1. California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
2. Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
3. Center for Integrative Imaging, Hefei National Laboratory for Physical Sciences at the Microscale, CAS Center for Excellence in Brain Science and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, PR China
4. Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine Chicago, IL 60611, USA
5. Present address: Department of Pharmacology, University of Michigan Medical School, University of Michigan, Ann Arbor, MI, USA.
6. Present address: College of Biological Sciences, University of Minnesota, 420 Washington, Avenue SE, Minneapolis, MN 55455, USA.