Bacteria are single-celled organisms wherein the intracellular components such as proteins, DNA and metabolites do not exist in individual components, but are contained by the cell membrane. They constitute some of the earliest forms of life (over three billion years old), and have an aggregate biomass that is larger than that of all animals and plants combined, numbering over five nonillion (5 x 10^{30}). Despite their simplicity, the operations and interactions of bacteria are not fully understood, yet microbial communities play a significant role in bioremediation, plant growth promotion, human and animal digestion, disease and drive elemental cycles, the carbon-cycle and the cleaning of water. Thus, it is of significant interest to further understand microbial populations. An interdisciplinary approach toward the understanding of cooperative and anti-cooperative behavior in microbial populations with a focus on signaling methods such as molecular diffusion and electron transfer will be undertaken. The research objective is to investigate biological group behaviors that exploit a variety of coupling mechanisms in order to form structures. In particular, microbial communities that are able to form structures at different scales will be examined. Problems relevant to two key applications motivate the research: microbial fuel cell optimization and infection initiation and suppression and the relationship to quorum sensing. In quorum sensing, when the concentration of a compound produced by the bacteria exceeds a threshold, the bacteria express new genes leading to new community behavior such as luminescence or infection.
The hope is that the fruits of the research will result in novel bio-inspired systems that naturally rely on principles of multi-modal sensing and different modalities of control and environmental conditions. More ambitiously, design methods by which structures in microbial communities can be induced are sought. Ongoing collaborations with biophysicists that have been instrumental in model design and validation via experimental data will be leveraged. Given the expertise of key collaborators, two strains of bacteria will be the focus: Pseudomonas aeruginosa and Shewanella oneidensis MR-1. In particular: (1) can one optimize the operation of microbial fuel cells exploiting electron transfer in bacterial populations and (2) can one design strategies to understand quorum sensing and potentially prevent infection without the use of antibiotics? Key questions to address include assessing what is the minimal amount information needed in order for distributed entities to form desired structures and geometries as well as engage in desired behaviors. Bacteria have limited capabilities and the distinctions between communication, respiration, and ingestion can often be minimal. These activities can provide either explicit or implicit avenues of communication and thus can exact a control. Specific problems include: molecular modulation design, bacterial cable formation via multi-terminal communication methods, models for quorum sensing including game theoretic approaches and multicellular interaction.
