Abundance and composition of airborne archaea during springtime mixed dust and haze periods in Beijing, China

Characteristics of airborne bacteria over inland and coastal atmosphere influenced by systemic air mass in northern China

Regional aerosol pollution frequently occurs in winter and spring in northern China. Here, we surveyed four air pollution, categorized as episodes influenced by northerly or southerly air mass, and discussed the bacterial communities in inland and coastal cities. Influenced by northerly airmass, the predominant bacterial phyla were Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria both in the inland and coastal cities. The opportunistic pathogen in the genus Staphylococcus was predominant, and the relative proportion increased with the intensification of air pollution. Gut bacteria of the genus Lactobacillus and aquatic bacteria of the family Flavobacteriaceae were enriched in the coastal city. Influenced by southerly air mass, combined with the transmission of dust air masses in the northwest, air pollution in spring showed obvious sand dust characteristics. The prevalence of the members from the phylum Cyanobacteria was markedly greater in inland city compared to the coastal city, especially in dust samples. This indicated the possibility of soil Cyanobacteria members, subsequently being transported from terrestrial to coastal areas via dust movements. The bacterial community dynamics was intimately linked to meteorological factors and air pollutants. In both cities, pathogenic bacteria predominate in haze pollution influenced by northernly air masses, while a higher proportion of soil bacteria originating from natural sources predominate in southern air mass samples. The impact of varying air masses was particularly pronounced in inland city. Meteorological factors instigated by seasonal changes-especially the transition of wind direction from winter to spring, accompanied by elevated wind speeds and rising temperatures-play a pivotal role in shaping bacterial community structure. This study examined the sea-land variations in bacterial communities transported by systemic air masses during typical air pollution events. These insights lay the groundwork for future research into the distribution, sources, and health risks of bioaerosols during air pollution.

Halophilic and Non-Halophilic Microbial Communities in Relation to Physico-Chemical Characteristics of Salt Mine Air

Salt mines are often used for halotherapy against lung and skin diseases. In addition to salt, they also contain various types of microorganisms, which remain poorly characterised. Here, we examined culturable halophilic and non-halophilic microbial populations in relation to the physico-chemical characteristics in the air of four different sites of the Bochnia Salt Mine, a popular halotherapy resort in Southern Poland. At the mine entrance, the temperature was highest (20.8°C) and decreased with increasing distance from the entrance (15.5°C at 2671 m from entrance), while humidity increased from 55.9% to 77.0%, as did the NaCl concentration. At the entrance, non-halophilic microorganisms prevailed, especially fungi that grew at 21°C. Halophiles gradually dominated with distance from the entrance, including halophilic archaea that grew at 28°C or 37°C on medium containing 15%, 20%, or 25% NaCl. Seven halophilic archaeal species were identified by 16S rRNA gene sequencing. The frequency of non-halophiles was inversely related to distance from the entrance, humidity, and presence of ions, while the reverse was seen for halophiles. An exception was the site used for halotherapy, where non-halophilic bacteria dominated. Thus, natural salt mines contain a wide variety of non-halophilic and halophilic microorganisms, including archaea, which may contribute to the halotherapeutic effects.

Comparison of airborne bacterial communities in PM2.5 between a dry-season haze period and a wet-season non-haze period in thailand

Thailand experiencing severe air pollution for over a decade. Although the physical and chemical properties of particulate matter have been extensively studied, the biological aspects, particularly microorganisms present in fine particles during haze and non-haze periods, are still unclear. To address this gap, we aim to profile the bacterial communities in PM2.5 in Bangkok and Chiang Mai, Thailand. The samples were collected during the haze and non-haze periods in 2021-2022. Using 16 S rRNA gene sequencing, we identified a markedly higher number of bacterial genera in Chiang Mai (247) compared to Bangkok (31). In Bangkok, Actinobacteriota (80.4%) and Proteobacteria (18.3%) dominated, whereas Chiang Mai's samples were enriched with Firmicutes (52.2%) and Bacteroidota (13.0%). Interestingly, Bangkok's samples were dominated by Cutibacterium (68.4%) and Enhydrobacter (14.6%), while Chiang Mai had Bacillus (11.0%) and Blautia (7.6%). Despite substantially higher PM2.5 levels during haze, alpha diversity analyses showed that bacterial community structure was more strongly influenced by geographic location than by haze conditions. Chiang Mai consistently exhibited greater microbial richness and evenness than Bangkok. These findings highlight the importance of biological factors in urban air pollution studies and underscore the need to incorporate the biological aspects into health risk assessments and air quality management strategies.

