ACTIVE PROJECTS

ELECTRICALLY CONDUCTIVE BIOMATERIALS

Bioelectronic materials interface biological organisms/materials with non-living electronic devices. Examples include implantable/wearable medical devices and biosensors, organ-machine interfaces, and implantable biological power sources. Peptides and proteins are ideal materials for bioelectronic devices due to their biocompatibility and their ability to assemble into versatile, hierarchical structures that exhibit impressive electronic properties that allow them to conduct electricity over micrometer length scales. In this lab, we primarily investigate 2 promising candidates for bioelectronic materials:

1. Protein nanowires from the bacteria Geobacter sulferreducens were recently found to be long filaments of polymerized cytochromes with stacked hemes that can transport electricity over long length scales. We are investigating the mechanism of electron transport within the protein nanowires that allows for long-range electron transport.

2. Synthetic peptides have been discovered that can self-assemble into high aspect ratio nanowires. These nanowires were found to be electrically conductive and possible candidate for bioelectronic devices. We are currently investigating the mechanism of self-assembly to create a robust and repeatable self-assembly process and the mechanism of electron conduction through the nanowire. Future applications include electrochemical enzyme biosensors and interfacing devices to manipulate human tissue cells.

ANTIBIOTIC RESISTANCE AND STRESS RESPONSES IN BACTERIA

Bacteria utilize a variety of survival strategies to adapt to the various stressors that constantly challenge them in the unique microenvironments they inhabit. Of these, alteration of their metabolic pathways stands as one of the most effective and conserved mechanisms of adaptation, resulting in microbial communities rich with metabolic heterogeneity. By utilizing modern spectroscopic methods to quantitatively assess these metabolic perturbations, we seek to understand the intricacies of metabolic adaptations to stress. We use various assays, such as the newly developed resazurin assay, surface-enhanced raman spectroscopy (SERS), Python-assisted modeling, and more. Recent findings advanced our understanding of metabolic consequences resulting from antibiotic actions, and enabled the development of novel ultra-fast antibiotic susceptibility testing methodology. Current studies seek to extend this understanding to environmental stressors such as nutrient limitation and osmotic stress that challenge both planktonic and biofilm-associated bacteria. The findings from these projects will advance our fundamental understanding of antibiotic resistance, environmental stress-responses, and the emergence of tolerance and persister cells.

PAST PROJECTS

CELL-TO-CELL COMMUNICATION IN BACTERIAL BIOFILMS

Bacterial biofilms are highly complex structures comprised of secreted extracellular polymeric substances that create large networks of dense cellular clusters. As diffusion through these structures is hindered, significant nutrient and metabolite gradients exist within a biofilm, particularly in regions that are in close proximity to cellular microclusters. Remarkably, the physiologies of microbes inhabiting these highly dynamic environments are intimately connected through a series of chemical signaling networks that have evolved to maximize community fitness. These chemical signals regulate a wide variety of processes such as nutrient cycling, stress responses, and dispersal. Our previous work has shown that rhamnolipid biosurfactants play an intimate role in Pseudomonas aeruginosa dispersal signaling through alteration of membrane permeability. We seek to expand our understanding of the role of rhamnolipids in cellular signaling by studying the differential effects of the various rhamnolipid congeners secreted by bacteria on bacterial membrane chemistry. Through our efforts in this set of projects, we aim to shed light on the physiochemical activities of the various biomolecules present in biofilms and elucidate their role in cell-to-cell communication.