The microbial diversity of the Su Bentu cave, Italy and the influence of human exploration.

Introduction: The microbial diversity in the Su Bentu Cave (Sardinia, Italy) was investigated by means of Illumina MiSeq analysis. The hypogean environment is of great interest for astrobiological research as cave conditions may resemble those in extra-terrestrial regions. Furthermore, they hold high potential to identify novel, extremely adapted organisms to severely oligo-trophic habitats. However, the influence of human is not neglectable and in-depth investigations are needed to determine the impact of exploration on an otherwise mostly pristine ecosystem. The cave investigated in this study develops for several kilometres into the mountain, two hundred metres below the topographic surface and is characterized by a strong air circulation. Its structure is composed of huge passages carved in limestone where an ephemeral underground stream creates some lakes, close to which seven samples of visible calcite rafts, manganese deposits and moonmilk (a hydrated calcium carbonate speleothem), were sampled during an expedition in 2014. Other samples were re-trieved from a frequently used campsite and from some dry cave passages leading deeper into the cave

Galileo dust data from the jovian system: 2000 to 2003

The Galileo spacecraft was orbiting Jupiter between Dec 1995 and Sep 2003. The Galileo dust detector monitored the jovian dust environment between about 2 and 370 R_J (jovian radius R_J = 71492 km). We present data from the Galileo dust instrument for the period January 2000 to September 2003. We report on the data of 5389 particles measured between 2000 and the end of the mission in 2003. The majority of the 21250 particles for which the full set of measured impact parameters (impact time, impact direction, charge rise times, charge amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in radius), most of them originating from Jupiter's innermost Galilean moon Io. Their impact rates frequently exceeded 10 min^-1. Surprisingly large impact rates up to 100 min^-1 occurred in Aug/Sep 2000 when Galileo was at about 280 R_J from Jupiter. This peak in dust emission appears to coincide with strong changes in the release of neutral gas from the Io torus. Strong variability in the Io dust flux was measured on timescales of days to weeks, indicating large variations in the dust release from Io or the Io torus or both on such short timescales. Galileo has detected a large number of bigger micron-sized particles mostly in the region between the Galilean moons. A surprisingly large number of such bigger grains was measured in March 2003 within a 4-day interval when Galileo was outside Jupiter's magnetosphere at approximately 350 R_J jovicentric distance. Two passages of Jupiter's gossamer rings in 2002 and 2003 provided the first actual comparison of in-situ dust data from a planetary ring with the results inferred from inverting optical images.Comment: 59 pages, 13 figures, 6 tables, submitted to Planetary and Space Scienc

The body composition monitor: a flexible tool for routine fluid management across the haemodialysis population

Bioimpedance measurements with the Body Composition Monitor (BCM) have been shown to improve fluid management in haemodialysis. However, there is a lack of a sufficiently robust evidence-base for use of the BCM outside of standard protocols. This study aims to define the error associated with BCM measurement using alternate paths and timings to allow the use of BCM with confidence in a range of clinical scenarios. BCM measurements were made in 48 healthy controls and in 48 stable haemodialysis patients before and immediately after dialysis. The effect of utilising alternative measurement paths was assessed using mixed effects models and the effect of measuring post-dialysis was assessed by comparing changes in BCM-measured overhydration (OH) with weight changes over dialysis. The data from healthy controls suggest that there is no difference in BCM-measured OH between all the whole-body paths other than the ankle-to-ankle measurement. Dialysis patients showed similar results other than having higher BCM-measured OH when measured across the site of a vascular access. There was good agreement between BCM-measured OH from the standard path and change in weight, suggesting post-dialysis measurements can be utilised. These results suggest BCM protocols can be flexible regarding measurement paths and timing of measurement to ensure as many patients as possible can benefit from the technology

Biology of a widespread uncultivated archaeon that contributes to carbon fixation in the subsurface

