On distinguishing the natural and human-induced sources of airborne pathogenic viable bioaerosols: characteristic assessment using advanced molecular analysis

Ambient air consists of bioaerosols that constitute many microbes from biosphere due to natural and anthropogenic activities. Size-dependent ambient measurements of bioaerosols at two seminatural and three anthropogenic coastal sites in southern tropical India were taken during the summer 2017. All the five sites considered in this study considerably contributed to the bioaerosol burden with larger contribution from the dumping yard site followed by the marshland site, wastewater treatment plant, composting site, and Indian Institute of Technology Madras. The colony-forming units concentration for all the sites ranged from 17 to 2750 m−3 for bacteria and 42–2673 m−3 for fungi. Firmicutes and Actinomycetes were the dominant phyla observed in 698 bacterial OTUs obtained, and Ascomycota and Zygomycota were the dominant phyla observed in 159 fungal OTUs obtained in the study. Further, the study revealed the presence of pathogenic and ice-nucleating bacteria and fungi in the bioaerosols that can largely affect the well-being of the human population and vegetation in this region. Moreover, the statistical analysis revealed high bacterial abundance and diversity at the grit chamber of wastewater treatment plant and high fungal abundance and diversity at the dumping yard. Further, principal coordinate analysis of the sites studied inferred that the marshland, wastewater treatment plant, and the dumping yard sites shared similar microbial community composition indicating the existence of similar source materials and activities at the sites. Further, this study evidently brings out the fact that urban locations may play an important role in anthropogenic contribution of both pathogenic and ice-nucleating microorganisms. © 2020, Springer Nature Switzerland AG

