Freshwater Bacteria Can Methylate Selenium through the Thiopurine Methyltransferase Pathway

Involvement of the bacterial thiopurine methyltransferase (bTPMT) in natural selenium methylation by freshwater was investigated. A freshwater environment that had no known selenium contamination but exhibited reproducible emission of dimethyl selenide (DMSe) or dimethyl diselenide (DMDSe) when it was supplemented with an organic form of selenium [(methyl)selenocysteine] or an inorganic form of selenium (sodium selenite) was used. The distribution of the bTPMT gene (tpm) in the microflora was studied. Freshwater bacteria growing on 10 μM sodium selenite and 10 μM sodium selenate were isolated, and 4.5 and 10% of the strains, respectively, were shown by colony blot hybridization to hybridize with a Pseudomonas syringae tpm DNA probe. Ribotyping showed that these strains are closely related. The complete rrs sequence of one of the strains, designated Hsa.28, was obtained and analyzed. Its closest phyletic neighbor was found to be the Pseudomonas anguilliseptica rrs sequence. The Hsa.28 strain grown with sodium selenite or (methyl)selenocysteine produced significant amounts of DMSe and DMDSe. The Hsa.28 tpm gene was isolated by genomic DNA library screening and sequencing. BLASTP comparisons of the deduced Hsa.28 bTPMT sequence with P. syringae, Pseudomonas aeruginosa, Vibrio cholerae, rat, and human thiopurine methyltransferase sequences revealed that the levels of similarity were 52 to 71%. PCR-generated Escherichia coli subclones containing the Hsa.28 tpm open reading frame were constructed. E. coli cells harboring the constructs and grown with sodium selenite or (methyl)selenocysteine produced significant levels of DMSe and DMDSe, confirming that the gene plays a role in selenium methylation. The effect of strain Hsa.28 population levels on freshwater DMSe and DMDSe emission was investigated. An increase in the size of the Hsa.28 population was found to enhance significantly the emission of methyl selenides by freshwater samples supplemented with sodium selenite or (methyl)selenocysteine. These data suggest that bTPMT can play a role in natural freshwater selenium methylation processes.     

Heterogeneous Cell Density and Genetic Structure of Bacterial Pools Associated with Various Soil Microenvironments as Determined by Enumeration and DNA Fingerprinting Approach (RISA)

Abstract The cell density and the genetic structure of bacterial subcommunities (further named pools) present in the various microenvironments of a silt loam soil were investigated. The microenvironments were isolated first using a procedure of soil washes that separated bacteria located outside aggregates (outer part) from those located inside aggregates (inner part). A nondestructive physical fractionation was then applied to the inner part in order to separate bacteria located inside stable aggregates of different size (size fractions, i.e., two macroaggregate fractions, two microaggregate fractions, and the dispersible day fraction). Bacterial densities measured by acridine orange direct counts (AODC) and viable heterotrophic (VH) cell enumerations showed the heterogeneous quantitative distribution of cells in soil. Bacteria were preferentially located in the inner part with 87.6% and 95.4% of the whole AODC and VH bacteria, respectively, and in the microaggregate and dispersible clay fractions of this part with more than 70% and 80% of the whole AODC and VH bacteria, respectively. The rRNA intergenic spacer analysis (RISA) was used to study the genetic structure of the bacterial pools. Different fingerprints and consequently different genetic structures were observed between the unfractionated soil and the microenvironments, and also among the various microenvironments, giving evidence that some populations were specific to a given location in addition to the common populations of all the microenvironments. Cluster and multivariate analysis of RISA profiles showed the weak contribution of the pools located in the macroaggregate fractions to the whole soil community structure, as well as the clear distinction between the pool associated to the macroaggregate fractions and the pools associated to the microaggregate ones. Furthermore, these statistical analyses allowed us to ascertain the influence of the clay and organic matter content of microenvironments on the genetic structure relatedness between pools. Received: 15 December 1999; Accepted: 5 April 2000; Online Publication: 19 May 2000     

A soil microscale study to reveal the heterogeneity of Hg(II) impact on indigenous bacteria by quantification of adapted phenotypes and analysis of community DNA fingerprints

The short term impact of 50 μM Hg(II) on soil bacterial community structure was evaluated in different microenvironments of a silt loam soil in order to determine the contribution of bacteria located in these microenvironments to the overall bacterial response to mercury spiking. Microenvironments and associated bacteria, designated as bacterial pools, were obtained by successive soil washes to separate the outer fraction, containing loosely associated bacteria, and the inner fraction, containing bacteria retained into aggregates, followed by a physical fractionation of the inner fraction to separate aggregates according to their size (size fractions). Indirect enumerations of viable heterotrophic (VH) and resistant (Hg(R)) bacteria were performed before and 30 days after mercury spiking. A ribosomal intergenic spacer analysis (RISA), combined with multivariate analysis, was used to compare modifications at the community level in the unfractionated soil and in the microenvironments. The spatial heterogeneity of the mercury impact was revealed by a higher increase of Hg(R) numbers in the outer fraction and in the coarse size fractions. Furthermore, shifts in RISA patterns of total community DNA indicated changes in the composition of the dominant bacterial populations in response to Hg(II) stress in the outer and in the clay size fractions. The heterogeneity of metal impact on indigenous bacteria, observed at a microscale level, is related to both the physical and chemical characteristics of the soil microenvironments governing mercury bioavailability and to the bacterial composition present before spiking.     

