Mercury (Hg) is a trace element metal with toxic effects on wildlife, including bats. Texas is the largest producer of mercury pollution in the United States, yet only 2 other studies have measured the concentration of mercury in bats. We measured total mercury concentrations (THg) in fur (n=57) in the endangered species Tricolored bats (Pipistrellus subflavus) collected from two culverts in Fresstone County in East Central Texas. Fur THg concentrations were compared between sex, culverts, and previous studies in the U.S.. There was no significant difference in THg between sex or culvert, but there was a significant difference with the Tricolored bats in the Northeastern U.S.. However, the THg values were not significantly different from those of previous studies conducted in Texas. Additionally, the THg concentrations were compared with the 10 ug/g toxicity threshold levels commonly used, with 5.2% of Tricolored bats in this study exceeding this toxicity threshold. This suggests that THg may pose a risk to the health of bats in East Central Texas, and protective measures need to be implemented to protect this species.

The ClpXP protease plays a critical role in bacterial responses to external stressors, protein recycling, and virulence. The protease is highly conserved and composed of two subunits: ClpX, a regulatory ATPase, which recognizes and unfolds proteins, and ClpP, the proteolytic subunit. Our lab has identified that ClpX plays a role in resistance to cell-envelope targeting antibiotics and is critical for virulence in B. anthracis Sterne. However, it is unlikely that ClpX is directly mediating these effects. Rather, these effects are likely due to the dysregulation of the protein network maintained by ClpXP, which includes proteins involved in gene expression, such as transcription factors. Previously, we conducted a microarray and identified 119 differentially expressed genes between wild-type B. anthracis Sterne and a ΔclpX strain. One of the genes identified from the microarray is msrA/B, a fusion of the msrA and msrB methionine sulfoxide reductases (msr). Msr enzymes restore functionality to oxidized methionine residues; MsrA reduces S-form Met(O), and MsrB reduces R-form Met(O). Research with these enzymes has primarily focused on their role in resistance to reactive oxygen species (ROS). However, in S. aureus, msrA1 and msrB expression was induced upon exposure to oxacillin and other cell-wall active antimicrobial agents and not by ROS, indicating a potential connection between msrA/B and cell wall-targeting antibiotics. In B. anthracis Sterne, loss of msrA/B increases susceptibility to penicillin and vancomycin. However, this phenotype is not seen with cell-membrane targeting agents such as daptomycin, suggesting that the role of msrA/B in antimicrobial resistance may be limited to cell-wall active antibiotics. We are currently investigating the role in resistance to ROS but have seen no susceptibility to either H2O2 or paraquat. Future studies will look at changes in msrA/B expression in response to a variety of antibiotics and ROS stressors to better understand the role of this enzyme in regulating the response to these stressors in B. anthracis.

Alzheimer’s disease (AD) is a progressive neurodegenerative disease that affects millions worldwide and has shown increasing prevalence. The pathological hallmarks of AD include amyloid-beta (Aβ), tau hyperphosphorylation, and neuroinflammation. It has become increasingly apparent that oxidative stress from reactive oxygen species (ROS) accumulation plays a crucial role in AD disease progression. ROS contributes to neuronal dysfunction and death by inducing lipid peroxidation, mitochondrial impairment, and chronic inflammation. We utilized the HT-22 mouse neuronal cell line to investigate oxidative stress and potential neuroprotection in vitro following glutamate induced oxidative stress. To assess oxidative damage and neuron death, we utilize the MTT assay to measure cell viability following glutamate treatment. Novel antioxidant compounds synthesized from Dr. Green’s labs have been shown to be radical scavengers and increase expression of antioxidant pathways. We additionally pre-treated HT-22 cells with these novel antioxidant compounds prior to glutamate exposure to evaluate their effectiveness in scavenging ROS and preventing oxidative damage. Results from these experiments will lay the foundation for further testing to determine the mechanism in which these novel antioxidants show neuroprotective effects, which could provide valuable insight into antioxidant based therapeutic strategies for AD and other neurogenerative diseases.

Alzheimer’s disease (AD) was the fifth leading cause of death in people over 65 in 2021, and it is expected that 13 million Americans will have AD by 2050. AD is a neurodegenerative disease that is characterized clinically by the onset of memory loss and cognition decline in aging populations. These clinical manifestations of AD are a result of neuronal cell death. While our knowledge of the exact pathology of AD is still evolving, inflammation of the central nervous is known to be a factor in the onset and progression of AD. Microglial cells are one major cell type responsible for this inflammation. Microglial overactivation, which leads to the overproduction of proinflammatory cytokines, is thought to be a cause of the chronic inflammation seen in AD. Additionally, ferroptosis, which is a regulated form of cell death characterized by iron-dependent lipid peroxidation, is thought to be a major mechanism by which neurodegeneration occurs in AD. HT22, an immortalized cell line of mouse hippocampal neurons, are a commonly used model for studying ferroptosis. Furthermore, BV2 cells are an immortalized cell line of mouse microglial cells that produce inflammatory cytokines that can be removed in their “conditioned” media. We treated HT22 cells with glutamate to induce ferroptosis, and also with BV2-conditioned media, and measured the cell death via an MTT assay to investigate whether the proinflammatory cytokines produced by microglial cells also induces the neuronal cell death that occurs via ferroptosis. These studies are ongoing.

Wind energy is considered one of the fastest growing renewable energy sources. However, bat collision mortality has become an increasing issue for migratory bat species over the years. Researchers are interested in a sex bias in the mortality rates at wind farms. If females are being disproportionately killed, the population will not sustain itself over time and their numbers will decrease. The goal of my study was to determine the sex ratio of silver-haired bats killed at a wind farm and determine if females are experiencing higher mortality than males. These data allow scientists to implement curtailment that reduces collision fatalities. Curtailment is the turning off of wind turbines on low wind speed nights, the nights where bat mortalities are highest. Researchers can also use the information to target curtailment when females are at their highest risk for collisions. I extracted DNA from 66 bat samples originating from a wind farm in Southern Indiana. To determine the species for a subset of the samples I sequenced a portion of the mitochondrial cytochrome oxidase I gene which is the DNA barcode region that can be used to identify species, I then used X and Y genetic markers to determine the sex of all samples. Of the 66 samples, 9 were spot checked for species identification via sequencing and were identified as silver-haired bats. Out of the 66 samples, 29 (43%) samples were identified as female and 37 (66%) were identified as male. This ratio did not differ from a 50:50 sex ratio (x2=0.97, p = 0.32). We can conclude that our sample set has a 50:50 sex ratio of males to females for silver haired bats. We compared our data to previous studies on silver haired bats and noticed a similar pattern for several other states in the US. The only state to have a statistically significant difference in their sex ratio of females to males was Ohio, which had a sex ratio of 2.1 females for every male. Since the results indicate a 50:50 sex ratio, curtailment during migration periods could be equally effective for both sexes to maintain the population of silver haired bats over time. Further research also indicates that acoustic deterrence is an unequivocally effective method for deterring bats from wind turbines.