The stilbene biosynthetic pathway and its regulation in Scots pine

Conifers dominate the boreal forests of the Northern Hemisphere, and especially members of the family Pinaceae have great economic and ecological significance. Part of their success is thought to arise from the vast array of secondary metabolites they produce. The products of secondary metabolism are essential for plants to survive in the ever-changing environment. In Scots pine (Pinus sylvestris L.), two groups of secondary metabolites, stilbenes and resin acids, are crucial for decay resistance of heartwood timber and for active defense responses against herbivores and fungal pathogens. Several studies have shown that stilbenes improve decay resistance of pine heartwood. Since there is wide variation in the concentration of stilbenes between individuals and the trait has high heritability, it may be possible to breed heartwood that is more decay-resistant. However, breeding for heartwood properties is slow, since the decay resistance characteristics can be estimated at the earliest from 30-year-old trees. Early selection methods utilizing genetic markers or chemical screening are needed, but we do not yet understand which genes control the biosynthesis of stilbenes and what the genetic differences are between individuals that explain the variation in the capacity to produce stilbenes. Importantly, there is genetic correlation between stress-induced stilbene biosynthesis in seedlings and the heartwood stilbene content in their adult mother trees. Here, we examined the pine transcriptional responses under two conditions that were previously known to activate stilbene biosynthesis: heartwood formation in adult trees and ultraviolet (UV)-C treatment of needles in seedlings. We found that these two conditions had very little in common, except for the activation of stilbene pathway genes. For example, the regulators of the two responses seemed not to be shared. The activation of the stilbene pathway in response to UV-C treatment occurred a few hours after the onset of the treatment and was independent of translation. Stilbene biosynthesis seems to be an early defense response in Scots pine. Heartwood formation, an important developmental process in the senescence of secondary xylem, is poorly understood. Based on transcriptomic analysis, stilbene biosynthesis occurs in situ in the transition zone between the sapwood and heartwood, but resin acids were synthesized primarily in the sapwood. Bifunctional nuclease, an enzyme involved in the process of developmentally programmed cell death (dPCD), is a useful marker for heartwood formation and aided us in defining the timing of the process, from spring to late autumn. Expression of this marker, which is strictly confined to dPCD conditions, further clarified that heartwood formation truly is a process that is initiated by intrinsic programming instead of environmental cues. The transcriptomic data revealed that the expression of the previously characterized pinosylvin O-methyltransferase gene, PMT1, was not induced under stilbene-forming conditions. A new PMT-encoding gene, PMT2, was identified by coexpression analysis. The gene showed an inducible expression pattern very similar to that of the stilbene synthase gene under all conditions studied. PMT2 furthermore methylated pinosylvin with high specificity, in contrast to PMT1, which accepted several substrates.Pohjoisen pallonpuoliskon kasvillisuus on havumetsien hallitsemaa ja etenkin mäntykasvien (Pinaceae) heimoon kuuluu taloudellisesti ja ekologisesti merkittäviä lajeja. Yksi selitys havupuiden menestykselle saattaa olla niiden kyky tuottaa laaja kirjo erilaisia sekundaariyhdisteitä. Männyn (Pinus sylvestris L.) tärkeimpiin sekundaariyhdisteisiin kuuluvat stilbeenit ja terpeenit toimivat puolustuksessa tuholaisia ja patogeenejä vastaan. Aikaisemmat tutkimukset ovat osoittaneet, että aktiivisen puolustuksen lisäksi etenkin stilbeenit parantavat männyn sydänpuun lahonkestävyyttä. Sydänpuun stilbeenien määrä vaihtelee huomattavasti yksilöiden välillä ja ominaisuus on periytyvä, mikä mahdollistaa sydänpuun lahonkestävyyden parantamisen jalostuksen keinoin. Sydänpuun laatuominaisuuksien jalostus on kuitenkin hidasta ja varhaisvalintaan soveltuvien geenimerkkien tunnistaminen nopeuttaisi jalostusprosessia. Emme kuitenkaan vielä tiedä, mitkä geenit säätelevät stilbeenien biosynteesiä ja selittävät erot sydänpuun stilbeenien määrässä. Stilbeenien tuotanto käynnistyy erilaisten stressitekijöiden vaikutuksesta neulasissa ja mantopuussa. Indusoituva tuotanto korreloi sydänpuun stilbeenien määrän kanssa ja tätä voidaan mahdollisesti hyödyntää kemiallisessa seulonnassa taimien varhaisvalinnassa. Tässä väitöskirjassa tutkittiin muutoksia männyn transkriptomissa sydänpuun muodostumisen aikana ja UV-C käsittelyn seurauksena. Stilbeenien biosynteesireitin entsyymejä koodavat geenit aktivoituivat kummassakin tapauksessa, mutta muuten transkriptomeilla oli hyvin vähän yhteistä. Esimerkiksi yhteisiä transkriptiota sääteleviä tekijöitä ei löydetty ja vaikuttaakin siltä, että eri transkriptiofaktorit säätelevät stilbeenien biosynteesireittiä sydänpuun kehityksen aikana ja stressitekijöiden vaikutuksesta. Sydänpuun muodostumisen aikana puussa tapahtuvat kemialliset ja rakenteelliset muutokset tunnetaan joillakin lajeilla hyvin, mutta itse prosessin ajoittuminen sekä käynnistymiseen ja säätelyyn vaikuttavat tekijät ovat vielä suurelta osin tuntemattomia. Stilbeenin biosynteesistä vastaavat geenit ilmenivät vaihettumisvyöhykkeellä mantopuun ja sydänpuun välissä, jossa sydänpuun muodostuminen käynnistyy ja näin tukee aiempaa käsitystä stilbeenien in situ biosynteesistä. Hartsihappojen biosynteesistä vastaavat geenit taas ilmenivät lähinnä mantopuussa, jolloin ne todennäköisesti kuljetetaan vaihettumisvyöhykkeelle sen ulkopuolelta. Ohjelmoidulla solukuolemalla on suuri merkitys sekä kasvin kehityksessä, että stressivasteissa. Bifunktionaalinen nukleaasi (BFN) on entsyymi, joka on yhdistetty aiemmissa tutkimuksissa spesifisesti kasvien kehityksellisiin tapahtumiin. Entsyymiä koodaavan geenin havaittiin ilmenevän ainoastaan vaihettumisvyöhykkeellä. Tämä tukee hypoteesia, jonka mukaan sydänpuun muodostuminen on sisäisesti säädelty eikä ympäristötekijöiden laukaisema tapahtuma. Bifunktionaalinen nukleaasi toimi myös hyödyllisenä markkerina sydänpuun muodostumisen ajoittamisessa keväästä myöhäiseen syksyyn. Transkriptiodata paljasti, että aiemmin tunnistettu stilbeenireitin viimeistä reaktiota katalysoiva metyylitransferaasientsyymiä (PMT1) koodaava geeni ei indusoitunut tutkituissa stilbeenejä tuottavissa olosuhteissa. Tunnistimme uuden metyylitransferaasia koodaavan geenin (PMT2), jonka ekspressioprofiili vastasi stilbeenireitin toisen entsyymin, stilbeenisyntaasin ekspressiota kaikissa tutkituissa olosuhteissa. PMT2 metyloi spesifisesti pinosylviiniä kun taas PMT1 metyloi stilbeenien lisäksi useita rakenteellisesti erilaisia substraatteja

