Airborne microbes significantly influence environmental processes and human exposure, yet they remain poorly characterized in Africa. This study presents a regional survey of airborne bacterial and fungal communities across 10 sites in five East African countries: Burundi, the Democratic Republic of the Congo, Kenya, Rwanda, and Tanzania. Polyurethane foam passive air samplers (PUF-PASs) were deployed concurrently, and airborne bacterial and fungal communities were characterized using 16S rRNA gene and ITS amplicon sequencing. Genus-level analyses identified both bacterial taxa (Massilia, Sphingomonas, Pseudomonas, Bacillus, and Kocuria) and fungal genera (Cladosporium, Alternaria, Aspergillus, Curvularia, and Penicillium) that are commonly detected in outdoor air and urban atmospheric environments. Beta-diversity analysis revealed no significant country-level differences in bacterial communities (ANOSIM (R = -0.045, p = 0.597)), while fungal communities exhibited significant differences among countries (ANOSIM (R = 0.652, p = 0.002)). Cross-border comparisons showed that nearby sites within 10 km did not consistently share similar microbial profiles. These findings indicate a broadly shared regional bacterial aerobiome, with more pronounced spatial structuring among fungal communities. This study serves as a proof-of-concept demonstration that PUF-PASs can be used to characterize airborne microbial communities in East Africa, while highlighting the need for future bioaerosol research with enhanced temporal replication and broader spatial coverage to support long-term public health surveillance in the African region.

Exposure to particulate matter (PM) is a major global health concern, yet the potential relationships between its chemical and microbial components remains poorly understood, particularly in rapidly urbanizing, understudied settings. This study presents an integrated assessment of polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs), bacteria, and fungi in both fine (PM2.5) and coarse (PM10) aerosols across urban, roadside, and rural sites in sub-Saharan Africa, with a focus on Rwanda across dry and wet seasons. Microbial analysis revealed that the richness and community structure of the airborne bacterial and fungal communities varied with land-use type, linked with PAH/NPAH abundance, PM size fraction, and season. Spearman correlation coefficient confirmed that bacterial communities were more strongly associated with PAH and NPAH compounds, whereas fungal communities were shaped primarily by environmental factors. One bacterial genus, Sphingobium, exhibited evidence of selective enrichment within the PAH rich PM2.5 size fraction, highlighting the potential for direct interaction between the biological and chemical compositions in air. We provide a critical baseline for African cities where air quality data are scarce. Current air quality standards, which prioritize chemical thresholds, overlook the biological burden carried by PM.

Hot springs, with their well-characterized major abiotic variables and island-like habitats, are ideal systems for studying microbial biogeography. Photosynthetic biofilms are a major biological feature of hot springs but despite this large-scale studies are scarce, leaving critical questions about the drivers of spatial turnover unanswered. Here, we analysed 395 photosynthetic biofilms from neutral-alkaline hot springs (39–66 °C, pH 6.4–9.0) across a 2100 km latitudinal gradient in Southeast Asia. The Cyanobacteria-dominated communities were categorized into six biogeographic regions, each characterized by a distinct core microbiome and biotic interactions. We observed a significant decline in the explanatory power of major abiotic variables with increasing spatial scale, from 62.6

Marine fuel oil (MFO) spills in tropical coastal environments are under-characterized despite increasing risk from maritime activities. Microbial and geochemical responses to the June 2024 Marine Honour MFO spill on Singapore's intertidal sediments were analyzed in real time over 185 days. Using metagenomics and hydrocarbon profiling, microbial community shifts and hydrocarbon degradation were quantified across visibly oiled (high-impact) and clean (low-impact) sites. Microbiomes at all sites adapted rapidly to the spill through increased diversity and abundance of genes encoding alkane and aromatic compound degradation, detoxification, and biosurfactant production. The dominant hydrocarbon-degrading bacteria differed markedly from those reported in other crude oil spills and in regions with different climates. Oil deposition intensity strongly influenced microbial succession and hydrocarbon-degrading gene profiles, and this reflected early toxicity constraints in heavily oiled areas. The persistence of hydrocarbon degradation genes beyond hydrocarbon detection in sediments suggested long-term functional priming may occur. The study provides novel genome-resolved insight into the microbial response to MFO pollution, advances understanding of marine environmental biodegradation, and provides urgently needed baseline data for oil spill response strategies in Southeast Asia and beyond.

