The Komeili Lab uses bacterial magnetosomes as a model system to study the molecular mechanisms governing the biogenesis and maintenance of bacterial organelles.
Ph.D. Cell Biology UCSF, 2001
B.S. Biology MIT, 1996
Bacteria are highly organized cells with many ultrastructural similarities to eukaryotes. In addition to a highly dynamic cytoskeleton composed of homologues of actin, tubulin and intermediate filaments, many prokaryotes possess intracellular membranous organelles. My lab uses the magnetosomes of magnetotactic bacteria as a model system to study the molecular mechanisms governing the biogenesis and maintenance of bacterial organelles. Using a variety of approaches, we identify and investigate key genes involved in controlling magnetosome formation and function.
Assembly and Subcellular Organization of Bacterial Organelles
It has become increasing clear that bacterial cells are highly organized with many ultrastructural similarities to eukaryotic cells. In addition to a dynamic cytoskeleton composed of homologues of actin, tubulin and intermediate filaments, many bacteria also possess intracellular membranous organelles. Our lab uses magnetosomes as a model system for studying the molecular mechanisms of organelle biogenesis and maintenance in bacteria.
The magnetosome chains of magnetotactic bacteria are one of the best-studied examples of membranous bacterial organelles. Magnetosome chains (see figure above) contain 15-20 approximately 50-nm magnetite crystals that act like the needle of a compass to orient magnetotactic bacteria in geomagnetic fields, thereby simplifying their search for their preferred microaerophilic environments. The unique properties of magnetosomal magnetite crystals have drawn attention to their potential use in biotechnology, bioremediation, and geobiology and have made them a genetically tractable system for the study of biomineralization. In addition to these applications, the cell biological characteristics of magnetosomes make them ideal for the study of organelle biology in bacteria. Each magnetite crystal within a magnetosome is surrounded by a lipid bilayer, and specific soluble and transmembrane proteins are sorted to the magnetosome membrane. These results suggest that to build a magnetosome a bacterium must be able to generate a membranous comparmtent, target the appropriate set of proteins to this membrane and control their number and position within a cell.
My lab uses a combination of cell biological, genetic and biochemical approaches to define the physical characteristics of the magnetosome and identify key genes involved in controlling its production and function. Our earlier work showed that the magnetosome membrane is an independent organelle that pre-exists the formation of magnetite and that magnetite synthesis proceeds simultaneously from multiple adjacent magnetosomes. Recently, the work of several groups including ours has led to the identification of a large genomic region with many genes encoding proteins that are localized to the magnetosome and are essential for magnetite formation. The challenge now is to understand the specific functions of these genes and how their products interact to form a magnetosome.
More information at: http://www.komeililab.org
Komeili A. Molecular Mechanisms of Compartmentalization and Biomineralization in Magnetotactic Bacteria. FEMS Microbiol Rev. 2011 Nov 17. [Epub ahead of print]
Draper O, Byrne ME, Li Z, Keyhani S, Barrozo JC, Jensen G, Komeili A. MamK, a bacterial actin, forms dynamic filaments in vivo that are regulated by the acidic proteins MamJ and LimJ. Mol Microbiol. 2011 Oct;82(2):342-54. pdf
Zeytuni N, Ozyamak E, Ben-Harush K, Davidov G, Levin M, Gat Y, Moyal T, Brik A, Komeili A, Zarivach R. Self-recognition mechanism of MamA, a magnetosome-associated TPR-containing protein, promotes complex assembly. Proc Natl Acad Sci U S A. 2011 Aug 16;108(33):E480-7. pdf
Quinlan A, Murat D, Vali H, Komeili A. The HtrA/DegP family protease MamE is a bifunctional protein with roles in magnetosome protein localization and magnetite biomineralization. Mol Microbiol. 2011 Mar 18. Epub Ahead of Print
Topp S, Reynoso CM, Seeliger JC, Goldlust IS, Desai SK, Murat D, Shen A, Puri AW, Komeili A, Bertozzi CR, Scott JR, Gallivan JP. Synthetic Riboswitches that Induce Gene Expression in Diverse Bacterial Species. Appl Environ Microbiol. 2010 Dec;76(23):7881-4. Fulltext
Murat D, Byrne M, Komeili A. Cell Biology of Prokaryotic Organelles. Cold Spring Harb Perspect Biol. 2010 Oct 1. Fulltext
Byrne ME, Ball DA, Guerquin-Kern JL, Rouiller I, Wu TD, Downing KH, Vali H, Komeili A. Desulfovibrio magneticus RS-1 contains an iron- and phosphorus-rich organelle distinct from its bullet-shaped magnetosomes. Proc Natl Acad Sci U S A. 2010 Jul 6;107(27):12263-8. Open Access
Murat D, Quinlan A, Vali H, Komeili A. Comprehensive genetic dissection of the magnetosome gene island reveals the step-wise assembly of a prokaryotic organelle. Proc Natl Acad Sci U S A. 2010 Mar 23;107(12):5593-8. Open Access
Komeili A. Molecular mechanisms of magnetosome formation. Annu Rev Biochem. 2007;76:351-66. Review. pdf
Komeili A, Li Z, Newman DK, Jensen GJ. Magnetosomes are cell membrane invaginations organized by the actin-like protein MamK. Science. 2006 Jan 13;311(5758):242-5. pdf
Komeili A. Cell biology of magnetosome formation. In "Magnetoreception and Magnetosomes in Bacteria." Ed. D. Schüler. Berlin: Springer-Verlag. 2006. pp 163-174.
Weiss BP, Kim SS, Kirschvink JL, Kopp RE, Sankaran M, Kobayashi A, Komeili A. Magnetic tests for magnetosome chains in Martian meteorite ALH84001. Proc Natl Acad Sci U S A. 2004 Jun 1;101(22):8281-4.
Komeili A, Vali H, Beveridge TJ, Newman DK. Magnetosome vesicles are present before magnetite formation, and MamA is required for their activation. Proc Natl Acad Sci U S A. 2004 Mar 16;101(11):3839-44.
Weiss B.P., Kim S.S., Kirschvink J.L. , Sankaran M., Kobayashi A., Komeili A.. Ferromagnetic resonance and low temperature magnetic tests for biogenic magnetite. Earth and Planetary Science Letters. 2004; 224:73-89.
Komeili A, O'Shea EK. New perspectives on nuclear transport. Annual Review of Genetics. 2001; 35:341-64.
Komeili A, Wedaman KP, O'Shea EK, Powers T. Mechanism of Metabolic Control. Target of rapamycin signaling links nitrogen quality to the activity of the Rtg1 and Rtg3 transcription factors. J Cell Biol. 2001; 151:863-878.
Komeili A, O'Shea EK. Nuclear transport and transcription. Curr Opin Cell Biol. 2000; 12:355-60.
Komeili A, O'Shea EK. Roles of phosphorylation sites in regulating activity of the transcription factor Pho4. Science. 1999; 284:977-80.
Honors and Awards
Winkler Family Fund - 2008
Hellman Family Fund - 2008
Fellowship in Science and Engineering - Packard Foundation - 2007
Junior Faculty Fellowship - Hellman Family Foundation - 2007