Nuclear Pore-Like Structures in a Compartmentalized Bacterium.

Planctomycetes are distinguished from other Bacteria by compartmentalization of cells via internal membranes, interpretation of which has been subject to recent debate regarding potential relations to Gram-negative cell structure. In our interpretation of the available data, the planctomycete Gemmata obscuriglobus contains a nuclear body compartment, and thus possesses a type of cell organization with parallels to the eukaryote nucleus. Here we show that pore-like structures occur in internal membranes of G.

Crosstalk between sugarcane and a plant-growth promoting Burkholderia species.

Bacterial species in the plant-beneficial-environmental clade of Burkholderia represent a substantial component of rhizosphere microbes in many plant species. To better understand the molecular mechanisms of the interaction, we combined functional studies with high-resolution dual transcriptome analysis of sugarcane and root-associated diazotrophic Burkholderia strain Q208. We show that Burkholderia Q208 forms a biofilm at the root surface and suppresses the virulence factors that typically trigger immune response in plants.

Structural studies of planctomycete Gemmata obscuriglobus support cell compartmentalisation in a bacterium.

Members of phylum Planctomycetes have been proposed to possess atypical cell organisation for the Bacteria, having a structure of sectioned cells consistent with internal compartments surrounded by membranes. Here via electron tomography we confirm the presence of compartments in the planctomycete Gemmata obscuriglobus cells. Resulting 3-D models for the most prominent structures, nuclear body and riboplasm, demonstrate their entirely membrane - enclosed nature.

Towards understanding the molecular mechanism of the endocytosis-like process in the bacterium Gemmata obscuriglobus.

An endocytosis-like process of protein uptake in the planctomycete Gemmata obscuriglobus is a recently discovered process unprecedented in the bacterial world. The molecular mechanisms underlying this process are not yet characterized. A homolog of the MC (membrane-coating) proteins of eukaryotes has been proposed to be involved in the mechanism of this process, but its relationship to eukaryote proteins is controversial.

Isolation and diversity of planctomycetes from the sponge Niphates sp., seawater, and sediment of Moreton Bay, Australia.

Planctomycetes are ubiquitous in marine environment and were reported to occur in association with multicellular eukaryotic organisms such as marine macroalgae and invertebrates. Here, we investigate planctomycetes associated with the marine sponge Niphates sp. from the sub-tropical Australian coast by assessing their diversity using culture-dependent and -independent approaches based on the 16S rRNA gene.

Nested bacterial boxes: nuclear and other intracellular compartments in planctomycetes.

Bacteria in the phylum Planctomycetes and some related phyla challenge our concept of the typical bacterium as consisting of cells without internal compartments or membrane-bounded organelles. Cells of all species of planctomycetes examined consist of at least two major compartments, and there are two other types of compartmentation in which a third compartment is formed either by a double-membrane envelope around the nucleoid in the case of the aerobic Gemmata obscuriglobus or by a single but potentially energized membrane in the case of the anaerobic ammonium-oxidizing anammox planctomycetes. We examine here the nature of these planctomycete compartments in relation to function and their relationship to the endomembranes defining them, and discuss the implications of the remarkable compartment-confined process of protein uptake in Gemmata, which resembles receptor- and clathrin-mediated endocytosis of eukaryotes.

Electron tomography of the nucleoid of Gemmata obscuriglobus reveals complex liquid crystalline cholesteric structure.

The nucleoid of the planctomycete Gemmata obscuriglobus is unique within the Bacteria in being both highly condensed and enclosed by a double-membrane nuclear envelope, seemingly analogous to the nucleus of eukaryotes. Here we have applied electron tomography to study high-pressure frozen, cryosubstituted cells of G. obscuriglobus and found multiple nested orders of DNA organization within the condensed nucleoid structure.

Keys to eukaryality: planctomycetes and ancestral evolution of cellular complexity.

Planctomycetes are known to display compartmentalization via internal membranes, thus resembling eukaryotes. Significantly, the planctomycete Gemmata obscuriglobus has not only a nuclear region surrounded by a double-membrane, but is also capable of protein uptake via endocytosis. In order to clearly analyze implications for homology of their characters with eukaryotes, a correct understanding of planctomycete structure is an essential starting point.

Genomic rearrangements at the FRA2H common fragile site frequently involve non-homologous recombination events across LTR and L1(LINE) repeats.

Common fragile sites (cFSs) are non-random chromosomal regions that are prone to breakage under conditions of replication stress. DNA damage and chromosomal alterations at cFSs appear to be critical events in the development of various human diseases, especially carcinogenesis. Despite the growing interest in understanding the nature of cFS instability, only a few cFSs have been molecularly characterised.

