedeiro em selecionar e sustentar micro-organismos e funções benéficas na rizosfera. / The process of domestication and subsequent plant breeding were key to support human population growth over the last decades. However, plant breeding has neglected the important role of the rhizosphere microbiome on plant performance. In this context, this research aimed the study of common bean rhizosphere microbiome in a wild and in a cultivated genotype to determine the composition and functionality of their microbial community. We tested the hypothesis that ancestor materials have higher ability to host beneficial microorganisms in the rhizosphere when compared to modern cultivars. The common bean genotype IAC Alvorada and wild common bean Wild Mex were grown in highly biodiverse soil (Amazonian Dark Earth - ADE) and the total DNA from bulk soil and each common bean rhizosphere was extracted for sequencing by using Illumina MiSeq platform. In addition, rhizosphere soil was also used to isolate and select antagonistic bacteria against soil borne pathogens Rhizoctonia solani and Fusarium oxysporum f. sp. phaseoli. Using cultivation-dependent approach, 11 bacteria were isolated and showed antagonistic in vitro activity against the evaluated pathogens. The bacterial isolates were identified belonging to Streptomyces, Kitasatospora, Alcaligenes, Achromobacter, Pseudomonas, Stenotrophomonas, Brevibacillus and Paenibacillus genus. The cultivation- independent approach revealed that microbial community composition in the Wild Mex bean rhizosphere was characterized by higher relative abundance of bacterial phyla Acidobacteria, Verrucomicrobia, Gemmatimonadetes and fungal phylum Glomeromycota when compared with IAC Alvorada cultivated bean, which showed a higher relative abundance of bacterial phyla Firmicutes, Planctomycetes, Deinococcus-Thermus and fungal phylum Ascomycota. Wild Mex rhizosphere microbiome showed higher relative frequency of nitrogenfixing, nitrifying, antagonists and plant growth promoting microorganisms. The wild bean also showed higher relative abundance of functions related to nitrogen fixation, siderophore and indole acetic acid (IAA) production, when compared with IAC Alvorada bean. The distribut ion pattern observed in the functions ordination analysis of Wild Mex was different from the bulk soil and IAC Alvorada patterns. The results showed that wild genotype is more selective for recruiting microorganisms and functions in the rhizosphere when compared with modern cultivar. In conclusion, the results revealed that domestication and plant breeding potentially undermined rhizosphere microbiome composition and functions debilitating the host\'s abilit y to select and support beneficial microbes.

Salt marshes provide a range of ecosystem services and yet are subjected to anthropogenic impacts that alter the biogeochemical processes underlying these services. In particular, human activities may modify salt marsh greenhouse gas (carbon dioxide, methane, nitrous oxide) emissions by changing plant and microbial communities, hydrological regime, and sediment chemistry. Quantifying the effects of human impacts on greenhouse gas emissions is important for complete carbon budgets, and for effective management of salt marshes and the ecosystem services they provide. In Chapters 1 and 2, I investigate the effects of hydrology and plant invasion on greenhouse gas emissions. First, I show how the restriction and restoration history of four salt marshes influence methane flux in unpredictable ways. Despite comparable salinity, methane emissions from one partially restored marsh were 25 times higher than unimpacted reference sites 13+ years after restoration, but emissions from other restored sites were equal or lower. Next, I show that greenhouse gas emissions associated with invasive Phragmites australis are not different from those associated with native Spartina alterniflora. These Chapters demonstrate the de-coupling of greenhouse gas emissions, and carbon sequestration more generally, from ecosystem degradation and restoration. In Chapters 3 and 4, I quantify greenhouse gas fluxes and microbial community structure under precipitation changes that may occur with global climate change. In a field experiment, doubled rainfall and drought had significant transient impacts on porewater salinity following storms, and on the community structure of plants (doubled rainfall) or microbes (drought), yet greenhouse gas fluxes and other biogeochemical processes were not affected. The absence of biogeochemical change indicates functional redundancy and resistance or resilience exist in the microbial community, suggesting marshes may continue providing services as precipitation changes. In a lab experiment, rewetting intact cores to simulate tidal inundation or rainstorms produced a nitrous oxide pulse 10-20x the baseline flux rates, without changing the microbial community. A model of rewetting event frequency suggests that pulsed emissions may be responsible for the majority of marsh nitrous oxide emission. Precipitation change may increase coastal nitrous oxide emission if it causes more or stronger storms, and thus more rewetting events.

