laser-induced-fluorescence-emission-life-as-novel-non-invasive-tool

Laser-Induced Fluorescence Emission (L.I.F.E.) as Novel Non-Invasive Tool for In-Situ Measurements of Biomarkers in Cryospheric Habitats

Global warming affects microbial communities in a variety of ecosystems, especially cryospheric habitats. However, little is known about ...

University of Innsbruck

University of Vienna

We used in situ hybridization with fluorescently labeled rRNA-targeted oligonucleotide probes concurrently with measurements of bacterial carbon production, biomass, and extracellular polymeric substances (EPS) to describe the bacterial community in sediments along a glacial stream. The abundance of sediment-associated Archaea, as detected with the ARCH915 probe, decreased downstream of the glacier snout, and a major storm increased their relative abundance by a factor of 5.5 to 7.9. Bacteria of the Cytophaga-Flavobacterium group were also sixfold to eightfold more abundant in the storm aftermath. Furthermore, elevated numbers of Archaea and members of the Cytophaga-Flavobacterium group characterized the phylogenetic composition of the supraglacial ice community. We postulate that glacial meltwaters constitute a possible source of allochthonous bacteria to the stream biofilms. Although stream water temperature increased dramatically from the glacier snout along the stream (3.5 km), sediment chlorophyll a was the best predictor for bacterial carbon production and specific growth rates along the stream. Concomitant with an increase in sediment chlorophyll a, the EPS carbohydrate-to-bacterial-cell ratio declined 11- to 15-fold along the stream prior to the storm, which is indicative of a larger biofilm matrix in upstream reaches. We assume that a larger biofilm matrix is required to assure prolonged transient storage and enzymatic processing of allochthonous macromolecules, which are likely the major substrate for microbial heterotrophs. Bacteria of the Cytophaga-Flavobacterium cluster, which are well known to degrade complex macromolecules, were most abundant in these stream reaches. Downstream, higher algal biomass continuously supplies heterotrophs with easily available exudates, therefore making a larger matrix unnecessary. As a result, bacterial carbon production and specific growth rates were higher in downstream reaches.

Phylogenetic and functional heterogeneity of sediment biofilms along environmental gradients in a glacial stream.

Bacterial production in glacial runoff and aquatic habitats along a c. 500 m transect from the ablation area of a Svalbard glacier (Midre Lovénbreen, 79 degrees N, 12 degrees E) down to a series of proglacial lakes in its forefield were assessed. In addition, a series of in situ experiments were conducted to test how different nutrient sources (glacial flour and dissolved organic matter derived from goose faeces) and temperature affect bacterial abundance and production in these ecosystems. Bacterial abundance and production increased significantly along this transect and reached a maximum in the proglacial lakes. Bacterial diversity profiles as assessed by denaturing gradient gel electrophoresis indicated that communities in glacial runoff were different from those in proglacial lakes. Heterotrophic bacterial production was mainly controlled by temperature and phosphorus limitation. Addition of both glacial flour and dissolved organic matter derived from goose faeces stimulated bacterial production in those lakes. The results suggest that glacial runoff sustains an active bacterial community which is further stimulated in proglacial lakes by higher temperatures and nutrient inputs from bird faeces. Thus, as in maritime temperate and Antarctic settings, bacterial communities developing in the recently deglaciated terrain of Svalbard receive important inputs of nutrients via faunal transfers from adjacent ecosystems.

Factors influencing bacterial dynamics along a transect from supraglacial runoff to proglacial lakes of a high Arctic glacier [corrected].

The diversity of highly active bacterial communities in cryoconite holes on three Arctic glaciers in Svalbard was investigated using terminal restriction fragment length polymorphism (T-RFLP) of the 16S rRNA locus. Construction and sequencing of clone libraries allowed several members of these communities to be identified, with Proteobacteria being the dominant one, followed by Cyanobacteria and Bacteroidetes. T-RFLP data revealed significantly different communities in holes on the (cold) valley glacier Austre Brøggerbreen relative to two adjacent (polythermal) valley glaciers, Midtre Lovénbreen and Vestre Brøggerbreen. These population compositions correlate with differences in organic matter content, temperature and the metabolic activity of microbial communities concerned. No within-glacier spatial patterns were observed in the communities identified over the 2-year period and with the 1 km-spaced sampling. We infer that surface hydrology is an important factor in the development of cryoconite bacterial communities.

