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Publication Restricted The Role of PBP1B and ppGpp in ß-Lactam Resistance and Characterization of Mecillinam Heteroresistance in Escherichia coli MG1655(2025-12-09)β-lactams are the most widely prescribed class of antibiotics. Overproduction of the alarmone ppGpp in Escherichia coli confers resistance to the β-lactams mecillinam, meropenem, and doripenem, which target penicillin-binding protein 2 (PBP2) and disrupt cell wall synthesis. This resistance requires PBP1B, a related cell wall synthase, and DksA, a transcription factor that binds ppGpp. We sought to uncover the mechanism by which ppGpp and PBP1B cause resistance to these β-lactams. Measuring minimum inhibitory concentrations (MICs) of PBP1B separation-of-function mutants revealed that full enzymatic activity of PBP1B is essential for resistance. Prior work showed that overproduction of ppGpp upregulates expression of the PBP1B activator lpoB. An LpoB-bypass PBP1B mutant revealed that the LpoB-PBP1B interaction is partially required for resistance. Separately, we also report the first evidence of mecillinam heteroresistance (HR), a subpopulation-driven resistance phenotype. HR was detected in E. coli by Etests and measured with population analysis profiling (PAP). The HR observed was unstable, exhibiting a decrease in antibiotic resistance in the absence of selective pressure. Mutants lacking ppGpp, DksA, and PBP1B exhibited reduced HR. HR was not dependent on the recombinase protein RecA, which has previously been implicated in HR to other antibiotics. qPCR analysis of select mecillinam resistance genes revealed unstably increased copy number of ftsZ, dksA, and mrcB (encodes PBP1B) in the resistant subpopulation. These findings highlight the roles of ppGpp, DksA, and PBP1B in β-lactam resistance and uncover HR as an additional survival pathway during mecillinam exposure.Publication Open Access A foundational summary dataset for "Persistent warm water anomalies before and after marine heatwaves amplify heat exposure and associated risks"(2026-05-22)Marine heatwaves (MHWs) are a major threat to marine ecosystems globally, yet standard MHW definitions, despite providing consistent metrics, do not capture pre- and post-event warm anomalies, leading to systematic underestimation of total heat exposure experienced by marine ecosystems. Here, we analyze over 2,580 MHW events from 54 stations across 20 US estuaries to provide a comprehensive characterization of pre- and post-MHW thermal anomalies. We show that pre- and post-event phases are largely independent of core MHW metrics and often persist longer than the MHW itself. Although these phases are less intense than the MHW event, when combined with the MHW itself, they account for a substantial increase in total heat exposure—resulting in an approximately 153% higher cumulative intensity (°C·days) compared to the MHW alone—that cannot be reliably inferred from standard metrics. We present a new framework to quantify pre- and post-event anomalies that can be broadly applied across coastal and open-ocean systems. This framework is critical for understanding MHWs, assessing ecological impacts, guiding laboratory experiments, and informing ecosystem management.Publication Embargo The Effects of Salinity and Phytoplankton Food on Larval Cloning and Regeneration in the Sea Star Asterias forbesi(2026-05-08)Larvae of the sea star Asterias forbesi, a keystone species of the North American Atlantic coast, are able to clone by fissioning perpendicular to the anterior-posterior axis. Both anterior and posterior pieces have the capacity to regenerate, forming two genetically identical larvae. In other species of sea stars, the frequency of larval cloning has been shown to vary in response to environmental conditions, such as the abundance of phytoplankton, which serves as a food resource for larvae. Phytoplankton abundance and salinity fluctuate in the intertidal habitat of A. forbesi, as transient algal blooms often form when freshwater from land runoff inputs nutrients into coastal waters. In my thesis I examine the effects that salinity, food quantity, and food type have on cloning frequency and the effects that temperature and food have on regeneration success after fissioning. High food levels led to increased cloning frequency, and larvae fed Rhodomonas lens cloned more than those fed other species of algae, although the latter difference was not statistically significant. Salinity had no effect on clone production over the entire larval period, but larvae cultured at low salinity cloned earlier in the larval period than those cultured in normal salinity seawater. No environmental factors were shown to affect the frequency of regeneration success after cloning, but posterior clones regenerated three times more often than anterior clones, a result in line with prior research. My results therefore demonstrate that environmental factors affect cloning frequency, which could indicate that cloning is an adaptive trait in A. forbesi under particular environmental conditions. However, differential regeneration success likely results primarily from as yet unidentified internal mechanisms in the larva and not from environmental factors.Publication Restricted Digging Up Dirt: Margaret Cavendish and the Early Modern Englishwoman's Scientific Relationship with Nature(2026-05-04)To borrow inspiration from a significant historical feminist figure: I believe women belong in all rooms where science is happening. By writing this thesis, I am interested in discovering the difference between “men’s science” and “women’s science” in England during the 17th century. I have a specific interest in the spaces where these forms of science were practiced, what rules governed those spaces, and the main pillars of thought upheld by the scientists in those spaces. I seek to analyze how these spaces are discussed in Margaret Cavendish’s body of literary work, and in so doing, analyze how she uses these spaces to her advantage in the world outside her writing.Person Metadata only