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1.
Geobiology ; 15(2): 324-339, 2017 03.
Article in English | MEDLINE | ID: mdl-28042698

ABSTRACT

Anoxygenic, photosynthetic bacteria are common at redox boundaries. They are of interest in microbial ecology and geosciences through their role in linking the carbon, sulfur, and iron cycles, yet much remains unknown about how their flexible carbon metabolism-permitting either autotrophic or heterotrophic growth-is recorded in the bulk sedimentary and lipid biomarker records. Here, we investigated patterns of carbon isotope fractionation in a model photosynthetic sulfur-oxidizing bacterium, Allochromatium vinosum DSM180T . In one treatment, A. vinosum was grown with CO2 as the sole carbon source, while in a second treatment, it was grown on acetate. Different intracellular isotope patterns were observed for fatty acids, phytol, individual amino acids, intact proteins, and total RNA between the two experiments. Photoautotrophic CO2 fixation yielded typical isotopic ordering for the lipid biomarkers: δ13 C values of phytol > n-alkyl lipids. In contrast, growth on acetate greatly suppressed intracellular isotopic heterogeneity across all molecular classes, except for a marked 13 C-depletion in phytol. This caused isotopic "inversion" in the lipids (δ13 C values of phytol < n-alkyl lipids). The finding suggests that inverse δ13 C patterns of n-alkanes and pristane/phytane in the geologic record may be at least in part a signal for photoheterotrophy. In both experimental scenarios, the relative isotope distributions could be predicted from an isotope flux-balance model, demonstrating that microbial carbon metabolisms can be interrogated by combining compound-specific stable isotope analysis with metabolic modeling. Isotopic differences among molecular classes may be a means of fingerprinting microbial carbon metabolism, both in the modern environment and the geologic record.


Subject(s)
Carbon Isotopes/analysis , Chromatiaceae/chemistry , Chromatiaceae/growth & development , Acetates/metabolism , Amino Acids/analysis , Carbon Cycle , Carbon Dioxide/metabolism , Chromatiaceae/metabolism , Fatty Acids/analysis , Phytol/analysis , Proteins/analysis , RNA, Bacterial/analysis
2.
Org Biomol Chem ; 14(1): 335-44, 2016 Jan 07.
Article in English | MEDLINE | ID: mdl-26611567

ABSTRACT

DC-SIGN (dendritic cell-specific ICAM-3 grabbing non-integrin) is a C-type lectin receptor (CLR) present, mainly in dendritic cells (DCs), as one of the major pattern recognition receptors (PRRs). This receptor has a relevant role in viral infection processes. Recent approaches aiming to block DC-SIGN have been presented as attractive anti-HIV strategies. DC-SIGN binds mannose or fucose-containing carbohydrates from viral proteins such as the HIV envelope glycoprotein gp120. We have previously demonstrated that multivalent dendrons bearing multiple copies of glycomimetic ligands were able to inhibit DC-SIGN-dependent HIV infection in cervical explant models. Optimization of glycomimetic ligands requires detailed characterization and analysis of their binding modes because they notably influence binding affinities. In a previous study we characterized the binding mode of DC-SIGN with ligand 1, which shows a single binding mode as demonstrated by NMR and X-ray crystallography. In this work we report the binding studies of DC-SIGN with pseudotrisaccharide 2, which has a larger affinity. Their binding was analysed by TR-NOESY and STD NMR experiments, combined with the CORCEMA-ST protocol and molecular modelling. These studies demonstrate that in solution the complex cannot be explained by a single binding mode. We describe the ensemble of ligand bound modes that best fit the experimental data and explain the higher inhibition values found for ligand 2.


Subject(s)
Cell Adhesion Molecules/chemistry , Lectins, C-Type/chemistry , Receptors, Cell Surface/chemistry , Trisaccharides/pharmacology , Binding Sites/drug effects , Cell Adhesion Molecules/metabolism , Crystallography, X-Ray , Dendritic Cells , Humans , Lectins, C-Type/metabolism , Ligands , Models, Molecular , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular , Protein Binding/drug effects , Receptors, Cell Surface/metabolism , Structure-Activity Relationship , Trisaccharides/chemical synthesis , Trisaccharides/chemistry
3.
Geobiology ; 12(5): 451-68, 2014 Sep.
Article in English | MEDLINE | ID: mdl-24976102

ABSTRACT

Mahoney Lake represents an extreme meromictic model system and is a valuable site for examining the organisms and processes that sustain photic zone euxinia (PZE). A single population of purple sulfur bacteria (PSB) living in a dense phototrophic plate in the chemocline is responsible for most of the primary production in Mahoney Lake. Here, we present metagenomic data from this phototrophic plate--including the genome of the major PSB, as obtained from both a highly enriched culture and from the metagenomic data--as well as evidence for multiple other taxa that contribute to the oxidative sulfur cycle and to sulfate reduction. The planktonic PSB is a member of the Chromatiaceae, here renamed Thiohalocapsa sp. strain ML1. It produces the carotenoid okenone, yet its closest relatives are benthic PSB isolates, a finding that may complicate the use of okenone (okenane) as a biomarker for ancient PZE. Favorable thermodynamics for non-phototrophic sulfide oxidation and sulfate reduction reactions also occur in the plate, and a suite of organisms capable of oxidizing and reducing sulfur is apparent in the metagenome. Fluctuating supplies of both reduced carbon and reduced sulfur to the chemocline may partly account for the diversity of both autotrophic and heterotrophic species. Collectively, the data demonstrate the physiological potential for maintaining complex sulfur and carbon cycles in an anoxic water column, driven by the input of exogenous organic matter. This is consistent with suggestions that high levels of oxygenic primary production maintain episodes of PZE in Earth's history and that such communities should support a diversity of sulfur cycle reactions.


Subject(s)
Chromatiaceae/genetics , Chromatiaceae/metabolism , Lakes/microbiology , Sulfur/metabolism , British Columbia , Genome, Bacterial , Molecular Sequence Data , Oxidation-Reduction , Phylogeography , Sequence Analysis, DNA
4.
Perspect Psychiatr Care ; 13(4): 156-62, 1975.
Article in English | MEDLINE | ID: mdl-1044024

ABSTRACT

The holiday season is clearly a time of great emotional conflict, especially for schizophrenics. Both the occurrence of the holiday season and the psychoanalytic group process itself stimulate regression in the schizophrenic which uncovers the frustration and anger associated with dependency needs. The therapist who understands the pychodynamics set in motion by the holidays and by psychoanalytic group pschotherapy can utilize the content of group interaction during the holiday season to stimulate group process, the expression of mutual concerns, and cohesion among the members.


Subject(s)
Holidays , Psychoanalytic Therapy , Psychotherapy, Group , Schizophrenia/therapy , Anger , Anxiety/etiology , Attitude of Health Personnel , Defense Mechanisms , Dependency, Psychological , Depression/etiology , Female , Group Processes , Humans , Male , Regression, Psychology
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