Life Sciences Commons^™

Comparative Analysis Of Rhizosphere And Endosphere Microbiome Of Different Blueberry Species (Vaccinium Sp.), Niladri Bhowmik

Master's Theses

Blueberries are an important agricultural commodity in all over the United States. Due to its health benefits, there is a huge demand globally, thus expanding the industry. Breeding programs are essential to maintain such industries. Challenges that play a role in contemporary breeding programs are various biotic and abiotic stress factors. Studies have shown that microorganisms are recruited by plants to alleviate them during stressful conditions. Though blueberries have been cultivated for about 100 years, how the microbiome has been affected due to this is poorly understood. We hypothesized that interspecific crosses and artificial selection have significantly changed the microbiome …

Polycyclic Aromatic Hydrocarbons And The Microbiomes Of Two Benthic Species, Samantha Ells

Master's Theses

The presence of oil has been shown to affect the microbiomes of the water column, sediments, and organisms, both by altering the diversity and the composition of those microbial communities. If the microbiome is altered it may no longer provide benefits to its host organism, impacting its ability to survive. Thus, it is important to understand the effects of large-scale contamination events including the Deepwater Horizon oil spill. This study set out to examine the effects of oil exposure on the microbiome of two benthic species, southern flounder (Paralichthys lethostigma) and eastern oysters (Crassostrea virginica) to further understand the effects …

How Historic Shipwrecks Influence Dispersal Of Deep-Sea Microbiomes, Rachel Moseley

Master's Theses

This thesis investigates how historic shipwrecks potentially shape dispersal of deep-sea microbiomes. Processes impacting dispersal of microbiomes around artificial structures in the ocean and how they connect to other deep-sea habitats is unknown. Dispersal processes are explained for some macroorganisms by theories in ecology, specifically the Theory of Island Biogeography and the Wooden Stepping Stone hypothesis. These have not been investigated for microorganisms, and thus this work will probe if they are applicable to microbial biogeography in this habitat. Experiments were conducted to establish new “island-like” features in near proximity (25-125 m) to wooden-hulled historic shipwrecks in the northern Gulf …

Microplastic Abundance, Distribution And Impacts On Sargassum-Associated Juvenile Fishes In The Gulf Of Mexico, Olivia Lestrade

Master's Theses

Microplastics are a concern in marine environments because they are highly durable, ubiquitous, and can be mistaken for food and ingested by small organisms. Pelagic Sargassum, an important habitat for larval and juvenile stages of many fish species, is found in large surface aggregations, and may provide complex structure in which microplastics become trapped. This could lead to greater risk of microplastic ingestion by fish early life stages associated with Sargassum habitats. To better understand the impacts of microplastics within Sargassum communities, this study examined 1) microplastic concentrations and ingestion by juvenile fishes associated with Sargassum; 2) the microbial …

Elucidating The Molecular Pathways Involved In The Fitness And Water Stress Response Of Pseudomonas Synxantha 2-79 In The Plant Rhizosphere, Clint Henry D. Pablo

Master's Theses

Pseudomonas synxantha 2-79 is a biocontrol agent that represents beneficial indigenous rhizobacteria that are broadly distributed in the Pacific Northwest, USA and flourish in the rhizosphere of commercially grown wheat under surprisingly arid conditions. The molecular adaptation of 2-79-like bacteria to plants growing in dry soils is poorly understood. We hypothesized that the ability of 2-79 to colonize and persist in the rhizosphere of water-stressed plants is underpinned by the formation of hydrating biofilms and the utilization of root exudates that contain plant-derived osmoprotectants called quaternary ammonium compounds (QACs). We tested this hypothesis by identifying waters stress response pathways in …

Development Of An Attenuated Zika Virus By Editing The 5’ Untranslated Region, E. Ashley Thompson

Master's Theses

Zika Virus (ZIKV) is a mosquito-transmitted flavivirus that usually causes no symptoms to mild febrile in humans, and it has been regarded as an insignificant pathogen to public health. However, recent outbreaks of ZIKV infection have revealed that ZIKV can cause severe neurological effects in adults, such as Guillain-Barre Syndrome (GBS), and in infants whose mothers acquired the virus during pregnancy, causing Congenital Zika Syndrome (CZS). Currently, no approved vaccine is available and there is a critical need to develop an effective and safe vaccine. While most vaccine developmental strategies target the viral prM-E protein of ZIKV, we aimed to …

The Thiol Specific Antioxidant (Tsa1) Gene Is Required For Survival In Macrophages And Oxidative Stress Resistance In Histoplasma Capsulatum, Lauren Kennedy

Master's Theses

Histoplasma capsulatum(Hc) is a pathogenic fungus that causes one of the most common invasive fungal respiratory diseases, Histoplasmosis. Histoplasmaundergoes a dimorphic shift from mold to yeast which is crucial to pathogenesis of the organism.

