The matrix of extracellular polymer secretions (EPS) that surround bacteria is the defining attribute of biofilms. Biofilms exhibit a high level of organization, and 3D microphysical architecture, and cell-to-cell chemical communication networks. This allows bacteria to act as coordinated groups of cells and facilitates greater metabolic efficiency and flexibility. The unique properties of EPS are instrumental in this organization. EPS localizes chemical signaling (i.e. quorum sensing), antibiotics, extracellular enzymes; and conserves water during desiccation (i.e. water loss). Together, the biofilm EPS underlies the adaptability and resiliency of bacteria in both natural systems and hospital-disease settings.
Our laboratory probes biofilms under in-situ and manipulated conditions. We utilize various chemical/biological analyses as well as non-destructive spectroscopic and imaging techniques including confocal scanning laser microscopy (CSLM), scanning- (SEM) and transmission- (TEM) electron microscopy, atomic force microscopy (AFM), NMR, Infared- (FT-IR) and Raman-spectroscopy. The interdisciplinary nature of our research has provided interesting collaborations with colleagues in chemistry, marine sciences, biology, geology, engineering and medicine.
Fundamental properties of extracellular (EPS) matrices: (glass formation, porosity, mineral precipitation) under different environmental- and infection- conditions. Organization of the biofilm matrix and extracellular activities depend upon EPS. Our studies are investigating: (1) compositions, functional groups, and pore-spacing between adjacent EPS polymers that affect nanoparticle penetration; (2) how certain EPS form a glass state to protect extracellular molecules during desiccation; and (3) how EPS may promote or inhibit precipitation of calcium carbonate (CaCO3); an important sink for CO2 in climate change.
Quorum Sensing (QS) under Natural Conditions: Bacterial cell-cell communication, called quorum sensing occurs within biofilms. QS allows bacterial cells to cooperatively conduct group activities through coordinated gene expression. It contributes important roles in infections through secretion of virulence factors, extracellular enzymes that hydrolyze antibiotics, and other activities. We are studying QS signaling with hypersaline microbial mats and infections, how QS signals travel within EPS, genes expressed during quorum sensing, and how signals and cells are protected by components of EPS during desiccation.
Novel Antibiotics and Infection control: Novel antibiotics and interactions with biofilms. We are isolating novel antibiotics from unique microbial systems such as hypersaline microbial mats. We are also exposing bacteria to unique stresses and stimulating the silent genome of bacteria to produce novel antibiotics. We collaborate with chemists in the design antimicrobial polymers, which inhibit antibiotic degrading enzymes (beta-lactamases). This will enhance the efficacy of existing antibiotics.
Engineered Nanoparticles for Combating Infections: Nanoparticles (NP) are extremely small (1-100 nm). Due to their small size and surface groups they have unique physical and chemical properties and can be chemically altered to carry drugs. At present, we are using nanoparticles as ‘Antibiotic Delivery Vehicles’ (ADV) to enhance the potency of present-day antibiotics. We are attempting to understand how surface properties of NPs may be altered to better penetrate biofilm EPS and more efficiently destroy infections.