Explore the vast range of titles available.

Laurens Baas Becking was a pioneer in the field of microbial ecology and the father of Geobiology. This is the first English translation of Baas Becking's Geobiologie: of Inleiding tot de Millieukunde published in Dutch in 1934. This book provides a fascinating view of how organisms have both adapted to and shaped their environment, from all types of settings ranging from lakes to the oceans, to acidic peats and salt ponds, drawing heavily on Baas Becking's own keen observations. Although written 80 years ago, Baas Becking's insights feel surprisingly modern and provide a unique insight into the fields of evolution of microbial ecology and geobiology. This book should appeal to anyone interested in microbial ecology, geobiology, biogeochemistry and the history of science. The translated text is accompanied by extensive footnotes and by an Editor's summary at the end of each chapter placing Baas Becking's writing in the context of modern developments in the field.

Nests and eggs represent the beginning of life for many vertebrates. Determining the nesting strategies of extant amniotes is crucial in elucidating the evolution and diversification of reproductive traits as nesting materials are poorly preserved in the fossil record. Avian and chelonian nests are particularly rare compared to non-avian dinosaurs.The goal of this dissertation is to investigate and describe the sedimentology, taphonomy, and ecology of two fossil nesting localities and examine modern eggshell porosity via micro-CT images. I characterized two nesting localities, one from the Late Cretaceous Kaiparowits Formation in Grand Staircase-Escalante National Monument outside of Escalante, Utah, the second in the Eocene Bridger Formation east of Lyman, Wyoming, in terms of sedimentology and stratigraphy and taphonomy. Eggshell from the Kaiparowits Formation is identified as testudine and unique characteristics of the shell unit height-to-width ratio, egg size, eggshell thickness, and ornamentation warrant the naming of a new ootaxa, Testudoolithus tuberi. The distribution of eggshell is interpreted as resulting from nest predation. The Bridger Formation eggshell material is similar since the distribution and preservation of half eggs is interpreted as being caused by predation. Both of the nesting localities are imbedded in greenish-gray mudstones overlying and under lithic sandstones, suggesting flood-plain deposition. The avian eggshell is named a new ootaxon as well, (Doolithus bridgerensis), from the number of observable ultrastructural layers.Micro-CT images of modern rigid-shelled amniotes, including birds, crocodylians, a tortoise, and a gecko, reveals a complex network of internal pores that do not connect to the external surface of the eggshell. The functional pores tend to be cylindrical to trumpet-shaped in birds and pear-shaped in the tortoise, but are bowl-shaped in the gecko, conical in the crocodylian genera Crocodylus and Osteolaemus, and globular in Melanosuchus niger. Eggs in open and closed nesting strategies have generally similar functional eggshell porosity ranges of 0.1-0.8% sample volume. However, covered nesters generally have higher total porosities of 2.9-16.1%. The internal porosity arises from the interstitial spaces between mineralized egg units. The functional value of the internal porosity is yet unknown, but may improve properties of shell insulation and retention of water vapor.

Autotrophic respiratory reduction using inorganic electron donors like hydrogen and sulfide is well established for certain groups of arsenic reducing bacteria. Here we report a novel strain of the genus Clostridium (strain IDSBR-1) which is able to grow under anoxic conditions by autotrophic respiration of Sb(V), thereby reducing it to form Sb(III)-bearing trioxide mineral phases using hydrogen as an chemolithotrophic electron donor. This organism is also able to grow as a heterotroph using organic electron donors. The bacterium can also respire arsenate and nitrate as terminal electron acceptors for hydrogen and lactate. Growth in pure culture via dissimilatory autotrophic and heterotrophic Sb(V) reduction was quantified by direct cell counting. This study provides the first direct evidence of bacterial growth via dissimilatory autotrophic respiration of Sb(V) and provides the potential for industrial and bioremediation applications and other environmental bacteria that reduce toxic aqueous Sb(V) to insoluble and immobile Sb(III) mineral phases.

In the Sichuan Basin and surrounding areas, the terminal Ediacaran Dengying Formation hosts diverse microbialite forms. Interest in this formation has mainly centered around oil and gas reservoir development, but recent research aims to characterize its paleobiology via petrographic and molecular fossil analysis. This study aims to characterize the paleobiology and diagenetic history of samples from the Moxi area (central basin), Micangshan Uplift (NW basin margin), and Dabashan thrust belt (N basin margin). Moxi samples are all core samples of Dengying Member 4. Michangshan and Dabashan samples are from outcrop; the Micangshan samples are from Dengying Member 3 and the Dabashan samples are from unknown members of the Dengying Formation and underlying the Doushantuo Formation. All samples were photographed using a petrographic microscope in plane-polarized light (transmitted and reflected), with crossed nicols and in blue-violet light. Hydrocarbon geochemistry and extractable biomarkers were isolated from outcrop samples and characterized. Microbialites in the core samples are mostly stromatolitic and occasionally thrombolitic in texture, while outcrop microbialites are oncolitic and thrombolitic. All samples show putative evidence of hydrothermal alteration and tectonic strain. Extractable biomarkers were limited to a low concentration of n-alkanes with an abnormal distribution of chain lengths. Kerogen geochemical data confirms the samples’ low amenability to biomarker extraction; the maximum hydrogen index (HI) is 51 for all Dengying samples and among the samples with acceptable total organic carbon (> 0.5%) the maximum HI is only 6. Based on mass spectra and free oil measurements, extracted hydrocarbons can be attributed to contamination. The Dengying Formation represents a microbially-dominated system that preserves no convincing evidence of eukaryotes, despite the presence of putative metazoans in nearby sections of the Doushantuo. Extraction of saturated alkanes produced poor yields in the outcrop samples and would likely not be feasible for the core samples based on petrographic analysis showing thermal and tectonic stress. Literature has drawn mixed conclusions about the Dengying Formation’s potential as a source of geologic biomarkers; this study provides more evidence that the Dengying is unlikely to yield any significant biomarker information.