Rapid growth and high cloud-forming potential of anthropogenic sulfate aerosol in a thermal power plant plume during COVID lockdown in India

The COVID lockdown presented an interesting opportunity to study the anthropogenic emissions from different sectors under relatively cleaner conditions in India. The complex interplays of power production, industry, and transport could be dissected due to the significantly reduced influence of the latter two emission sources. Here, based on measurements of cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosols during the lockdown, we report an episodic event resulting from distinct meteorological conditions. This event was marked by rapid growth and high hygroscopicity of new aerosol particles formed in the SO2 plume from a large coal-fired power plant in Southern India. These sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions provides important new clues to delineate the contributions of different anthropogenic emission sectors and further to understand their perturbations of past and future climate forcing

Chemical kinetics of near-surface ozone at a suburban location in India

The spatial gradient in near-surface ozone (O3) is controlled by its production, sink, and net transport (advection/convection and diffusive) in the atmosphere. In this work, we used continuous long-term measurements of O3, oxides of nitrogen (NOx = NO + NO2), and meteorological data in the suburban location of Shadnagar, India. Data analyses were performed to investigate the governing processes that control O3 variability on diurnal and seasonal time scales. The role of chemistry in O3 variability, including both formation and destruction processes, was investigated using known chemical kinetics and a radiative transfer model. The residual between observations and chemical estimation was further analyzed to examine the role of transport and unresolved processes/uncertainty in the dataset. The O3 residual was duly validated using model reanalysis data of O3 and meteorological parameters to further estimate the O3 transport. Our analyses show that the average net production and net transport of near-surface O3 are 3.18 and 0.87 ppbv/h, respectively, while horizontal advection is 0.01 ppbv/h in the daytime. The production of ozone was found to be dominant, indicating the influx of ozone at the site. Overall, our results highlight that spatio-temporal variability in near-surface ozone is strongly controlled by net production in Shadnagar and may be applicable in similar environments globally

Assessment of aerosol optical and micro-physical features retrieved from direct and diffuse solar irradiance measurements from Skyradiometer at a high altitude station at Merak

Optical and micro-physical features of aerosol are reported using Skyradiometer (POM-01L, Prede, Japan) observations taken from a high-altitude station Merak, located in north-eastern Ladakh of the western trans-Himalayas region during January 2011 to December 2013. The observed daily mean aerosol optical depth (AOD, at 500 nm) at the site varied from 0.01 to 0.14. However, 75 % of the observed AOD lies below 0.05 during the study period. Seasonal peaks of AOD occurred in spring as 0.06 and minimum in winter as 0.03 which represents the aged background aerosols at the site. Yearly mean AOD at 500 nm is found to be around 0.04 and inter-annual variations of AOD is very small (nearly +/- 0.01). Angstrom exponent (a) varied seasonally from 0.73 in spring to 1.5 in autumn. About 30 % of the observed a lies below 0.8 which are the indicative for the presence of coarse-mode aerosols at the site. The station exhibits absorbing aerosol features which prominently occurred during spring and that may be attributed by the transported anthropogenic aerosol from Indo-Gangatic Plain (IGP). Results were well substantiated with the air mass back-trajectory analysis. Furthermore, seasonal mean of single scattering albedo (SSA at 500 nm) varied from of 0.94 to 0.98 and a general increasing trend is noticed from 400 to 870 nm wavelengths. These features are apparently regional characteristics of the site. Aerosol asymmetry factor (AS) decreases gradually from 400 to 870 nm and varied from 0.66 to 0.69 at 500 nm across the seasons. Dominance of desert-dust aerosols, associated by coarse mode, is indicated by tri-modal features of aerosol volume size distribution over the station during the entire seasons

Observations of particle number size distributions and new particle formation in six Indian locations

