Microbiology Commons^™

Incomplete Denitrification In Thermus Species, Chrisabelle Mefferd

UNLV Theses, Dissertations, Professional Papers, and Capstones

Members the bacterial genus Thermus have been shown to be incomplete denitrifiers, terminating with nitrite or nitrous oxide (N2O). However, the ability to carry out denitrification and the evolution of nitrogen oxide reductase genes in Thermus remains poorly understood. This study tests the hypothesis that incomplete denitrification is common in Thermus and seeks to uncover patterns in the evolution of denitrification pathways in Thermus. Denitrification capacity was determined in a collection of 25 strains representing ten species of Thermus and phylogenetic analysis was performed to determine whether denitrification genes evolved horizontally in Thermus. No strains in this study reduced nitrate …

Natural And Lignocellulose-Enriched Microbial Communities In Great Boiling Spring, Nv, Jessica Cole

UNLV Theses, Dissertations, Professional Papers, and Capstones

The natural microbial communities present in Great Boiling Spring were investigated and contrasted against those present after in situ enrichment with lignocellulose. High-throughput cultivation-independent DNA sequencing of the V8 region of the small subunit (SSU) rRNA gene generated a total of 274,119 quality-filtered pyrosequencing fragments. Twelve natural spring samples were analyzed, including four high-temperature water samples and eight sediment samples ranging from 87 - 62 °C. Eight lignocellulosic enrichments incubated in the spring sediment and water at two high-temperature sites were analyzed. The natural water communities were found to be extremely uneven but relatively constant throughout time. The natural sediment …

Nitrite Oxidation In Geothermal Springs: Evidence Of An Upper Temperature Limit For Thermophilic Nitrite-Oxidizing Bacteria Of 60 - 65 °C, Tara Edwards

UNLV Theses, Dissertations, Professional Papers, and Capstones

Despite growing evidence of the importance of nitrification in terrestrial geothermal environments, little is known about nitrite oxidation in these environments. In order to further our knowledge, this study combined cultivation-dependent and -independent approaches with measurements of nitrogen speciation along the outflow channels of two Great Basin geothermal springs. Enrichment cultures were inoculated with sediment slurries from sites ranging in temperature from 42 - 87 °C at the sources and along the outflows of >15 hot springs. While attempts to enrich nitrite-oxidizing bacteria (NOB) from sites greater than or equal to 61 °C were unsuccessful, NOB were enriched from five …

Survey Of Glycerol Dialkyl Glycerol Tetraethers (Gdgts) In Nevada And California Hot Springs And Selected T Thermophiles, Julienne J. Paraiso, Amanda Jean Williams, Brian P. Hedlund, Chuanlun L. Zhang

McNair Poster Presentations

Glycerol dialkyl glycerol tetraethers (GDGTs) are core membrane lipids of many Archaea and some Bacteria found ubiquitously in soils and in many aqueous environments. Here, we examined the GDGT concentration in forty sediment samples from geothermal hot springs in the Great Basin (USA). Sediment samples were collected in tandem with extensive geochemical and site characterization. Hot spring temperatures ranged from 31 to 95°C and pH values from 6.8 to 10.7. Parametric Pearson's correlation coefficients and nonparametric Spearman's rho values were calculated to identify significant correlations between GDGT profiles and geochemical analytes. Isoprenoidal GDGTs (iGDGTs) negatively correlated with pH and positively …

Exploring Diversity Of Nitrate Reducing Thermophiles In Nevada Hot Springs, Jenny Lam, Jeremy A. Dodsworth, Brian P. Hedlund

Undergraduate Research Opportunities Program (UROP)

High rates of denitrification have been measured in Nevada geothermal hot springs, but little is known about the thermophiles that contribute to this activity. We hypothesize that heterotrophic bacteria in the genus Thermus are the most important denitrifiers in the springs. Alternatively, other microorganisms including chemolithotrophs may also be important. To test these hypotheses, several different strategies will be used to try to enrich and isolate nitrate-reducing microorganisms. Isolates will be identified by 16S rRNA gene PCR and sequencing. Subsequently, representative isolates will be chosen for nitrate reductase gene (narG) sequencing and for studies on the kinetics of nitrate reduction …

Characterization Of Aerobic Respiration In Great Basin Hot Springs, Caitlin N. Murphy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Despite a wide diversity of possible electron donors available to fuel chemolithotrophy, it has been proposed that hydrogen is the single most important electron donor in geothermal ecosystems. To directly test this hypothesis, a simple system was devised to determine whether microorganisms in hot spring water and sediment are capable of using hydrogen and other electron donors for aerobic respiration using microrespirometry. The protocol for these experiments was developed using pure cultures of Thermocrinis ruber to determine the effect of growth conditions on the rate of oxygen consumption following the addition of electron donors. For field experiments, samples were collected …

Microbial Nitrogen Cycling In Nevada Geothermal Springs, Mitchell G. Chaires, Jeremy A. Dodsworth, Brian P. Hedlund

Undergraduate Research Opportunities Program (UROP)

Hot spring habitats above maximum photosynthetic temperature (73 ºC) are not well understood with respect to nitrogen (N) cycling. Few predictions have been made, and even fewer measurements of in situ activities have been reported. Thermodynamic calculations based on in situ chemical and temperature measurements will be used to predict the occurrence of the specific N-cycling reactions. In addition, these measurements in two springs will aid in an attempt to cultivate ammonia oxidizing species.

Denitrification In Great Basin Hot Springs, Austin Mcdonald, Brian P. Hedlund

Undergraduate Research Opportunities Program (UROP)

Hydrogen has been proposed to fuel primary production in the Aquificae dominated hot springs of Yellowstone National Park (Spear, et al. 2005), a finding the authors generalized to all hot springs. However, clone libraries derived from Great Basin springs contain few 16S ribosomal RNA (rRNA) gene sequences from Aquificae and many from unknown microorganisms. In the same springs, alternative electron donors rival the reducing power of hydrogen. This project will try to cultivate the uncharacterized microbes of two Great Basin springs and determine which electron donors they can use.

Nitrogen is key to life. In its reduced form, ammonia, it …

Genomic Foundations Of Carbon Fixation In Bacteria Living In Hot Springs, Rachel K. Skinner, Brian P. Hedlund, Jeremy A. Dodsworth

Undergraduate Research Opportunities Program (UROP)

Photosynthesis does not occur above 73°C, so organisms living above this temperature must obtain useable carbon by some other mechanism. It is generally assumed that carbon is fixed by thermophiles through the process of chemolithoautotrophy; however, primary production has never been demonstrated to occur in hot springs >73°C. We have shown that two organisms, Thermocrinis and Pyrobaculum, make up more than 90% of the cells in an 80°C Great Basin hot spring, Great Boiling Spring. We hypothesize that these organisms fix carbon in the hot spring via the reverse tricarboxylic acid (rTCA) cycle. To test this hypothesis we will: i) …