O processo de domesticação e posterior melhoramento das plantas cultivadas foram essenciais para o sustento do crescimento populacional observado na recente história da humanidade. Porém, no processo de melhoramento das culturas não foi considerado o importante papel que o microbioma rizosférico desempenha nas plantas. Neste contexto, esta pesquisa foi direcionada ao estudo do microbioma rizosférico do feijoeiro, considerando um genótipo selvagem e outro cultivado, a fim de determinar a composição e funcionalidade do microbioma em cada rizosfera. Assim, para testar a hipótese de que materiais ancestrais têm maior capacidade de hospedar micro-organismos benéficos na rizosfera quando comparados a cultivares modernas, os genótipos de feijão cultivado IAC Alvorada e selvagem Wild Mex foram cultivados em Terra Preta da Amazônia (TPA), solo caracterizado por abrigar uma grande diversidade microbiana. O DNA total do solo rizosférico de cada genótipo de feijão e do bulk soil foi extraído para realizar o sequenciamento metagenômico usando a plataforma Illumina MiSeq. O solo rizosférico também foi usado para isolar e selecionar bactérias antagonistas a fungos radiculares patógenos do feijoeiro, Rhizoctonia solani e Fusarium oxysporum f. sp. phaseoli. A abordagem dependente de cultivo permitiu recuperar 11 bactérias que apresentaram atividade antagônica in vitro contra os patógenos avaliados, os isolados bacterianos foram identificados como pertencentes aos gêneros Streptomyces, Kitasatospora, Alcaligenes, Achromobacter, Pseudomonas, Stenotrophomonas, Brevibacillus e Paenibacillus. A abordagem independente de cultivo revelou que a composição da comunidade microbiana na rizosfera do feijão selvagem Wild Mex foi caracterizada pela maior abundância relativa dos filos bacterianos Acidobacteria, Verrucomicrobia, Gemmatimonadetes, e do filo fúngico Glomeromycota quando comparada com a composição da rizosfera do genótipo cultivado IAC Alvorada, a qual foi constituída em maior proporção pelos filos bacterianos Firmicutes, Planctomycetes, Deinococcus-Thermus e pelo filo fúngico Ascomycota. No nível taxonômico de gênero, a comunidade microbiana da rizosfera do feijão selvagem Wild Mex apresentou maior frequência relativa de gêneros fixadores do nitrogênio, nitrificadores, antagonistas e promotores do crescimento vegetal. A rizosfera do feijão selvagem Wild Mex apresentou maior abundância relativa de funções relacionadas à fixação do nitrogênio, produção de sideróforos e de ácido indol acético (AIA), quando comparada com o genótipo cultivado IAC Alvorada. O padrão de distribuição observado na análise de ordenação das funções no microbioma da rizosfera do feijão selvagem Wild Mex foi diferente do padrão encontrado no bulk soil e na rizosfera do feijão cultivado IAC Alvorada. Os resultados indicaram que o genótipo selvagem é mais seletivo no recrutamento de micro-organismos e funções na rizosfera quando comparado com o cultivar moderno. Em conclusão, os resultados revelaram que o processo de domesticação e melhoramento genético das plantas cultivadas potencialmente debilitou a capacidade do hospedeiro em selecionar e sustentar micro-organismos e funções benéficas na rizosfera. / The process of domestication and subsequent plant breeding were key to support human population growth over the last decades. However, plant breeding has neglected the important role of the rhizosphere microbiome on plant performance. In this context, this research aimed the study of common bean rhizosphere microbiome in a wild and in a cultivated genotype to determine the composition and functionality of their microbial community. We tested the hypothesis that ancestor materials have higher ability to host beneficial microorganisms in the rhizosphere when compared to modern cultivars. The common bean genotype IAC Alvorada and wild common bean Wild Mex were grown in highly biodiverse soil (Amazonian Dark Earth - ADE) and the total DNA from bulk soil and each common bean rhizosphere was extracted for sequencing by using Illumina MiSeq platform. In addition, rhizosphere soil was also used to isolate and select antagonistic bacteria against soil borne pathogens Rhizoctonia solani and Fusarium