Genome Analysis of Planctomycetes Inhabiting Blades of the Red Alga

Porphyra is a macrophytic red alga of the Bangiales that is important ecologically and economically. We describe the genomes of three bacteria in the phylum Planctomycetes (designated P1, P2 and P3) that were isolated from blades of Porphyra umbilicalis (P.um.1). These three Operational Taxonomic Units (OTUs) belong to distinct genera; P2 belongs to the genus Rhodopirellula, while P1 and P3 represent undescribed genera within the Planctomycetes. Comparative analyses of the P1, P2 and P3 genomes show large expansions of distinct gene families, which can be widespread throughout the Planctomycetes (e.g., protein kinases, sensors/response regulators) and may relate to specific habitat (e.g., sulfatase gene expansions in marine Planctomycetes) or phylogenetic position. Notably, there are major differences among the Planctomycetes in the numbers and sub-functional diversity of enzymes (e.g., sulfatases, glycoside hydrolases, polysaccharide lyases) that allow these bacteria to access a range of sulfated polysaccharides in macroalgal cell walls. These differences suggest that the microbes have varied capacities for feeding on fixed carbon in the cell walls of P.um.1 and other macrophytic algae, although the activities among the various bacteria might be functionally complementary in situ. Additionally, phylogenetic analyses indicate augmentation of gene functions through expansions arising from gene duplications and horizontal gene transfers; examples include genes involved in cell wall degradation (e.g., κ-carrageenase, alginate lyase, fucosidase) and stress responses (e.g., efflux pump, amino acid transporter). Finally P1 and P2 contain various genes encoding selenoproteins, many of which are enzymes that ameliorate the impact of environmental stresses that occur in the intertidal habitat

The Compartmentalized Bacteria of the Planctomycetes-Verrucomicrobia-Chlamydiae Superphylum Have Membrane Coat-Like Proteins

Compartmentalized bacteria have proteins that are structurally related to eukaryotic membrane coats, and one of these proteins localizes at the membrane of vesicles formed inside bacterial cells

Biopearling of Interconnected Outer Membrane Vesicle Chains by a Marine Flavobacterium

Large surface-to-volume ratios provide optimal nutrient uptake conditions for small microorganisms in oligotrophic habitats. The surface area can be increased with appendages. Here, we describe chains of interconnecting vesicles protruding from cells of strain Hel3_A1_48, affiliating with Formosa spp. within the Flavobacteriia and originating from coastal free-living bacterioplankton. The chains were up to 10 μm long and had vesicles emanating from the outer membrane with a single membrane and a size of 80 to 100 nm by 50 to 80 nm. Cells extruded membrane tubes in the exponential phase, whereas vesicle chains dominated on cells in the stationary growth phase. This formation is known as pearling, a physical morphogenic process in which membrane tubes protrude from liposomes and transform into chains of interconnected vesicles. Proteomes of whole-cell membranes and of detached vesicles were dominated by outer membrane proteins, including the type IX secretion system and surface-attached peptidases, glycoside hydrolases, and endonucleases. Fluorescein-labeled laminarin stained the cells and the vesicle chains. Thus, the appendages provide binding domains and degradative enzymes on their surfaces and probably storage volume in the vesicle lumen. Both may contribute to the high abundance of these Formosa-affiliated bacteria during laminarin utilization shortly after spring algal blooms

Pre-assembled Nuclear Pores Insert into the Nuclear Envelope during Early Development.

International audienceNuclear pore complexes (NPCs) span the nuclear envelope (NE) and mediate nucleocytoplasmic transport. In metazoan oocytes and early embryos, NPCs reside not only within the NE, but also at some endoplasmic reticulum (ER) membrane sheets, termed annulate lamellae (AL). Although a role for AL as NPC storage pools has been discussed, it remains controversial whether and how they contribute to the NPC density at the NE. Here, we show that AL insert into the NE as the ER feeds rapid nuclear expansion in Drosophila blastoderm embryos. We demonstrate that NPCs within AL resemble pore scaffolds that mature only upon insertion into the NE. We delineate a topological model in which NE openings are critical for AL uptake that nevertheless occurs without compromising the permeability barrier of the NE. We finally show that this unanticipated mode of pore insertion is developmentally regulated and operates prior to gastrulation

Protein uptake by bacteria: An endocytosis-like process in the planctomycete Gemmata obscuriglobus

Endocytosis is a fundamental process of membrane-trafficking in eukaryotes, but has not been known to occur in bacteria or archaea. The origin of endocytosis is central to the understanding of evolution of the first eukaryotes and their endomembrane systems. In a recent study we have established that an endocytosis-like process for uptake of proteins into cells occurs in a bacterium, Gemmata obscuriglobus, a member of the distinctive phylum Planctomycetes of peptidoglycan-less budding bacteria. Members of this phylum characteristically possess cells divided into compartments separated by internal membranes and in the case of G. obscuriglobus these compartments include one where a double membrane envelope surrounds its nucleoid DNA, as well as an outer ribosome- free region of cytoplasm. Proteins can be internalized by cells from the external milieu and collected into this ribosome-free compartment, and this process is energy-dependent and appears to be receptor-mediated. As in eukaryote endocytosis, internalized proteins are associated with vesicles, and can be subjected to proteolytic degradation. The discovery of this process in a bacterium has significant implications for our understanding of the origins of endocytosis in eukaryotes