Bacterial Cytoplasm (bacterial + cytoplasm)

Distribution by Scientific Domains

Selected Abstracts

Enzymology and molecular biology of prokaryotic sulfite oxidation,

Ulrike Kappler
Abstract Despite its toxicity, sulfite plays a key role in oxidative sulfur metabolism and there are even some microorganisms which can use it as sole electron source. Sulfite is the main intermediate in the oxidation of sulfur compounds to sulfate, the major product of most dissimilatory sulfur-oxidizing prokaryotes. Two pathways of sulfite oxidation are known: (1) direct oxidation to sulfate catalyzed by a sulfite:acceptor oxidoreductase, which is thought to be a molybdenum-containing enzyme; (2) indirect oxidation under the involvement of the enzymes adenylylsulfate (APS) reductase and ATP sulfurylase and/or adenylylsulfate:phosphate adenylyltransferase with APS as an intermediate. The latter pathway allows substrate phosphorylation and occurs in the bacterial cytoplasm. Direct oxidation appears to have a wider distribution; however, a redundancy of pathways has been described for diverse photo- or chemotrophic, sulfite-oxidizing prokaryotes. In many pro- and also eukaryotes sulfite is formed as a degradative product from molecules containing sulfur as a heteroatom. In these organisms detoxification of sulfite is generally achieved by direct oxidation to sulfate. [source]

Staphylococcus aureus haem oxygenases are differentially regulated by iron and haem

Michelle L. Reniere
Summary Iron acquisition is a vital process for most pathogenic bacteria, as iron is a limiting nutrient during infection. Staphylococcus aureus, an increasingly important pathogen, acquires iron from host haem via elaboration of the iron-regulated surface determinant system (Isd). IsdG and IsdI are haem oxygenases that have been proposed to degrade exogenous haem in the bacterial cytoplasm as a mechanism to liberate free iron for use as a nutrient source. Herein, we report that IsdG and IsdI are both important for S. aureus growth on haemin as a sole iron source and are necessary for full S. aureus pathogenesis. Investigations into the regulation of these enzymes revealed that IsdG and IsdI are differentially regulated by iron and haem through both transcriptional and post-transcriptional mechanisms. Additionally, IsdI was found to be expressed in infected tissues at the sites of abscess formation, suggesting that abscesses are iron-starved microenvironments inside the host. These findings suggest that S. aureus differentially regulates IsdG and IsdI in response to alterations in iron and haem availability during infection. [source]

TlpC, a novel chemotaxis protein in Rhodobacter sphaeroides, localizes to a discrete region in the cytoplasm

G. H. Wadhams
Summary TlpC is encoded in the second chemotaxis operon of Rhodobacter sphaeroides. This protein shows some homology to membrane-spanning chemoreceptors of many bacterial species but, unlike these, is essential for R. sphaeroides chemotaxis to all compounds tested. Genomic replacement of tlpC with a C-terminal gfp fusion demonstrated that TlpC localized to a discrete cluster within the cytoplasm. Immunogold electron microscopy also showed that TlpC localized to a cytoplasmic electron-dense region. Correct TlpC,GFP localization depended on the downstream signalling proteins, CheW3, CheW4 and CheA2, and was tightly linked to cell division. Newly divided cells contained a single cluster but, as the cell cycle progressed, a second cluster appeared close to the initial cluster. As elongation continued, these clusters moved apart so that, on septation, each daughter cell contained a single TlpC cluster. The data presented suggest that TlpC is either a cytoplasmic chemoreceptor responding to or integrating global signals of metabolic state or a novel and essential component of the chemotaxis signalling pathway. These data also suggest that clustering is essential for signalling and that a mechanism may exist for targeting and localizing proteins within the bacterial cytoplasm. [source]

Type III-dependent translocation of the Xanthomonas AvrBs3 protein into the plant cell

Boris Szurek
Summary Many plant pathogenic bacteria utilize a conserved type III secretion system (TTSS) to deliver effector proteins into the host tissue. Indirect evidence has suggested that at least some effector proteins are translocated from the bacterial cytoplasm into the plant cell. Using an immunocytochemical approach, we demonstrate that the type III effector AvrBs3 from Xanthomonas campestris pv. vesicatoria localizes to nuclei of infected pepper leaves. Importantly, AvrBs3 translocation was observed in situ in native tissues of susceptible and resistant plants. AvrBs3 was detected in the nucleus as soon as 4 h post infection, which was dependent on a functional TTSS and the putative translocator HrpF. N-terminal AvrBs3 deletion derivatives are no longer secreted by the TTSS in vitro and could not be detected inside the host cells, suggesting that the N-terminus of AvrBs3 is important for secretion. Deletion of the nuclear localization signals in the AvrBs3 C-terminus, which are required for the AvrBs3-mediated induction of the hypersensitive reaction in resistant pepper plants, abolished AvrBs3 localization to the nucleus. This is the first report on direct evidence for translocation of a native type III effector protein from a plant pathogenic bacterium into the host cell. [source]

IpgD, a protein secreted by the type III secretion machinery of Shigella flexneri, is chaperoned by IpgE and implicated in entry focus formation

Kirsten Niebuhr
Invasion of epithelial cells by Shigella flexneri involves entry and intercellular dissemination. Entry of bacteria into non-phagocytic cells requires the IpaA,D proteins that are secreted by the Mxi,Spa type III secretion machinery. Type III secretion systems are found in several Gram-negative pathogens and serve to inject bacterial effector proteins directly into the cytoplasm of host cells. In this study, we have analysed the IpgD protein of S. flexneri, the gene of which is located on the virulence plasmid at the 5, end of the mxi,spa locus. We have shown that IpgD (i) is stored in the bacterial cytoplasm in association with a specific chaperone, IpgE; (ii) is secreted by the Mxi,Spa type III secretion system in amounts similar to those of the IpaA,D proteins; (iii) is associated with IpaA in the extracellular medium; and (iv) is involved in the modulation of the host cell response after contact of the bacterium with epithelial cells. This suggests that IpgD is an effector that might be injected into host cells to manipulate cellular processes during infection. [source]

Production of Lewis x Tetrasaccharides by Metabolically Engineered Escherichia coli

CHEMBIOCHEM, Issue 2 2006
Claire Dumon Dr.
Abstract Two tetrasaccharides carrying the trisaccharidic Lewis x motif on a GlcNAc or a Gal residue were produced on the gram-scale by high-cell-density cultures of metabolically engineered Escherichia coli strains that overexpressed the Helicobacter pylori futA gene for ,-3 fucosyltransferase and the Neisseria meningitidis lgtB gene for ,-4 galactosyltransferase. The first compound Gal,-4(Fuc,-3)GlcNAc,-4GlcNAc was produced by glycosylation of chitinbiose, which was endogenously generated in the bacterial cytoplasm by the successive action of the rhizobial chitin-synthase NodC and the Bacillus circulans chitinase A1, whose genes were additionally expressed in the E. coli strain. The second compound, Gal,-4(Fuc,-3)GlcNAc,-3Gal, was produced from exogenously added Gal by a strain that was deficient in galactokinase activity and overexpressed the additional N. meningitidis lgtA gene for ,-3 N-acetylglucosaminyltransferase. [source]