Titanospirillum velox: a huge, speedy, sulfur-storing spirillum from Ebro Delta microbial mats.
(25/2084)
A long (20-30 micrometer), wide (3-5 micrometer) microbial-mat bacterium from the Ebro Delta (Tarragona, Spain) was grown in mixed culture and videographed live. Intracellular elemental sulfur globules and unique cell termini were observed in scanning-electron-microprobe and transmission-electron micrographs. A polar organelle underlies bundles of greater than 60 flagella at each indented terminus. These Gram-negative bacteria bend, flex, and swim in a spiral fashion; they translate at speeds greater than 10 body lengths per second. The large size of the spirillum permits direct observation of cell motility in single individual bacteria. After desiccation (i.e., absence of standing water for at least 24 h), large populations developed in mat samples remoistened with sea water. Ultrastructural observations reveal abundant large sulfur globules irregularly distributed in the cytoplasm. A multilayered cell wall, pliable and elastic yet rigid, distends around the sulfur globules. Details of the wall, multiflagellated termini, and large cytoplasmic sulfur globules indicate that these fast-moving spirilla are distinctive enough to warrant a genus and species designation: Titanospirillum velox genus nov., sp. nov. The same collection techniques at a similar habitat in the United States (Plum Island, northeast Essex County, Massachusetts) also yielded large populations of the bacterium among purple phototrophic and other inhabitants of sulfurous microbial-mat muds. The months-long survival of T. velox from Spain and from the United States in closed jars filled with mud taken from both localities leads us to infer that this large spirillum has a cosmopolitan distribution. (+info)
The Escherichia coli ssuEADCB gene cluster is required for the utilization of sulfur from aliphatic sulfonates and is regulated by the transcriptional activator Cbl.
(26/2084)
The growth properties of an Escherichia coli strain carrying a chromosomal deletion of the ssuEADCB genes (formerly designated ycbPONME) indicated that the products of this gene cluster are required for the utilization of sulfur from aliphatic sulfonates. Sequence similarity searches indicated that the proteins encoded by ssuA, ssuB, and ssuC are likely to constitute an ABC type transport system, whereas ssuD and ssuE encode an FMNH(2)-dependent monooxygenase and an NAD(P)H-dependent FMN reductase, respectively (Eichhorn, E., van der Ploeg, J. R., and Leisinger, T. (1999) J. Biol. Chem. 274, 26639-26646). Synthesis of beta-galactosidase from a transcriptional chromosomal ssuE'-lacZ fusion was repressed by sulfate or cystine and depended on the presence of a functional cbl gene, which encodes a LysR-type transcriptional regulator. Electrophoretic mobility shift assays with the ssu promoter region and measurements of beta-galactosidase from plasmid-encoded ssuE'-'lacZ fusions showed that full expression of the ssu operon required the presence of a Cbl-binding site upstream of the -35 region. CysB, the LysR transcriptional regulator for the cys genes, was not required for expression of a chromosomal ssuE'-lacZ fusion although the ssu promoter region contained three CysB-binding sites. Integration host factor could also occupy three binding sites in the ssu promoter region but had no influence on expression of a chromosomal ssuE'-lacZ fusion. (+info)
Sulfuric acid on Europa and the radiolytic sulfur cycle.
(27/2084)
A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes. (+info)
Proline-rich antimicrobial peptide, PR-39 gene transduction altered invasive activity and actin structure in human hepatocellular carcinoma cells.
(28/2084)
PR-39 is an endogenous proline-rich antimicrobial peptide which induces the synthesis of syndecan-1, a transmembrane heparan sulphate proteoglycan involved in cell-to-matrix interactions and wound healing. Previously, we revealed that the expression of syndecan-1 was reduced in human hepatocellular carcinomas with high metastatic potential and speculated that syndecan-1 played an important role in inhibition of invasion and metastasis. It is assumed that a modification of this process with PR-39 and syndecan-1 may result in a new strategy by which it can inhibit the invasion and metastasis. Therefore, we transduced a gene of PR-39 into human hepatocellular carcinoma cell line HLF, which shows a low expression of syndecan-1 and a high in vitro invasive activity, and examined whether this procedure could reduce the invasive activity of tumour cells. In two transfectants with PR-39 gene, the syndecan-1 expression was induced and the invasive activity in type I collagen-coated chamber was inhibited. Moreover, these transfectants showed the suppression of motile activity assayed by phagokinetic tracks in addition to the disorganization of actin filaments observed by a confocal imaging system. In contrast, five transfectants with syndecan-1 gene in the HLF cells revealed suppression of invasive activity but did not alter the motile activity and actin structures of the cell. These results suggest that PR-39 has functions involved in the suppression of motile activity and alteration of actin structure on human hepatocellular carcinoma cells in addition to the suppression of invasive activity which might result from the induction of syndecan-1 expression. (+info)
Dimethylsulfoniopropionate and methanethiol are important precursors of methionine and protein-sulfur in marine bacterioplankton.
