Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, CA 92697, USA.|Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, CA 92697, USA.|Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, CA 92697, USA.|Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, CA 92697, USA.