<p>Primary biological aerosol particles (PBAPs) are present globall... more <p>Primary biological aerosol particles (PBAPs) are present globally, contributing to the total observed aerosol loads. Yet, PBAPs likely form a smaller fraction of the total aerosol budget compared to other types of particles such as dust. According to the IPCC AR5 report, the terrestrial emission flux of PBAPs is highly uncertain and was estimated within the range of 50-1000 Tg/yr. Burrows et al. (2009) estimated the global emissions of bacteria-containing particles to range between 0.4 to 1.8 Tg/yr, with a median of 0.74 Tg/yr. However, PBAPs comprise a large fraction of the submicron particles > 0.2 mm in the middle to the upper troposphere and they can be dispersed to distant locations and high altitudes from their source regionss. PBAPs have the potential to play a key role in cloud formation by acting as cloud condensation nuclei (CCN), and ice nucleating particles (INP) active at high sub-zero temperatures, potentially impacting the Earth’s hydrological cycle and climate.</p><p>Recent observations suggest that the PBAP concentrations have likely been underestimated in global modeling studies (summarized in Huang et al., 2021). For example, the fragmented biological particles and microbial exudates still cannot be detected with many commonly used techniques and, therefore they were not accounted for in the previous global modeling studies. Other recent studies presented a novel secondary biological aerosol production. Moreover, observations revealed that biological INPs from marine surfaces may be of higher imporatance than what has previously been considered in modeling studies. PBAPs' emission flux is therefore not yet well constrained, and the uncertainty in their emission estimation remains unresolved and requires deeper investigation. Consequently, the climatic impacts and feedbacks of PBAPs remain highly uncertain.</p><p>In this study, we build and integrate for the first time a new emission model for PBAPs in the GISS-E2.1 Earth system model in order to calculate the total emission flux of PBAPs from terrestrial and marine surfaces into the atmosphere and estimate their transport and sinks. In this model, we consider different types of PBAPs, i.e., bacteria and fungal spores. For bacteria we used the estimated flux-rates from Burrows et al. (2009) for different ecosystems. In a later step, we will update those values for each ecosystem using recent observations, especially over the marine areas and land ice. For fungal spores, we used the parameterization of Janssen et al. (2021).</p><p>We present preliminary results of the emission fluxes, burdens, concentrations, lifetime, and direct radiative forcing due to aerosol-radiation interactions of PBAPs and validate them using previous studies. For example, the lifetime of bacteria of size 1 micron is calculated to equal 3.5 days, which is comparable with the 3.4 days estimated by Burrows et al. (2009). </p><p> </p><p>References</p><p>Burrows, S. M. et al., ACP 2009, 9(23),9281, doi: https://doi.org/10.5194/acp-9-9281-2009.</p><p>Huang, S. et al., Environment International 2021, 146., doi: https://doi.org/10.1016/j.envint.2020.106197</p><p>Janssen et al., ACP 2021, 21(6), 4381., doi: https://doi.org/10.5194/acp-21-4381-2021</p>
Living on a farm has been linked to a lower risk of immunoregulatory disorders, such as asthma, a... more Living on a farm has been linked to a lower risk of immunoregulatory disorders, such as asthma, allergy, and inflammatory bowel disease. It is hypothesized that a decrease in the diversity and composition of indoor microbial communities is a sensible explanation for the upsurge in immunoregulatory diseases, with airborne bacteria contributing to this protective effect. However, the composition of this potentially beneficial microbial community in various farm and suburban indoor environments is still to be characterized. We collected settled airborne dust from stables and the associated farmers' homes and from suburban homes using electrostatic dust collectors (EDCs) over a period of 14 days. Then, quantitative PCR (qPCR) was used to assess bacterial abundance. The V3-V4 region of the bacterial 16S rRNA gene was amplified and sequenced using Ilumina MiSeq in order to assess microbial diversity. The Divisive Amplicon Denoising Algorithm (DADA2) algorithm was used for the inference of amplicon sequence variants from amplicon data. Airborne bacteria were significantly more abundant in farmers' indoor environments than in suburban homes (p < 0.001). Cow farmers' homes had significantly higher bacterial diversity than pig farmers' and suburban homes (p < 0.001). Bacterial taxa, such as Firmicutes, Prevotellaceae, Lachnospiraceae, and Lactobacillus were significantly more abundant in farmers' homes than suburban homes, and the same was true for beneficial intestinal bacterial species, such as Lactobacillus amylovorus, Eubacterium hallii, and Faecalibacterium prausnitzii. Furthermore, we found a higher similarity between bacterial communities in individual farmers' homes and their associated cow stables than for pig stables. Our findings contribute with important knowledge on bacterial composition, abundance, and diversity in different environments, which is highly valuable in the discussion on how microbial exposure may contribute to the development of immunemediated diseases in both children and adults.
