Emerging roles of the exopolysaccharide matrix and surface sensing in bacterial communication and ecology
Abstract
Bacteria interact with surfaces in the natural environment and can form complex multispecies biofilm communities. These communities are fundamental to the biology of bacteria. Not only do biofilms contribute to problems in human health and disease (such as persistent infections), they also present new opportunities in the context of energy and the environment (such as extracellular electron conduction, engineering microbial fuel cells or sensors, and control of biofouling). One of the defining characteristics of bacterial biofilms is the existence of a matrix of exopolysaccharides (EPS) and extracellular DNA (eDNA). In the last 30 years, the field has elucidated a number of the interesting roles of these matrix polymers as molecular glues in biofilm development. Recent work suggest that the matrix can contribute much more broadly, and that EPS is potentially implicated in foundational processes that allow bacteria to sense and respond to surfaces, and processes that allow biofilm assembly in the context of multi-species communities. A recent, exciting finding by the Parsek and Wong laboratories described the deposition of trails of the exopolysaccharide {EPS) PSL on surfaces by Pseudomonas aeruginosa that impacts bacterial sociology: Bacterial trail following behavior was found to be important for the formation of initial, small cellular aggregates that eventually gave rise to larger microcolonies, the first social step in biofilm formation. Equally important from an engineering perspective, our recent studies of bacterial surface sensing are beginning to reveal key components of the signaling framework that controls the biosynthesis of EPS In this proposal, rather than using simple engineering methods to make artificial assemblies of bacteria that look like biofilms, we aim to develop a toolbox for exploiting and reprogramming natural bacterial pathways for biofilm formation. Our recent work on surface sensing suggests that this level of control is possible for the first time. In order to achieve these goals, we plan to leverage recently developed state-of the-art tools not traditionally used in microbiology, such as the tracking of entire bacterial communities at single cell resolution, machine learning, synchrotron x-ray methods, and theoretical physics. Specifically, we aim to investigate two emerging social roles of EPS: (1) We hypothesize that EPS, whether on cell surfaces or on trails, can help cells sense and identify one another, and influence subsequent behavior. Such EPS-enabled molecular barcoding of single bacteria, combined with their technology for sensing and responding to EPS via diguanylate cyclase upregulation, cdiGMP production and EPS biosynthesis, can in principle be harnessed to codify design rules for bottom-up assembly of biofilms via cell-cell recognition. (2) We hypothesize that bacteria-secreted EPS trails can provide a programmable and dynamic map for biofilm organization: This includes the formation and evolution of microcolonies in single species biofilms, and spatial organization of multi-species biofilm formation, where cells can have complex competitive or collaborative relations with one another. Moreover, as an exploratory direction, we will examine how intrinsic interactions between dissimilar polymers within the EPS matrix (such as oppositely charged PEL and extracellular DNA) can lead to unanticipated spatial self-organization. The long term goal is deterministic biofilm design. If our proposal is successful and we elucidate EPS-dependent rules for biofilm development, the new ability to manipulate the biofilm development program can in principle form the basis of damage-tolerant, self-assembling biofilm device architectures: Only a few cells are necessary to grow a device. Moreover, as long as a few cells survive, the device can grow back.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810254
Entities
People
- Gerard Wong
Organizations
- Army Contracting Command
- United States Army
- University of California, Los Angeles