High-temperature streamer biofilm communities (SBCs) are often dominated by Aquificota, which can comprise over 90% of the microbial population in shallow water channels, such as those found at Mammoth hot springs of Yellowstone National Park and the Rehai hot springs in China. This study examines SBCs from the Dusun Tua (DT) hot spring in Malaysia (75 °C, pH 7.6), where Aquificota accounted for only ~ 35% of the total amplicon sequence variants. Amplicon and hybrid metagenomic sequencing revealed a more balanced microbial community, co-dominated by Aquificota, Chloroflexota, Desulfobacterota, Bacteroidota, Deinococcota, and Candidatus Hydrothermae, along with Thermoproteota and Micrarchaeota. To our knowledge, the co-dominance of Aquificota and Chloroflexota in SBCs has not been previously reported. The unexpected abundance of Chloroflexota may stem from dispersal from upstream Cyanobacteriota-Chloroflexota biofilms, contributing to community diversification. Genome-resolved analyses identified more than 60 medium- to high-quality metagenome-assembled genomes (MAGs), suggesting that biofilm formation was initially driven by chemoautotrophic sulfur oxidation and CO₂ fixation, followed by the gradual integration of heterotrophic taxa. Nitrogen cycling and hydrogen oxidation are likely to contribute additional sources of energy. The presence of diverse CAZymes suggests that plant litter may serve as an additional carbon source. Genome-centric analyses across multiple phyla indicated that extracellular polymeric substances (EPS), curli fibers, and other matrix components contribute to the biofilm matrix, enhancing structural resilience and supporting persistence under harsh conditions. Overall, this study highlights the distinct microbial ecology of the DT SBC and broader metabolic roles beyond Aquificota dominance. The genes identified in this study may hold biotechnological potential and serve as a valuable resource for future enzyme discovery and functional screening.

Marine fuel oil (MFO) spills in tropical coastal environments are under-characterized despite increasing risk from maritime activities. Microbial and geochemical responses to the June 2024 Pasir Panjang MFO spill on Singapore’s intertidal sediments were analyzed in real time over 185 days. Using metagenomics and hydrocarbon profiling, microbial community shifts and hydrocarbon degradation were quantified across visibly oiled (high-impact) and clean (low-impact) sites. Microbiomes at all sites adapted rapidly to the spill through increased diversity and abundance of genes encoding alkane and aromatic compound degradation, detoxification, and biosurfactant production. Oil deposition intensity strongly influenced microbial succession and hydrocarbon-degrading gene profiles, and this reflected early toxicity constraints in heavily oiled areas. The persistence of hydrocarbon degradation genes beyond hydrocarbon detection in sediments suggested long-term functional priming may occur. The study provides novel genome-resolved insight into the microbial response to MFO pollution, advances understanding of marine environmental biodegradation, and provides urgently needed baseline data for oil spill response strategies in Southeast Asia and beyond.

A unicellular-colonial cyanobacterium, designated "BRSZ," was isolated from a neutral-alkaline hot spring in Thailand. Morphological characterization revealed distinctive features consistent with those of the genus Gloeocapsa. Physiological assessments demonstrated that BRSZ is a moderately thermophilic and halotolerant cyanobacterium with the potential for chemoheterotrophic growth in dark conditions. Molecular phylogenetic analysis based on 16S ribosomal RNA (rRNA) gene sequences placed BRSZ within a well-defined Gloeocapsa clade, a finding corroborated by 16S-23S internal transcribed spacer (ITS) rRNA secondary structure analyses. Genome comparisons, including average nucleotide identity (ANI), genome-to-genome distance (GGD), and digital DNA-DNA hybridization (dDDH), between strain BRSZ and closely related taxa showed an ANI value of 95.45 %, near the lower boundary of the species delineation threshold (95-96 %). A GGD of 0.0374 (>0.0258) and dDDH of 69 % (<70 %) further supported genomic differentiation. Genome-based analysis revealed a mycosporine-like amino acid biosynthetic gene cluster likely involved in sunscreen compound production. Cultivation-based production of a UV-absorbing compound confirmed the functional relevance of this gene cluster. These findings expand the described diversity within the Gloeocapsa complex and enhance our understanding of the taxonomy of this group. In addition, they underscored the importance of hot spring environments as sources of novel extremophiles.