Transport of microbes in the atmosphere allows them to spread and to colonize new habitats. To su... more Transport of microbes in the atmosphere allows them to spread and to colonize new habitats. To survive the harsh environmental conditions encountered in the atmosphere, these microorganisms have to possess properties that allow them to resist atmospheric stress. We combined physiological experiments and genome analysis of Pseudomonas syringae strain R10.79, previously isolated from rain, to decipher the strain’s ability to withstand these challenges and identify the mechanisms behind the resistance. We used laboratory experiments to simulate different atmospheric stress factors and evaluated cell survival using fluorescent staining and flow cytometry. We found that while P. syringae R10.79 was resistant to oxidative, osmotic, UVB radiation-induced and freezing stress, it was sensitive to desiccation on surfaces. Strain R10.79 possesses a range of genes that would allow the strain to mitigate atmospheric stresses, such as cold shock and osmotic shock genes as well as genes encoding for properties that relate to UV irradiation resistance. Studying the substrate spectrum of strain R10.79, we uncovered that it can utilize carbon compounds abundant in the atmosphere including acetate, succinate and formate. In addition, strain R10.79 possesses metabolic pathways to utilize formaldehyde and methanol as sole carbon sources. These compounds could support the metabolic activity of strain R10.79 while suspended in the atmosphere during periods with sufficiently high relative humidity. Finally, we found that when growing on acetate, strain R10.79 produces several volatile organic compounds such as isoprene and methanol, for which we propose biochemical pathways and which are relevant for atmospheric chemistry and climate. The results reported in this study will support our general aim at establishing this strain as a model organism to study microbial responses to atmospheric conditions.
The Arctic is undergoing dramatic climatic changes that cause profound transformations in its ter... more The Arctic is undergoing dramatic climatic changes that cause profound transformations in its terrestrial ecosystems and consequently in the microbial communities that inhabit them. The assembly of these communities is affected by aeolian deposition. However, the abundance, diversity, sources and activity of airborne microorganisms in the Arctic are poorly understood. We studied bacteria in the atmosphere over southwest Greenland and found that the diversity of bacterial communities correlated positively with air temperature and negatively with relative humidity. The communities consisted of 1.3×10 3 ± 1.0×10 3 cells m −3 , which were aerosolized from local terrestrial environments or transported from marine, glaciated and terrestrial surfaces over long distances. On average, airborne bacterial cells displayed a high activity potential, reflected in the high 16S rRNA copy number (590 ± 300 rRNA cell −1), that correlated positively with water vapor pressure. We observed that bacterial clades differed in their activity potential. For instance, a high activity potential was seen for Rubrobacteridae and Clostridiales, while a low activity potential was observed for Proteobacteria. Of those bacterial families that harbor ice-nucleation active species, which are known to facilitate freezing and may thus be involved in cloud and rain formation, cells with a high activity potential were rare in air, but were enriched in rain.
Supplementary information for Atmospheric fluorescent bioaerosol concentrations measured during 1... more Supplementary information for Atmospheric fluorescent bioaerosol concentrations measured during 18 months in a coniferous forest in the south of Sweden.
Biological aerosol particles affect human health, are essential for microbial-and gene dispersal,... more Biological aerosol particles affect human health, are essential for microbial-and gene dispersal, and have been proposed as important agents for atmospheric processes. However, the abundance and size distributions of atmospheric biological particles are largely unknown. In this study we used a laser-induced fluorescence instrument to measure fluorescent biological aerosol particle (FBAP) concentrations for 18 months (October 2020-April 2022) at a rural, forested site in Sweden. The aim of this study was to investigate FBAP number concentrations (NFBAP) over time and analyze their relationship to meteorological parameters. The NFBAP was highest in the summer and lowest in winter, exhibiting a ~3-fold difference between these seasons. The median NFBAP was 0.0050, 0.0025, 0.0027 and 0.0126 cm-3 in fall, winter, spring, and summer, respectively, and constituted ~0.1-0.5 % of the total supermicron particle number. The NFBAP were dominated by the smallest measured size fraction (1-3 µm), suggesting that the main portion of the biological particles measured were due to single bacterial cells, fungal spores, and bacterial agglomerates. The NFBAP were significantly correlated with increasing air temperature (P<0.01) in all seasons. For most of the campaign NFBAP was seen to increase with wind speed (P<0.01), while the relationship with relative humidity was for most part of the campaign nonsignificant (46 %) but to a large part (30 %) negative (P<0.05). Our results indicate that NFBAP were highest during warm and dry conditions when wind speeds were high, suggesting that a major part of the FBAP in the spring and summer were due to mechanical aerosol generation and release mechanisms. In the fall, relative humidity may have been a more important factor for bioaerosol release. This is one of the longest time series of atmospheric FBAP, which are highly needed for estimates of bioaerosol background concentrations in comparable regions.
