Trace gas oxidation as a novel microbial dispersal trait.

Atmospheric chemosynthesis is a recently proposed form of chemoautotrophic microbial primary production. The proposed process relies on the oxidation of trace concentrations of hydrogen (≤530 ppbv), carbon monoxide (≤90 ppbv), and methane (≤1,870 ppbv) gases using high-affinity enzymes. Atmospheric hydrogen and carbon monoxide oxidation have been primarily linked to microbial growth in desert surface soils scarce in liquid water and organic nutrients, and low in photosynthetic communities. It is well established that the oxidation of trace hydrogen and carbon monoxide gases widely supports the persistence of microbial communities in a diminished metabolic state, with the former potentially providing a reliable source of metabolic water. Microbial atmospheric methane oxidation also occurs in oligotrophic desert soils and is widespread throughout copiotrophic environments, with established links to microbial growth. Despite these findings, the direct link between trace gas oxidation and carbon fixation remains disputable. Here, we review the supporting evidence, outlining major gaps in our understanding of this phenomenon, and propose approaches to validate atmospheric chemosynthesis as a primary production process. We also explore the implications of this minimalistic survival strategy in terms of nutrient cycling, climate change, aerobiology, and astrobiology.

Diverse aerobic bacteria use atmospheric hydrogen (H2) and carbon monoxide (CO) as energy sources to support growth and survival. Such trace gas oxidation is recognised as a globally significant process that serves as the main sink in the biogeochemical H2 cycle and sustains microbial biodiversity in oligotrophic ecosystems. However, it is unclear whether archaea can also use atmospheric H2. Here we show that a thermoacidophilic archaeon, Acidianus brierleyi (Thermoproteota), constitutively consumes H2 and CO to sub-atmospheric levels. Oxidation occurs across a wide range of temperatures (10 to 70 °C) and enhances ATP production during starvation-induced persistence under temperate conditions. The genome of A. brierleyi encodes a canonical CO dehydrogenase and four distinct [NiFe]-hydrogenases, which are differentially produced in response to electron donor and acceptor availability. Another archaeon, Metallosphaera sedula, can also oxidize atmospheric H2. Our results suggest that trace gas oxidation is a common trait of Sulfolobales archaea and may play a role in their survival and niche expansion, including during dispersal through temperate environments.

Carbon monoxide (CO) gas is colorless, odorless, highly toxic and extremely dangerous. Natural sources account for 40% of the CO in the environment while 40% is the result of human activities. It is produced by the incomplete combustion of fuels and exhaust emission [1]. The Zinc oxide (ZnO) is an n-type metal oxide semiconductor (MOS) that has been widely used for gas sensors along many years because of their chemical response to different adsorbed gases, high chemical stability, amenability to doping, non-toxicity, affordability and relative fabrication simplicity. It has a wide range of electronic, chemical and physical characteristics and has become a well-known commercial sensor because of the sensitivity of its properties to variations in its chemical environment [2,3]. In the present work we use ZnO films for sensing of carbon monoxide, The ZnO films are deposited by a Sputtering system using radiofrequency (RF), on substrates of silicon (001) p-type with a size of 1.5 x 1.5 cm2, the substrates were washed using a conventional washing method. ZnO was deposited on the substrate during a fixed deposit period of 45 minutes with a thickness of approximately 150 nm, at a base pressure of 7.1 mTorr, a power of 125 W and an Ar flow of 10%, the blank of ZnO has purity of 99.99%, the deposit was made at room temperature. After the deposit of ZnO films, the metallic interdigitated was definite using lithography, whose design presents variations between the distance of the fingers of 200, 400 and 800 microns as well as the metal thereof, for which aluminum was used, with a thickness of 50 nm, gold with thickness of 25 nm and gold /aluminum with 25 nm and 50 nm thickness respectively, this to be able to study the effect of metals, as well as the distance between the fingers of the interdigitate. The deposited films are applied to measure the detection properties of the gas.The gas detection properties are evaluated by measuring the changes of the resistance of the sensor in air and CO gas. The metallic interdigitate definite on the ZnO films using two different metals. As expected, the films with a distance between fingers of 800 micros in the interdigitate, were those that presented the greatest response to the gas of interest, this because the surface exposed to gas was larger with respect to the other two designs. The best response to different concentrations of CO was found with the use of Al as the metallic interdigit contact, the difference being greater at high concentrations of CO, and at a relatively low measuring temperature of 240 ° C with respect to the other two metal contacts, as can be observed in Fig. 1.