Possible interactions between bacterial diversity, microbial activity and supraglacial hydrology of cryoconite holes in Svalbard.

Snow environments can occupy over a third of land surface area, but little is known about the dynamics of snowpack bacteria. The effect of snow melt on bacterial community structure and diversity of surface environments of a Svalbard glacier was examined using analyses of 16S rRNA genes via T-RFLP, qPCR and 454 pyrosequencing. Distinct community structures were found in different habitat types, with changes over 1 week apparent, in particular for the dominant bacterial class present, Betaproteobacteria. The differences observed were consistent with influences from depositional mode (snowfall vs aeolian dusts), contrasting snow with dust-rich snow layers and near-surface ice. Contrary to that, slush as the decompositional product of snow harboured distinct lineages of bacteria, further implying post-depositional changes in community structure. Taxa affiliated to the betaproteobacterial genus Polaromonas were particularly dynamic, and evidence for the presence of betaproteobacterial ammonia-oxidizing bacteria was uncovered, inviting the prospect that the dynamic bacterial communities associated with snowpacks may be active in supraglacial nitrogen cycling and capable of rapid responses to changes induced by snowmelt. Furthermore the potential of supraglacial snowpack ecosystems to respond to transient yet spatially extensive melting episodes such as that observed across most of Greenland's ice sheet in 2012 merits further investigation. 

The dynamic bacterial communities of a melting High Arctic glacier snowpack.

Abstract We have developed a portable dual-wavelength laser fluorescence spectrometer as part of a multi-instrument optical probe to characterize mineral, organic, and microbial species in extreme environments. Operating at 405 and 532 nm, the instrument was originally designed for use by human explorers to produce a laser-induced fluorescence emission (L.I.F.E.) spectral database of the mineral and organic molecules found in the microbial communities of Earth's cryosphere. Recently, our team had the opportunity to explore the strengths and limitations of the instrument when it was deployed on a remote-controlled Mars analog rover. In February 2013, the instrument was deployed on board the Magma White rover platform during the MARS2013 Mars analog field mission in the Kess Kess formation near Erfoud, Morocco. During these tests, we followed tele-science work flows pertinent to Mars surface missions in a simulated spaceflight environment. We report on the L.I.F.E. instrument setup, data processing, and performance during field trials. A pilot postmission laboratory analysis determined that rock samples acquired during the field mission exhibited a fluorescence signal from the Sun-exposed side characteristic of chlorophyll a following excitation at 405 nm. A weak fluorescence response to excitation at 532 nm may have originated from another microbial photosynthetic pigment, phycoerythrin, but final assignment awaits development of a comprehensive database of mineral and organic fluorescence spectra. No chlorophyll fluorescence signal was detected from the shaded underside of the samples.

Field trial of a dual-wavelength fluorescent emission (L.I.F.E.) instrument and the Magma White rover during the MARS2013 Mars analog mission.

We highlight the role of COSPAR and the scientific community in defining and updating the framework of planetary protection. Specifically, we focus on Mars "Special Regions," areas where strict planetary protection measures have to be applied before a spacecraft can explore them, given the existence of environmental conditions that may be conducive to terrestrial microbial growth. We outline the history of the concept of Special Regions and inform on recent developments regarding the COSPAR policy, namely, the MEPAG SR-SAG2 review and the Academies and ESF joint committee report on Mars Special Regions. We present some new issues that necessitate the update of the current policy and provide suggestions for new definitions of Special Regions. We conclude with the current major scientific questions that remain unanswered regarding Mars Special Regions.

Planetary Protection and Mars Special Regions--A Suggestion for Updating the Definition.