&amp;lt;p&amp;gt;The properties and formation of clouds are one of the largest sources of... more &amp;lt;p&amp;gt;The properties and formation of clouds are one of the largest sources of uncertainties in climate models. Hereby, ice nucleating particles (INPs) play a major role since they directly affect the ice formation in clouds. To better characterize the impact of INPs, measuring devices are necessary to reliably determine the freezing temperatures of various aerosols.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We have developed a new ice nucleation assay, AU-Micro-INC, to measure the freezing temperatures with high accuracy. 96-well and 384-well plates can be inserted into a gallium matrix which ensures good thermal contact to the underlying cooling system. A Peltier element in combination with a vapor chamber provide a homogeneous cooling of the system. The freezing temperatures are measured with an infrared thermal camera with high precision.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The setup is validated using well-studied samples such as Snomax&amp;lt;sup&amp;gt;&amp;amp;#174;&amp;lt;/sup&amp;gt; and Illite NX.&amp;amp;#160;Further, the new setup is applied to sea water, sea surface microlayer, and sea ice samples previously collected in Kobbefjord and Nuup Kangerluaand in proximity of Nuuk, Greenland and preliminary data will be shown.&amp;amp;#160;&amp;lt;/p&amp;gt;
Ice nucleation particles play a crucial role in atmospheric processes e.g., they can trigger ice ... more Ice nucleation particles play a crucial role in atmospheric processes e.g., they can trigger ice formation in clouds and thus influence their lifetime and optical properties. The quantification and characterisation of these particles require reliable and precise measurement techniques. In this study, we present a novel droplet freezing instrument to measure immersion freezing of biotic and abiotic ice-nucleating particles within the temperature range of 0°C to -25°C. Immersion freezing of the samples is investigated using 384-well PCR plates with a sample volume of 30 μl. Nucleation events are detected with high precession using a thermal camera that records the increase in infra-red emission due to the latent heat release. To maximize the thermal contact between the PCR plate and the surrounding cooling unit we use a gallium bath as a mount for the PCR plate. The combination of good thermal connectivity and precise temperature recording enables accurate and reproducible detection o...
Identifying and quantifying nitrogen pools is essential for understanding the nitrogen cycle in a... more Identifying and quantifying nitrogen pools is essential for understanding the nitrogen cycle in aquatic ecosystems. The ubiquitous diatoms represent an overlooked nitrate pool as they can accumulate nitrate intracellularly and utilize it for nitrogen assimilation, dissipation of excess photosynthetic energy, and Dissimilatory Nitrate Reduction to Ammonium (DNRA). Here, we document the global co-occurrence of diatoms and intracellular nitrate in phototrophic microbial communities in freshwater (n = 69), coastal (n = 44), and open marine (n = 4) habitats. Diatom abundance and total intracellular nitrate contents in water columns, sediments, microbial mats, and epilithic biofilms were highly significantly correlated. In contrast, diatom community composition had only a marginal influence on total intracellular nitrate contents. Nitrate concentrations inside diatom cells exceeded ambient nitrate concentrations ∼100-4000-fold. The collective intracellular nitrate pool of the diatom community accounted for <1% of total nitrate in pelagic habitats and 65-95% in benthic habitats. Accordingly, nitrate-storing diatoms are emerging as significant contributors to benthic nitrogen cycling, in particular through Dissimilatory Nitrate Reduction to Ammonium activity under anoxic conditions.
