Comparative genomics and mutagenesis analyses of choline metabolism in the marine Roseobacter clade

Choline is ubiquitous in marine eukaryotes and appears to be widely distributed in surface marine waters; however, its metabolism by marine bacteria is poorly understood. Here, using comparative genomics and molecular genetic approaches, we reveal that the capacity for choline catabolism is widespread in marine heterotrophs of the marine Roseobacter clade (MRC). Using the model bacterium Ruegeria pomeroyi, we confirm that the betA, betB and betC genes, encoding choline dehydrogenase, betaine aldehyde dehydrogenase and choline sulfatase, respectively, are involved in choline metabolism. The betT gene, encoding an organic solute transporter, was essential for the rapid uptake of choline but not glycine betaine (GBT). Growth of choline and GBT as a sole carbon source resulted in the re-mineralization of these nitrogen-rich compounds into ammonium. Oxidation of the methyl groups from choline requires formyltetrahydrofolate synthetase encoded by fhs in R.pomeroyi, deletion of which resulted in incomplete degradation of GBT. We demonstrate that this was due to an imbalance in the supply of reducing equivalents required for choline catabolism, which can be alleviated by the addition of formate. Together, our results demonstrate that choline metabolism is ubiquitous in the MRC and reveal the role of Fhs in methyl group oxidation in R.pomeroyi

Le Songe d’une nuit d’été

Si aimer le théâtre est le premier plaisir, très vite il est suivi de tous les autres… Jouer : Plaisir ; Lire : Plaisir, Voir : Plaisir. Grandir, augmenter sa culture, aller au théâtre, c’est aussi apprendre à mieux lire, à mieux voir, à être un spectateur de plus en plus critique, donc un « bon » spectateur. Pourquoi on a aimé ou pas ? Jeu ? mise en scène ? Texte ? là sont les vraies questions. Au fur et à mesure de l’apprentissage, on « voit » mieux, on confronte ce que l’on a vu avec ce qu..

Temporal patterns of biological dimethylsulfide (DMS) consumption during laboratory-induced phytoplankton bloom cycles

Phytoplankton bloom cycles were followed for 9 d in two 20 l carboy mesocosms filled with water from the offshore plume of Mobile Bay Alabama, USA, and incubated under fluorescent light. One of the blooms was enriched by addition of nitrate+phosphate (+nutrients), and both blooms were used to study how dimethylsulfide (DMS) concentrations and biological consumption varied over the bloom cycles. Peaks of algal biomass (15-22 µg chlorophyll a l-1) in the blooms were followed within 1 d by peaks of the DMS precursor, particulate dimethylsulfoniopropionate (DMSPp; 100-140 nM). DMS concentrations increased rapidly during the early bloom, rising from 1 nM on Day 1 up to 12 nM in the unamended carboy and up to 17 nM in the +nutrient carboy on Day 6. Maximum values for DMS concentrations, DMS consumption rates (as measured with 35S-DMS), and bacterial production were observed during the early decline of phytoplankton biomass. DMS consumption rates were initially 0.8 nM d-1 and increased to 3.1 nM d-1 in the unamended carboy and to 9.1 nM d-1 in the +nutrient carboy. Rate constants for DMS consumption (0.25-0.95 d-1) initially decreased as DMS concentrations increased, resulting in longer turnover times for DMS during the peak and early decline of the blooms. Assimilation of DMS-sulfur by bacterioplankton accounted for 4-22% of the total DMS consumption and higher rates of DMS assimilation occurred in the +nutrients bloom. Despite a bloom and decline of total heterotrophic bacterial abundances, bacterial community composition at the major phylogenetic group level remained relatively constant in both blooms, although the alpha proteobacteria showed a temporal increase in abundance in the +nutrient carboy. The concentration ratios of DMS:chlorophyll a and DMS:DMSP displayed non-linear, sigmoidal patterns over the bloom cycles and these ratios were not substantially affected by the nutrient amendment. Our results demonstrate that uncoupling of DMS production and biological consumption can occur early in a bloom cycle, causing DMS concentrations to rise significantly before biological consumption responds to draw down the DMS

High dimethylsulfide photolysis rates in nitrate-rich Antarctic waters

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 31 (2004): L11307, doi:10.1029/2004GL019863.The photochemistry of dimethylsulfide (DMS) was examined in the Southern Ocean to assess its impact on the biogeochemical dynamics of DMS in Antarctic waters. Very high DMS photolysis rate constants (0.16–0.23 h−1) were observed in surface waters exposed to full sunlight. DMS photolysis rates increased linearly with added nitrate concentrations, and 35% of the DMS loss in unamended samples was attributed to the photochemistry of ambient nitrate (29 μM). Experiments with optical filters showed that the UV-A band of sunlight (320–400 nm) accounted for ~65% of DMS photolysis suggesting that dissolved organic matter was the main photosensitizer for DMS photolysis. During the austral spring, DMS photolysis was the dominant loss mechanism under non-bloom and non-ice cover conditions owing to the high doses and deep penetration of UV radiation in the water column, low observed microbial consumption rates, and high in situ nitrate concentrations.This work was supported by NSF (OPP- 0230499, DJK; OPP-0230497, RPK)

