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Undergraduate Research Opportunities Program

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Office of Undergraduate Education

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Now showing 1 - 10 of 82

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.
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.
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.
Neurobehavioral Patterns during Action Observation and Execution of Complex Goal-Directed Movements

(Georgia Institute of Technology, 2019-05) Atawala, Neel

The production and mastery of complex action begins with action understanding, a process which arises from the observation of others. The mechanisms through which humans engage in action understanding are still debated, and several conceptual theories, such as the direct matching hypothesis and teleological stance theory, attempt to explain the underlying mechanisms. Tool-use utilizes the visual streams and the frontoparietal networks in order to encode the visual features of the task and the control of grasp. Areas in the frontoparietal network have been associated with action understanding due to the presence of mirror neurons. The visual streams, a network that interconnects occipital, parietal, and temporal areas, encode object shape, size, orientation, and use as well as eye movements during the online control of movement. Prior to the execution of movement such as in tool use, one must engage in motor planning, a three stage process that consists of: 1) task recognition 2) coordination of required motor sequences, and 3) performance of the task. Second order motor planning requires both knowledge and planning of immediate task demands (first order motor planning) along with the planning of the subsequent steps during reach and grasp. The purpose of this study is to analyze the neurobehavioral encoding of action intent during action observation and execution of a second order motor task using electroencephalography (EEG) and eye tracking. The results may help us uncover the neurobehavioral mechanisms in action understanding that we can leverage and target for more effective neurorehabilitative therapies.
Developing appropriate methodology for assessing anti-pathogen properties of mucus-enriched water from corals

(Georgia Institute of Technology, 2019-05) Jarvis, Simone

Global coral reef health is in rapid decline. A major contributor to this trend is warming ocean temperatures. As ocean temperature increases, corals become more susceptible to diseases that lead to bleaching and tissue mortality. Vibrio coralliilyticus is one of the few documented coral bleaching pathogens. Previous studies developed methods to quantify V. coralliilyticus metabolism and developed culturing procedures to test the anti-Vibrio potency of mucus-enriched water from numerous coral species. However, the best way to collect and process mucus-enriched water from corals was not determined. Previous efforts obtained mucus-enriched water via coral fragmentation and agitation in seawater. This methodology detected anti-Vibrio activity from several species, but required destructive sampling of the corals. This prevents collecting data over multiple time points without confounding time with previous damage. This study evaluates the effectiveness of less destructive methodologies for sampling mucus-enriched coral water. This study evaluated the effectiveness of the less destructive method of slowly sucking coral mucus from colonies in the field using a syringe. Tests using this method on mucus enriched water from 9 species of coral detected no anti-pathogen activity. In contrast, tests using the fragmentation and shaking method found significant anti-pathogen activity in 3 of the 4 species tested. the less destructive method assayed here, is ineffective at assessing the anti-pathogen potential of corals.
Glucose protects E. coli from death by the Vibrio cholerae type VI secretion system

(Georgia Institute of Technology, 2019-05) Nichols, Holly L.

Vibrio cholerae, the causative agent of the intestinal disease cholera, interacts with other bacteria in dense multispecies communities within both host and environmental settings. Using the harpoon-like type VI secretion system (T6SS), V. cholerae delivers toxic effector proteins into neighboring cells, causing cell lysis and death. The T6SS is frequently studied in V. cholerae using a qstR* mutant which constitutively expresses the T6SS. A qstR* V. cholerae strain can effectively kill target species Escherichia coli, Aeromonas veronii., and T6SS-sensistive V. cholerae cells in a standardized lab killing assay, causing a drop in viable cell counts of five orders of magnitude. This study finds that addition of glucose to a standardized killing assay against qstR* V. cholerae restores E. coli survival by three to four orders of magnitude, though the same effect is not found for Aeromonas or T6SS-sensitive V. cholerae. A growth assay revealed that E. coli doubling time does not affect killing by V. cholerae. Additional evidence shows that E. coli does not produce a diffusible molecule that represses the T6SS of V. cholerae. Investigation by fluorescence microscopy revealed that E. coli cells when entirely surrounded by V. cholerae cells survive in the presence but not the absence of glucose, which suggests that glucose causes a relevant physiological change in individual E. coli cells. We propose that further study should focus on the E. coli capsule as a potential mechanism for surviving T6SS attack. This study makes an unprecedented case that attack via the T6SS can be thwarted by sugar metabolism in target cells.
Joint Stiffness Fluctuations are Potentially Associated with Postural Sway

(Georgia Institute of Technology, 2019-05) Gidwani, Simran

Joint stiffness can be induced by simultaneous contraction of muscles on opposite sides of the joint. When the electrical oscillations of these antagonistic muscles are in-phase, fluctuations in joint stiffness can occur, which can pose a threat to those with a neuromuscular deficit, as they will not be able to adequately control these fluctuations. In an attempt to develop rehabilitation programs to train these individuals on how to control these fluctuations, electrical activity of the muscles in the lower leg, and postural sway were measured. It was hypothesized that the amplitude coherence of low-frequency, in-phase oscillations of antagonistic muscles was positively correlated with postural sway. Data collection occurred while subjects were standing in the tandem stance, a position of induced coactivation of the antagonistic muscles of the lower leg. Electrical activity of the right tibialis anterior, medial gastrocnemius, and soleus were measured and analyzed against center-of-pressure power, a measure of postural sway. EMG measurements, such as amplitude coherence and power spectral density, were only analyzed at low-frequencies (0-3 Hz) at which the oscillations were in-phase. Data analysis yielded no significant correlations between amplitude coherence and center-of-pressure power, and no significant correlations between power spectral density and center-of-pressure power. Future modifications to this study can incorporate visual feedback in order for subjects to be able to modulate their muscle activity to hit a specific target of co-activation, and COP sway will be measured simultaneously.