207 research outputs found
High rates of denitrification and nitrous oxide emission in arid biological soil crusts from the Sultanate of Oman
No full textUsing a combination of process rate determination, microsensor profiling and molecular techniques, we demonstrated that denitrification, and not anaerobic ammonium oxidation (anammox), is the major nitrogen loss process in biological soil crusts from Oman. Potential denitrification rates were 584±101 and 58±20??mol N?m?2?h?1 for cyanobacterial and lichen crust, respectively. Complete denitrification to N2 was further confirmed by an 15NO3? tracer experiment with intact crust pieces that proceeded at rates of 103±19 and 27±8??mol N?m?2?h?1 for cyanobacterial and lichen crust, respectively. Strikingly, N2O gas was emitted at very high potential rates of 387±143 and 31±6??mol N?m?2?h?1 from the cyanobacterial and lichen crust, respectively, with N2O accounting for 53–66% of the total emission of nitrogenous gases. Microsensor measurements revealed that N2O was produced in the anoxic layer and thus apparently originated from incomplete denitrification. Using quantitative PCR, denitrification genes were detected in both the crusts and were expressed either in comparable (nirS) or slightly higher (narG) numbers in the cyanobacterial crusts. Although 99% of the nirS sequences in the cyanobacterial crust were affiliated to an uncultured denitrifying bacterium, 94% of these sequences were most closely affiliated to Paracoccus denitrificans in the lichen crust. Sequences of nosZ gene formed a distinct cluster that did not branch with known denitrifying bacteria. Our results demonstrate that nitrogen loss via denitrification is a dominant process in crusts from Oman, which leads to N2O gas emission and potentially reduces desert soil fertility
Bacterial and fungal communities in biological soil crusts from Oman
No full textBiological soil crusts (biocrusts) occur within drylands throughout the world, covering ~12% of the global terrestrial soil surface. Their occurrence in the deserts of the Arabian Peninsula has rarely been reported and their spatial distribution, diversity, and microbial composition remained largely unexplored. We investigated biocrusts at six different locations in the coastal and central deserts of Oman. The biocrust types were characterized, and the bacterial and fungal community compositions of biocrusts and uncrusted soils were analysed by amplicon sequencing. For each sample two different libraries were prepared: one for the V3V4 hypervariable region of the 16S rRNA gene (bacteria), and the other for the internal transcribed spacer 1 (ITS1; fungi). Sequences were processed in R using dada2. The code for sequence processing as well as statistical analysis, final OTU and taxonomy tables were archived on PANGAEA alongside the environmental information
Diatom communities on commercial biocidal fouling control coatings after one year of immersion in the marine environment
No full textLittle is known about the effect of commercial biocidal fouling control coatings on fouling diatom communities and their growth forms after long periods of exposure in the marine tropical environment. The current study investigated the abundance and composition of fouling diatom communities developed on 11 commercially available biocidal antifouling coatings, covering the three main technology types in recent historic use (Self-Polishing Copolymers, Self-Polishing Hybrid and Controlled Depletion Polymers) after one year of static immersion at two locations in Muscat, Oman (Marina Shangri La and Marina Bandar Rowdha). Light microscopy demonstrated that the total abundance of diatoms and the relative abundance of growth forms were significantly affected by the choice of biocidal antifouling coating and experimental location. Using scanning electron microscopy, a total of 21 diatom genera were identified which were grouped into adnate, motile, plocon and erect growth forms. The adnate growth forms, mainly the genera Amphora, Cocconeis and Mastogloia, dominated the other growth forms in terms of their relative abundance. Current results revealed the importance of exposure location and choice of biocidal antifouling coating on the relative abundance of diatom growth forms
Geochemical and microbiological fingerprinting of airborne dust that fell in Canberra, Australia, in October 2002
