Project Summary/Abstract This proposal requests funding and demonstrates the need to replace a 13-year old workhorse LSRII w/ High Throughput Sampler (HTS) flow cytometer operating within the Princeton University Flow Cytometry Resource Facility (FCRF) with a new state-of-the art FACSymphony A3 Flow Cytometer w/ HTS. The existing LSRII was purchased in 2007 and neither Cytek Biosciences nor BD Biosciences will be providing annual service contracts on this system by the end of 2020 and 2022, respectively. This well-utilized flow cytometer is maintained by FCRF staff and is operated by research laboratory clients who are staff trained to run their experiments on the system independently. The FCRF is a well-established and financially subsidized Shared Resource Laboratory operating at Princeton University within the Department of Molecular Biology for 31 years. The FCRF operates with two full time staff and provides service to the Princeton research community; it is the only flow cytometry core facility on campus. The flow cytometry and fluorescence activated cell sorting (FACS) services provided by the FCRF have become the primary tools for the characterization and isolation of specific populations within a mixed biological sample and are therefore essential to an ever-growing number of researchers. Replacement of the LSRII w/HTS by the state-of-the-art FACSymphony A3 Flow Cytometer will enhance the research capabilities at Princeton University and will allow our researchers to continue uninterrupted their ongoing research projects. This 5-laser, 23-color detection system allows for great flexibility in employing diverse fluorescence in flow cytometry experiments with the increased sensitivity offered by the gel-coupled flow cell, multiple excitation laser lines, efficient fluorescence collection optics and the new low-noise VPX electronics of the system. The addition of the FACSymphony A3 Flow Cytometer will have an impact on multiple NIH-funded research laboratories at Princeton in diverse research areas including: immune system response to metastatic breast cancer, viral infection and immunity, bacterial virulence and biofilm formation, antibiotic resistance and bacterial persisters, discovery of small molecules with antibiotic properties, identifying glycolytic cell types, and cell signaling network dynamics, among others. Many of these projects have obvious health-related implications. The FACSymphony A3 will dramatically improve the research capabilities of NIH- funded research laboratories and will have a sustained and powerful impact on both the quality and quantity of the research projects conducted at Princeton University.