Ground-based and Airborne Telescopes VII, Oct 1, 2018
The Exo-Life Finder (ELF) will be an optical system with the resolving power of a ≥20m telescope ... more The Exo-Life Finder (ELF) will be an optical system with the resolving power of a ≥20m telescope optimized for characterizing exoplanets and detecting exolife. It will allow for direct detection of Earth-size planets in commonly-considered water-based habitable zones (WHZ) of nearby stars and for generic exolife studies. Here we discuss capabilities of the ELF to detect biosignatures and technosignatures in exoplanetary atmospheres and on their surfaces in the visual and near infrared. We evaluate sensitivity limits for mid- and low-resolution spectral, photometric and polarimetric measurements, analyzed using atmosphere models and light-curve inversions. In particular, we model and estimate integration times required to detect O2, O3, CO2, CH4, H2O and other biosignature gases and habitability markers. Disequilibrium biosignature pairs such as O2+CH4 or CO2+CH4–CO are also explored. Photosynthetic and non-photosynthetic pigments are other important biosignatures that ELF will search for in atmospheres and on resolved surfaces of exoplanets, in the form of bioaerosols and colonies of organisms. Finally, possible artificial structures on exoplanet surfaces and in near-exoplanet space can be detected. Practical instrument requirements are formulated for detecting these spectral and structural biosignatures and technosignatures. It is imperative that such a study is applied first to characterize the nearest exoplanet Proxima b, then to search for exo-Earths in the Alpha Cen A and B system and other near-Sun stars, and finally to explore larger exoplanets around more distant stars.
Journal Of Geophysical Research: Atmospheres, Feb 12, 2018
Ice nucleation active bacteria have attracted particular attention due to their unique ability to... more Ice nucleation active bacteria have attracted particular attention due to their unique ability to produce specific ice nucleation proteins (INpros), which are the most efficient ice nuclei known as they induce nucleation at temperatures close to 0°C. Our model bacterium Pseudomonas syringae strain R10.79 produced INpros containing 67 tandem repeats, forming the proposed ice-binding surface. To understand the role of the INpro repeats as well as the role of intermolecular interactions between INpros for their ice nucleation behavior, we produced a truncated version of the protein with only 16 tandem repeats (INpro 16R). The purified INpro 16R produced oligomers of varying sizes. Immersion freezing ice nucleation behavior of purified INpro 16R was characterized by droplet-freezing assays and in the Leipzig Aerosol Cloud Interaction Simulator. Predominant INpro 16R oligomers introduced into Leipzig Aerosol Cloud Interaction Simulator as single particles with diameters of 50 nm or 70 nm were ice nucleation active at temperatures of À26°C and À24°C, respectively. These are much lower temperatures compared to that of intact INpros (À12°C). The data clearly indicated that the number of repeats determines the ice nucleation temperature. In addition, ice nucleation between À9°C and À10°C, comparable to the activity of intact INpro, was caused by higher-order INpro 16R oligomers. This supported previous observations that INpro oligomerization increases the ice-binding surface, thereby affecting ice nucleation activity. In conclusion, both repeat number and oligomerization contribute in a seemingly independent manner to the nucleation mechanism of INpros.
Outdoor field measurements of bioaerosols are performed within a wide range of basic and applied ... more Outdoor field measurements of bioaerosols are performed within a wide range of basic and applied scientific disciplines, each with its own goals, assumptions, and terminology. This article contains brief reviews of outdoor field bioaerosol research from these diverse interests, with emphasis on perspectives from the atmospheric sciences. The focus is on a high-level discussion of pressing scientific questions, grand challenges, and needs for cross-disciplinary collaboration. The research topics, in which bioaerosol field measurement is important, include (i) atmospheric physics, clouds, climate, and hydrological cycle; (ii) atmospheric chemistry; (iii) airborne allergencontaining particles; (iv) airborne human pathogens and national security; (v) airborne livestock and crop pathogens; and (vi) biogeography and biodiversity. We concisely review bioaerosol impacts and discuss properties that distinguish bioaerosols from abiological aerosols. We give extra focus to regions of specific interest, i.e., forests, polar regions, marine and coastal environments, deserts, urban and rural areas, and summarize key considerations related to bioaerosol measurements, such as of fluxes, of long-range transport, and of sampling from both stationary and vessel-driven platforms. Keeping in mind a series of key scientific questions posed within the diverse communities, we suggest that pressing scientific questions include the following: (i) emission sources and flux estimates; (ii) spatial distribution; (iii) changes in distribution; (iv) atmospheric aging; (v) metabolic activity; (vi) urbanization of allergies; (vii) transport of human pathogens; and (viii) climate-relevant properties.
