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Undergraduate Research Opportunities Program

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Using Polymorphic Microsatellites to Determine the Population Genetics of Vespula maculifrons

(Georgia Institute of Technology, 2019-12) Thompson, Veronica

Social insects have an interesting genetic history and are studied in order to discern how their social behaviors affects their genetic makeup. The eastern yellowjacket Vespula maculifrons is one such species whose altruistic behaviors and caste system should negatively affect their genetic diversity but instead has fluorished for many years as a dominant species in their ecosystem. We investigated whether V. maculifrons follows the pattern of other social insects in having a small genetic diversity and therefore, a small effective population size. We sequenced seventeen polymorphic microsatellites of V. maculifrons of three different years that were chosen in accordance to the temporal method. We performed a Fixation Index test on the data with the three years as subpopulations in order to determine the differences in allele frequency amongst the groups over time. This was done in order to support our theory that V. maculifrons has a low amount of genetic diversity, which correlates to low amounts of allele fixation, and therefore a low effective population size. We found that the fixation index was significantly low, which supported this idea that not many alleles have gone to fixation. This would indicate that the effective population size is low because the population is still affected by genetic drift. In the future, a concrete calculation of the effective population size will be performed with combinations of multiple equations that can account for the many unique social traits of Vespula maculifrons. This will then help in order to add more information to the gap of knowledge on the fascinating genetic makeup of these unique social organisms.
Testing how methods impact the results of interspecific competition research

(Georgia Institute of Technology, 2019-12) Woo, Esther

There are currently two methods that can be used to measure interspecific competition, pairwise and mutual invasion. Both can be used to generate niche difference (ND) and relative fitness difference (RFD) values, as well as determine if two species are able to coexist. Although the newer method, mutual invasion, has been in use for eight years, there has not yet been a study that compares the two. In order to determine if the method impacts the results found in a study, two simple experiments were conducted concurrently. The five-week long experiment involved determining whether Colpidium striatum and Tetrahymena pyriformis are able to coexist. Upon completion, both methods concluded that they could coexist. Despite reaching the same conclusion, it is still unknown if other species pairings or more complex experiments would alter these results.
Development of a Wireless, Commercial Electromyography System for Use in Athletics and Physical Therapy

(Georgia Institute of Technology, 2019-12) Brooksher, Riley

Electromyography is a muscle activity recording technique that is not often used in a clinical setting due to difficulties in reproducibility. In this paper I aim to create a wireless, wearable system for electromyography. This system is built into a pair of compression shorts, and sends both electromyography and positional data from inertial measurement units to users’ mobile devices. This system is primarily useful in physical therapy and athletic fields, as quantitative information on user gait can improve in the healing and training processes.
Effects of Acute and Chronic Inflammation on Vasopressin Expression in the Paraventricular Nucleus of the Hypothalamus

(Georgia Institute of Technology, 2019-12) Patel, Shivany

Inflammation can lead to a suite of behavioral changes known as sickness behaviors, which have been implicated in the etiology of chronic inflammatory disease. Here, we examine the role of acute and chronic induction of inflammation on vasopressin (AVP) expression in the paraventricular nucleus of the hypothalamus (PVN) of female mice. To test, adult female C57B6/J mice were injected with lipopolysaccharide (LPS) at two different dosages and schedules to induce acute (1.0mg/kg, once) and chronic (0.25mg/kg LPS, eight times) inflammatory responses. The acute dose has previously been demonstrated to induce sickness behaviors, as measured by the open field test and a social interaction test; however, these measures were unaffected by the chronic administration of LPS. AVP mRNA expression in the PVN was measured using fluorescent in situ hybridization (FISH) and fluorescent microscopy. Both the acute and chronic administration of LPS resulted in an increase in PVN AVP expression without a change in the area of this expression. This increase in AVP in the PVN occurred despite the lack of sickness behavior, suggesting that further work is necessary to characterize the role of AVP in the PVN in these chronic and acute inflammatory responses.
How Cognitive Load Difficulty Affects Cognitive Mapping and Individual Differences in Navigation