Atmospheric new particle formation (NPF) is a crucial process driving aerosol number concentrations in the atmosphere; it can significantly impact the evolution of atmospheric aerosol and cloud processes. This study analyses at least 1 year of asynchronous particle number size distributions from six different locations in India. We also analyze the frequency of NPF and its contribution to cloud condensation nuclei (CCN) concentrations. We found that the NPF frequency has a considerable seasonal variability. At the measurement sites analyzed in this study, NPF frequently occurs in March–May (pre-monsoon, about 21 % of the days) and is the least common in October–November (post-monsoon, about 7 % of the days). Considering the NPF events in all locations, the particle formation rate (JSDS) varied by more than 2 orders of magnitude (0.001–0.6 cm−3s−1) and the growth rate between the smallest detectable size and 25 nm (GRSDS-25 nm) by about 3 orders of magnitude (0.2–17.2 nm h−1). We found that JSDS was higher by nearly 1 order of magnitude during NPF events in urban areas than mountain sites. GRSDS did not show a systematic difference. Our results showed that NPF events could significantly modulate the shape of particle number size distributions and CCN concentrations in India. The contribution of a given NPF event to CCN concentrations was the highest in urban locations (4.3 × 103cm−3 per event and 1.2 × 103cm−3 per event for 50 and 100 nm, respectively) as compared to mountain background sites (2.7 × 103cm−3 per event and 1.0 × 103cm−3 per event, respectively). We emphasize that the physical and chemical pathways responsible for NPF and factors that control its contribution to CCN production require in situ field observations using recent advances in aerosol and its precursor gaseous measurement techniques

Isoprene suppression of new particle formation : Potential mechanisms and implications

Secondary aerosols formed from anthropogenic pollutants and natural emissions have substantial impacts on human health, air quality, and the Earth's climate. New particle formation (NPF) contributes up to 70% of the global production of cloud condensation nuclei (CCN), but the effects of biogenic volatile organic compounds (BVOCs) and their oxidation products on NPF processes in forests are poorly understood. Observations show that isoprene, the most abundant BVOC, suppresses NPF in forests. But the previously proposed chemical mechanism underlying this suppression process contradicts atmospheric observations. By reviewing observations made in other forests, it is clear that NPF rarely takes place during the summer when emissions of isoprene are high, even though there are sufficient concentrations of monoterpenes. But at present it is not clear how isoprene and its oxidation products may change the oxidation chemistry of terpenes and how NOx and other atmospheric key species affect NPF in forest environments. Future laboratory experiments with chemical speciation of gas phase nucleation precursors and clusters and chemical composition of particles smaller than 10 nm are required to understand the role of isoprene in NPF. Our results show that climate models can overpredict aerosol's first indirect effect when not considering the absence of NPF in the southeastern U.S. forests during the summer using the current nucleation algorithm that includes only sulfuric acid and total concentrations of low-volatility organic compounds. This highlights the importance of understanding NPF processes as function of temperature, relative humidity, and BVOC compositions to make valid predictions of NPF and CCN at a wide range of atmospheric conditions

Rapid night-time nanoparticle growth in Delhi driven by biomass-burning emissions

Measurements suggest that emissions from biomass burning drive the rapid growth of particles from nanoscale into sizes relevant for haze formation during the night in Delhi.Natural and anthropogenic biomass burning are among the major sources of particulate pollution worldwide that affects air quality, climate and human health. Delhi, one of the world's most populated cities, experiences severe haze events caused by particulate pollution during winter, but the underlying pathways remain poorly understood. Here we observe intense and frequent nocturnal particle growth events during haze development in Delhi from measurements of aerosols and gases during January-February at the Indian Institute of Technology in Delhi. The particle growth events occur systematically despite the unfavourable condition for new-particle formation, including the lack of photochemical production of low-volatility vapours and considerable loss of vapours under extremely polluted conditions. We estimate that this process is responsible for 70% of the total particle-number concentration during haze. We identify that the condensation of primary organic vapours from biomass burning is the leading cause of the observed growth. The sharp decrease in night-time temperatures and rapid increase in biomass-burning emissions drive these primary organic vapours out of equilibrium, resulting in their condensation and the growth of nanoparticles into sizes relevant for haze formation. This high impact of primary biomass-burning emissions on night-time nanoparticle growth is unique compared with most urban locations globally, where low-volatility vapours formed through oxidation during the day drive particle growth and haze formation. As uncontrolled biomass burning for residential heating and cooking is rife in the Indo-Gangetic plain, we expect this growth mechanism to be a source of ultrafine particles, affecting the health of 5% of the world's population and impacting the regional climate. Our work implies that regulating uncontrolled biomass-combustion emissions may help inhibit nocturnal haze formation and improve human health in India.Peer reviewe