&amp;amp;lt;p&amp;amp;gt;Primary biological aerosol particles (PBAPs) are present globall... more &amp;amp;lt;p&amp;amp;gt;Primary biological aerosol particles (PBAPs) are present globally, contributing to the total observed aerosol loads. Yet, PBAPs likely form a smaller fraction of the total aerosol budget compared to other types of particles such as dust. According to the IPCC AR5 report, the terrestrial emission flux of PBAPs is highly uncertain and was estimated within the range of 50-1000 Tg/yr. Burrows et al. (2009) estimated the global emissions of bacteria-containing particles to range between 0.4 to 1.8 Tg/yr, with a median of 0.74 Tg/yr. However, PBAPs comprise a large fraction of the submicron particles &amp;amp;gt; 0.2 mm in the middle to the upper troposphere and they can be dispersed to distant locations and high altitudes from their source regionss. PBAPs have the potential to play a key role in cloud formation by acting as cloud condensation nuclei (CCN), and ice nucleating particles (INP) active at high sub-zero temperatures, potentially impacting the Earth&amp;amp;amp;#8217;s hydrological cycle and climate.&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;Recent observations suggest that the PBAP concentrations have likely been underestimated in global modeling studies (summarized in Huang et al., 2021). For example, the fragmented biological particles and microbial exudates still cannot be detected with many commonly used techniques and, therefore they were not accounted for in the previous global modeling studies. Other recent studies presented a novel secondary biological aerosol production. Moreover, observations revealed that biological INPs from marine surfaces may be of higher imporatance than what has previously been considered in modeling studies. PBAPs&amp;#39; emission flux is therefore not yet well constrained, and the uncertainty in their emission estimation remains unresolved and requires deeper investigation. Consequently, the climatic impacts and feedbacks of PBAPs remain highly uncertain.&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;In this study, we build and integrate for the first time a new emission model for PBAPs in the GISS-E2.1 Earth system model in order to calculate the total emission flux of PBAPs from terrestrial and marine surfaces into the atmosphere and estimate their transport and sinks. In this model, we consider different types of PBAPs, i.e., bacteria and fungal spores. For bacteria we used the estimated flux-rates from Burrows et al. (2009) for different ecosystems. In a later step, we will update those values for each ecosystem using recent observations, especially over the marine areas and land ice. For fungal spores, we used the parameterization of Janssen et al. (2021).&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;We present preliminary results of the emission fluxes, burdens, concentrations, lifetime, and direct radiative forcing due to aerosol-radiation interactions of PBAPs and validate them using previous studies. For example, the lifetime of bacteria of size 1 micron is calculated to equal 3.5 days, which is comparable with the 3.4 days estimated by Burrows et al. (2009).&amp;amp;amp;#160;&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;&amp;amp;amp;#160;&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;References&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;Burrows, S. M. et al., ACP 2009, 9(23),9281, doi: https://doi.org/10.5194/acp-9-9281-2009.&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;Huang, S. et al., Environment International 2021, 146., doi: https://doi.org/10.1016/j.envint.2020.106197&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;Janssen et al., ACP 2021, 21(6), 4381., doi: https://doi.org/10.5194/acp-21-4381-2021&amp;amp;lt;/p&amp;amp;gt;
Living on a farm has been linked to a lower risk of immunoregulatory disorders, such as asthma, a... more Living on a farm has been linked to a lower risk of immunoregulatory disorders, such as asthma, allergy, and inflammatory bowel disease. It is hypothesized that a decrease in the diversity and composition of indoor microbial communities is a sensible explanation for the upsurge in immunoregulatory diseases, with airborne bacteria contributing to this protective effect. However, the composition of this potentially beneficial microbial community in various farm and suburban indoor environments is still to be characterized. We collected settled airborne dust from stables and the associated farmers' homes and from suburban homes using electrostatic dust collectors (EDCs) over a period of 14 days. Then, quantitative PCR (qPCR) was used to assess bacterial abundance. The V3-V4 region of the bacterial 16S rRNA gene was amplified and sequenced using Ilumina MiSeq in order to assess microbial diversity. The Divisive Amplicon Denoising Algorithm (DADA2) algorithm was used for the inference of amplicon sequence variants from amplicon data. Airborne bacteria were significantly more abundant in farmers' indoor environments than in suburban homes (p < 0.001). Cow farmers' homes had significantly higher bacterial diversity than pig farmers' and suburban homes (p < 0.001). Bacterial taxa, such as Firmicutes, Prevotellaceae, Lachnospiraceae, and Lactobacillus were significantly more abundant in farmers' homes than suburban homes, and the same was true for beneficial intestinal bacterial species, such as Lactobacillus amylovorus, Eubacterium hallii, and Faecalibacterium prausnitzii. Furthermore, we found a higher similarity between bacterial communities in individual farmers' homes and their associated cow stables than for pig stables. Our findings contribute with important knowledge on bacterial composition, abundance, and diversity in different environments, which is highly valuable in the discussion on how microbial exposure may contribute to the development of immunemediated diseases in both children and adults.
