Biological Sciences

Lunchbags are a weekly gathering of students and faculty of the Biological Sciences Department. 

Lunchbags have moved to Thursdays and are held from 12:15 - 1:00 pm in McConnell 103 unless otherwise noted. 

Lunch is provided for the first 35 attendees, please bring your own beverage.  All members of the Smith Community are welcome.  For more information, contact adonahue@smith.edu.  

Mar 23: Life Sciences Jeopardy!

Join the BIO Liaisons as they host the first ever annual Life Sciences Jeopardy game! 

Attendees will be split into teams to answer trivia questions about Smith, the field of biology, our BIO faculty, etc. 

******Winning team will receive a PRIZE!******

Mar 30: Biology Advising Session

This is a great opportunity to meet the BIO faculty and student liaisons and to ask questions.

Please note that this Advising Session does not replace the one-on-one meeting with your academic advisor.

Apr 6: Preliminary Honors Presentations

Vivian Li, Sabra Mouhi

April 13: Preliminary Masters Presentations

Billie Cullison, Jailene Gonzalez, Andrew Gonzalez

Life Sciences Colloquia Presentations are part of the Spring 2023 Mary Elizabeth Dickason King M.D. Annual Lecture Series in the Life Sciences in Memory of Professor Howard Parshley.

Thursdays at 4:30 pm in McConnell 103

Coffee, tea and light snacks will be served in the McConnell Foyer at 4:15 pm 

March 23   Mei Wu, Harvard

"Killing Superbugs by Inducing Bacteria-Specific Phototoxicity"

Chronic wound infections caused by multidrug-resistant (MDR) bacteria, or superbugs, pose a serious threat to public health due to limited treatment options and prolonged care. To address this challenge, we have developed a novel microbicidal strategy by combining two non-antibiotic and natural modalities: blue light and small natural compounds. The combined strategy effectively eliminates a range of MDR bacteria and their polymicrobial biofilms in vitro and in vivo in a safe and rapid manner, regardless of antibiotic susceptibility.  This strategy can also reverse antibiotic resistance.  Several small natural compounds are identified, such as carvacrol and thymol, and they can be photo-catalytically oxidized to a "photosensitizer" that is more effective in killing bacteria than the compound itself when exposed to blue light. We name these compounds "pro-photosensitizers" analogous to the prodrug that is activated only in bacteria. The pro-photosensitizer triggers two autoxidation cycles that interact with each other, resulting in the generation of a high level of cytotoxic reactive oxygen species (ROS) in the presence of blue light.  This phototoxic reaction occurs exclusively in bacteria due to abundant porphyrins-like compounds produced in bacteria over mammalian cells.  The phototoxic reaction can be further augmented by specific compounds that facilitate the synthesis of endogenous photosensitizers.  The microbicidal alternatives are safe and effective in the fight against MDR pathogens, making them a promising option for addressing the challenge of chronic wound infections caused by superbugs.

March 30  ChangHui Pak, University of Massachusetts, Amherst

"Dissecting the Neurodevelopmental Role of Schizophrenia Gene Variant NRXN1 at Single Cell Resolution in iPSC-derived Human Brain Organoid Model"

De novo mutations and copy number variations (CNVs) in NRXN1 (2p16.3) pose a significant risk for schizophrenia (SCZ). How NRXN1 CNVs impact cortical development in a cell type-specific manner and how disease genetic background modulates these phenotypes are unclear. Here, we leveraged human pluripotent stem cell-derived brain organoid models carrying NRXN1 heterozygous deletions in isogenic and SCZ patient genetic backgrounds and conducted single-cell transcriptomic analysis over the course of cortical brain organoid development from 3 weeks to 3.5 months. From the dataset consisting of 141,039 high-quality single cell transcriptomes, we identified that maturing glutamatergic and GABAergic neurons as being consistently impacted due to NRXN1 CNVs irrespective of genetic background, contributed in part by altered gene modules in ubiquitin-mediated pathways, splicing, and synaptic signaling. Moreover, while isogenic NRXN1 CNVs impact the differentiation and maturation of neurons and astroglia, cell composition and developmental trajectories of early neural progenitors are affected in SCZ-NRXN1 CNVs. Our study reveals developmental timing-dependent NRXN1 CNV-induced cellular mechanisms in SCZ at single-cell resolution and highlights the emergence of disease-specific transcriptomic signatures and cellular vulnerabilities, which can arise from the interaction between genetic variants and disease background. Finally, this single cell dataset provides a valuable community resource that allows an in-depth temporal analysis on the genetic effects of schizophrenia risk variants.

April 6  Alex Stevens, University of California, San Diego

"Intracellular Transport Susceptibility to Viral Antagonism"

Viruses interact with the intracellular transport machinery to promote viral replication. Such host–virus interactions can drive host gene adaptation, leaving signatures of pathogen-driven evolution in host genomes. Here, we leverage these genetic signatures to identify the dynein activating adaptor, ninein-like (NINL), as a critical component in the antiviral innate immune response and as a target of viral antagonism. Unique among genes encoding components of active dynein complexes, NINL has evolved under recurrent positive (diversifying) selection, particularly in its carboxy-terminal cargo-binding region. Consistent with a role for NINL in host immunity, we demonstrate that NINL knockout cells exhibit an impaired response to interferon, resulting in increased permissiveness to viral replication. Moreover, we show that proteases encoded by diverse picornaviruses and coronaviruses cleave and disrupt NINL function in a host- and virus-specific manner. Our work reveals the importance of NINL in the antiviral response and the utility of using signatures of host–virus genetic conflicts to uncover new components of antiviral immunity and targets of viral antagonism.

April 20  John T Lill, The George Washington University

"Cascading Effects of an Ecological Pulse: Direct and Indirect Effects of the Brood X Cicada Emergence on an Eastern Temperate Forest"

The simultaneous regional emergence of billions of periodical cicadas results in a massive ecological perturbation of eastern North American forests, the nature and extent of which until now have remained largely unexplored. Once every 13 or 17 years, vast numbers of nymphal cicadas, constituting an estimated 0.5-3.7 metric tons ha^-1 of insect biomass, concurrently emerge from the soil and briefly satiate an entire guild of naive consumers, offering a rare opportunity to assess the cascading impacts of an ecosystem-wide resource pulse on a complex food web. In this study, we quantified the effects of the 2021 Brood X emergence, which spanned 15 states in the eastern USA, on components of three trophic levels: the diets and foraging activities of avian insectivores, the density of forest caterpillars that constitute the birds’ usual prey, and the increased damage inflicted by these caterpillars on their white oak host plants. We found that during the emergence, a phylogenetically diverse assemblage of local bird species, spanning a range of feeding guilds and three orders of magnitude in body mass, opportunistically switched their foraging to include cicadas as a significant portion of their diets. This dietary shift, in turn, precipitated an ecological release of avian predation for a community of tree-feeding caterpillars. During the peak of the emergence, bird attacks on plasticine caterpillar models declined three-fold and concurrently, caterpillar densities and accumulated herbivory levels on their host oak leaves more than doubled relative to the same trees sampled in non-cicada emergence years. Because in any given year large areas of the eastern United States are anticipating, experiencing, or recovering from an onslaught of periodical cicadas, developing a detailed understanding of the trophic implications of these emergences is critical for interpreting the population and community dynamics of eastern North American forests. In addition to our scientific findings, I will also discuss our cicada-themed educational outreach activities and materials.