(Georgia Institute of Technology, 2019-12) Churaman, Tanya

In order to study the effects of varying the levels of cognitive load and individual differences upon cognitive mapping, forty-eight young adults participated in this virtual navigation study. To compare different levels of cognitive load, half of the participants trained in an Abstract Virtual Environment (low cognitive load) while the other half trained in a Realistic Virtual Environment (high cognitive load). After the training, participants were exposed to a series of navigational and pointing tasks to analyze the effects of the training environments – the different levels of cognitive load. It was observed that Abstraction was beneficial to participants in the training phase for the pointing task. In addition, in the testing phase, there was a noticeable trend of Abstraction also being beneficial for some of the pointing and navigational tasks. However, in one of the navigational tasks in the testing phase, Abstraction was shown to be more beneficial to those with a high spatial working memory. Thus, a lower cognitive load via Abstraction can be beneficial to navigation and creating a cognitive map. Further research should be conducted in which varying levels of Abstraction (cognitive load) is combined with other visual design elements, such as Translucency, in order to analyze if a conjunction of other variables alongside with cognitive load could potentially increase spatial abilities in individuals.
Neural Activation During Dual-task Processing with Simultaneous Stimulus Presentation

(Georgia Institute of Technology, 2019-08) Alfonso, Juliana

Despite extensive literature regarding response time cost in dual-task processing, the predominant procedures do not isolate task-processing from stimulus processing. The purpose of this study was to investigate the neural correlates of motor learning and dual-task processing using a procedure in which stimulus processing was held constant. Participants learned to make bimanual or unimanual hand responses to indicate the individual or associated pairs of stimuli in two types of tasks. In the independent task (two-set task), participants made a response with the left hand corresponding to the left image shown on the screen and a response with the right hand based on the right image, simultaneously. In the relational task (one-set task), the individuals respond with button-presses to the pair of images shown. Subjects performed an equal number of trials per condition and neural activation during each trial was recorded using fMRI. Preliminary behavioral results showed that there was a significant interaction between task condition and response type, as well as a greater response time-cost for bimanual responses in the independent condition. Imaging analysis suggests significantly greater neural activation in the inferior frontal sulcus (IFS) during the independent task (p<0.01). These preliminary results seem to support the behavioral findings of Schumacher et al. (2018) and implicate, at a neural activation level, a dissociation in the location of task-processing between the independent and relational tasks.
Enrichment and Isolation of Iron-Oxidizing Bacteria from an Ancient Earth Analogue

(Georgia Institute of Technology, 2019-08) Ghazi, Layla

Fe2+ was an abundant component of ancient anoxic oceans and could have acted as a respiratory electron donor. The overall goals of this study were to test whether anaerobic microbial growth could occur with Fe2+ as the electron donor in Fe2+-rich sediments from an ancient ocean analogue (Lake Matano, Indonesia) and to determine the taxonomic identity of the bacteria. Sediments were incubated with Fe2+ sulfide as the electron donor in a nitrogen:carbon dioxide (90/10%) atmosphere. Manganese (III), nitrate, nitrite, and oxygen were provided as electron acceptors. With Mn3+ as the electron acceptor, cultures showed some evidence of growth near the middle of the gradient tube. However, orange Fe3+ oxides were absent, suggesting that anaerobic Fe2+ oxidation had not occurred. Ferric oxides were also absent in tubes containing nitrate and nitrite. A white precipitate was present in cultures with Mn3+, which indicated that the microbes reduced Mn3+ to Mn2+. The precipitate was not present in uninoculated controls. With oxygen as the electron donor, a layer of orange Fe3+ oxide minerals formed near the water-air interface, indicative of growth of microaerophilic Fe2+-oxidizing bacteria. This layer did not form in uninoculated controls. Our preliminary results suggest that anaerobic Lake Matano enrichments are capable of Fe2+ oxidation using oxygen but not alternative electron acceptors. After subsequent transfers of the enrichments that showed growth of microaerophilic Fe2+-oxidizing bacteria, the bacteria were isolated and their 16S rRNA gene was sequenced. Sequences were most similar to the Betaproteobacteria genus Comamonas and the Alphaproteobacteria genus Skermanella. Some species of Comamonas are known to oxidize Fe2+, while the exact mechanism of the metabolism of Skermanella are not well known. The presence of microaerophilic Fe2+ oxidizing bacteria from Lake Matano, Indonesia serves as a link between understanding the transition from an anoxic to an oxic world.
Expansion of Mitochondrial and Nuclear Heme Sensor Library

(Georgia Institute of Technology, 2019-05) Atuluru, Pranusha

The long-term objective of the work in the lab is to determine the mechanisms by which cells sense and respond to the utilization of heme, an essential nutrient. Heme is an iron-containing compound of the porphyrin class that enables proteins to carry out an array of functions. Heme-dependent processes require that heme be dynamically mobilized to hemoproteins in almost every subcellular compartment. Although it is understood that the cytotoxicity and hydrophobicity of heme requires heme be tightly regulated by the cell, the method by which this is done is unknown [1]. The primary factor that limits the understanding of heme mobilization and trafficking is the lack of tools available to sense heme, more specifically labile heme. The Reddi lab is working to develop ratiometric fluorescent sensors to offer better insight into subcellular labile heme pools relevant for heme trafficking and signaling. HS1 (Heme Sensor 1) is mutated at either the His or Met in the heme-binding coordinating bundle of cytochrome to create sensors of different affinity. Ten new mutant sensors were created from the original HS1 and HS1-M7A, and it is seen that two sensors, H102C and H102C-M7H, are the most suitable sensors to be used in the mitochondria, nucleus and cytosol. With the use of these sensors, different pathways of heme trafficking and signaling can be studied in the cell.
A Novel Vibrio cholerae Type VI Secretion System Gene Cluster is Involved in Interbacterial Competition