Age of spent Octopus vulgaris and stress mark analysis using beaks of wild individuals

Age estimation of the cephalopod Octopus vulgaris by using beaks has improved in recent years, but maximum age and longevity in the wild have not been confirmed due to the low availability of senescent wild octopuses. In this study, a beak analysis of lateral wall surfaces (LWS) from 20 spent specimens confirmed the 1-year lifecycle of the species in Central East Atlantic waters. Stress marks (checks) were clearly located in the daily increment sequence of rostrum sagittal sections (RSS). The highest daily variations in sea surface temperature (ΔT) that occurred during the last months of their lifetimes coincided with the locations of the marks on the beak, enabling confirmation of O. vulgaris beaks as life recorders for the first time. It also supports the daily deposition of RSS beak increments in the wild. Individuals were grouped into two main zones, at 20ºN and 18ºN, respectively. Both groups showed different thermal check patterns, in accordance with the oceanographic differences. Two other checks (not coinciding with high values of ΔT) were observed in RSS at averages of 15 and 28 days before death, respectively, which were interpreted as responding to senescent-related events.     

Oxidation and removal of industrial textile dyes by a novel peroxidase extracted from post-harvest lentil (Lens culinaris L.) stubble

The degradation and removal of a series of dyes used in the textile industry for polyester/wool (PES/WO) blends and present in effluents, such as Green, Ash-Grey, Black, Navy Blue, Red and Yellow Domalan, and Orange and Red Bemacid, by catalytic action, in the presence of H₂O₂, of extracts of a novel peroxidase from postharvest lentil stubble was investigated. The extracts of this peroxidase (LSP) were effective in degrading these lastgeneration textile dyes, especially Green Domalan, Orange Bemacid, Grey and Black Domalan. A sensitivity study was carried out for Green Domalan biodegradation to determine the effects of process parameters such as pH, H₂O₂, enzyme and dye concentrations, contact and centrifugation times, and temperature. Standard ecotoxicity studies performed with Vibrio fischeri revealed that the dye solutions treated with peroxidase and H₂O₂ were less ecotoxic than the untreated ones.     

Distribution and genetic diversity of bacterial thiopurine methyltransferases in soils emitting dimethyl selenide

Dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe) emissions by soil samples spiked with selenite or (methyl)selenocysteine, with or without a supplement of nutrient broth and glucose were measured. DMSe was the main form of volatile Se produced, and was observed for both Se-substrates. DMDSe was only emitted from soils spiked with (methyl)selenocysteine. Two bacterial thiopurine methyltransferases (TPMTs), TPMT-I and TPMT-E, have been reported to be involved in DMSe and DMDSe emissions [J. Bacteriol. 184 (2002) 3146; Appl. Environ. Microbiol. 69 (2003) 3784]. To establish if these TPMTs or other members of their gene family could have contributed to the DMSe emissions observed, the diversity of bTPMT gene (tpm) sequences among the soils of this study was investigated. Total DNAs from these soils were extracted and screened using the tpm PTCF2-PTCR2 consensus primers defined to PCR amplify this gene family. The PCR products obtained from two soils were cloned, analysed by PCR-RFLP, and sequenced. Their analysis showed an important diversity of tpm lineages (around 12) in soils. Phylogenetic analysis of the deduced TPMT sequences of these soils revealed lineages not previously recorded in the databases, sequences closely related or identical to freshwater TPMTs, or sequences encoding TPMTs closely related to those of Pseudomonas fragi TPMT-K, Pseudomonas Hsa.28 TPMT-I, or Colwellia psychrerythraea TPMT-Z. Nested PCRs, allowing detection of about 13 distinct tpm soil and freshwater lineages by PTCF2-PTCR2 PCR screenings, were performed on the soil total DNAs. These PCRs confirmed the sequencing data, and allowed to recover lineages not detected by the cloning strategy. These results indicate that soils, like the freshwater samples, harbour TPMT-I gene sequences but may also have distinct tpm lineages. This study further supports our hypothesis that TPMTs contribute to DMSe soil emissions.     

Genome sequence of the human- and animal-pathogenic strain Nocardia cyriacigeorgica GUH-2

The pathogenic strain Nocardia cyriacigeorgica GUH-2 was isolated from a fatal human nocardiosis case, and its genome was sequenced. The complete genomic sequence of this strain contains 6,194,645 bp, an average G+C content of 68.37%, and no plasmids. We also identified several protein-coding genes to which N. cyriacigeorgica's virulence can potentially be attributed.     

Hierro intravenoso,recuperación funcional y delirium en pacientes con fractura de cadera. Estudio FEDEREF. Ensayo clínico unicéntrico aleatorizado,controlado con placebo,doble ciego. Número EudraCT: 2014-001923-53

Introduction

There are no previous studies evaluating the effect of intravenous iron therapy on functional and cognitive status of patients with hip fracture (HF).

Mitochondrial energetic metabolism: A simplified model of TCA cycle with ATP production

Mitochondria play a central role in cellular energetic metabolism. The essential parts of this metabolism are the tricarboxylic acid (TCA) cycle, the respiratory chain and the adenosine triphosphate (ATP) synthesis machinery. Here a simplified model of these three metabolic components with a limited set of differential equations is presented. The existence of a steady state is demonstrated and results of numerical simulations are presented. The relevance of a simple model to represent actual in vivo behavior is discussed.