Showing papers by "Arash Komeili published in 2006"

Magnetosomes Are Cell Membrane Invaginations Organized by the Actin-Like Protein MamK

Abstract: Magnetosomes are membranous bacterial organelles sharing many features of eukaryotic organelles. Using electron cryotomography, we found that magnetosomes are invaginations of the cell membrane flanked by a network of cytoskeletal filaments. The filaments appeared to be composed of MamK, a homolog of the bacterial actin-like protein MreB, which formed filaments in vivo. In a mamK deletion strain, the magnetosome-associated cytoskeleton was absent and individual magnetosomes were no longer organized into chains. Thus, it seems that prokaryotes can use cytoskeletal filaments to position organelles within the cell.

Cell Biology of Magnetosome Formation

Abstract: Magnetosome chains are the intracellular structures that allow magnetotactic bacteria to align in and navigate along geomagnetic fields (Bazylinski and Frankel 2004). These organelles are typically defined as a unit consisting of a magnetite or greigite crystal surrounded by a lipid bilayer membrane (Balkwill et al. 1980). Although these magnetic minerals are the usual targets of most studies of magnetotactic bacteria it is the magnetosome membrane that fascinates cell biologists. One of the cornerstones of cell biology has been that membrane-bound organelles are unique to eukaryotes. However, it is now known that membranous organelles exist in many prokaryotes raising the possibility that the endo-membrane system of eukaryotic cells might have originated in prokaryotes (Jetten et al. 2003; Seufferheld et al. 2003; Fuerst 2005). Magnetosomes are one of the best-studied examples of these prokaryotic organelles with the potential to be an ideal system for the study of organelle development in prokaryotes. This work provides a review of the current knowledge of magnetosomes from a cell biological perspective focusing on the composition and formation of the magnetosome membrane and the cytoskeletal framework organizing individual magnetosomes into chains.