oxysporum f. sp. phaseoli. Using cultivation-dependent approach, 11 bacteria were isolated and showed antagonistic in vitro activity against the evaluated pathogens. The bacterial isolates were identified belonging to Streptomyces, Kitasatospora, Alcaligenes, Achromobacter, Pseudomonas, Stenotrophomonas, Brevibacillus and Paenibacillus genus. The cultivation- independent approach revealed that microbial community composition in the Wild Mex bean rhizosphere was characterized by higher relative abundance of bacterial phyla Acidobacteria, Verrucomicrobia, Gemmatimonadetes and fungal phylum Glomeromycota when compared with IAC Alvorada cultivated bean, which showed a higher relative abundance of bacterial phyla Firmicutes, Planctomycetes, Deinococcus-Thermus and fungal phylum Ascomycota. Wild Mex rhizosphere microbiome showed higher relative frequency of nitrogenfixing, nitrifying, antagonists and plant growth promoting microorganisms. The wild bean also showed higher relative abundance of functions related to nitrogen fixation, siderophore and indole acetic acid (IAA) production, when compared with IAC Alvorada bean. The distribut ion pattern observed in the functions ordination analysis of Wild Mex was different from the bulk soil and IAC Alvorada patterns. The results showed that wild genotype is more selective for recruiting microorganisms and functions in the rhizosphere when compared with modern cultivar. In conclusion, the results revealed that domestication and plant breeding potentially undermined rhizosphere microbiome composition and functions debilitating the host\'s abilit y to select and support beneficial microbes.

Carrion decomposition is an essential ecosystem function as it is an important component of nutrient cycling. Carrion decomposition has primarily been attributed to insect consumption, with little attention given to microbial communities or their potential interactions with insects. The first objective was to use passive insect-trapping methods to assess primary colonizer communities on swine carcasses between two treatments: 1) carrion with access to insects and 2) carrion excluded from insect access for five days using exclusion cages. Despite similarities between succession patterns within each treatment, carcasses initially exposed to insects had significantly fewer insect taxa. Therefore, collections of adult insect communities associated with carrion are promising as an indication of whether or not there has been a delay in insect colonization of a resource. There has yet to be a study documenting bacterial communities during carrion decomposition. The second objective was to describe bacterial community succession and composition during decomposition in the presence and absence of naturally occurring insects. Total genomic DNA was used to identify bacterial community composition via a modified bacterial tagged encoded FLX amplicon pyrosequencing. I obtained 378,904 sequences and documented distinct bacterial community successional trajectories associated with insect access and exclusion carcasses. By the fifth day of decomposition, Proteus was the dominant (72%) bacterial genus on exclusion carcasses while Psychrobacillus (58%) and Ignatzschineria (18%) were dominant bacterial genera on insect carcasses. These data are the first to document bacterial community composition and succession on carrion. My final objective was to assess microbial community function in response to carrion insect colonization using metabolic profiling. I characterized microbial community metabolic function in the presence and absence of the primary necrophagous insects. I documented significant microbial community metabolic profile changes during active decomposition of carcasses. Mean carcass microbial community metabolic function with insect access continuously decreased over decomposition during both field seasons. Thus demonstrating microbial metabolic activity may have discriminatory power to differentiate early and late stages of decomposition. Overall, my data contributes to an understudied area of microbial research important to organic matter decomposition, forensic entomology, and microbial-insect ecological interactions.

