Faculty Directory

B. TaylorBarry Taylor, PhD

Vice Chancellor for Research Affairs
Professor
Department of Biochemistry and Microbiology
Loma Linda University
Loma Linda, California 92350
Phone: (909) 558-8544
Fax: (909) 558-0244
bltaylor@llu.edu

Research Summary


* How do cells sense oxygen and energy? Bacteria have the remarkable ability to navigate to the precise concentration of oxygen that is optimal for growth. This behavior is called aerotaxis. My laboratory investigates the signal transduction pathways for aerotaxis in E. coli and other bacteria as model systems for learning how oxygen receptors might function in higher organisms. We identified two oxygen transducers, the Aer and Tsr proteins in E. coli. The Aer protein has a PAS domain that is similar to domains in human oxygen-sensing proteins, such as hypoxia-inducible factor-1. Understanding human responses to hypoxia is of considerable medical importance, and our studies of Aer are suggesting shared mechanisms for PAS-domain-containing proteins.

* Structure-function studies of the aerotaxis transducer Aer and PAS domains. We have identified residues in Aer that are important for signal transduction, including residues that transform a positive signal into a negative response. Current projects will determine the structure of Aer, the role of the critical residues and the function of FAD, PAS, and HAMP domains in signaling by Aer. A combination of genetic, molecular biology, and biochemical strategies are utilized in answering these questions. This provides students with a broad exposure to current techniques and allows each to extensively pursue a methodology of choice. By forming chimeras with PAS domains of other oxygen sensing proteins we hope to identify common signal transduction strategies for oxygen receptors.

* Ecological role of bacterial behavior to oxygen. Studies in collaboration with Dr. Igor Zhulin and other investigators are aimed at determining how aerotaxis provides a selective advantage to bacteria in their natural environment. Important findings include evidence that the bacteria migrate to a niche where the cellular energy levels are highest for growth. E. coli does not sense oxygen directly. Instead, Aer and Tsr monitor the energy level of the bacteria. By monitoring their own energy, bacteria can avoid not only hypoxic micro-environments but other environments that do not support maximal energy in the bacteria. The concept of energy-sensing has been proposed previously, but the Aer signal transduction pathway now provides a mechanism for energy-sensing behavior.

Selected Publications

Edwards, JC, MS Johnson, and BL Taylor. Differentiation between electron transport sensing and proton motive force sensing by the Aer and Tsr receptors for aerotaxis. 2006. Mol Microbiol. In press.

Watts, KJ, MS Johnson, and BL Taylor. 2006. Minimal requirements for oxygen sensing by the aerotaxis receptor Aer. Mol Microbiol. 59(4):1317-1326.

Watts, KJ, K Sommer, SL Fry, MS Johnson, and BL Taylor. 2006. Function of the N-terminal cap of the PAS domain in signaling by the aerotaxis receptor Aer. J Bacteriol. 188(6):2154-2162.

Amin, D, BL Taylor, and MS Johnson. 2005. Topology and boundaries of the aerotaxis receptor Aer in the membrane of Escherichia coli. J. Bacteriol. 188(3):894-901.

Ma, Q, MS Johnson, and BL Taylor. 2005. Genetic analysis of the HAMP Domain of the Aer aerotaxis sensor localizes FAD-binding determinants to the AS-2 helix. J Bacteriology. 187(1): 193-201.

Ma Q, Johnson MS, Taylor BL. Genetic analysis of the HAMP domain of the Aer aerotaxis sensor localizes FAD-binding determinants to the AS-2 helix. J Bacteriology 187(1): 193-201, 2004.

Hermann S, Ma Q,. Johnson MS, Repik A, Taylor BL. PAS domain of the Aer redox sensor requires C-terminal residues form native fold and FAD binding. J Bacteriology 186(20):6782-6791, 2004.

Watts KJ, Ma Q, Johnson MS, Taylor BL. Interactions between the PAS and HAMP domains of the Escherichia coli aerotaxis receptor Aer. J Bacteriology 186(21):7440-7449, 2004.

Repik A, Rebbapragada A, Johnson MS, Haznedar JO, Zhulin IB, Taylor BL. PAS domain residues involved in signal transduction by the Aer redox sensor of Escherichia coli, Mol Microbiol 36:806-16, 2000.

Taylor BL , Zhulin IB, Johnson MS. Aerotaxis and other energy-sensing behavior in bacteria, Annu Rev Microbiol 53:103-128, 1999.

Taylor BL , Zhulin IB. PAS Domains: Internal sensors of oxygen, redox potential, and light. Microbiol Mol Biol Rev 62:479-506, 1999.

Taylor BL, Johnson MS. Rewiring a receptor: Negative output from positive input. FEBS Lett 425:377-381, 1998.

Rebbapragada A, Johnson MS, Harding GP, Zuccarelli AJ, Fletcher HM, Zhulin IB, Taylor BL. The Aer protein and the serine chemoreceptor Tsr independently sense intracellular energy levels and transduce oxygen, redox, and energy signals for Escherichia coli behavior. Proc Natl Acad Sci USA 94:10541-10546, 1997.

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