Intellectual Merit: The overall goal of this research is to understand the contribution of extracellular chemical signaling in the exchange of genetic material that accelerates bacterial adaptation. Although a transient human pathogen, Vibrio cholerae is an endemic marine microbe often found attached to the exoskeleton of arthropods, which are composed of the most abundant polymer in the ocean, chitin. V. cholerae is a member of a distinctive group of bacteria shown to be naturally competent to take up extracellular DNA and incorporate this genetic material onto their chromosomes. This method of horizontal gene transfer, termed natural transformation, occurs in V. cholerae in response to two environmental signaling pathways; a chitin utilization system that results in production of a regulator (TfoX), and a cell-cell communication (Quorum Sensing; QS) system that induces production of the transcription factor (HapR). The genes and network connections that link TfoX and HapR to DNA uptake are not known. Thus, this project will address the following aims. Aim 1: To identify genes that participate in horizontal gene transfer in response to extracellular QS signal molecules and to chitin. Aim 2: To define regulatory pathways connecting QS and chitin signaling to natural transformation. Aim 3: To examine the function of natural transformation network components. Aim 4: To determine the functionality of QS- and chitin-induced pathways in diverse V. cholerae environmental isolates. The research in this proposal is designed to exploit our understanding of chitin utilization and the V. cholerae QS paradigm for the identification of novel natural transformation genes. This research will dissect the role that both habitat and genetics play in bacterial evolution.
Broader Impacts: The applicant engages in teaching and service to integrate individuals in the academic community with members of the broader society in the process of modern scientific inquiry. Dr. Hammer teaches a Prokaryotic Molecular Genetics course for upper-level undergraduates and graduate students; and has established research collaborations with colleagues within the Unites States and other countries, to promote scientific and cultural exchange opportunities for his lab members. He initiated a substantial outreach program in 2009 that is expanded here, hosting a fifth grade teacher to work as a summer intern in his lab. Together Dr. Hammer and the teacher develop stimulating hands-on scientific exercises that engage ethnically diverse K-12 students in metro Atlanta. Activities are shared with local educators and will be presented at regional or national meetings including the National Science Teachers Association conference. Dr. Hammer is also an active teacher and mentor for students at all levels and post-doctoral fellows.
