305,240 research outputs found
BOSS CYANO EXPERIMENT ON THE EXPOSE-R2 SPACE MISSION: ENHANCED SURVIVAL OF CHROOCOCCIDIOPSIS BIOFILMS TO SPACE AND SIMULATED MARS CONDITIONS COMPARED TO PLANKTONIC COUNTERPARTS
No full textThe Biofilm Organisms Surfing Space (BOSS) experiment is part of the EXPOSE-R2 space mission.
In one part of the BOSS experiment three Chroococcidiopsis desert stains (CCMEE 057, CCMEE 029
and CCMEE 064), were exposed to Low Earth Orbit (LEO) in the dried state either as biofilms or
multilayered planktonic samples. Cells were exposed for 16 months to space and Mars-like conditions
outside the International Space Station. Exposure parameters included temperature variations, ionizing
radiation, vacuum or simulated Martian atmosphere and pressure, and Mars-like solar UV irradiation. In
parallel to exposure in LEO, replicates of the experiment were performed on the ground: Some were kept
in the dark under ambient conditions, while others were exposed to stressors (extreme temperature cycles,
Mars-simulated atmosphere or vacuum, and UV
ux) mimicking those undergone during the EXPOSE-R2
space mission, based on data recorded in-
ight. Cyanobacteria were analyzed post-
ight using confocal
microscopy, PCR-based assays and colony forming ability tests. Results are consistent with previous
ground-based simulations of the mission1,2 and demonstrate an overall higher resistance of biofilms when
compared to planktonic as suggested by their increased viability and lower amounts of DNA damage.
1. Baqué, M., Scalzi, G., Rabbow, E., Rettberg, P. Billi, D. Biofilm and Planktonic Lifestyles
Differently Support the Resistance of the Desert Cyanobacterium Chroococcidiopsis Under Space and
Martian Simulations. Orig. life Evol. Biosph. 43, 377-389 (2013).
2. Baqué, M., de Vera, J.-P., Rettberg, P. Billi, D. The BOSS and BIOMEX space experiments on the
EXPOSE-R2 mission: Endurance of the desert cyanobacterium Chroococcidiopsis under simulated space
vacuum, Martian atmosphere, UVC radiation and temperature extremes. Acta Astronaut. 91, 180-186
(2013)
Biofilm and Planktonic Lifestyles Differently Support the Resistance of the Desert Cyanobacterium Chroococcidiopsis Under Space and Martian Simulations
No full textWhen Chroococcidiopsis sp. strain CCMEE 057 from the Sinai Desert and strain CCMEE 029 from the Negev Desert were exposed to space and Martian simulations in the dried status as biofilms or multilayered planktonic samples, the biofilms exhibited an enhanced rate of survival. Compared to strain CCMEE 029, biofilms of strain CCME 057 better tolerated UV polychromatic radiation (5 × 10⁵ kJ/m² attenuated with a 0.1 % neutral density filter) combined with space vacuum or Martian atmosphere of 780 Pa. CCMEE 029, on the other hand, failed to survive UV polychromatic doses higher than 1.5 × 10³ kJ/m². The induced damage to genomic DNA, plasma membranes and photosynthetic apparatus was quantified and visualized by means of PCR-based assays and CLSM imaging. Planktonic samples of both strains accumulated a higher amount of damage than did the biofilms after exposure to each simulation; CLSM imaging showed that photosynthetic pigment bleaching, DNA fragmentation and damaged plasma membranes occurred in the top 3–4 cell layers of both biofilms and of multilayered planktonic samples. Differences in the EPS composition were revealed by molecular probe staining as contributing to the enhanced endurance of biofilms compared to that of planktonic samples. Our results suggest that compared to strain CCMEE 029, biofilms of strain CCMEE 057 might better tolerate 1 year’s exposure in space during the next EXPOSE-R2 mission
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Damage Escape and Repair in Dried Chroococcidiopsis spp. from Hot and Cold Deserts Exposed to Simulated Space and Martian Conditions
No full textThe cyanobacterium Chroococcidiopsis, overlain by 3mm of Antarctic sandstone, was exposed as dried multilayers
to simulated space and martian conditions. Ground-based experiments were conducted in the context of
Lichens and Fungi Experiments (EXPOSE-E mission, European Space Agency), which were performed to
evaluate, after 1.5 years on the International Space Station, the survival of cyanobacteria (Chroococcidiopsis),
lichens, and fungi colonized on Antarctic rock. The survival potential and the role played by protection and
repair mechanisms in the response of dried Chroococcidiopsis cells to ground-based experiments were both
investigated. Different methods were employed, including evaluation of the colony-forming ability, single-cell
analysis of subcellular integrities based on membrane integrity molecular and redox probes, evaluation of the
photosynthetic pigment autofluorescence, and assessment of the genomic DNA integrity with a PCR-based
assay. Desiccation survivors of strain CCMEE 123 (coastal desert, Chile) were better suited than CCMEE
134 (Beacon Valley, Antarctica) to withstand cellular damage imposed by simulated space and martian conditions.
