Quorum sensing is a regulatory mechanism used by bacteria to control a variety of processes in response to cell densities in bacterial communities. The acyl-homoserine lactone (AHL) dependent quorum-sensing system is found in over 90 gram-negative bacterial species, and is responsible for regulating processes, including bioluminescence, antibiotic production, plasmid conjugal transfer, biofilm production, and pathogenesis in plants and animals. This project focuses on understanding how the enzymes known as AHL synthases make the AHLs in the cell. It will provide new insight into the mechanism by which AHL synthases select and act on substrates with different acyl-chain lengths to produce different forms of AHLs. It will also determine the degree to which the acyl-ACP pool modulates the types of AHLs produced, which may be a crucial aspect of controlling the behavior of bacterial communities in response to environmental stimuli. This research will also have a broad impact of a practical nature because AHL mediated quorum sensing contributes to agricultural crop losses, damage to industrial equipment and aquaculture though marine biofouling, and loss of human and animal lives through bacterial infections. Broader Impacts This project will provide training and education to several early-stage scientists, including undergraduate researchers and graduate level trainees from under-represented groups in the Denver area. One undergraduate student comes from the Community College of Aurora through the Stride Toward Encouraging Profession in Science (STEPS) program. This project will provide education and training of students from under-represented populations who have not had any research experience as undergraduates, but who need this experience in order to move into graduate or professional schools. These students will come from institutions where there was little opportunity for research for them in the Denver area and from a collaborator at a primarily undergraduate institution. The project will also provide valuable research experience for both Masters and Ph.D. graduate students. Therefore, through several avenues, this project will introduce new people from diverse backgrounds to research, help the development of new graduate students, and generate additional diversity among the scientific community.
This project provided research experience and training to several students (broader impact) who contributed directly to understanding mechanisms that regulate how bacteria communicate (intellectual merit). Bacteria communicate with each other in order to regulate the behaviors that they engage in as a group rather than as individuals. This communication is mediated by small chemical signals, called acyl-homoserine lactones (AHLs), which are made by enzymes in the bacteria and detected by AHL receptors in the same or other bacteria. The project sought to understand how such a variety of signals can be produced through identifying signals produced by certain enzymes and by studying how they are detected specifically by AHL receptors. The findings of the research include: identification of AHL profiles in two species of bacteria, discovery that human taste cells can detect the bacterial AHL signals, analysis of the interactions between AHL molecules and a bacterial AHL receptor, analyses of role of substrates in the production of AHLs in the test tube and in bacteria. These results have been published in five articles, one methods paper, and a high profile review article. One manuscript is still under preparation. Nine students, who come from under-represented groups in the biophysical sciences, and one postdoctoral fellow worked with the PI and the collaborators using a range of methods, including, microbiology, genetics, biochemistry, biophysics and structural biology. At a state of the art facility in the high powered research environment of a Medical School, they learned how to develop a hypothesis, execute experimental methodologies, collect and analyze data, and present their data to a group at least two times each. Five of them are co-authors of published papers and two will co-author two manuscripts that are in preparation. The training provided to these students enabled all but one of them to pursue further research and education in the biological sciences.