(29/2084)
Organic sulfur compounds are present in all aquatic systems, but their use as sources of sulfur for bacteria is generally not considered important because of the high sulfate concentrations in natural waters. This study investigated whether dimethylsulfoniopropionate (DMSP), an algal osmolyte that is abundant and rapidly cycled in seawater, is used as a source of sulfur by bacterioplankton. Natural populations of bacterioplankton from subtropical and temperate marine waters rapidly incorporated 15 to 40% of the sulfur from tracer-level additions of [(35)S]DMSP into a macromolecule fraction. Tests with proteinase K and chloramphenicol showed that the sulfur from DMSP was incorporated into proteins, and analysis of protein hydrolysis products by high-pressure liquid chromatography showed that methionine was the major labeled amino acid produced from [(35)S]DMSP. Bacterial strains isolated from coastal seawater and belonging to the alpha-subdivision of the division Proteobacteria incorporated DMSP sulfur into protein only if they were capable of degrading DMSP to methanethiol (MeSH), whereas MeSH was rapidly incorporated into macromolecules by all tested strains and by natural bacterioplankton. These findings indicate that the demethylation/demethiolation pathway of DMSP degradation is important for sulfur assimilation and that MeSH is a key intermediate in the pathway leading to protein sulfur. Incorporation of sulfur from DMSP and MeSH by natural populations was inhibited by nanomolar levels of other reduced sulfur compounds including sulfide, methionine, homocysteine, cysteine, and cystathionine. In addition, propargylglycine and vinylglycine were potent inhibitors of incorporation of sulfur from DMSP and MeSH, suggesting involvement of the enzyme cystathionine gamma-synthetase in sulfur assimilation by natural populations. Experiments with [methyl-(3)H]MeSH and [(35)S]MeSH showed that the entire methiol group of MeSH was efficiently incorporated into methionine, a reaction consistent with activity of cystathionine gamma-synthetase. Field data from the Gulf of Mexico indicated that natural turnover of DMSP supplied a major fraction of the sulfur required for bacterial growth in surface waters. Our study highlights a remarkable adaptation by marine bacteria: they exploit nanomolar levels of reduced sulfur in apparent preference to sulfate, which is present at 10(6)- to 10(7)-fold higher concentrations. (+info)
Sequential biosynthesis of sulfated and/or sialylated Lewis x determinants by transferases of the human bronchial mucosa.
(30/2084)
The structural determination of sulfated carbohydrate chains from a cystic fibrosis patient respiratory mucins has shown that sulfation may occur either on the C-3 of the terminal Gal, or on the C-6 of the GlcNAc residue of a terminal N -acetyllactosamine unit. The two enzymes responsible for the transfer of sulfate from PAPS to the C-3 of Gal or to the C-6 of GlcNAc residues have been characterized in human respiratory mucosa. These two enzymes, in conjunction with fucosyl- and sialyltransferases, allow the synthesis of different sulfated epitopes such as 3-sulfo Lewis x (with a 3- O -sulfated Gal), 6-sulfo Lewis x and 6-sulfo-sialyl Lewis x (with a 6- O -sulfated GlcNAc). In the present study, the sequential biosynthesis of these epitopes has been investigated using microsomal fractions from human respiratory mucosa incubated with radiolabeled nucleotide-sugars or PAPS, and oligosaccharide acceptors, mostly prepared from human respiratory mucins. The structures of the radiolabeled products have been determined by their coelution in HPAEC with known oligosaccharidic standards. In the biosynthesis of 6- O -sulfated carbohydrate chains by the human respiratory mucosa, the 6- O -sulfation of a terminal nonreducing GlcNAc residue precedes beta1-4-galactosylation, alpha2-3-sialylation (to generate 6-sulfo-sialyl- N -acetyllactosamine), and alpha1-3-fucosylation (to generate the 6-sulfo-sialyl Lewis x determinant). The 3- O -sulfation of a terminal N -acetyllactosamine may occur if this carbohydrate unit is not substituted. Once an N -acetyllactosamine unit is synthesized, alpha1-3-fucosylation of the GlcNAc residue to generate a Lewis x structure blocks any further substitution. Therefore, the present study defines the pathways for the biosynthesis of Lewis x, sialyl Lewis x, sulfo Lewis x, and 6-sulfo-sialyl Lewis x determinants in the human bronchial mucosa. (+info)
Clinical correlation of hepatic flow studies.
(31/2084)
In 100 consecutive hepatic flow studies, 84 were read as negative. Of these, 73 (87%) also had negative static images. Knowing the nature of the primary tumor did not definitively aid in predicting whether hepatic meastases would have detectable early flow. Five cases showed early flow without defects seen in the static images. Three of these were probably related to lymphomas or allied disorders with altered flow. Two cases were in individuals with gastric carcinoma who had abdoninal radiation. One extrahepatic tumor was detected in the series. (+info)
Effect of various ions, pH, and osmotic pressure on oxidation of elemental sulfur by Thiobacillus thiooxidans.
(32/2084)
The oxidation of elemental sulfur by Thiobacillus thiooxidans was studied at pH 2.3, 4.5, and 7.0 in the presence of different concentrations of various anions (sulfate, phosphate, chloride, nitrate, and fluoride) and cations (potassium, sodium, lithium, rubidium, and cesium). The results agree with the expected response of this acidophilic bacterium to charge neutralization of colloids by ions, pH-dependent membrane permeability of ions, and osmotic pressure. (+info)