The sulfur cycle

Author Posting. © Oceanography Society, 2007. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 20, 2 (2007): 117-123.The ocean represents a major reservoir of sulfur on Earth, with large quantities in the form of dissolved sulfate and sedimentary minerals (e.g., gypsum and pyrite). Sulfur occurs in a variety of valence states, ranging from –2 (as in sulfide and reduced organic sulfur) to +6 (as in sulfate). Sulfate is the most stable form of sulfur on today’s oxic Earth; weathering and leaching of rocks and sediments are its main sources to the ocean. In addition, the reduced inorganic forms of sulfur, with oxidation states of –2 and 0 (as in elemental sulfur) are quite common in anoxic environments, with sulfur compounds of mixed valence states (e.g., thiosulfate and polythionates) produced transiently. The natural release of volatile organic sulfur compounds from the ocean, mainly as dimethyl sulfide (DMS), transports sulfur from the ocean to terrestrial regions, and it also affects atmospheric chemistry and the climate system. While they remain very important, natural sulfur emissions have currently been overtaken by anthropogenic emissions, primarily from the burning of fossil fuels.Preparation of this manuscript was partially supported by National Science Foundation grant OCE-0452333 and a fellowship from the Hanse- Wissenschaftskolleg (http://www. h-w-k.de) to SMS, National Science Foundation grants OPP-0230497 and OPP-0083078 to RPK, as well as the Research Center Ocean Margins (RCOM) of the University of Bremen (Germany) to HNSV (RCOM-Nr. 0476)

Provider-initiated HIV testing in health care settings: Should it include client-centered counselling?

To increase access to HIV testing, the WHO and CDC have recommended implementing provider-initiated HIV testing (PITC). To address the resource limitations of the PITC setting, WHO and CDC suggest that patient-provider interactions during PITC may need to focus on providing information and referrals, instead of engaging patients in client-centered counselling, as is recommended during client-initiated HIV testing. Providing HIV prevention information has been shown to be less effective than client-centered counselling in reducing HIV-risk behaviour and STI incidence. Therefore, concerns exist about the efficacy of PITC as an HIV prevention approach. However, reductions in HIV incidence may be greater if more people know their HIV status through expanded availability of PITC, even if PITC is a less effective prevention intervention than is client-initiated HIV testing for individual patients. In the absence of an answer to this public health question, adaptation of effective brief client-centered counselling approaches to PITC should be explored along with research assessing the efficacy of PITC

A novel pathway producing dimethylsulphide in bacteria is widespread in soil environments

The volatile compound dimethylsulphide (DMS) is important in climate regulation, the sulphur cycle and signalling to higher organisms. Microbial catabolism of the marine osmolyte dimethylsulphoniopropionate (DMSP) is thought to be the major biological process generating DMS. Here we report the discovery and characterisation of the first gene for DMSP-independent DMS production in any bacterium. This gene, mddA, encodes a methyltransferase that methylates methanethiol (MeSH) and generates DMS. MddA functions in many taxonomically diverse bacteria including sediment-dwelling pseudomonads, nitrogen-fixing bradyrhizobia and cyanobacteria, and mycobacteria, including the pathogen Mycobacterium tuberculosis. The mddA gene is present in metagenomes from varied environments, being particularly abundant in soil environments, where it is predicted to occur in up to 76% of bacteria. This novel pathway may significantly contribute to global DMS emissions, especially in terrestrial environments, and could represent a shift from the notion that DMSP is the only significant precursor of DMS

Variability of atmospheric dimethylsulphide over the southern Indian Ocean due to changes in ultraviolet radiation

Dimethylsulphide (DMS) is a climatically important component of global biogeochemical cycles, through its role in the sulphur cycle. Changes in ultraviolet radiation (UV) exhibit both positive and negative forcings on the dynamics of production and turnover of DMS and its precursor dimethylsulphoniopropionate (DMSP). In this study we investigate the net forcing of UV on atmospheric DMS. The work is based on a 10-year record of observed DMS at Amsterdam Island in the southern Indian Ocean, and satellite-based retrievals of surface UV and photosynthetically active radiation (PAR). The results show an inverse relationship between UV radiation and atmospheric DMS associated with extreme changes (defined as the greatest 5%) in daily UV, independent of changes in wind speed, sea surface temperature, and PAR

Retrospektive Erhebung der Polytraumadaten von 2007 - 2010 an der Berufsgenossenschaftlichen Unfallklinik Tübingen und am Universitätsklinikum Tübingen - Untersuchung prognostischer Faktoren im Hinblick auf Outcome -

480 Traumapatienten mit einem ISS >= 16 wurden ohne Altersbeschränkung in die Studie eingeschlossen. Der ISS-Mittelwert lag bei 30,2. Dieses Patientenkollektiv entsprach bei der Alters- und Geschlechtsverteilung sowie bei der Verteilung der Unfallarten den Angaben anderer Studien und des TR-DGU. Im Einklang mit der Literatur ließen sich im Schockraum als wichtige Prognosefaktoren im Hinblick auf Letalität Alter, ISS, GCS, Hb, Quick, PTT, BE, Laktat, pH und EK-Gabe bestätigen. Auch hinsichtlich der Entwicklung von Spätkomplikationen wie MOV und Sepsis zeigten sich in der hier vorliegenden Untersuchung diese Parameter mit Ausnahme des Alters und des BE als gute prognostische Faktoren. Außerdem ließen sich beim Vergleich der erhobenen Befunde mit den TR-DGU-Jahresberichten 2011 - 2013 für das Gesamtkollektiv des TR-DGU bzw. für die Patienten des TZT die bereits in den letzten Jahren in der Literatur beschriebenen Tendenzen in der Schwerverletzten-Versorgung weitgehend erkennen, wie zunehmendes Patientenalter, Abnahme des ISS-Mittelwertes, Zunahme des GCS-Mittelwertes am Unfallort, Rückgang der präklinischen Intubationsrate, Rückgang der präklinisch gegebenen Volumenmenge mit Verbesserung der Gerinnungssituation (Quick, PTT) und des Hb-Wertes bei Klinikaufnahme, Rückgang der Bluttransfusionen im Schockraum, Rückgang der Intensiv- und Beatmungszeit, Verbesserung des Outcomes nach GOS 2 - 5 sowie Rückgang der Letalität (GOS 1)