Atmospheric aerosols (suspension of solid or liquid particles in the present in the atmosphere) can harbor a diverse array of airborne microorganisms and upon deposition into terrestrial or marine systems, airborne microbes can alter function and biogeochemical cycles of the receiving ecosystems. My work focuses on aerosols and their impact on marine environments. The three chapters in this thesis examine 1) the abundance and diversity of airborne microorganisms over the Mediterranean Sea, 2) the impacts of airborne microorganisms on the northern Red Sea surface water microbial diversity and function, and 3) the efficiency of three types of aerosol sampling instrumentation. In the first study, I described the abundance and genetic diversity of airborne bacteria in air samples collected over an East-West transect of the entire Mediterranean Sea and investigated 1) the controls on the diversity of airborne microbes, and 2) the source of the microbes comprising the aerosol microbiome over the Mediterranean Sea. The results show that airborne bacteria represent diverse groups with the most abundant bacteria from the Firmicutes (Bacilli and Clostridia) and Proteobacteria (Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria) phyla. Most of the bacteria in the samples have previously been observed in the air at other open ocean locations, in the air over the Mediterranean Sea during dust storms, and in surface water of the Mediterranean Sea. The results demonstrate that airborne bacterial diversity is positively correlated with the mineral dust content in the aerosols and the taxonomic composition differed between major basins of the Mediterranean Sea. In the second study, a mesocosm experiment was conducted to elucidate 1) how bioaerosols collected during dust-events impact prokaryotic and eukaryotic relative abundance in the northern Red Sea (NRS) surface water, and 2) how the changes in community structure affect biogeochemical cycles of the NRS. Results show that the airborne microorganisms and viruses suppressed primary production (as much as 50%), increased bacterial production (as much as 55%), and decreased the diversity of eukaryotes. These results suggest that airborne microorganisms have implications for the carbon cycle in low nutrient low chlorophyll marine ecosystems. The final chapter tests the efficiency of samples collected with three instruments (a membrane filtration device, a liquid impinger, and a portable electrostatic precipitator bioaerosol collector) for culture-dependent (colony-forming units) and culture-independent (DNA yield) studies. The results show that the electrostatic precipitator collected microorganisms significantly more efficiently than the membrane filtration and liquid impingement in both types of studies over the same time interval, primarily due to its higher flowrate.

Antimony (Sb) is a relatively unstudied heavy metal. To further our understanding of its fate and transport, we have set out to determine the fractionation of 121Sb and 123Sb during anaerobic respiration. We have conducted research to demonstrate that bacteria isolated from a hypersaline environment can use antimonite [Sb(V)] as a terminal electron acceptor for anaerobic respiration. We set out to determine if Sb fractionation occurs during this metabolism. Our preliminary results are not conclusive, but we believe that further research on isolate bacteria from Mono Lake will prove that Sb fractionation occurs during respiration.

Deep-sea vent and subsurface microorganisms are metabolically diverse and often display unique adaptive strategies that operate under elevated pressure conditions. However, because high hydrostatic pressure (HHP) laboratory cultivation has not been widely adopted, knowledge of how these microorganisms function in native high-pressure environments is limited. To explore how elevated pressures affect the metabolism and physiology of deep-sea and subsurface microorganisms, growth of a model extremophile, Archaeoglobus fulgidus (type strain VC16), was investigated up to 98 MPa in batch cultures for both chemoorganoheterotrophic and chemolithoautotrophic metabolisms. A. fulgidus is an anaerobic, hyperthermophilic sulfate reducing archaeon, first isolated from a shallow marine vent but has been commonly identified in high-pressure marine environments (to 2-4 km below sea level, 20-40 MPa), including deep-sea hydrothermal vents, deep geothermal wells, and deep oil reservoirs. In heterotrophic HHP cultivation experiments, exponential growth was observed up to 60 MPa. Cell densities were comparable from 0.1-40 MPa, while lower cell densities were observed at 50 MPa and 60 MPa and growth was inhibited at 70 MPa. A. fulgidus displayed both piezotolerance and moderate piezophily under certain heterotrophic HHP conditions. In autotrophic HHP conditions, A. fulgidus displayed piezotolerance with similar growth rates and maximum cell densities observed at up to 40 MPa and little to no growth was observed at 60 MPa. A. fulgidus biofilm production was observed in certain heterotrophic conditions from 0.1-50 MPa under HHP batch cultivation conditions due to both low calcium concentrations in the growth medium and the presence of a stainless steel needle that created a nucleation site. This suggests that biofilm production here was a response to growth medium chemistry and surface area, and was not related to the elevated pressure conditions. Here, A. fulgidus was shown to grow, and in some cases also produce biofilm, over a range of elevated pressure conditions. To the extent of our knowledge, piezotolerance to HHP for both heterotrophic and autotrophic metabolisms have not been previously measured for a single species. A. fulgidus’ metabolic plasticity and capacity for biofilm production reflects adaptive mechanisms that lend insight into how this species thrives in extreme and fluctuating environments.