Transport of microbes in the atmosphere allows them to spread and to colonize new habitats. To su... more Transport of microbes in the atmosphere allows them to spread and to colonize new habitats. To survive the harsh environmental conditions encountered in the atmosphere, these microorganisms have to possess properties that allow them to resist atmospheric stress. We combined physiological experiments and genome analysis of Pseudomonas syringae strain R10.79, previously isolated from rain, to decipher the strain’s ability to withstand these challenges and identify the mechanisms behind the resistance. We used laboratory experiments to simulate different atmospheric stress factors and evaluated cell survival using fluorescent staining and flow cytometry. We found that while P. syringae R10.79 was resistant to oxidative, osmotic, UVB radiation-induced and freezing stress, it was sensitive to desiccation on surfaces. Strain R10.79 possesses a range of genes that would allow the strain to mitigate atmospheric stresses, such as cold shock and osmotic shock genes as well as genes encoding for properties that relate to UV irradiation resistance. Studying the substrate spectrum of strain R10.79, we uncovered that it can utilize carbon compounds abundant in the atmosphere including acetate, succinate and formate. In addition, strain R10.79 possesses metabolic pathways to utilize formaldehyde and methanol as sole carbon sources. These compounds could support the metabolic activity of strain R10.79 while suspended in the atmosphere during periods with sufficiently high relative humidity. Finally, we found that when growing on acetate, strain R10.79 produces several volatile organic compounds such as isoprene and methanol, for which we propose biochemical pathways and which are relevant for atmospheric chemistry and climate. The results reported in this study will support our general aim at establishing this strain as a model organism to study microbial responses to atmospheric conditions.
The Arctic is undergoing dramatic climatic changes that cause profound transformations in its ter... more The Arctic is undergoing dramatic climatic changes that cause profound transformations in its terrestrial ecosystems and consequently in the microbial communities that inhabit them. The assembly of these communities is affected by aeolian deposition. However, the abundance, diversity, sources and activity of airborne microorganisms in the Arctic are poorly understood. We studied bacteria in the atmosphere over southwest Greenland and found that the diversity of bacterial communities correlated positively with air temperature and negatively with relative humidity. The communities consisted of 1.3×10 3 ± 1.0×10 3 cells m −3 , which were aerosolized from local terrestrial environments or transported from marine, glaciated and terrestrial surfaces over long distances. On average, airborne bacterial cells displayed a high activity potential, reflected in the high 16S rRNA copy number (590 ± 300 rRNA cell −1), that correlated positively with water vapor pressure. We observed that bacterial clades differed in their activity potential. For instance, a high activity potential was seen for Rubrobacteridae and Clostridiales, while a low activity potential was observed for Proteobacteria. Of those bacterial families that harbor ice-nucleation active species, which are known to facilitate freezing and may thus be involved in cloud and rain formation, cells with a high activity potential were rare in air, but were enriched in rain.
Supplementary information for Atmospheric fluorescent bioaerosol concentrations measured during 1... more Supplementary information for Atmospheric fluorescent bioaerosol concentrations measured during 18 months in a coniferous forest in the south of Sweden.
Biological aerosol particles affect human health, are essential for microbial-and gene dispersal,... more Biological aerosol particles affect human health, are essential for microbial-and gene dispersal, and have been proposed as important agents for atmospheric processes. However, the abundance and size distributions of atmospheric biological particles are largely unknown. In this study we used a laser-induced fluorescence instrument to measure fluorescent biological aerosol particle (FBAP) concentrations for 18 months (October 2020-April 2022) at a rural, forested site in Sweden. The aim of this study was to investigate FBAP number concentrations (NFBAP) over time and analyze their relationship to meteorological parameters. The NFBAP was highest in the summer and lowest in winter, exhibiting a ~3-fold difference between these seasons. The median NFBAP was 0.0050, 0.0025, 0.0027 and 0.0126 cm-3 in fall, winter, spring, and summer, respectively, and constituted ~0.1-0.5 % of the total supermicron particle number. The NFBAP were dominated by the smallest measured size fraction (1-3 µm), suggesting that the main portion of the biological particles measured were due to single bacterial cells, fungal spores, and bacterial agglomerates. The NFBAP were significantly correlated with increasing air temperature (P<0.01) in all seasons. For most of the campaign NFBAP was seen to increase with wind speed (P<0.01), while the relationship with relative humidity was for most part of the campaign nonsignificant (46 %) but to a large part (30 %) negative (P<0.05). Our results indicate that NFBAP were highest during warm and dry conditions when wind speeds were high, suggesting that a major part of the FBAP in the spring and summer were due to mechanical aerosol generation and release mechanisms. In the fall, relative humidity may have been a more important factor for bioaerosol release. This is one of the longest time series of atmospheric FBAP, which are highly needed for estimates of bioaerosol background concentrations in comparable regions.