(Georgia Institute of Technology, 2019-05) Williams, Kenneth G.

The waterborne pathogen Vibrio cholerae inhabits microbiomes on chitinous crustaceans in marine environments and within the gastrointestinal tracts of animals, including humans, after ingestion of contaminated water. All sequenced isolates of V. cholerae contain genes encoding for a Type Six Secretion System (T6SS), a harpoon-like apparatus capable of delivering toxic effectors into neighboring cells and conferring a competitive advantage in dense microbial communities. The T6SS has been primarily studied in host-derived V. cholerae isolates, which have four T6 loci: a main cluster encoding structural and regulatory components, and four auxiliary (Aux1-3) clusters that each encode an effector toxin and cognate immunity protein to avoid kin or self-intoxication. We applied a predictive algorithm we developed to the genome sequences from a set of environmental isolates and identified in two isolates a novel Aux cluster which we named Aux5. Aux5 was predicted to encode a T6 effector with homology to T6-secreted lipase of Pseudomonas aeruginosa. Due to limited genetic tractability of the environmental isolate, the Aux5 cluster was horizontally transferred onto the chromosome of a host-derived, reference V. cholerae strain that is naturally transformable on chitin. The transformed strain killed the parental reference strain in a T6SS-dependent manner. Disruption of the Aux5 effector gene (Tse5) abolished the ability of the transformed strain to kill its parent. These results demonstrate 1) the V. cholerae T6 arsenal includes a novel Aux5 effector, and 2) non-native auxiliary clusters can be acquired by natural transformation and utilized for T6-mediated competition. We predict that horizontal exchange of active T6 loci allows rapid adaptation of bacteria in host and environmental microbiomes.
Investigating the aggregation of Alzheimer’s disease-associated proteins in S. cerevisiae

(Georgia Institute of Technology, 2019-05) Denniss, Julia Marie

Alzheimer’s disease (AD) is the most common type of dementia and is associated with roughly 500,000 new cases each year (2). AD is associated with the aggregation of two proteins in the brain, A-beta peptide (Aβ) and microtubule associated protein tau (MAPT). Aβ and MAPT are capable of adopting a cross-β fibrous protein structure, which can be reproduced and spread via nucleated polymerization and are termed amyloids. Despite such a broad biological impact of amyloids and prions, the mechanism of their initial formation in vivo remains a mystery. In this thesis, I will investigate proteins associated with AD, and the properties of these proteins that control their aggregation. Recent research has indicated that the U1 small nuclear ribonuclear protein 70 (U1-70k) can form detergent-insoluble aggregates in a manner specific to Alzheimer’s disease. U1-70k is strongly correlated with Aβ and tau, both proteins known to play a highly important role in the Alzheimer’s disease cascade and plaque formation. It has been shown that misfolded forms of U1-70k can sequester natively folded U1-70k proteins and cause them to form insoluble aggregates, a characteristic of amyloids (8). The mechanism behind this conversion remains elusive, however. Our research focuses on determining which domains and combinations of domains of the U1-70k protein are necessary for aggregation, and we also examine its interactions with Aβ. Through plasmid construction, expression, and observation under fluorescence microscopy (FM), we demonstrate that the N(1-99) domain alone cannot induce aggregation, but the C(182-437) domain, combined N and M domains, and M(100-181) domain are capable of inducing aggregation. Further SDD-AGE and Western blot analyses indicate that the aggregates formed by the C(182-437) domain are detergent-insoluble, while those formed by the N and M domains as well as the M(100-181) domain alone are detergent-soluble. This leads us to hypothesize that the aggregates formed by the M domain are reversible stress granules. Furthermore, the N and M domains also co-aggregate with Aβ, though the C(182-437) domain does not. We also examine tau’s suitability as a model in yeast for protein interactions and find that its aggregation is transformant-specific and cannot be cured by Hsp104, a heat shock protein found in yeast cells. We find that wild-type repeat domains of tau, the 244-372 amino acid region, aggregates are detergent-soluble.