The thiol specific antioxidant gene, Tsa1,is strongly upregulated in the yeast (pathogenic) morphotype. This data led to the hypothesis that this gene plays a role in protecting Hcfrom host mediated oxidative attack. To characterize Tsa1 function, a knockdown strain (tsa1-RNAi) was created by RNAi gene silencing. Expression of Tsa1in the tsa1-RNAistrain was reduced to 10% that …

The Effect Of Historic Shipwrecks On Sediment Microbiomes In The Northern Gulf Of Mexico, Melissa Brock

Master's Theses

Microorganisms are ubiquitously distributed across all aquatic habitats, but it is the environmental conditions of a habitat that determine which microorganisms can thrive in terms of abundance or metabolic activity. Habitats that experience consistent physical and chemical environmental conditions repeatedly favor specific taxonomic groups which may result in a microbial assemblage that is commonly associated with that habitat (i.e., a core microbiome). Core microbiomes have been identified for a variety of natural marine habitats including methane seeps, wood falls, octocoral, and deep-sea sediments. However, it was unknown if the presence of man-made structures on the seafloor, including historic shipwrecks, also …

The Evolutionary Diversity And Biological Function Of Phenazine Metabolite Biosynthesis In Burkholderia Spp, Samuel Hendry

Master's Theses

Burkholderia encompass a group of ubiquitous Gram-negative bacteria that include numerous saprophytes, as well as several species that cause infections in animals, immunocompromised patients, and plants. Some species of Burkholderia produce colored redox-active secondary metabolites called phenazines (Phz). In the model opportunistic pathogen Pseudomonas aeruginosa, phenazines strongly contribute to the competitiveness, formation of biofilms, and virulence in multiple models of infection. Similar depth of knowledge on the diversity, biosynthesis, and biological functions of phenazines in Burkholderiais missing. This project aimed to bridge this gap in knowledge by focusing on phenazine pathways of B. lata and closely related …

The Role And Contribution Of Saprotrophic Fungi During Standing Litter Decomposition Of Two Perennial Grass Species, Schizachyrium Scoparium And Schizachyrium Tenerum, Matthew Lodato

Master's Theses

In terrestrial ecosystems, most of the plant biomass produced enters the detrital pool, where microbial decomposers colonize, enzymatically degrade, and assimilate plant litter carbon and nutrients in amounts sufficient to bring about the decomposition of plant litter. Here, I estimated the biomass and production of fungi and microbial respiration associated with decaying Schizachyrium scoparium and Schizachyrium tenerum leaf litter, and constructed a partial organic matter budget estimating C flow into and through fungal decomposers. Significant losses in S. scoparium (57%) and S. tenerum (68%) leaf mass was observed during litter decomposition along with concomitant increases in fungal biomass, which reached …

Detection, Activity Measurement And Phylogeny Of Ureolytic Bacteria Isolated From Elasmobranch Tissue, Yimu Yang

Master's Theses

Free-ranging marine elasmobranch tissue-associated micro-organisms were cultured from free-ranging Atlantic stingray (Dasyatis sabina) and Atlantic sharpnose sharks (Rhizoprionodon terraenovae). 16S rRNA gene phylogeny indicated bacteria community structure in both elasmobranchs were under phylum Proteobacteria, Firmicutes and Actinobacteria. By conducting split-plot ANOVA, we found the microbial richness is significantly different (P=0.0814) between two superorders of elasmobranch, which may largely due to their preferred habitats and feeding habits. Urease presentence and activity was detected in phylogenetically diverse bacterial strains. Species with high urea-hydrolyzing ability, such as Micrococcus luteus (shark blood isolate: 46.84 mU/mg protein; stingray blood isolate: 24.36 …

The Elasmobranch-Microbe Relationship: Trimethylamine N-Oxide Synthesis, Urea Hydrolysis, And Microbe-Osmolyte Interactions In The Atlantic Stingray, Dasyatis Sabina, Kaitlin Kelly Doucette

