Molekularbiologische und strukturelle Untersuchungen zur Biologie des neuartigen, kälteliebenden SM1 Euryarchaeons und seiner verschiedenen Lebensgemeinschaften

Extreme Biotope mit z.B. hoher Salinität, extremen pH- Werten und hohen Temperaturen wurden lange Zeit als typisches Habitat für Archaea angesehen. Kultivierungs- unabhängige molekulare Untersuchungen auf Basis ribosomaler RNA- Gensequenzen haben jedoch ihre globale Verbreitung in Nieder- bis Moderattemperatur- Biotopen bewiesen. Bis heute sind diese Archaea quasi nicht kultivierbar und ihre offensichtliche ökologische Signifikanz bleibt nach wie vor verborgen. Vor kurzem entdeckten Mitarbeiter der AG Prof. Dr. Robert Huber im Regensburger Raum ein einzigartiges archaeell/bakterielles Konsortium, welches in Form makroskopisch sichtbarer, neuartiger, mikrobieller Perlenketten in kaltem (10°C), sulfidhaltigen Quellwasser vorkommt. Im Inneren einer Perle formt das neuartige SM1 Euryarchaeon eine Mikrokolonie, die äußere Hülle wird durch filamentöse S- oxidierende Bakterien aufgebaut. Unter aeroben Bedingungen (Sippenauer Moor) bildet das SM1 Euryarchaeon zusammen mit Thiothrix sp., bei geringeren Sauerstoffkonzentrationen (Islinger Mühlbach) zusammen mit dem neuartigen epsilon- Proteobakterium IMB1 eine, vielleicht sogar auf eine Symbiose basierende, stabile Gemeinschaft. Durch eine neu etablierte Methode, der in situ- Kultivierung, ist es gelungen, diese mikrobiellen Perlenkettengemeinschaften schnell und zuverlässig in größeren Mengen an Polyethylennetzen direkt im natürlichen Biotop ('natürlicher Chemostat') zu züchten. Aus ca. 10.000 Perlen, die nun wöchentlich geerntet werden konnten, wurde das SM1 Euryarchaeon durch verschiedene physikalische Sedimentations- und Zentrifugationsschritte bis zu einer Reinheit von ca. 98% von Begleitorganismen separiert. Aufgrund dieser hohen Reinheit, der guten Lebensfähigkeit und der ausreichend gewinnbaren Menge an Zellen konnte die erhaltene, natürlich gewachsene SM1- Fraktion wie eine im Labor züchtbare (Rein-)Kultur biologisch detailliert untersucht werden. Auf diesem Weg konnten z.B. die optimalen physiologischen Bedingungen für das SM1 Euryarchaeon (Temperatur: -2°C bis +30°C; neutraler pH, Niedersalz) bestimmt und die Monophylie der aufgereinigten SM1- Zellen durch Immuno- FISH gezeigt werden. Im Rahmen struktureller Untersuchungen wurden auf der Zelloberfläche jeder der nur etwa 0,6 µm großen SM1- Zellen ca. 100 filamentöse Anhängsel mit einer ungewöhnlich komplexen Struktur entdeckt: nanometerdicke, stacheldrahtartige, in der Zellwand verankerte Filamente tragen an ihren Enden winzige, mit Widerhaken besetzte Tripel- Haken (Ø 60 nm). Da diese Struktur innerhalb der Prokaryonten eine neue Klasse filamentöser Zellanhängsel repräsentiert, wurde für sie die Bezeichnung 'Hamus' (lateinisch für: Haken, Widerhaken, Angel; Plural: 'Hami') vorgeschlagen. Die über eine breite pH- und Temperaturspanne stabilen Hami sind hauptsächlich aus einem 120 kDa Protein aufgebaut, das auch auf genetischer Ebene erfasst werden konnte. Dieses perfekte mechanische Nano- Werkzeug, welches die Natur im Laufe der Evolution für die Zelladhäsion geschaffen hat, könnte sich sogar auf dem Gebiet der Nanobiotechnologie als nützlich erweisen. Das aus dieser Arbeit gewonnene Wissen erweitert unser Verständnis bezüglich unkultivierter, kälte-liebender Archaea als wichtiger Bestandteil von mikrobiellen Gemeinschaften in nicht extremen Ökosystemen

Hardy Bacterium Isolated From Two Geographically Distinct Spacecraft Assembly Cleanroom Facilities