A super sandstorm altered the abundance and composition of airborne bacteria in Beijing

Sandstorm, which injects generous newly emerging microbes into the atmosphere covering cities, adversely affects the air quality in built environments. However, few studies have examined the change of airborne bacteria during severe sandstorm events. In this work, we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia on March 15th, 2021, which affected large areas of China and Mongolia. The characteristics of the sandstorm were compared with those of the subsequent clean and haze days. The composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction (qPCR) and high-throughput sequencing technology. During the sandstorm, the particulate matter (PM) concentration and bacterial richness were extremely high (PM2.5: 207 µg/m3; PM10: 1630 µg/m3; 5700 amplicon sequence variants/m3). In addition, the sandstorm brought 10 pathogenic bacterial genera to the atmosphere, posing a grave hazard to human health. As the sandstorm subsided, small bioaerosols (0.65-1.1 µm) with a similar bacterial community remained suspended in the atmosphere, bringing possible long-lasting health risks.

On-Site Bioaerosol Sampling and Airborne Microorganism Detection Technologies

Bioaerosols are small airborne particles composed of microbiological fragments, including bacteria, viruses, fungi, pollens, and/or by-products of cells, which may be viable or non-viable wherever applicable. Exposure to these agents can cause a variety of health issues, such as allergic and infectious diseases, neurological disorders, and cancer. Therefore, detecting and identifying bioaerosols is crucial, and bioaerosol sampling is a key step in any bioaerosol investigation. This review provides an overview of the current bioaerosol sampling methods, both passive and active, as well as their applications and limitations for rapid on-site monitoring. The challenges and trends for detecting airborne microorganisms using molecular and immunological methods are also discussed, along with a summary and outlook for the development of prompt monitoring technologies.

Aeromicrobiology: A global review of the cycling and relationships of bioaerosols with the atmosphere

Airborne microorganisms and biological matter (bioaerosols) play a key role in global biogeochemical cycling, human and crop health trends, and climate patterns. Their presence in the atmosphere is controlled by three main stages: emission, transport, and deposition. Aerial survival rates of bioaerosols are increased through adaptations such as ultra-violet radiation and desiccation resistance or association with particulate matter. Current research into modern concerns such as climate change, global gene transfer, and pathogenicity often neglects to consider atmospheric involvement. This comprehensive review outlines the transpiring of bioaerosols across taxa in the atmosphere, with significant focus on their interactions with environmental elements including abiotic factors (e.g., atmospheric composition, water cycle, and pollution) and events (e.g., dust storms, hurricanes, and wildfires). The aim of this review is to increase understanding and shed light on needed research regarding the interplay between global atmospheric phenomena and the aeromicrobiome. The abundantly documented bacteria and fungi are discussed in context of their cycling and human health impacts. Gaps in knowledge regarding airborne viral community, the challenges and importance of studying their composition, concentrations and survival in the air are addressed, along with understudied plant pathogenic oomycetes, and archaea cycling. Key methodologies in sampling, collection, and processing are described to provide an up-to-date picture of ameliorations in the field. We propose optimization to microbiological methods, commonly used in soil and water analysis, that adjust them to the context of aerobiology, along with other directions towards novel and necessary advancements. This review offers new perspectives into aeromicrobiology and calls for advancements in global-scale bioremediation, insights into ecology, climate change impacts, and pathogenicity transmittance.

Depth-Dependent Distribution of Prokaryotes in Sediments of the Manganese Crust on Nazimov Guyots of the Magellan Seamounts

Deep ocean polymetallic nodules, rich in cobalt, nickel, and titanium which are commonly used in high-technology and biotechnology applications, are being eyed for green energy transition through deep-sea mining operations. Prokaryotic communities underneath polymetallic nodules could participate in deep-sea biogeochemical cycling, however, are not fully described. To address this gap, we collected sediment cores from Nazimov guyots, where polymetallic nodules exist, to explore the diversity and vertical distribution of prokaryotic communities. Our 16S rRNA amplicon sequencing data, quantitative PCR results, and phylogenetic beta diversity indices showed that prokaryotic diversity in the surficial layers (0-8 cm) was > 4-fold higher compared to deeper horizons (8-26 cm), while heterotrophs dominated in all sediment horizons. Proteobacteria was the most abundant taxon (32-82%) across all sediment depths, followed by Thaumarchaeota (4-37%), Firmicutes (2-18%), and Planctomycetes (1-6%). Depth was the key factor controlling prokaryotic distribution, while heavy metals (e.g., iron, copper, nickel, cobalt, zinc) can also influence significantly the downcore distribution of prokaryotic communities. Analyses of phylogenetic diversity showed that deterministic processes governing prokaryotic assembly in surficial layers, contrasting with stochastic influences in deep layers. This was further supported from the detection of a more complex prokaryotic co-occurrence network in the surficial layer which suggested more diverse prokaryotic communities existed in the surface vs. deeper sediments. This study expands current knowledge on the vertical distribution of benthic prokaryotic diversity in deep sea settings underneath polymetallic nodules, and the results reported might set a baseline for future mining decisions.