Carbon monoxide (CO) gas is colorless, odorless and highly toxic. Natural sources account for 40% of the CO in the environment while 40% is the result of human activities. It is produced by the incomplete combustion of fuels and exhaust emission [1]. Zinc oxide (ZnO) is an n-type metal oxide semiconductor (MOS) that has been widely used for gas sensors along many years because of their chemical response to different adsorbed gases, high chemical stability, amenability to doping, non-toxicity, affordability, and relative fabrication simplicity. It has a wide range of electronic, chemical, and physical characteristics and has become a well-known material for commercial sensors because of the sensitivity of its properties under variations of its chemical environment [2,3]. In the present work we use ZnO films for sensing carbon monoxide with the resistive method. The ZnO films were deposited by a sputtering system using radiofrequency (RF), upon substrates of (001) p-type,1.5 x 1.5 cm2 sized silicon. The substrates were washed with a conventional RCA cleaning procedure. ZnO was deposited on the substrate for 45 minutes, obtaining a thickness of approximately 150 nm, under a pressure of 7.1 mTorr, a power of 125 W and an Ar flow of 10%, the blank of ZnO has purity of 99.99%, the deposit was made at room temperature. After the deposition, the metallic interdigitated electrodes were defined by using lithography. Designed electrodes have different distances between the fingers namely: 200, 400 and 800 microns. Also, different metals were used: 50 nm thick aluminum, 25 nm thick gold and 25 nm/50 nm thick gold /aluminum layers.The gas detection properties were evaluated by measuring the changes of the resistance of the sensing structure under air and CO gas. Results for ZnO structures using two different contact metals. The best response to different concentrations of CO was found with the use of Al as the metallic contact, the difference being greater at high concentrations of CO, and at a relatively low measuring temperature of 240 °C with respect to the other two metal contacts. As expected, the films with a distance between fingers of 800 micros in the interdigitate electrodes were those that presented the greatest response to the gas of interest, this because the surface exposed to gas was larger with respect to the other two designs.

Soil microorganisms globally are thought to be sustained primarily by organic carbon sources. Certain bacteria also consume inorganic energy sources such as trace gases, but they are presumed to be rare community members, except within some oligotrophic soils. Here we combined metagenomic, biogeochemical and modelling approaches to determine how soil microbial communities meet energy and carbon needs. Analysis of 40 metagenomes and 757 derived genomes indicated that over 70% of soil bacterial taxa encode enzymes to consume inorganic energy sources. Bacteria from 19 phyla encoded enzymes to use the trace gases hydrogen and carbon monoxide as supplemental electron donors for aerobic respiration. In addition, we identified a fourth phylum (Gemmatimonadota) potentially capable of aerobic methanotrophy. Consistent with the metagenomic profiling, communities within soil profiles from diverse habitats rapidly oxidized hydrogen, carbon monoxide and to a lesser extent methane below atmospheric concentrations. Thermodynamic modelling indicated that the power generated by oxidation of these three gases is sufficient to meet the maintenance needs of the bacterial cells capable of consuming them. Diverse bacteria also encode enzymes to use trace gases as electron donors to support carbon fixation. Altogether, these findings indicate that trace gas oxidation confers a major selective advantage in soil ecosystems, where availability of preferred organic substrates limits microbial growth. The observation that inorganic energy sources may sustain most soil bacteria also has broad implications for understanding atmospheric chemistry and microbial biodiversity in a changing world.