Airborne microorganisms which dispersed from the Gobi Desert throughout East Asia via long-range dust transports, are believed to maintain their viability against atmospheric stressors that influence ecosystem dynamics and human health during deposition in downwind environments. However, the adaptative mechanisms that facilitate microbial tolerance to environmental stressor, and the persistence of factors such as antibiotic resistance relevant to human health have not been determined. Here, we described the metagenomic and physiological interrogation of airborne bacteria collected from aerosols at an altitude of 500 m using a balloon-mounted sampler and at a parallel site 3 m above the ground in the dust-source region of Gobi Desert. The shotgun metagenomic DNA sequencing which determine was performed for characterizing the taxonomic compositions of airborne bacteria and their potential functions. The communities were dominated by species in the phyla Actinobacteria, Bacillota, Bacteroidota, and Pseudomonadota (Alpha). Metabolic-pathway analysis revealed that Gobi Desert bioaerosols were enriched in functions associated with antibiotic resistance, cell-membrane transporters, and/or environmental adaptation. The antibiotic and osmotic-change resistances were confirmed among viable bacteria isolates showing higher level of resistances in the aerosols collected at 500 m than those of 3 m. These findings suggest that elevated altitudes result in environmental filtering that allows bacterial taxa to survive long-term transport to distant locations during dust events and transfer antibiotic resistance.

Abstract Hot springs are tractable model systems in microbial ecology for investigating the interactions of photosynthetic microbial biofilms. This is because they occur across broad geographic scales, possess readily identified major abiotic variables, and are subject to minimal influence from metazoans. Despite this regional scale investigations are lacking, and major questions persist concerning the evolutionary drivers responsible for biofilm turnover at broad geographic scales. Here, we present the largest study to date, incorporating concurrent measurement of biotic and abiotic diversity and rigorous statistical analysis and modelling. We characterized 395 biofilms from neutral-alkaline hot springs spanning a 2,100km latitudinal gradient in Southeast Asia. The data clearly resolved six biogeographic regions with each defined by a core microbiome comprising specific cyanobacteria and other diverse photosynthetic, chemoheterotrophic, and chemoautotrophic taxa. Our findings demonstrated that the most influential abiotic variables (pH, conductivity, carbonate) accounted for relatively little of the observed variation in biofilm communities, and that extensive biotic interactions spanned multiple trophic levels. Importantly, we present quantitative evidence that stochasticity due to ecological drift was the most important evolutionary driver of spatial turnover at a regional scale. These insights establish a pivotal milestone in understanding of this model system, fostering enhanced testing and comparison with more intricate microbial ecosystems.