&amp;lt;p&amp;gt;The properties and formation of clouds are one of the largest sources of... more &amp;lt;p&amp;gt;The properties and formation of clouds are one of the largest sources of uncertainties in climate models. Hereby, ice nucleating particles (INPs) play a major role since they directly affect the ice formation in clouds. To better characterize the impact of INPs, measuring devices are necessary to reliably determine the freezing temperatures of various aerosols.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We have developed a new ice nucleation assay, AU-Micro-INC, to measure the freezing temperatures with high accuracy. 96-well and 384-well plates can be inserted into a gallium matrix which ensures good thermal contact to the underlying cooling system. A Peltier element in combination with a vapor chamber provide a homogeneous cooling of the system. The freezing temperatures are measured with an infrared thermal camera with high precision.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The setup is validated using well-studied samples such as Snomax&amp;lt;sup&amp;gt;&amp;amp;#174;&amp;lt;/sup&amp;gt; and Illite NX.&amp;amp;#160;Further, the new setup is applied to sea water, sea surface microlayer, and sea ice samples previously collected in Kobbefjord and Nuup Kangerluaand in proximity of Nuuk, Greenland and preliminary data will be shown.&amp;amp;#160;&amp;lt;/p&amp;gt;
Ice nucleation particles play a crucial role in atmospheric processes e.g., they can trigger ice ... more Ice nucleation particles play a crucial role in atmospheric processes e.g., they can trigger ice formation in clouds and thus influence their lifetime and optical properties. The quantification and characterisation of these particles require reliable and precise measurement techniques. In this study, we present a novel droplet freezing instrument to measure immersion freezing of biotic and abiotic ice-nucleating particles within the temperature range of 0°C to -25°C. Immersion freezing of the samples is investigated using 384-well PCR plates with a sample volume of 30 μl. Nucleation events are detected with high precession using a thermal camera that records the increase in infra-red emission due to the latent heat release. To maximize the thermal contact between the PCR plate and the surrounding cooling unit we use a gallium bath as a mount for the PCR plate. The combination of good thermal connectivity and precise temperature recording enables accurate and reproducible detection o...
Identifying and quantifying nitrogen pools is essential for understanding the nitrogen cycle in a... more Identifying and quantifying nitrogen pools is essential for understanding the nitrogen cycle in aquatic ecosystems. The ubiquitous diatoms represent an overlooked nitrate pool as they can accumulate nitrate intracellularly and utilize it for nitrogen assimilation, dissipation of excess photosynthetic energy, and Dissimilatory Nitrate Reduction to Ammonium (DNRA). Here, we document the global co-occurrence of diatoms and intracellular nitrate in phototrophic microbial communities in freshwater (n = 69), coastal (n = 44), and open marine (n = 4) habitats. Diatom abundance and total intracellular nitrate contents in water columns, sediments, microbial mats, and epilithic biofilms were highly significantly correlated. In contrast, diatom community composition had only a marginal influence on total intracellular nitrate contents. Nitrate concentrations inside diatom cells exceeded ambient nitrate concentrations ∼100-4000-fold. The collective intracellular nitrate pool of the diatom community accounted for <1% of total nitrate in pelagic habitats and 65-95% in benthic habitats. Accordingly, nitrate-storing diatoms are emerging as significant contributors to benthic nitrogen cycling, in particular through Dissimilatory Nitrate Reduction to Ammonium activity under anoxic conditions.