The role of aerial dispersal in shaping patterns of biodiversity remains poorly understood, mainly due to a lack of coordinated efforts in gathering data at appropriate temporal and spatial scales. It has been long known that the rate of dispersal to an ecosystem can significantly influence ecosystem dynamics, and that aerial transport has been identified as an important source of biological input to remote locations. With the considerable effort devoted in recent decades to understanding atmospheric circulation in the south-polar region, a unique opportunity has emerged to investigate the atmospheric ecology of Antarctica, from regional to continental scales. This concept note identifies key questions in Antarctic microbial biogeography and the need for standardized sampling and analysis protocols to address such questions. A consortium of polar aerobiologists is established to bring together researchers with a common interest in the airborne dispersion of microbes and other propagules in the Antarctic, with opportunities for comparative studies in the Arctic. 

Aerobiology Over Antarctica - A New Initiative for Atmospheric Ecology.

A critical aspect regarding the global dispersion of pathogenic microorganisms is associated with atmospheric movement of soil particles. Especially, desert dust storms can transport alien microorganisms over continental scales and can deposit them in sensitive sink habitats. In winter 2014, the largest ever recorded Saharan dust event in Italy was efficiently deposited on the Dolomite Alps and was sealed between dust-free snow. This provided us the unique opportunity to overcome difficulties in separating dust associated from "domestic" microbes and thus, to determine with high precision microorganisms transported exclusively by desert dust.

Legal immigrants: invasion of alien microbial communities during winter occurring desert dust storms.

Atmospheric dispersal of bacteria is increasingly acknowledged as an important factor influencing bacterial community biodiversity, biogeography and bacteria-human interactions, including those linked to human health. However, knowledge about patterns in microbial aerobiology is still relatively scarce, and this can be attributed, in part, to a lack of consensus on appropriate sampling and analytical methodology. In this study, three different methods were used to investigate aerial biodiversity over Svalbard: impaction, membrane filtration and drop plates. Sites around Svalbard were selected due to their relatively remote location, low human population, geographical location with respect to air movement and the tradition and history of scientific investigation on the archipelago, ensuring the presence of existing research infrastructure. The aerial bacterial biodiversity found was similar to that described in other aerobiological studies from both polar and non-polar environments, with Proteobacteria, Actinobacteria, and Firmicutes being the predominant groups. Twelve different phyla were detected in the air collected above Svalbard, although the diversity was considerably lower than in urban environments elsewhere. However, only 58 of 196 bacterial genera detected were consistently present, suggesting potentially higher levels of heterogeneity. Viable bacteria were present at all sampling locations, showing that living bacteria are ubiquitous in the air around Svalbard. Sampling location influenced the results obtained, as did sampling method. Specifically, impaction with a Sartorius MD8 produced a significantly higher number of viable colony forming units (CFUs) than drop plates alone.

Characterisation of Arctic Bacterial Communities in the Air above Svalbard.

Ultra-oligotrophic Lake Untersee is among the largest and deepest surface lakes of Central Queen Maud Land in East Antarctica. It is dammed at its north end by the Anuchin Glacier and the ice-cover dynamics are controlled by sublimation - not melt - as the dominating ablation process and therefore surface melt during austral summer does not provide significant amounts of water for recharge compared to subsurface melt of the Anuchin Glacier. Several studies have already described the structure and function of the microbial communities within the water column and benthic environments of Lake Untersee, however, thus far there have been no studies that examine the linkages between the lake ecosystem with that of the surrounding soils or the Anuchin Glacier. The glacier may also play an important role as a major contributor of nutrients and biota into the lake ecosystem. Based on microbial 16S rRNA amplicon sequencing, we showed that the dominant bacterial signatures in Lake Untersee, the Anuchin Glacier and its surrounding soils were affiliated with , , , , and . Aerosol and local soil depositions on the glacier surface resulted in distinct microbial communities developing in glacier ice and cryoconite holes. Based on a source tracking algorithm, we found that cryoconite microbial assemblages were a potential source of organisms, explaining up to 36% of benthic microbial mat communities in the lake. However, the major biotic sources for the lake ecosystem are still unknown, illustrating the possible importance of englacial and subglacial zones. The Anuchin Glacier may be considered as a vector in a biological sense for the bacterial colonization of the perennially ice-covered Lake Untersee. However, despite a thick perennial ice cover, observed "lift-off" microbial mats escaping the lake make a bidirectional transfer of biota plausible. Hence, there is an exchange of biota between Lake Untersee and connective habitats possible despite the apparent sealing by a perennial ice cover and the absence of moat areas during austral summer.