Human activities that disrupt soil properties are fundamentally changing ecosystems. Soil degradation decreases microbial abundance and activity, leading to changes in nutrient availability, soil organic matter, and plant growth and establishment. Land use and land cover change are widespread and increasing in semiarid regions of the southwestern US, which results in reductions of native plant and microbial abundance and community diversity. Here we studied the effects of soil degradation and amendments (biochar and woodchips) on microbial activity, soil carbon and nitrogen availability, and plant growth of ten semi-arid plants species native to the southwestern US. Results show that woodchip amendments result in poor overall plant growth, while biochar amended soils promoted plant growth when soil quality was reduced. Additionally, amendments had a strong influence on microbial activity, while the presence and species identity of plants did not. Biochar amended soils led to increases in the potential activities of enzymes involved in the degradation of carbon, nitrogen, and phosphorus rich substrates. Woodchips, caused an increase of potential activity in enzymes involved in the degradation of sugar and proteins. These results show that microbes and plants respond differently to soil treatments and suggest that microbial responses may function as earlier indicators of the success of re-vegetation attempts.

Antarctic glacier forfields are extreme environments and pioneer sites for ecological succession. The Antarctic continent shows microbial community development as a natural laboratory because of its special environment, geographic isolation and little anthropogenic influence. Increasing temperatures due to global warming lead to enhanced deglaciation processes in cold-affected habitats and new terrain is becoming exposed to soil formation and accessible for microbial colonisation. This study aims to understand the structure and development of glacier forefield bacterial communities, especially how soil parameters impact the microorganisms and how those are adapted to the extreme conditions of the habitat. To this effect, a combination of cultivation experiments, molecular, geophysical and geochemical analysis was applied to examine two glacier forfields of the Larsemann Hills, East Antarctica. Culture-independent molecular tools such as terminal restriction length polymorphism (T-RFLP), clone libraries and quantitative real-time PCR (qPCR) were used to determine bacterial diversity and distribution. Cultivation of yet unknown species was carried out to get insights in the physiology and adaptation of the microorganisms. Adaptation strategies of the microorganisms were studied by determining changes of the cell membrane phospholipid fatty acid (PLFA) inventory of an isolated bacterium in response to temperature and pH fluctuations and by measuring enzyme activity at low temperature in environmental soil samples. The two studied glacier forefields are extreme habitats characterised by low temperatures, low water availability and small oligotrophic nutrient pools and represent sites of different bacterial succession in relation to soil parameters. The investigated sites showed microbial succession at an early step of soil formation near the ice tongue in comparison to closely located but rather older and more developed soil from the forefield. At the early step the succession is influenced by a deglaciation-dependent areal shift of soil parameters followed by a variable and prevalently depth-related distribution of the soil parameters that is driven by the extreme Antarctic conditions. The dominant taxa in the glacier forefields are Actinobacteria, Acidobacteria, Proteobacteria, Bacteroidetes, Cyanobacteria and Chloroflexi. The connection of soil characteristics with bacterial community structure showed that soil parameter and soil formation along the glacier forefield influence the distribution of certain phyla. In the early step of succession the relative undifferentiated bacterial diversity reflects the undifferentiated soil development and has a high potential to shift according to past and present environmental conditions. With progressing development environmental constraints such as water or carbon limitation have a greater influence. Adapting the culturing conditions to the cold and oligotrophic environment, the number of culturable heterotrophic bacteria reached up to 108 colony forming units per gram soil and 148 isolates were obtained. Two