Beyond the bacterium: planctomycetes challenge our concepts of microbial structure and function.

Planctomycetes form a distinct phylum of the domain Bacteria and possess unusual features such as intracellular compartmentalization and a lack of peptidoglycan in their cell walls. Remarkably, cells of the genus Gemmata even contain a membrane-bound nucleoid analogous to the eukaryotic nucleus. Moreover, the so-called 'anammox' planctomycetes have a unique anaerobic, autotrophic metabolism that includes the ability to oxidize ammonium; this process is dependent on a characteristic membrane-bound cell compartment called the anammoxosome, which might be a functional analogue of the eukaryotic mitochondrion.

Making heads or tails of the HU proteins in the planctomycete Gemmata obscuriglobus.

Gemmata obscuriglobus has a highly condensed nucleoid which is implicated in its resistance to radiation. However, the mechanisms by which such compaction is achieved, and the proteins responsible, are still unknown. Here we have examined the genome of G.

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.

Turning the table: plants consume microbes as a source of nutrients.

Interactions between plants and microbes in soil, the final frontier of ecology, determine the availability of nutrients to plants and thereby primary production of terrestrial ecosystems. Nutrient cycling in soils is considered a battle between autotrophs and heterotrophs in which the latter usually outcompete the former, although recent studies have questioned the unconditional reign of microbes on nutrient cycles and the plants' dependence on microbes for breakdown of organic matter. Here we present evidence indicative of a more active role of plants in nutrient cycling than currently considered.

Endocytosis-like protein uptake in the bacterium Gemmata obscuriglobus.

Endocytosis is a process by which extracellular material such as macromolecules can be incorporated into cells via a membrane-trafficking system. Although universal among eukaryotes, endocytosis has not been identified in Bacteria or Archaea. However, intracellular membranes are known to compartmentalize cells of bacteria in the phylum Planctomycetes, suggesting the potential for endocytosis and membrane trafficking in members of this phylum.

Cathepsin D protects human neuroblastoma cells from doxorubicin-induced cell death.

High incidence of chemotherapy resistance is the primary cause of treatment failure in a subset of neuroblastomas with amplified MYCN. We have reported previously that ectopic MYCN expression promotes proliferation of neuroblastoma Tet21N cells and simultaneously sensitizes them to the drug-induced apoptosis. In search for genes that are involved in MYCN-dependent regulation of drug resistance, we used a function-based gene cloning approach and identified CTSD encoding for a lysosomal aspartyl protease cathepsin D.

Suppression of polyploidy by the BRCA2 protein.

Mounting evidence implicates BRCA2 not only in maintenance of genome integrity but also in cell-cycle checkpoints. However, the contribution of BRCA2 in the checkpoints is still far from being understood. Here, we demonstrate that breast cancer cells MX-1 are unable to maintain genome integrity, which results in gross polyploidization.

Novel aphidicolin-inducible common fragile site FRA9G maps to 9p22.2, within the C9orf39 gene.

Common fragile sites represent a component of normal chromosome structure that form gaps and breaks on metaphase chromosomes after partial inhibition of DNA synthesis. In humans, cytogenetic locations of 89 common fragile sites are listed in the Genome Database; however, the exact number of fragile sites remains unknown. The application of high resolution mapping approaches continues to reveal new common fragile sites in the human genome.

FRA1E common fragile site breaks map within a 370kilobase pair region and disrupt the dihydropyrimidine dehydrogenase gene (DPYD).

Common fragile sites represent components of normal chromosome structure that are particularly prone to breakage under replication stress. Although the cytogenetic locations of 88 common fragile sites are listed in the Genome database, the DNA at only 14 of them has been defined and characterized at the molecular level. Here, we identify the precise genomic position of the common fragile site FRA1E, mapped to the chromosomal band 1p21.

Low-frequency common fragile sites: link to neuropsychiatric disorders?

Common fragile sites are unstable chromosomal regions that predispose chromosomes to breakage and rearrangements. Recombinogenic DNA sequences encompassing these sites may contribute to both germinal and somatic genomic mutations, and the genomic instability at these regions might cause severe inherited disorders or predispose to cancer. In this review, we discuss the characterization of common fragile site FRA13A within the neurobeachin gene, which is involved in development and function of the central nervous system.

The neurobeachin gene spans the common fragile site FRA13A.

Common fragile sites are normal constituents of chromosomal structure prone to chromosomal breakage. In humans, the cytogenetic locations of more than 80 common fragile sites are known. The DNA at 11 of them has been defined and characterized at the molecular level.