Ground-based and Airborne Telescopes VII, Oct 1, 2018
The Exo-Life Finder (ELF) will be an optical system with the resolving power of a ≥20m telescope ... more The Exo-Life Finder (ELF) will be an optical system with the resolving power of a ≥20m telescope optimized for characterizing exoplanets and detecting exolife. It will allow for direct detection of Earth-size planets in commonly-considered water-based habitable zones (WHZ) of nearby stars and for generic exolife studies. Here we discuss capabilities of the ELF to detect biosignatures and technosignatures in exoplanetary atmospheres and on their surfaces in the visual and near infrared. We evaluate sensitivity limits for mid- and low-resolution spectral, photometric and polarimetric measurements, analyzed using atmosphere models and light-curve inversions. In particular, we model and estimate integration times required to detect O2, O3, CO2, CH4, H2O and other biosignature gases and habitability markers. Disequilibrium biosignature pairs such as O2+CH4 or CO2+CH4–CO are also explored. Photosynthetic and non-photosynthetic pigments are other important biosignatures that ELF will search for in atmospheres and on resolved surfaces of exoplanets, in the form of bioaerosols and colonies of organisms. Finally, possible artificial structures on exoplanet surfaces and in near-exoplanet space can be detected. Practical instrument requirements are formulated for detecting these spectral and structural biosignatures and technosignatures. It is imperative that such a study is applied first to characterize the nearest exoplanet Proxima b, then to search for exo-Earths in the Alpha Cen A and B system and other near-Sun stars, and finally to explore larger exoplanets around more distant stars.
Journal Of Geophysical Research: Atmospheres, Feb 12, 2018
Ice nucleation active bacteria have attracted particular attention due to their unique ability to... more Ice nucleation active bacteria have attracted particular attention due to their unique ability to produce specific ice nucleation proteins (INpros), which are the most efficient ice nuclei known as they induce nucleation at temperatures close to 0°C. Our model bacterium Pseudomonas syringae strain R10.79 produced INpros containing 67 tandem repeats, forming the proposed ice-binding surface. To understand the role of the INpro repeats as well as the role of intermolecular interactions between INpros for their ice nucleation behavior, we produced a truncated version of the protein with only 16 tandem repeats (INpro 16R). The purified INpro 16R produced oligomers of varying sizes. Immersion freezing ice nucleation behavior of purified INpro 16R was characterized by droplet-freezing assays and in the Leipzig Aerosol Cloud Interaction Simulator. Predominant INpro 16R oligomers introduced into Leipzig Aerosol Cloud Interaction Simulator as single particles with diameters of 50 nm or 70 nm were ice nucleation active at temperatures of À26°C and À24°C, respectively. These are much lower temperatures compared to that of intact INpros (À12°C). The data clearly indicated that the number of repeats determines the ice nucleation temperature. In addition, ice nucleation between À9°C and À10°C, comparable to the activity of intact INpro, was caused by higher-order INpro 16R oligomers. This supported previous observations that INpro oligomerization increases the ice-binding surface, thereby affecting ice nucleation activity. In conclusion, both repeat number and oligomerization contribute in a seemingly independent manner to the nucleation mechanism of INpros.
Outdoor field measurements of bioaerosols are performed within a wide range of basic and applied ... more Outdoor field measurements of bioaerosols are performed within a wide range of basic and applied scientific disciplines, each with its own goals, assumptions, and terminology. This article contains brief reviews of outdoor field bioaerosol research from these diverse interests, with emphasis on perspectives from the atmospheric sciences. The focus is on a high-level discussion of pressing scientific questions, grand challenges, and needs for cross-disciplinary collaboration. The research topics, in which bioaerosol field measurement is important, include (i) atmospheric physics, clouds, climate, and hydrological cycle; (ii) atmospheric chemistry; (iii) airborne allergencontaining particles; (iv) airborne human pathogens and national security; (v) airborne livestock and crop pathogens; and (vi) biogeography and biodiversity. We concisely review bioaerosol impacts and discuss properties that distinguish bioaerosols from abiological aerosols. We give extra focus to regions of specific interest, i.e., forests, polar regions, marine and coastal environments, deserts, urban and rural areas, and summarize key considerations related to bioaerosol measurements, such as of fluxes, of long-range transport, and of sampling from both stationary and vessel-driven platforms. Keeping in mind a series of key scientific questions posed within the diverse communities, we suggest that pressing scientific questions include the following: (i) emission sources and flux estimates; (ii) spatial distribution; (iii) changes in distribution; (iv) atmospheric aging; (v) metabolic activity; (vi) urbanization of allergies; (vii) transport of human pathogens; and (viii) climate-relevant properties.
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Papers by Tina Temkiv