Subsurface microbial life contributes significantly to biogeochemical cycling, yet it remains largely uncharacterized, especially its archaeal members. This 'microbial dark matter' has been explored by recent studies that were, however, mostly based on DNA sequence information only. Here, we use diverse techniques including ultrastuctural analyses to link genomics to biology for the SM1 Euryarchaeon lineage, an uncultivated group of subsurface archaea. Phylogenomic analyses reveal this lineage to belong to a widespread group of archaea that we propose to classify as a new euryarchaeal order ('Candidatus Altiarchaeales'). The representative, double-membraned species 'Candidatus Altiarchaeum hamiconexum' has an autotrophic metabolism that uses a not-yet-reported Factor(420)-free reductive acetyl-CoA pathway, confirmed by stable carbon isotopic measurements of archaeal lipids. Our results indicate that this lineage has evolved specific metabolic and structural features like nano-grappling hooks empowering this widely distributed archaeon to predominate anaerobic groundwater, where it may represent an important carbon dioxide sink

Resonant Cavity Perturbation: A Promising New Method for the Assessment of Total Body Water in Children

The accurate measurement of total body water (TBW) in children has important clinical and nutritional applications. Resonant cavity perturbation (RCP) is a new method for estimating TBW. This method measures the dielectric properties of the body which are related to body water. For RCP measurements, each subject lay supine on a bed inside a screened room which acts as a resonant cavity. A network analyser measures the frequencies of two low-order cavity resonances of the room, with electric-field vectors that were respectively vertical and horizontal, the resonant frequency shifts relative to the empty room are then derived. These frequency shifts correlates with TBW. The aims of this present study were to a) develop TBWRCP predictive equations for children using TBWdil as the criterion method, b) cross-validate the derived equations, c) determine precision of the TBWRCP method, and d) compare the criterion method TBWdil with three methods of estimating TBW: RCP, MFBIS and Anthropometry. Predictive equations, independent of sex, were developed with linear regression in a group of 36 children. The relationship between combined RCP frequency shifts and TBWdilution had an r2=0.90 and standard error of the estimate (SEE) =1.42kg. Multiple regression analysis, that included a term for body mass index, only had a small effect on r2=0.93 and SEE=1.25kg. In-vivo TBW precision for the vertical, horizontal and combined frequency modes ranged from 0.7 to 3.4%. Bland Altman analysis indicated close agreement between the criterion method TBWdil and the three other methods of TBW estimation. Mean differences were TBWRCP(2) = 0.01+/-1.34kg, TBWMFBIS = 0.45+/-1.35kg, TBWAnthropometry = 0.29+/-1.29kg. Currently the RCP method does not significantly improve the prediction of TBW compared to MFBIS and anthropometry in this initial study. However the derived equation was independent of sex and body size had only a small effect

Analysis of bacterial profiles of AGBRESA participants – a study concerning terrestrial astronauts under simulated microgravity

Introduction: Long-term space missions are accompanied by harmful environmental conditions like microgravity. Due to the reduced gravity, astronauts adapt to their environment resulting in tissue fluidic shifts. Since the knowledge about microbiome data in space is sparse and conduction of experiments at the ISS is complex, suitable analogs are needed. Therefore, the first cooperative bed-rest study called Artificial Gravity Bed-Rest study with ESA (AGBRESA), by NASA, ESA and DLR offered optimal features to investigate possible correlations between microbial shifts and physiological microgravity by using -6° head-downtilt (HDT). The aim of this survey was to identify changes within the standardized conditions, such as diet and wrongly distributed tissue fluids to reveal causal connections among health state and microbial communities

MEXEM – Mars Exposed Extremophile Mixture – a space experiment to investigate the capability of anaerobic organisms to survive on Mars