No full textDuring the night of 22-23 October 2002, a large amount of airborne dust fell with rain over Canberra, located some 200 km from Australia's east coast, and at an average altitude of 650 m. It is estimated that during that night about 6 g m-2 of aeolian dust fell. We have conducted a vast number of analyses to "fingerprint" some of the dust and used the following techniques: grain size analysis; scanning electron microscope imagery; major, trace, and rare earth elemental, plus Sr and Nd isotopic analyses; organic compound analyses with respective compound-specific isotope analyses; pollen extraction to identify the vegetation sources; and molecular cloning of 16S rRNA genes in order to identify dust bacterial composition. DNA analyses show that most obtained 16S rRNA sequences belong mainly to three groups: Proteobacteria (25%), Bacteriodetes (23%), and gram-positive bacteria (23%). In addition, we investigated the meteorological conditions that led to the dust mobilization and transport using model and satellite data. Grain sizes of the mineral dust show a bimodal distribution typical of proximal dust, rather than what is found over oceans, and the bimodal aspect of size distribution confirms wet deposition by rain droplets. The inorganic geochemistry points to a source along/near the Darling River in NW New South Wales, a region that is characteristically semiarid, and both the organic chemistry and palynoflora of the dust confirm the location of this source area. Meteorological reconstructions of the event again clearly identify the area near Bourke-Cobar as being the source of the dust. This study paves the way for determining the export of Australian airborne dust both in the oceans and other continents.No Full Tex
Intracellular nitrate storage by diatoms - Source data
No full textIntracellular nitrate storage by diatoms can be an important nitrogen pool in freshwater and marine ecosystems
Peter Stief, Clemens Schauberger, Marie B. Lund, Andreas Greve, Raeid M. M. Abed, Mohammad A. A. Al-Najjar, Karl Attard, Stefano Bonaglia, Jörg S. Deutzmann, Belén Franco-Cisterna, Emilio García-Robledo, Moritz Holtappels, Uwe John, Adele Maciute, Michael J. Magee, Rie Pors, Tina Santl-Temkiv, Anja Scherwass, Duygu S. Sevilgen, Dirk de Beer, Ronnie N. Glud, Andreas Schramm, and Anja Kamp</p
Environmental conditions during a 6 month biofouling experiment in the Arabian Gulf
No full textThe development of a mature biofouling community on solid surfaces in the marine environment primarily involves the availability of colonizing bacterial communities and their ability to persist over time in any given environment. This study was undertaken as part of a collaborative project titled Biotechnological Applications of Marine Biofilms developing on solid surfaces in the Arabian Gulf funded by research grant (SQU-GCC/CL/17/02). The succession of marine biofouling communities (mature biofilms) on plastic panels were investigated over a period of six months in four locations in the Arabian Gulf (Fintas and Salmiya marinas in Kuwait, and Bandar Rowdha and Al Mouj marinas in Oman). Monthly assessment of the physico-chemical parameters of the seawater at each location was done using portable meters (thermometer, refractometer, pH meter, turbidity meter and conductivity/TDS meter). The concentrations of nutrients and elements were analysed using ion chromatography (IC) and inductively coupled plasma optical emission spectrometry (ICP-OES), respectively
Diversität, Salzanpassung und Rolle im Kohlenstoffkreislauf von Mikroorganismen aus der oxischen Schicht hypersaliner mikrobieller Matten aus einer Gezeitenzone
No full textThe main objective of this thesis was to study the diversity, salinity adaptation, and role in carbon cycling of microorganisms inhabiting the oxic layer of intertidal hypersaline microbial mats. For this purpose, mats from the Arabian Gulf coast of Abu Dhabi, United Arab Emirates (UAE), which are subjected to multiple harsh environmental conditions, were investigated. The mats possessed a high microbial diversity and the inhabiting microorganisms showed adaptation mechanisms to strong salinity fluctuations, desiccation, high UV and light intensities, and high temperatures. A new salinity-driven taxis of cyanobacteria in the mat from the upper tidal zone was discovered and termed as Halotaxis. Moreover, this study showed that mats from different tidal positions adjust the structure and function of their bacterial communities in response to the salinity range they experience. Furthermore, cyanobacterial cultures with associated bacteria, obtained from the mats, provided manifold, very complex, and highly specific interactions with a high potential for biotechnological purposes, e.g. for the discovery of new bioactive substances
Nucleic Acid-Based Techniques for Studying Diversity and Activity of Bacterial Communities in Oil-Contaminated Sediments
No full textDetection and Capturing of 14C Radioactively-Labeled Small Subunit rRNA from Mixed Microbial Communities of a Microbial Mat Using Magnetic Beads
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