Earlier studies have confirmed that a tenacious hardy bacterial population manages to persist and survive throughout a spacecraft assembly process. The widespread detection of these organisms underscores the challenges in eliminating them completely. Only comprehensive and repetitive microbial diversity studies of geographically distinct cleanroom facilities will bolster the understanding of planetary protection relevant microbes. Extensive characterizations of the physiological traits demonstrated by cleanroom microbes will aid NASA in gauging the forward contamination risk that hardy bacteria (such as Tersicoccus phoenicis) pose to spacecraft. This study reports on the isolation and identification of two gram-positive, non-motile, non-spore-forming bacterial strains from the spacecraft assembly facilities at Kennedy Space Center, Florida, USA and Centre Spatial Guyanais, Kourou, French Guiana. DNA-DNA relatedness values between the novel strains indicates that these novel strains were indeed members of a same species. Phylogenetic evidence derived from a 16S ribosomal DNA analysis indicated that both the novel strains are less closely related to all other Arthrobacter species

Guided optimization of fluid status in haemodialysis patients

Background. Achieving normohydration remains a non-trivial issue in haemodialysis therapy. Guiding the haemodialysis patient on the path between fluid overload and dehydration should be the clinical target, although it can be difficult to achieve this target in practice. Objective and clinically applicable methods for the determination of the normohydration status on an individual basis are needed to help in the identification of an appropriate target weight

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

Novel Species of Non-Spore-Forming Bacteria

While cataloging cultivatable microbes from the airborne biological diversity of the atmosphere of the Regenerative Enclosed life-support Module Simulator (REMS) system at Marshall Space Flight Center, two strains that belong to one novel bacterial species were isolated. Based on 16S rRNA gene sequencing and the unique morphology and the taxonomic characteristics of these strains, it is shown that they belong to the family Intrasporangiaceae, related to the genus Tetrasphaera, with phylogenetic distances from any validly described species of the genus Tetrasphaera ranging from 96.71 to 97.76 percent. The fatty acid profile supported the affiliation of these novel strains to the genus Tetrasphaera except for the presence of higher concentrations of octadecenoic acid (C18:0) and cis-9-octadecenoic acid (C18:1), which discriminates these strains from other valid species. In addition, DNA-DNA hybridization studies indicate that these strains belong to a novel species that could be readily distinguished from its nearest neighbor, Tetrasphaera japonica AMC 5116T, with less than 20 percent DNA relatedness. Physiological and biochemical tests show few phenotypic dissimilarities, but genotypic analysis allowed the differentiation of these gelatin-liquefying strains from previously reported strains. The name Tetrasphaera remsis sp. Nov. is proposed with the type strain 3-M5-R-4(sup T) (=ATCC BAA-1496(sup T)=CIP 109413(sup T). The cells are Gram-positive, nonmotile, cocci, in tetrad arrangement and clusters. Spore formation is not observed. No species of Tetrashpaera has ever been isolated from airborne samples. Previous discoveries have come from soil and activated sludge samples. As other species of this genus have demonstrated enhanced biological phosphorus removal activity, further tests are required to determine if this newly discovered species would have bioremediation applications

Cometary dust collected by MIDAS on board Rosetta II. Particle shape descriptors and pristineness evaluation

The MIDAS (Micro-Imaging Dust Analysis System) atomic force microscope on board the Rosetta comet orbiter investigated and measured the 3D topography of a few hundred nm to tens of $\mu$m sized dust particles of 67P/Churyumov-Gerasimenko with resolutions down to a few nanometers, giving insights into the physical processes of our early Solar System. We analyze the shapes of the cometary dust particles collected by MIDAS on the basis of a recently updated particle catalog with the aim to determine which structural properties remained pristine. We develop a set of shape descriptors and metrics such as aspect ratio, elongation, circularity, convexity, and particle surface/volume distribution, which can be used to describe the distribution of particle shapes. Furthermore, we compare the structure of the MIDAS dust particles and the clusters in which the particles were deposited to those found in previous laboratory experiments and by Rosetta/COSIMA. Finally, we combine our findings to calculate a pristineness score for MIDAS particles and determine the most pristine particles and their properties. We find that the morphological properties of all cometary dust particles at the micrometer scale are surprisingly homogeneous despite originating from diverse cometary environments (e.g., different collection targets that are associated with cometary activities/source regions and collection velocities/periods). We next find that the types of clusters found by MIDAS show good agreement with those defined by previous laboratory experiments, however, there are some differences to those found by Rosetta/COSIMA. Based on our result, we rate 19 out of 1082 MIDAS particles at least moderately pristine, i.e., they are not substantially flattened by impact, not fragmented, and/or not part of a fragmentation cluster.Comment: 40 pages, 31 figures, 1 online tabl