The discovery of deep-sea hydrothermal vents in 1977 revealed an ecosystem supported by chemosynthesis with a rich diversity of invertebrates, Archaea and Bacteria. While the invertebrate vent communities are largely composed of endemic species and exist in different biogeographical provinces, the possible factors influencing the distribution patterns of free-living Archaea and Bacteria are still being explored. In particular, how differences in the geologic setting of vent fields influence microbial communities and populations associated with active vent deposits remains largely unknown. The overall goal of the studies presented in this dissertation was to examine the links between the geologic setting of hydrothermal vent fields and microorganisms associated with actively venting mineral deposits at two levels of biological organization. At the community level, bar-coded pyrosequencing of a segment of the archaeal and bacterial 16S rRNA gene was employed to characterize and compare the microbial communities associated with numerous deposits from several geochemically different vent fields. Results from these studies suggest that factors influencing end-member fluid chemistry, such as host-rock composition and degassing of magmatic volatiles, help to structure the microbial communities at the vent field scale. At the population level, targeted cultivation-dependent and -independent studies were conducted in order to expand our understanding of thermoacidophily in diverse hydrothermal environments. Results of these studies expanded the phylogenetic and physiological diversity of thermoacidophiles in deep-sea vent environments and provided clues to factors that are influencing the biogeography of an important thermoacidophilic archaeal lineage. Overall, these studies have increased our understanding of the interplay between geologic processes and microorganisms in deep-sea hydrothermal environments.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nutrition and Food Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 370-377. / by James Chi-Yung Leung. / Ph.D.

The purpose of the present work was three-fold: (1) to determine the number of microorganisms found in root beer ready for consumer used, (2) to study the effects of various temperatures and durations of incubation on this microbial population, and (3) to characterize the predominant species of contaminating bacteria.

No description available.

Both in-situ and ex-situ giant pandas (Ailuropoda melanoleuca), display shifts in bamboo species and part preference throughout the year. The effects of this shifting preference on gastrointestinal (GIT) microbiota were observed using traditional culturing methods to characterize normal GIT microflora from fecal samples and behavioral feeding data of adult male and female pandas over a fourteen-month period. Linear and quadratic fits were used to determine any significant relationships between the time of year and part preference on the GIT microflora (P<0.05). Significant values for time of year were observed with the linear fit in total aerobes (P-value=0.0368), streptococci (P-value=0.0120), and lactobacilli (P-value=0.0166) and quadratic fits in streptococci (P-value=0.0382) and Bacteroides spp. (P-value=0.0134) at á=0.05. Significant linear relationships were observed with part preference and lactobacilli and Bacteroides spp., P-values of 0.0028 and 0.0030, respectively, indicating that part preference and time of year may affect the flux of panda GIT microflora.

No description available.

The lethal effect of ultraviolet (UV) light on microorganisms is well known and many studies have been undertaken into the effects of UV induced damage. Most of this work has been experimental; by comparison relatively little theoretical work has been undertaken to analyse the kinetics of the UV inactivation process, or to develop quantitative methodologies to support the experimental work. This paper presents a new and simple model for quantifying the photolysis rate. A theoretical study is also presented in this paper which quantifies photolysis rates for E. coli O26 and E. coli O157:H7. This study uses experimental data collected by Tosa and Hirata, and reveals the photolysis rate for E. coil O26 during the UV irradiation process to be 4.69 x 10(-3) m2 J(-1). By comparison, E. coli O157:H7 is much more susceptible to UV induced damage than E. coli O26, having a photolysis constant of only 2.09 x 10(-3) m2 J(-1).

This work represents a study on the biological oxidation of molybdenite, MoS2. The principal objective of this study was to investigate the possibility of the biological oxidation of molybdenite, to determine the physical and chemical conditions under which the oxidative process occurs, and to develop a strain of bacteria or alter the activity of the microorganisms by acclimatization to increase their activity on sulfide minerals, in particular molybdenite. Minerals used in this study were pyrite (FeS2), chalcopyrite (CuFeS2), molybdenite concentrate, and molybdenite ore. The microorganisms used in this investigation were autotrophic bacteria obtained from the leaching streams of Bingham Canyon, Utah. The apparatus consisted of sixty-four airlift percolators containing Ottawa sand (SiO2) as a dispersing medium for the finely divided sulfide minerals. The studies were perfomed by inoculating the solutions in the percolators with active cultures and comparing the amount of soluble molybdenum and other desired components produced with the amount found in a controlled sample. The effect of the following ions in the nutrient requirements: phosphate, ferrous iron, cupric copper, and aluminum on the molybdenite oxidative process were studied. The result of mixing pyrite and chalcopyrite with molybdenite concentrate for oxidation was also determined. The effect of the molybdate ion and phosphate ion concentrations were determined on the biological oxidation of pyrite. Studies were performed on the biological oxidation of molybdenite ore and molybdenite ore mixed with pyrite to determine the percentage molybdenum solublized, also the relative oxidation states or the solublized molybdenum. The effect of repeated bacterial transfer and molybdenite ore particle size was determined upon the biological oxidation. There were no components found in the Bingham Canyon streams that would precipitate the molybdate ion. Although these results were obtained from a synthetic media under laboratory conditions, they have provided conclusive evidence that it is possible to oxidize molybdenite by the aid of soil microorganisms.

<p> The thickening and classifying characteristics of small size hydrocyclones were investigatedo Test slurries, consisting of mixed cultures of microorganisms in water. were partitioned into two fractions by hydrocyclones ranginq in size from 2 mm to 10 mm body diameter which operated at inlet pressures ranging from 80 to 200 psi and volume splits ranginq from 1.0 to 3.0. </p> <p> The classtfyino response was defined in terms of the relative magnitudes of the specific growth rate of the two fractions as determined by coincident observation of duplicate batch biological reactors each seeded with one portion of the partitioned slurry. </p> <p> The thickening response was defined by the Rietema-Tenbergen separation efficiency. </p> <p> The biokinetic aspects of this investigation are emphasized in this manuscript. </p> / Thesis / Master of Engineering (MEngr)

This study investigates if the area around Kiruna, Northern Sweden has experienced large shifts in weather conditions and whether these have affected organism abundances. With a significant increase in global temperature and an increase in average temperature of 1.9 °C in Sweden during the last 130 years, it is crucial to understand the effect of climate change on organisms. The Swedish Defense Research Agency deployed an air filter station to monitor radioactive fallout. The archived filters allowed for the creation of a high-resolution time series of organism composition ranging from 1974 to 2008, based on DNA sequencing. The organisms were clustered into 17 distinct clusters based on their similarities in time series patterns.  This study found that Cluster 2 (plant pathogenic bacteria), Cluster 3 (wetland microorganisms) and Cluster 5 (planktonic bacteria) exhibited changepoint correlations with relevant climate variables. Plotting the 3 clusters and their relevant climate variables revealed that sea surface temperatures have a positive influence on the abundance of both Cluster 2 and 5. Frost change days negatively influenced Cluster 2. Dry spells positively influenced Cluster3 and 5. Additionally, the results suggest that air pressure and water deficiency in soil are predictors for Cluster 5. Overall, these findings provide insights into how climate change affects different organisms and can help inform future management decisions for these ecosystems.