Abstract Background Hot spring biofilms provide a window into the survival strategies of microbial communities in extreme environments and offer potential for biotechnological applications. This study focused on green and brown biofilms thriving on submerged plant litter within the Sungai Klah hot spring in Malaysia, characterised by temperatures of 58–74 °C. Using Illumina shotgun metagenomics and Nanopore ligation sequencing, we investigated the microbial diversity and functional potential of metagenome-assembled genomes (MAGs) with specific focus on biofilm formation, heat stress response, and carbohydrate catabolism. Results Leveraging the power of both Illumina short-reads and Nanopore long-reads, we employed an Illumina-Nanopore hybrid assembly approach to construct MAGs with enhanced quality. The dereplication process, facilitated by the dRep tool, validated the efficiency of the hybrid assembly, yielding MAGs that reflected the intricate microbial diversity of these extreme ecosystems. The comprehensive analysis of these MAGs uncovered intriguing insights into the survival strategies of thermophilic taxa in the hot spring biofilms. Moreover, we examined the plant litter degradation potential within the biofilms, shedding light on the participation of diverse microbial taxa in the breakdown of starch, cellulose, and hemicellulose. We highlight that Chloroflexota and Armatimonadota MAGs exhibited a wide array of glycosyl hydrolases targeting various carbohydrate substrates, underscoring their metabolic versatility in utilisation of carbohydrates at elevated temperatures. Conclusions This study advances understanding of microbial ecology on plant litter under elevated temperature by revealing the functional adaptation of MAGs from hot spring biofilms. In addition, our findings highlight potential for biotechnology application through identification of thermophilic lignocellulose-degrading enzymes. By demonstrating the efficiency of hybrid assembly utilising Illumina-Nanopore reads, we highlight the value of combining multiple sequencing methods for a more thorough exploration of complex microbial communities.

Water availability is the dominant driver of microbial community structure and function in desert soils. However, these habitats typically only receive very infrequent large-scale water inputs (e.g., from precipitation and/or run-off). In light of recent studies, the paradigm that desert soil microorganisms are largely dormant under xeric conditions is questionable. Gene expression profiling of microbial communities in desert soils suggests that many microbial taxa retain some metabolic functionality, even under severely xeric conditions. It, therefore, follows that other, less obvious sources of water may sustain the microbial cellular and community functionality in desert soil niches. Such sources include a range of precipitation and condensation processes, including rainfall, snow, dew, fog, and nocturnal distillation, all of which may vary quantitatively depending on the location and geomorphological characteristics of the desert ecosystem. Other more obscure sources of bioavailable water may include groundwater-derived water vapour, hydrated minerals, and metabolic hydro-genesis. Here, we explore the possible sources of bioavailable water in the context of microbial survival and function in xeric desert soils. With global climate change projected to have profound effects on both hot and cold deserts, we also explore the potential impacts of climate-induced changes in water availability on soil microbiomes in these extreme environments.

The atmosphere is a major route for microbial intercontinental dispersal, including harmful microorganisms, antibiotic resistance genes, and allergens, with strong implications in ecosystem functioning and global health. Long-distance dispersal is facilitated by air movement at higher altitudes in the free troposphere and is affected by anthropogenic forcing, climate change, and by the general atmospheric circulation, mainly in the intertropical convergence zone. The survival of microorganisms during atmospheric transport and their remote invasive potential are fundamental questions, but data are scarce. Extreme atmospheric conditions represent a challenge to survival that requires specific adaptive strategies, and recovery of air samples from the high altitudes relevant to study harmful microorganisms can be challenging. In this paper, we highlight the scope of the problem, identify challenges and knowledge gaps, and offer a roadmap for improved understanding of intercontinental microbial dispersal and their outcomes. Greater understanding of long-distance dispersal requires research focus on local factors that affect emissions, coupled with conditions influencing transport and survival at high altitudes, and eventual deposition at sink locations.

The dispersion of microorganisms through the atmosphere is a continual and essential process that underpins biogeography and ecosystem development and function. Despite the ubiquity of atmospheric microorganisms globally, specific knowledge of the determinants of atmospheric microbial diversity at any given location remains unresolved. Here we describe bacterial diversity in the atmospheric boundary layer and underlying soil at twelve globally distributed locations encompassing all major biomes, and characterise the contribution of local and distant soils to the observed atmospheric community. Across biomes the diversity of bacteria in the atmosphere was negatively correlated with mean annual precipitation but positively correlated to mean annual temperature. We identified distinct non-randomly assembled atmosphere and soil communities from each location, and some broad trends persisted across biomes including the enrichment of desiccation and UV tolerant taxa in the atmospheric community. Source tracking revealed that local soils were more influential than distant soil sources in determining observed diversity in the atmosphere, with more emissive semi-arid and arid biomes contributing most to signatures from distant soil. Our findings highlight complexities in the atmospheric microbiota that are relevant to understanding regional and global ecosystem connectivity.