For a species to be able to respond to environmental change, it must either succeed in following its optimal environmental conditions or in persisting under suboptimal conditions, but we know very little about what controls these capacities. We parameterized species distribution models (SDMs) for 135 plant species from the Algerian steppes. We interpreted low false‐positive rates as reflecting a high capacity to follow optimal environmental conditions and high false‐negative rates as a high capacity to persist under suboptimal environmental conditions. We also measured functional traits in the field and built a unique plant trait database for the North‐African steppe. For both perennial and annual species, we explored how these two capacities can be explained by species traits and whether relevant trait values reflect species strategies or biases in SDMs. We found low false‐positive rates in species with small seeds, flowers attracting specialist pollinators, and specialized distributions (among annuals and perennials), low root:shoot ratios, wide root‐systems, and large leaves (perennials only) (R2 = .52–58). We found high false‐negative rates in species with marginal environmental distribution (among annuals and perennials), small seeds, relatively deep roots, and specialized distributions (annuals) or large leaves, wide root‐systems, and monocarpic life cycle (perennials) (R2 = .38 for annuals and 0.65 for perennials). Overall, relevant traits are rarely indicative of the possible biases of SDMs, but rather reflect the species' reproductive strategy, dispersal ability, stress tolerance, and pollination strategies. Our results suggest that wide undirected dispersal in annual species and efficient resource acquisition in perennial species favor both capacities, whereas short life spans in perennial species favor persistence in suboptimal environmental conditions and flowers attracting specialist pollinators in perennial and annual species favor following optimal environmental conditions. Species that neither follow nor persist will be at risk under future environmental change.

Gas emission from motor vehicle has become the origin of many serious issues including health and air-quality, green house effect, and other environment issues. While motor vehicle manufacturers have set a particular standard of gas emission and motor vehicle aging, usage has contributed to the increase of hazardous gas emission from vehicles. Therefore, developing a special material that can adsorb the emitted gases should be continuously demonstrated. This paper reports the fabrication of a high-performance material, i.e., asphalt naturally found in Buton Island, Indonesia (asbuton), composited of anatase TiO2 (ATi), for application in gas emission reduction, such as carbon monoxide (CO), carbon dioxide (CO2), and other hydrocarbon gases (HC). ATi was prepared by coating the pre-extracted asbuton with anatase TiO2 sol-gel via a spray-coating technique and annealed at 120 °C for 3 h. We found that the CO, CO2, and HC gases can be effectively adsorbed by the ATi adsorbent as high as 600, 1500, and 760 ppm, respectively, for exposure time of only 90 s each. The gas adsorption on the ATi obeys Langmuir and Freundlich isotherms. The maximum gas adsorption capacity was found to be as high as 95,238 and 2348 ppm (for CO2 and HC, respectively). The availability of abundant –OH active ligand on Si–OH and Ti–OH and highly porous structure, as judged from the FTIR and SEM analysis results, is assumed as the key reason for the high adsorption capacity of the ATi. The ATi should find a potential application in motor vehicle gas emission and air pollutant mitigation.

Efficient CO sensing by a CuO:Au nanocomposite thin film deposited by PLD on a Pyrex tube

Development of a monitoring tape for ammonia gas in air by fluorescence detection

It can be expected that there is a considerable correlation between combustion air flow rate and the concentrations of carbon monoxide, hydrocarbons and nitrogen oxide in the flue gas. The influence of temperature and oxygen concentration in the combustion zone on the concentrations of carbon monoxide, hydrocarbons and nitrogen oxide in the flue gas, for high and low combustion air flow, was analysed. Oxygen concentration for which the concentration of carbon monoxide is the lowest was determined, as well as the mutual relation between carbon monoxide and nitrogen oxide concentration.

