Coupled reductive and oxidative sulfur cycling in the phototrophic plate of a meromictic lake.

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.

Environmental constraints defining the distribution, composition, and evolution of chlorophototrophs in thermal features of Yellowstone National Park.

Chlorophotoautotrophy, the use of chlorophylls to convert light energy into chemical energy for carbon dioxide fixation, is the primary metabolic process linking the inorganic and organic carbon pools on Earth. To understand the potential effects of various environmental constraints on the evolution of chlorophototrophy better, we studied the distribution, diversity, and abundance of chlorophylls and genes involved in their synthesis along geothermal gradients in Yellowstone National Park, Wyoming. Genes involved in chlorophyll biosynthesis were constrained to temperatures of less than ~70 °C and were only detected at this elevated temperature when the pH was in the circumneutral to alkaline range. The upper temperature limit for the detection of chlL/bchL(1) and bchY(2) decreased systematically with increasingly acidic pH, an observation likely attributable to sulfide, which upon oxidation, generates acidic spring water and reduces the availability of bicarbonate the preferred source of inorganic carbon for phototrophs. Spring pH was also the best predictor of the phylogenetic diversity of chlL/bchL communities. The phylogenetic similarity of chlL/bchL genes between sites was significantly correlated with that of chlorophylls. The predominance of chlorophyll a and bacteriochlorophyll a among extracted pigments was consistent with predominance of chlL/bchL genes affiliated with the Cyanobacteria and Chloroflexiales, respectively, and might be related to the fact that the majority of these organisms are photoautotrophs. Together, these results suggest that a combination of temperature, pH, and/or sulfide influences the distribution, diversity, and evolution of chlorophotrophs and the chlorophylls that they synthesize.

Biosynthesis of the biomarker okenone: χ-ring formation.

Purple sulfur bacteria (PSB) mainly occur in anoxic aquatic and benthic environments, where they play important roles in cycling carbon and sulfur. Many PSB characteristically produce the unique keto-carotenoid, okenone, which is important not only for its light absorption and photoprotection properties but also because of its diagenesis product, okenane, which is a biomarker for ancient sediments derived from anoxic environments. The specific methylation pattern of the χ-ring of okenane is unlikely to be formed by diagenetic processes and should therefore reflect an enzymatic activity from okenone biosynthesis. This study describes two enzymes that produce the χ-ring of okenone, the only structural element of okenone preserved in okenane. Genes encoding enzymes of carotenogenesis were identified in the draft genome sequence of an okenone-producing PSB, Thiodictyon sp. strain CAD16. Two divergently transcribed genes encoded a CrtY-type lycopene cyclase and a CrtU/CruE-type γ-carotene desaturase/methyltransferase. Expression of crtY in Escherichia coli showed that this gene encoded a lycopene cyclase that produced γ-carotene as the only product. Although the sequence of the γ-carotene desaturase/methyltransferase was more similar to CrtU sequences of green sulfur bacteria than to CruE sequences of cyanobacteria, expression of the crtU gene in Chlorobaculum tepidum showed that the enzyme produced carotenoids with χ-rings rather than φ-rings. Phylogenetic analysis of the carotene desaturase/methyltransferases revealed that enzymes capable of converting ß-rings to χ-rings have independently evolved at least two times. These results indicate that it probably will not be possible to deduce the activity of carotene desaturase/methyltransferases solely from sequence data.

Rapid method for determination of the activity concentrations of (89)Sr and (90)Sr.

This paper describes a rapid method for determining the activity concentrations of (89)Sr and (90)Sr in air and water using LSC. After sample preparation strontium is separated by extraction chromatography. The chemical yield is determined by X-ray fluorescence. The spectra of the Cerenkov radiation and beta radiation are taken with a LSC. From both spectra the activities of strontium are calculated by means of a spectrum deconvolution method. The results can be obtained within 4.5 hours for particulate filters and 2 hours for water.

Aerial measurements on uranium ore mining, milling and processing areas in Germany.

The paper describes aerial measurements at several sites containing residues from uranium mines, waste rock dumps and tailings ponds of the Wismut company in Saxony and Thuringia. For the measurements, a computerized gamma-ray spectrometer equipped with a HPGe-detector and a NaI(Tl)-detector array with a volume of 121 was used. Radioactive anomalies from natural radionuclides have been detected and mapped. The activity concentrations of 226Ra, 228Th and 40K in areas with elevated radioactivity from natural radionuclides were determined from aerial measurements. Ground-based measurements--as far as available--confirmed these results. The mean 226Ra activity concentrations in the different waste rock dumps were found to be in the range 370 to 1600 Bq kg-1. The highest mean 226Ra activity concentrations were measured for the tailings ponds with values up to 1300 Bq kg-1. For 40K and 208Tl, activity concentrations of 860 and 40 Bq kg-1, respectively, were obtained as averages of all measurements. These values are commonly found in the environment. In general, there is reasonable agreement between the results measured with different detectors and measuring methods.

[Dendritic cells, T- and B-lymphocytes and macrophages in supraglottic and glottic squamous epithelial carcinoma. Location and correlation with prognosis of the illness]. / Dendritische Zellen, T-und B-Lymphozyten und Makrophagen im supraglottischen und glottischen Plattenepithelkarzinom. Lokalisation und Korrelation zur Prognose der Erkrankung.

Dendritic cells play an important role within the mucosal immune system of the upper aerodigestive tract. They process exogenous and endogenous antigens and are able to induce a cytotoxic Tc/s lymphocyte reaction against tumors. Recently published data indicate that the in vitro application of tumor lysate incubated dendritic cells can provide a defense against melanoma. Before these new therapeutic strategies are available for the therapy of laryngeal cancer, basic studies have to be performed concerning the distribution of dendritic cells and other subpopulations, such as T- and B-lymphocytes and macrophages. In the present study the distribution of these subpopulations were examined within the epithelial and connective tissue compartments ("tumor front") of 20T2 squamous cell carcinomas of the supraglottis and glottis. The number of dendritic cells was compared with clinical parameters to check whether a high number of dendritic cells could be correlated with a better prognosis. In contrast to T-lymphocytes, results showed that dendritic cells were mainly located within the epithelial compartment of the tumors, their number ranging from 20 cells/mm2 to > 700 cells/mm2. By comparing each patient's clinical course with the number of dendritic cells, findings showed that those patients who died within the first postoperative year were characterized by a very small number of dendritic cells within their tumor tissue (< 100 cells/mm2). Although the number of patients was low, results indicate that a high number of dendritic cells within tumor tissue suggest a better prognosis.