Assessing the habitability of Mars and detecting life, if it ever existed there, depends on knowledge of whether the combined environmental stresses experienced on Mars are compatible with life as we know it and whether a record of that life could ever be detected. So far, only few investigations were performed to understand the combined effect of different environmental stresses on survival and growth of anaerobic and extremophilic organisms. In the space experiment MEXEM (formerly known as MASE-in-SPACE) the hypothesis will be tested that selected terrestrial organisms, enrichment cultures and original samples from extreme Mars-analogue environments on Earth are able to withstand the Martian environ- mental stress factors due to their highly effective cellular and molecular adaptation and repair mechanisms. In addition, artificially fossilized and aged isolates from Mars-analogue environments on Earth will be examined and assessed with respect to their suitability for biosigna- ture identification. MEXEM samples will be (i) oxygen-depleted natural sediment samples, (ii) natural sediments spiked with selected, defined strains representative for the respective analogue site, (iii) individual (facultative) anaerobic / micro-aerophilic species including ciliates and viruses, (iv) defined mixtures of these biological entities, (v) isolated strains from samples collected inside the ISS and (vi) artificially fossilized isolates from the natural environments. Most of these samples and isolates were obtained from Mars-analogue envi- ronments on Earth in the frame of the EC funded project MASE (Grant Agreement 607297) and from the space experiment EXTREMOPHILES (PI C. Moissl-Eichinger). MEXEM will be flown outside on the ISS in the new exobiology facility ESA is building now. It offers the possibility to simulate of the martian environment, in particular the martian UV cl e, which cannot be done in the lab, but also martian atmosphere and pressure in LEO

A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2

The peculiar object P/2010 A2 was discovered by the LINEAR near-Earth asteroid survey in January 2010 and given a cometary designation due to the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized class of 'Main Belt Comets' (MBCs). If confirmed, this new object would greatly expand the range in heliocentric distance over which MBCs are found. Here we present observations taken from the unique viewing geometry provided by ESA's Rosetta spacecraft, far from the Earth, that demonstrate that the trail is due to a single event rather than a period of cometary activity, in agreement with independent results from the Hubble Space Telescope (HST). The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around February 10, 2009.Comment: Published in Nature on 14/10/2010. 25 pages, includes supplementary materia

The primordial nucleus of comet 67P/Churyumov-Gerasimenko

Context. We investigate the formation and evolution of comet nuclei and other trans-Neptunian objects (TNOs) in the solar nebula and primordial disk prior to the giant planet orbit instability foreseen by the Nice model. Aims. Our goal is to determine whether most observed comet nuclei are primordial rubble-pile survivors that formed in the solar nebula and young primordial disk or collisional rubble piles formed later in the aftermath of catastrophic disruptions of larger parent bodies. We also propose a concurrent comet and TNO formation scenario that is consistent with observations. Methods. We used observations of comet 67P/Churyumov-Gerasimenko by the ESA Rosetta spacecraft, particularly by the OSIRIS camera system, combined with data from the NASA Stardust sample-return mission to comet 81P/Wild 2 and from meteoritics; we also used existing observations from ground or from spacecraft of irregular satellites of the giant planets, Centaurs, and TNOs. We performed modeling of thermophysics, hydrostatics, orbit evolution, and collision physics. Results. We find that thermal processing due to short-lived radionuclides, combined with collisional processing during accretion in the primordial disk, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles like CO and CO2; they contain little to no amorphous water ice, and have experienced extensive metasomatism and aqueous alteration due to liquid water. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. Contrarily, comet nuclei have low density, high porosity, weak strength, are rich in supervolatiles, may contain amorphous water ice, and do not display convincing evidence of in situ metasomatism or aqueous alteration. We outline a comet formation scenario that starts in the solar nebula and ends in the primordial disk, that reproduces these observed properties, and additionally explains the presence of extensive layering on 67P/Churyumov-Gerasimenko (and on 9P/Tempel 1 observed by Deep Impact), its bi-lobed shape, the extremely slow growth of comet nuclei as evidenced by recent radiometric dating, and the low collision probability that allows primordial nuclei to survive the age of the solar system. Conclusions. We conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles. We argue that TNOs formed as a result of streaming instabilities at sizes below ∼400 km and that ∼350 of these grew slowly in a low-mass primordial disk to the size of Triton, Pluto, and Eris, causing little viscous stirring during growth. We thus propose a dynamically cold primordial disk, which prevented medium-sized TNOs from breaking into collisional rubble piles and allowed the survival of primordial rubble-pile comets. We argue that comets formed by hierarchical agglomeration out of material that remained after TNO formation, and that this slow growth was a necessity to avoid thermal processing by short-lived radionuclides that would lead to loss of supervolatiles, and that allowed comet nuclei to incorporate ∼3 Myr old material from the inner solar system