Titanium dioxide (TiO2) and gold doped TiO2 (Au-TiO2) thin films on langasite (LGS) substrates were employed for carbon monoxide (CO) sensing. These two types of sensors have interdigital electrodes with Ti, Ni and Au metallization film. Thin films of TiO2 were deposited using the radio frequency (RF) magnetron sputtering method. Both TiO2 and Au-TiO2 based gas sensors were exposed to low concentrations of CO gas in synthetic air at a temperature range between 230degC and 320degC and their electrical conductivity were measured. It has been observed that the device sensitivity is much greater for the Au-TiO2 based gas sensor. The response time of the sensor is shorter than that of commercial conductometric CO sensors.

The combustion of rich mixtures of methane representing natural gas in air or oxygenated air involving the uncatalyzed partial oxidation of methane is examined analytically with the view of hydrogen and/or synthesis gas (carbon monoxide and hydrogen) production from natural gas. This is carried out in turn for isothermal, constant pressure and constant volume combustion processes over the feed temperature range of 800–2000K and equivalence ratio of up to 3.5. The role of various operating parameters in establishing the yield of hydrogen is presented and discussed. The effectiveness of the controlled recirculation of combustion gases to the feed for enhancing the reaction and conversion rates of methane into hydrogen is examined. It is shown that there are some conditions that can be employed for such recirculation to yield significant increases in the conversion rate.

Atmosphere-dependent potentials at oxide interfaces

The production of specialized resting cells is a remarkable strategy developed by several organisms to survive unfavorable environmental conditions. Spores are specialized resting cells that are characterized by low to absent metabolic activity and higher resistance. Spore-like cells are known from multiple groups of bacteria, which can form spores under suboptimal growth conditions (e.g., starvation). In contrast, little is known about the production of specialized resting cells in archaea. In this study, we applied a culture-independent method that uses physical and chemical lysis, to assess the diversity of lysis-resistant bacteria and archaea and compare it to the overall prokaryotic diversity (direct DNA extraction). The diversity of lysis-resistant cells was studied in the polyextreme environment of the Salar de Huasco. The Salar de Huasco is a high-altitude athalassohaline wetland in the Chilean Altiplano. Previous studies have shown a high diversity of bacteria and archaea in the Salar de Huasco, but the diversity of lysis-resistant microorganisms has never been investigated. The underlying hypothesis was that the combination of extreme abiotic conditions might favor the production of specialized resting cells. Samples were collected from sediment cores along a saline gradient and microbial mats were collected in small surrounding ponds. A significantly different diversity and composition were found in the sediment cores or microbial mats. Furthermore, our results show a high diversity of lysis-resistant cells not only in bacteria but also in archaea. The bacterial lysis-resistant fraction was distinct in comparison to the overall community. Also, the ability to survive the lysis-resistant treatment was restricted to a few groups, including known spore-forming phyla such as Firmicutes and Actinobacteria. In contrast to bacteria, lysis resistance was widely spread in archaea, hinting at a generalized resistance to lysis, which is at least comparable to the resistance of dormant cells in bacteria. The enrichment of Natrinema and Halarchaeum in the lysis-resistant fraction could hint at the production of cyst-like cells or other resistant cells. These results can guide future studies aiming to isolate and broaden the characterization of lysis-resistant archaea.

Paschen’s law and deviation from Paschen’s law are studied in a face to face gas sensor based on Mn helical sculptured thin films with conical shape as cathode and anode electrodes. The sensor’s performance was investigated at dynamic pressures ranging from 0.1 to 1000 mbar and 3 to 200 μm gaps between the two electrodes and for nitrogen, air and carbon monoxide gases. Results showed that at distances more than 10 μm the Paschen’s law is satisfied but at lower than 10 μm distances between the two electrodes and pressures more than 250 mbar deviations occur from the Paschen’s law. Selectivity results of the sensor showed that under all conditions studied in this work and for all gases there is a good resolution between the results and this enhances with gas pressure. Comparison of the results of the present sensor with those reported in the literature showed higher sensitivity of the present work for different gases investigated.