title: The ultrastructure of Chlorobaculum tepidum revealed by cryo-electron tomography.
abstract: Chlorobaculum (Cba) tepidum is a green sulfur bacterium that oxidizes sulfide, elemental sulfur, and thiosulfate for photosynthetic growth. As other anoxygenic green photosynthetic bacteria, Cba tepidum synthesizes bacteriochlorophylls for the assembly of a large light-harvesting antenna structure, the chlorosome. Chlorosomes are sac-like structures that are connected to the reaction centers in the cytoplasmic membrane through the BChl α-containing Fenna-Matthews-Olson protein. Most components of the photosynthetic machinery are known on a biophysical level, however, the structural integration of light harvesting with charge separation is still not fully understood. Despite over two decades of research, gaps in our understanding of cellular architecture exist. Here we present an in-depth analysis of the cellular architecture of the thermophilic photosynthetic green sulfur bacterium of Cba tepidum by cryo-electron tomography. We examined whole hydrated cells grown under different electron donor conditions. Our results reveal the distribution of chlorosomes in 3D in an unperturbed cell, connecting elements between chlorosomes and the cytoplasmic membrane and the distribution of reaction centers in the cytoplasmic membrane.
authors.affiliation: Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, 4058 Basel, Switzerland; Focal Area Infection Biology, Biozentrum, University of Basel, 4058 Basel, Switzerland.
authors.forename: Misha
authors.initials: M
authors.lastname: Kudryashev
authors.affiliation: Division of Biochemistry, Department of Chemistry, University of Crete, 71003 Voutes, Heraklion, Greece.
authors.forename: Aikaterini
authors.initials: A
authors.lastname: Aktoudianaki
authors.affiliation: Division of Biochemistry, Department of Chemistry, University of Crete, 71003 Voutes, Heraklion, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Dedoglou
authors.affiliation: Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, 4058 Basel, Switzerland.
authors.forename: Henning
authors.initials: H
authors.lastname: Stahlberg
authors.affiliation: Division of Biochemistry, Department of Chemistry, University of Crete, 71003 Voutes, Heraklion, Greece. Electronic address: tsiotis@chemistry.uoc.gr.
authors.forename: Georgios
authors.initials: G
authors.lastname: Tsiotis
mesh_terms: D019414:Chlorobi / Q000502:physiology / Q000648:ultrastructure*; D003080:Cold Temperature; D055032:Electron Microscope Tomography / Q000379:methods*; D010788:Photosynthesis
keywords: Chlorosome; Cryo-electron tomography; Electron microscopy; Green sulfur bacteria