Seasonal variation characteristics of inhalable bacteria in bioaerosols and antibiotic resistance genes in Harbin

Bioaerosols have received extensive attention due to their impact on climate, ecological environment, and human health. This study aimed to reveal the driving factors that structure bacterial community composition and the transmission route of antibiotic resistance genes (ARGs) in PM_2.5. The results showed that the bacterial concentration in spring (8.76 × 10⁵ copies/m³) was significantly higher than that in summer (1.03 × 10⁵ copies/m³) and winter (4.74 × 10⁴ copies/m³). Low temperatures and air pollution in winter negatively affected bacterial concentrations. Keystone taxa were identified by network analysis. Although about 50 % of the keystone taxa had low relative abundances, the strong impact of complex interactions between keystone taxa and other taxa on bacterial community structure deserved attention. The bacterial community assembly was dominated by stochastic processes (79.3 %). Interactions between bacteria and environmental filtering together affected bacterial community composition. Vertical gene transfer played an important role in the transmission of airborne ARGs. Given the potential integration and expression of ARGs in recipients, the human exposure risk due to high concentrations of ARGs and mobile genetic elements cannot be ignored. This study highlights human exposure to inhalable bacterial pathogens and ARGs in urban areas.

Diverse Bathyarchaeotal Lineages Dominate Archaeal Communities in the Acidic Dajiuhu Peatland, Central China

Bathyarchaeota are believed to have roles in the carbon cycle in marine systems. However, the ecological knowledge of Bathyarchaeota is limited in peatland ecosystems. Here, we investigated the vertical distribution of Bathyarchaeota community structure using quantitative PCR and high-throughput sequencing technology of ribosomal 16S rRNA gene integrated with detailed chemical profiling in the Dajiuhu Peatland, central China. Eight archaeal phyla were observed in peat samples, which mainly composed of Bathyarchaeota with a mean relative abundance about 88%, followed by Thaumarchaeota (9%). Bathyarchaeota were further split into 17 subgroups, and some subgroups showed habitat specificity to peat horizons with distinct lithological and physicochemical properties, for example, Bathy-6 and Bathy-15 had preference for the acrotelm, Bathy-5b, Bathy-16, and Bathy-19 were enriched in the catotelm, Bathy-5a, Bathy-8, and Bathy-11 were specific for the clay horizon. This spatial distribution pattern of archaeal communities along peat profile was mainly influenced by water content as indicated by RDA ordination and permutational MANOVA, whereas organic matter content exclusively affected Bathyarchaeota distribution along the peat profile significantly. The abundance of archaeal 16S rRNA genes ranged from 10⁵ to 10⁷ copies per gram dry sediment, and the highest archaeal biomass was observed in the periodically oxic mesotelm horizon with more dynamic archaeal interaction relationship as indicated by the network analysis. Bathyarchaeota dominated the archaeal interaction network with 82% nodes, 96% edges, and 71% keystone species. Our results provide an overview of the archaeal population, community structure, and relationship with environmental factors that affect the vertical distribution of archaeal communities and emphasize the ecology of bathyarchaeotal lineages in terrestrial peatland ecosystems.

Insights into the Profile of the Human Expiratory Microbiota and Its Associations with Indoor Microbiotas

Microorganisms residing in the human respiratory tract can be exhaled, and they constitute a part of environmental microbiotas. However, the expiratory microbiota community and its associations with environmental microbiotas remain poorly understood. Here, expiratory bacteria and fungi and the corresponding microbiotas from the living environments were characterized by DNA amplicon sequencing of residents' exhaled breath condensate (EBC) and environmental samples collected from 14 residences in Nanjing, China. The microbiotas of EBC samples, with a substantial heterogeneity, were found to be as diverse as those of skin, floor dust, and airborne microbiotas. Model fitting results demonstrated the role of stochastic processes in the assembly of the expiratory microbiota. Using a fast expectation-maximization algorithm, microbial community analysis revealed that expiratory microbiotas were differentially associated with other types of microbiotas in a type-dependent and residence-specific manner. Importantly, the expiratory bacteria showed a composition similarity with airborne bacteria in the bathroom and kitchen environments with an average of 12.60%, while the expiratory fungi showed a 53.99% composition similarity with the floor dust fungi. These differential patterns indicate different relationships between expiratory microbiotas and the airborne microbiotas and floor dust microbiotas. The results here illustrated for the first time the associations between expiratory microbiotas and indoor microbiotas, showing a potential microbial exchange between the respiratory tract and indoor environment. Thus, improved hygiene and ventilation practices can be implemented to optimize the indoor microbial exposome, especially in indoor bathrooms and kitchens.