new psychrotolerant bacteria, Herbaspirillum psychrotolerans PB1T and Chryseobacterium frigidisoli PB4T, were characterised in detail and described as novel species in the family of Oxalobacteraceae and Flavobacteriaceae, respectively. The isolates are able to grow at low temperatures tolerating temperature fluctuations and they are not specialised to a certain substrate, therefore they are well-adapted to the cold and oligotrophic environment. The adaptation strategies of the microorganisms were analysed in environmental samples and cultures focussing on extracellular enzyme activity at low temperature and PLFA analyses. Extracellular phosphatases (pH 11 and pH 6.5), β-glucosidase, invertase and urease activity were detected in the glacier forefield soils at low temperature (14°C) catalysing the conversion of various compounds providing necessary substrates and may further play a role in the soil formation and total carbon turnover of the habitat. The PLFA analysis of the newly isolated species C. frigidisoli showed that the cold-adapted strain develops different strategies to maintain the cell membrane function under changing environmental conditions by altering the PLFA inventory at different temperatures and pH values. A newly discovered fatty acid, which was not found in any other microorganism so far, significantly increased at decreasing temperature and low pH and thus plays an important role in the adaption of C. frigidisoli. This work gives insights into the diversity, distribution and adaptation mechanisms of microbial communities in oligotrophic cold-affected soils and shows that Antarctic glacier forefields are suitable model systems to study bacterial colonisation in connection to soil formation. / Gletschervorfelder der Antarktis stellen extreme Habitate dar und sind Pionierstandorte biologischer Sukzession. Insbesondere unter Berücksichtigung zuletzt beobachteter und vorausgesagter Erwärmungstrends in der Antarktis und der Relevanz der Mikroorganismen für das Antarktische Ökosystem, ist es essentiell mehr Informationen über die Entwicklung frisch exponierter Gletschervorfelder zu erlangen. Ziel dieser Studie ist es, die Struktur und Entwicklung bakterieller Gletschervorfeldgemeinschaften zu verstehen, insbesondere wie die Mikroorganismen von den Bodenparametern beeinflusst werden und wie diese sich an die extremen Bedingungen des Habitats anpassen. Für die Untersuchung der Proben von zwei Gletschervorfeldern aus den Larsemann Bergen der Ostantarktis diente eine Kombination aus Kultivierungsexperimenten und molekularen, geophysikalischen und geochemischen Analysen. Die untersuchten Gletschervorfelder sind durch extrem niedrige Temperaturen, einer geringen biologischen Wasserverfügbarkeit und oligotrophe Nährstoffgehalte charakterisiert und zeigen unterschiedliche Entwicklungsstufen in Verbindung zu den Bodenparametern. In einem frühen Schritt der Bodenbildung in der Nähe der Gletscherzunge sind die Gemeinschaften undifferenziert, doch mit fortschreitender Entwicklung nimmt de Einfluss von Wasser- und Nährstofflimitationen zu. Nachdem die Kultivierungsbedingungen den kalten und nährstoffarmen Bedingungen des Habitats angepasst wurden, konnten 108 koloniebildende Einheiten heterotropher Bakterien pro Gramm Boden angereichert und daraus 148 Isolate gewonnen werden. Zwei neue psychrotolerante Bakterien, Herbaspirillum psychrotolerans PB1T und Chryseobacterium frigidisoli PB4T, wurden detailiert charakterisiert und als jeweils neue Spezies beschrieben. Die Anpassungsstrategien der Mikroorganismen an die extremen antarktischen Bedingungen zeigten sich in der Aktivität extrazellulärer Enzyme bei niedriger Temperatur, die mit derer temperierter Habitate vergleichbar ist, und in der Fähigkeit der Mikroorganismen, die Fettsäurezusammensetzung der Zellmembran zu ändern. Eine neue Fettsäure, die bisher in keinen anderen Mikroorganismus gefunden wurde, spielt eine entscheidende Rolle in der Anpassung des neu-beschriebenen Bakteriums C. frigidisoli an niedrige Temperaturen und saure pH-Werte. Diese Arbeit gibt einen Einblick in die Vielfalt, Verteilung und Anpassung mikrobieller Gemeinschaften in nährstoffarmen und Kälte-beeinflussten Habitaten und zeigt, dass Antarktische Gletschervorfelder geeignete Modellsysteme, um bakterielle Besiedelung in Verbindung zu Bodenbildung zu untersuchen.

Thesis (Ph. D.)--Miami University, Dept. of Microbiology, 2004. / Title from second page of PDF document. Includes bibliographical references (p. 133-140).