Source Environments of the Microbiome in Perennially Ice-Covered Lake Untersee, Antarctica.

Artificial snow production is a crucial part of modern skiing resorts in Austria and globally, and will develop even more so with changing precipitation patterns and a warming climate trend. Producing artificial snow requires major investments in energy, water, infrastructure and manpower for skiing resorts. In addition to appropriate meteorological conditions, the efficiency of artificial snow production depends on heterogeneous ice-nucleation, which can occur at temperatures as high as -2°C when induced by specific bacterial ice nucleating particles (INPs). We aimed to investigate the presence, source and ice nucleating properties of these particles in the water cycle of an alpine ski resort in Obergurgl, Tyrol, Austria. We sampled artificial snow, river water, water pumped from a storage pond and compared it to samples collected from fresh natural snow and aged piste snow from the area. Particles from each sampled system were characterized in order to determine their transport mechanisms at a ski resort. We applied a physical droplet freezing assay [DRoplet Ice Nuclei Counter Zurich (DRINCZ)] to heated and unheated samples to characterize the biological and non-biological component of IN-activity. Bacterial abundance and community structure of the samples was obtained using quantitative PCR and Illumina Mi-Seq Amplicon Sequencing, and their chemical properties were determined by liquid ion-chromatography, energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The results show the flow of biological and inorganic material from the river to the slopes, an uptake of new microorganisms through the air and the piping, and possible proliferation or introduction of ice nucleation active biological particles in aged piste snow. Natural snow, as the first stage in this system, had the lowest amount of ice nucleation active particles and the least amount of biological and mineral particles in general, yet shares some microbial characteristics with fresh artificial snow.

Article	Year
Phylogenetic and functional heterogeneity of sediment biofilms along environmental gradients in a glacial stream. Applied and environmental microbiology\| PubMed ID: 11157246	2001
Factors influencing bacterial dynamics along a transect from supraglacial runoff to proglacial lakes of a high Arctic glacier [corrected]. FEMS microbiology ecology\| PubMed ID: 17313580	2007
Possible interactions between bacterial diversity, microbial activity and supraglacial hydrology of cryoconite holes in Svalbard. The ISME journal\| PubMed ID: 20664552	2011
The dynamic bacterial communities of a melting High Arctic glacier snowpack. The ISME journal\| PubMed ID: 23552623	2013
Field trial of a dual-wavelength fluorescent emission (L.I.F.E.) instrument and the Magma White rover during the MARS2013 Mars analog mission. Astrobiology\| PubMed ID: 24823800	2014
Planetary Protection and Mars Special Regions--A Suggestion for Updating the Definition. Astrobiology\| PubMed ID: 26848950	2016
Aerobiology Over Antarctica - A New Initiative for Atmospheric Ecology. Frontiers in microbiology\| PubMed ID: 26909068	2016
Legal immigrants: invasion of alien microbial communities during winter occurring desert dust storms. Microbiome\| PubMed ID: 28283029	2017
Characterisation of Arctic Bacterial Communities in the Air above Svalbard. Biology\| PubMed ID: 28481257	2017
Source Environments of the Microbiome in Perennially Ice-Covered Lake Untersee, Antarctica. Frontiers in microbiology\| PubMed ID: 31134036	2019
Assessment of Artificial and Natural Transport Mechanisms of Ice Nucleating Particles in an Alpine Ski Resort in Obergurgl, Austria. Frontiers in microbiology\| PubMed ID: 31636618	2019

Birgit Sattler

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