Exposed dried cells of strain CCMEE 123 formed colonies, maintained subcellular integrities, and, depending
on the exposure conditions, also escaped DNA damage or repaired the induced damage upon
rewetting
Endurance of desert-cyanobacteria biofilms to space and simulated Mars conditions during the EXPOSE-R2 space mission
No full textThe aim of the experiment Biofilm Organisms Surfing Space (BOSS), part of the EXPOSE- R2 space mission, is to test whether biofilms can withstand long-term exposure to space and Martian conditions than planktonic counterpart. Three desert isolates of Chroococcidiopsis spp. were included in the BOSS experiment: strain CCMEE 029 from endolithic commu- nities in the Negev Desert, and strains CCMEE 057 and CCMEE 064 from endolithic and hypolithic communities in the Sinai Desert. Dried biofilms and dried multilayered planktonic samples were exposed to both ground-based simulations and to space and Martian simulated conditions in Low Earth Orbit (LEO) within the ESA facility EXPOSE-R2 outside the Inter- national Space Station. Samples were exposed for 16 months to space and Martian simulated conditions, characterized by temperature variations, ionizing radiation, vacuum or simulated Martian atmosphere, in the dark or under attenuated space and Mars-like and solar UV ir- radiation. The effects of those environments on cyanobacterial samples were investigated by using confocal laser scanning microscopy to visualize the biofilm architecture and quantify photosynthetic pigment autofluorescence, PCR-based assays to asses DNA damage and and colony forming ability to test the recovery upon rehydration. Results from the flight mission are consistent with previous ground-based simulations of the mission1,2 and demonstrate an overall higher resistance of biofilms when compared to the planktonic counterpart, showing the former an increased viability and lower amounts of DNA damage
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
Preservation of Biomarkers from Cyanobacteria Mixed with Mars Like Regolith Under Simulated Martian Atmosphere and UV Flux
No full textThe space mission EXPOSE-R2 launched on the 24th of July 2014 to the International Space Station is carrying the BIOMEX (BIOlogy and Mars EXperiment) experiment aimed at investigating the endurance of extremophiles and stability of biomolecules under space and Mars-like conditions. In order to prepare the analyses of the returned samples, ground-based simulations were carried out in Planetary and Space Simulation facilities. During the ground-based simulations, Chroococcidiopsis cells mixed with two Martian mineral analogues (phyllosilicatic and sulfatic Mars regolith simulants) were exposed to a Martian simulated atmosphere combined or not with UV irradiation corresponding to the dose received during a 1-year-exposure in low Earth orbit (or half a Martian year on Mars). Cell survival and preservation of potential biomarkers such as photosynthetic and photoprotective pigments or DNA were assessed by colony forming ability assays, confocal laser scanning microscopy, Raman spectroscopy and PCR-based assays. DNA and photoprotective pigments (carotenoids) were detectable after simulations of the space mission (570 MJ/m² of UV 200–400 nm irradiation and Martian simulated atmosphere), even though signals were attenuated by the treatment. The fluorescence signal from photosynthetic pigments was differently preserved after UV irradiation, depending on the thickness of the samples. UV irradiation caused a high background fluorescence of the Martian mineral analogues, as revealed by Raman spectroscopy. Further investigation will be needed to ensure unambiguous identification and operations of future Mars missions. However, a 3-month exposure to a Martian simulated atmosphere showed no significant damaging effect on the tested cyanobacterial biosignatures, pointing out the relevance of the latter for future investigations after the EXPOSE-R2 mission. Data gathered during the ground-based simulations will contribute to interpret results from space experiments and guide our search for life on Mars
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