Peptidoglycan Remodeling and Conversion of an Inner Membrane into an Outer Membrane during Sporulation.
Summary of "Peptidoglycan Remodeling and Conversion of an Inner Membrane into an Outer Membrane during Sporulation."
Two hallmarks of the Firmicute phylum, which includes the Bacilli and Clostridia classes, are their ability to form endospores and their "Gram-positive" single-membraned, thick-cell-wall envelope structure. Acetonema longum is part of a lesser-known family (the Veillonellaceae) of Clostridia that form endospores but that are surprisingly "Gram negative," possessing both an inner and outer membrane and a thin cell wall. Here, we present macromolecular resolution, 3D electron cryotomographic images of vegetative, sporulating, and germinating A. longum cells showing that during the sporulation process, the inner membrane of the mother cell is inverted and transformed to become the outer membrane of the germinating cell. Peptidoglycan persists throughout, leading to a revised, "continuous" model of its role in the process. Coupled with genomic analyses, these results point to sporulation as a mechanism by which the bacterial outer membrane may have arisen and A. longum as a potential "missing link" between single- and double-membraned bacteria.
Affiliation
Division of Biology, California Institute of Technology, Pasadena, CA, 91125, USA.
Journal Details
This article was published in the following journal.
Name: Cell
ISSN: 1097-4172
Pages: 799-812
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21884938
- DOI: http://dx.doi.org/10.1016/j.cell.2011.07.029
Medical and Biotech [MESH] Definitions
Alveolata
A group of three related eukaryotic phyla whose members possess an alveolar membrane system, consisting of flattened membrane-bound sacs lying beneath the outer cell membrane.
Bacterial Outer Membrane Proteins
Proteins isolated from the outer membrane of Gram-negative bacteria.
Glomerulonephritis, Membranous
A type of glomerulonephritis that is characterized by the accumulation of immune deposits (COMPLEMENT MEMBRANE ATTACK COMPLEX) on the outer aspect of the GLOMERULAR BASEMENT MEMBRANE. It progresses from subepithelial dense deposits, to basement membrane reaction and eventual thickening of the basement membrane.
Endoplasmic Reticulum
A system of cisternae in the CYTOPLASM of many cells. In places the endoplasmic reticulum is continuous with the plasma membrane (CELL MEMBRANE) or outer membrane of the nuclear envelope. If the outer surfaces of the endoplasmic reticulum membranes are coated with ribosomes, the endoplasmic reticulum is said to be rough-surfaced (ENDOPLASMIC RETICULUM, ROUGH); otherwise it is said to be smooth-surfaced (ENDOPLASMIC RETICULUM, SMOOTH). (King & Stansfield, A Dictionary of Genetics, 4th ed)
Cytochrome-b(5) Reductase
A FLAVOPROTEIN oxidoreductase that occurs both as a soluble enzyme and a membrane-bound enzyme due to ALTERNATIVE SPLICING of a single mRNA. The soluble form is present mainly in ERYTHROCYTES and is involved in the reduction of METHEMOGLOBIN. The membrane-bound form of the enzyme is found primarily in the ENDOPLASMIC RETICULUM and outer mitochondrial membrane, where it participates in the desaturation of FATTY ACIDS; CHOLESTEROL biosynthesis and drug metabolism. A deficiency in the enzyme can result in METHEMOGLOBINEMIA.
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