Master's Theses

The elasmobranch osmoregulatory strategy is predicated on the accumulation of nitrogenous compounds, primarily urea and trimethylamine n¬-oxide (TMAO). Despite the abundance of these plasma osmolytes, it is notable that elasmobranchs appear to lack urease and TMA oxidase (Tmase), enzymes that scavenge urea-nitrogen and synthesize TMAO, respectively. However, urease and Tmase are found in many species of bacteria. Therefore, I hypothesized that intestinal bacteria are responsible for urease and Tmase activity in elasmobranchs. Absent dietary nitrogen sources, I evaluated the effects of reduced intestinal microbiota on osmoregulation in Atlantic stingray (Dasyatis sabina) in vivo. D. sabina were given …

Fecal Bacterial Communities As An Indicator Of Trophic Interactions Among Anuran Larvae, Steven Jacob Everman

Master's Theses

Anurans are mass spawners, often with multiple females spawning together, resulting in thousands of tadpoles sharing a habitat. Such large numbers of tadpoles with limited dispersal can lead to intense competition for resources. Inter and intra-specific competition for food could have negative impacts on the growth and survival of smaller tadpoles. Fecal bacterial communities have the potential to be used as indicators of changes in diet making it possible to determine if tadpoles in the wild are eating the same food or not. After feeding on two prepared diets that differed in the percentage of complex carbohydrates, the fecal bacterial …

Stressed Induced Changes In Karenia Brevis Ribosomal Rna, David Scott Jayroe

Master's Theses

Karenia brevis is a toxic marine dinoflagellate that causes harmful algal blooms (HABs), also known as red tides, in the Gulf of Mexico. These blooms are responsible for massive fish kills, shellfish bed contaminations, adverse human health effects, and vast economic loss. For these reasons, extensive research has gone into understanding the mechanisms and dynamics of bloom behavior by studying K. brevis in the field and in the lab. In order to understand higher order bloom behavior and dynamics it is imperative to understand K. brevis at the cellular level. In growing K. brevis in vitro under a variety of …

Impacts Of The Deepwater Horizon Oil Spill On Microbial-Mediated Cellulose Decomposition In Mississippi Gulf Coast Salt Marshes, Jerrid Shawn Boyette

Master's Theses

Field studies were conducted to examine the effects of the Deepwater Horizon oil spill on rates of marsh organic matter decomposition. Decomposition in surface and subsurface marsh sediments was assessed in stands of Spartina alterniflora and Juncus roemerianus in 9 Mississippi Gulf Coast marshes exposed to differing oiling intensities. The cotton strip bioassay technique was used as a proxy for cellulose decomposition. In addition, rates of microbial respiration, fungal biomass (ergosterol) and nutrients (C:N, C:P) of surface sediment cotton strips were also quantified. Subsurface cotton strip decay, as determined by losses in tensile strength, were significantly different among marsh …

Characterizing The Persistence Of Sewage Enterococci In Mississippi Coastal Waters, Kimberly Anne-Marie Lewis

Master's Theses

Enterococci are microbiological indicators of marine recreation water quality.
Their reliability as fecal indicators is questioned as they are shown to persist in the environment. Multiple laboratory studies on their persistence have been done but few under natural environmental conditions. The purpose of this study was to investigate how long sewage enterococci and enterococcal DNA persist in beach water and to determine whether there is a difference in the genetic diversity and hardiness of sewage vs. environmental isolates. To study persistence, sewage was diluted with beach water, placed in microcosms, and deployed at a beach site in Longbeach and Pass …

Molecular Detection Of Tick-Borne Pathogens Associated With Ixodid Tick Species Infesting Migratory Songbirds And Ruminants, Nabanita Mukherjee

Master's Theses

Ticks are hematophagous arthropods and capable of inoculating various infectious agents to their vertebrate hosts. Ticks attached to birds and ruminants are capable of carrying tick-transmitted microorganisms. In our study, the prevalence of tick-borne pathogens was examined in ticks infesting migratory songbirds and Pakistani ruminants. During spring migration seasons, ticks were removed from northward-migrating songbirds in Louisiana and identified as Amblyomma Jongirostre, Amblyomma nodosum, Amb/yomma ca/caratum, Amblyomma maculatum, and Haemaphysalis species, all are considered as Neotropical ticks. Ticks removed from ruminants were identified as Hya/omma anatolicum, Hyalomma dromedarii, Rhipicephalus microplus, and Rhipicephalus sanguineus. A total of 112 and 72 bacterial …