In this study, the levels of fine particulate matter (PM2.5), polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) in PM2.5 samples were determined from 2020 to 2021 in Singapore. For analysis convenience, the sampling period was classified according to two monsoon periods and the inter-monsoon period. Considering Singapore’s typically tropical monsoon climate, the four seasons were divided into the northeast monsoon season (NE), southwest monsoon season (SW), presouthwest monsoon season (PSW) and prenortheast monsoon season (PNE)). The PM2.5 concentration reached 17.1 ± 8.38 μg/m3, which was slightly higher than that in 2015, and the average PAH concentration continuously declined during the sampling period compared to that reported in previous studies in 2006 and 2015. This is the first report of NPAHs in Singapore indicating a concentration of 13.1 ± 10.7 pg/m3. The seasonal variation in the PAH and NPAH concentrations in PM2.5 did not obviously differ owing to the unique geographical location and almost uniform climate changes in Singapore. Diagnostic ratios revealed that PAHs and NPAHs mainly originated from local vehicle emissions during all seasons. 2-Nitropyrene (2-NP) and 2-nitrofluoranthene (2-NFR) in Singapore were mainly formed under the daytime OH-initiated reaction pathway. Combined with airmass backward trajectory analysis, the Indonesia air mass could have influenced Singapore’s air pollution levels in PSW. However, these survey results showed that no effect was found on the concentrations of PAHs and NPAHs in PM2.5 in Indonesia during SW because of Indonesia’s efforts in the environment. It is worth noting that air masses from southern China could impact the PAH and NPAH concentrations according to long-range transportation during the NE. The results of the total incremental lifetime cancer risk (ILCR) via three exposure routes (ingestion, inhalation and dermal absorption) for males and females during the four seasons indicated a low long-term potential carcinogenic risk, with values ranging from 10−10 to 10−7. This study systematically explains the latest pollution conditions, sources, and potential health risks in Singapore, and comprehensively analyses the impact of the tropical monsoon system on air pollution in Singapore, providing a new perspective on the transmission mechanism of global air pollution.

Atmospheric transport is critical to dispersal of microorganisms between habitats, and this underpins resilience in terrestrial and marine ecosystems globally. A key unresolved question is whether microorganisms assemble to form a taxonomically distinct, geographically variable, and functionally adapted atmospheric microbiota. This question is made more complex by the unique challenges of separating potential contaminants from atmospheric signal, particularly given the ultra-low biomass of air and the long durations of sampling where contamination may occur. Here we adopted a comprehensive data filtering approach to mitigate contamination and characterise inter-continental patterns of microbial taxonomic and functional diversity in air within and above the atmospheric boundary layer and in underlying soils for 596 globally sourced samples. Bacterial and fungal assemblages in air were taxonomically structured and deviated significantly from purely stochastic assembly. Patterns differed with location and reflected climate, underlying surface cover and environmental filtering. Source-tracking indicated a complex recruitment process involving local soils plus globally distributed inputs from drylands and the phyllosphere. Assemblages displayed stress-response and metabolic traits relevant to survival in air, and taxonomic and functional diversity were correlated with macroclimate and atmospheric variables. Our findings highlight complexity in the atmospheric microbiota that is key to understanding regional and global ecosystem connectivity.

The western Pacific Ocean is particularly affected by dust aerosols due to the transport of desert-natural sand and industrially derived particulate matter with aerodynamic diameter < 2.5 μm (PM2.5) from continental Asia. Both oligotrophic and nutrient-sufficient surface water occurs in this region and these are speculated to support different microbial community dynamics. Here, we report evidence from four shipboard experiments in the western Pacific Ocean supplying oligotrophic and nutrient-sufficient surface waters with aerosol particles obtained from the nearby coastal mountains, to simulate dust and anthropogenic aerosol inputs in the ocean region. A sharp increase in nitrate for surface waters after addition of dust aerosols resulted in large increases in diatom abundance in oligotrophic waters, whilst in nutrient-sufficient waters the response of diatom population was reduced. The increase in organic matter provided by aerosol inputs and/or increase in phytoplankton biomass induced the growth of heterotrophic prokaryotes, such as Rhodobacteraceae and Alteromonadaceae populations, in both oligotrophic and nutrient-sufficient seawater. Anthropogenic and desert-natural dust is an important source of nitrate and organics to oceanic waters and such inputs can directly affect primary production and heterotrophic prokaryotic abundance in the ocean, implying consequences for the carbon cycle in these aerosol-affected waters.

Abstract Atmospheric transport is critical to dispersal of microorganisms between habitats and this underpins resilience in terrestrial and marine ecosystems globally. A key unresolved question is whether microorganisms assemble to form a taxonomically distinct, geographically variable, and functionally adapted atmospheric microbiome. Here we characterised globalscale patterns of microbial taxonomic and functional diversity in air within and above the atmospheric boundary layer and in underlying soils. Bacterial and fungal assemblages in air were taxonomically structured and deviated significantly from purely stochastic assembly. Patterns differed with location and reflected underlying surface cover and environmental filtering. Source-tracking indicated a complex recruitment process involving local soils plus globally distributed inputs from drylands and the phyllosphere. Assemblages displayed stressresponse and metabolic traits relevant to survival in air, and taxonomic and functional diversity were correlated with macroclimate and atmospheric variables. Our findings highlight complexity in the atmospheric microbiome that is key to understanding regional and global ecosystem connectivity.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Glacier forefields provide a unique chronosequence to assess microbial or plant colonization and ecological succession on previously uncolonized substrates. Patterns of microbial succession in soils of alpine and subpolar glacier forefields are well documented but those affecting high polar systems, including moraine rocks, remain largely unexplored. In this study, we examine succession patterns in pioneering bacterial, fungal and algal communities developing on moraine rocks and soil at the Hurd Glacier forefield (Livingston Island, Antarctica). Over time, changes were produced in the microbial community structure of rocks and soils (ice-free for different lengths of time), which differed between both substrates across the entire chronosequence, especially for bacteria and fungi. In addition, fungal and bacterial communities showed more compositional consistency in soils than rocks, suggesting community assembly in each niche could be controlled by processes operating at different temporal and spatial scales. Microscopy revealed a patchy distribution of epilithic and endolithic lithobionts, and increasing endolithic colonization and microbial community complexity along the chronosequence. We conclude that, within relatively short time intervals, primary succession processes at polar latitudes involve significant and distinct changes in edaphic and lithic microbial communities associated with soil development and cryptogamic colonization.

Many corals depend upon the highly specialised and intricate relationship they form with Symbiodiniaceae algal symbionts. Porites lutea is a massive reef-building coral found throughout Southeast Asia that hosts these endosymbionts obligately. Yet despite the prevalence and importance of P. lutea as one of the most dominant corals here, its associated Symbiodiniaceae communities have not been precisely characterised. In this study, we used high-throughput DNA amplicon sequencing of the nuclear internal transcribed spacer 2 (ITS2) to characterise the diversity, community structure and biogeographic distribution of Symbiodiniaceae in P. lutea throughout Singapore and Peninsular Malaysia. Consistent with previous studies, we found that Cladocopium was the most dominant genus among all samples, and Cladocopium C15 was the most dominant type (or subclade) with 100% occurrence in all samples from every study site. Results also revealed numerous Symbiodiniaceae types associated with P. lutea that were previously undetected in Southeast Asia. Endosymbiont diversity and community variation are driven by a combination of site-specific mean monthly cloud cover and variance in monthly sea surface temperature. This study contributes baseline data toward understanding differences in Symbiodiniaceae assemblages hosted by P. lutea, shedding light on how they might be indicative of particular environmental conditions and coral responses.