Genomics-based identification of a cold adapted clade in Deinococcus.

BACKGROUND: Microbes in the cold polar and alpine environments play a critical role in feedbacks that amplify the effects of climate change. Defining the cold adapted ecotype is one of the prerequisites for understanding the response of polar and alpine microbes to climate change. RESULTS: Here, we analysed 85 high-quality, de-duplicated genomes of Deinococcus, which can survive in a variety of harsh environments. By leveraging genomic and phenotypic traits with reverse ecology, we defined a cold adapted clade from eight Deinococcus strains isolated from Arctic, Antarctic and high alpine environments. Genome-wide optimization in amino acid composition and regulation and signalling enable the cold adapted clade to produce CO2 from organic matter and boost the bioavailability of mineral nitrogen. CONCLUSIONS: Based primarily on in silico genomic analysis, we defined a potential cold adapted clade in Deinococcus and provided an updated view of the genomic traits and metabolic potential of Deinococcus. Our study would facilitate the understanding of microbial processes in the cold polar and alpine environments.

The distribution and drivers of microbial pigments in the cryoconite of four Tibetan glaciers.

Microbial pigments play a significant role in glacier albedo reduction, thereby contributing to accelerated glacier retreat. The Tibetan Plateau has experienced rapid glacier retreat in recent decades due to global warming, yet there is limited understanding of microbial pigment distribution in the region. Here, we investigated the pigment concentration and composition in cryoconite from four glaciers. Our results showed that chlorophylls were the dominant pigments in Palong No. 4 (PL) and Jiemayangzong (JMYZ) glaciers located in the south of the Tibetan Plateau, while carotenoids were dominant in Qiangyong (QY) and Tanggula (TGL) glaciers located in the central region. Additionally, the chlorophyll b to chlorophyll a ratio, which is an indicator of the algae-to-cyanobacteria ratio, was higher in PL and JMYZ compared to QY and TGL. By using Random Forest Regression and Structural Equation Modelling, we determined that the concentrations of chlorophyll a, chlorophyll b, and carotenoids were associated with autotrophic bacteria relative abundance, climatic factors, and a combination of bacterial and climatic factors, respectively. This study is the first to describe the distribution of microbial pigments in cryoconite from Tibetan glaciers, providing additional support on the influence of algal pigment on glacier retreat.

The unique salt bridge network in GlacPETase: a key to its stability.

The extensive accumulation of polyethylene terephthalate (PET) has become a critical environmental issue. PET hydrolases can break down PET into its building blocks. Recently, we identified a glacial PET hydrolase GlacPETase sharing less than 31% amino acid identity with any known PET hydrolases. In this study, the crystal structure of GlacPETase was determined at 1.8 Å resolution, revealing unique structural features including a distinctive N-terminal disulfide bond and a specific salt bridge network. Site-directed mutagenesis demonstrated that the disruption of the N-terminal disulfide bond did not reduce GlacPETase's thermostability or its catalytic activity on PET. However, mutations in the salt bridges resulted in changes in melting temperature ranging from -8°C to +2°C and the activity on PET ranging from 17.5% to 145.5% compared to the wild type. Molecular dynamics simulations revealed that these salt bridges stabilized the GlacPETase's structure by maintaining their surrounding structure. Phylogenetic analysis indicated that GlacPETase represented a distinct branch within PET hydrolases-like proteins, with the salt bridges and disulfide bonds in this branch being relatively conserved. This research contributed to the improvement of our comprehension of the structural mechanisms that dictate the thermostability of PET hydrolases, highlighting the diverse characteristics and adaptability observed within PET hydrolases.IMPORTANCEThe pervasive problem of polyethylene terephthalate (PET) pollution in various terrestrial and marine environments is widely acknowledged and continues to escalate. PET hydrolases, such as GlacPETase in this study, offered a solution for breaking down PET. Its unique origin and less than 31% identity with any known PET hydrolases have driven us to resolve its structure. Here, we report the correlation between its unique structure and biochemical properties, focusing on an N-terminal disulfide bond and specific salt bridges. Through site-directed mutagenesis experiments and molecular dynamics simulations, the roles of the N-terminal disulfide bond and salt bridges were elucidated in GlacPETase. This research enhanced our understanding of the role of salt bridges in the thermostability of PET hydrolases, providing a valuable reference for the future engineering of PET hydrolases.

Glacier as a source of novel polyethylene terephthalate hydrolases.

Polyethylene terephthalate (PET) is a major component of microplastic contamination globally, which is now detected in pristine environments including Polar and mountain glaciers. As a carbon-rich molecule, PET could be a carbon source for microorganisms dwelling in glacier habitats. Thus, glacial microorganisms may be potential PET degraders with novel PET hydrolases. Here, we obtained 414 putative PET hydrolase sequences by searching a global glacier metagenome dataset. Metagenomes from the Alps and Tibetan glaciers exhibited a higher relative abundance of putative PET hydrolases than those from the Arctic and Antarctic. Twelve putative PET hydrolase sequences were cloned and expressed, with one sequence (designated as GlacPETase) proven to degrade amorphous PET film with a similar performance as IsPETase, but with a higher thermostability. GlacPETase exhibited only 30% sequence identity to known active PET hydrolases with a novel disulphide bridge location and, therefore may represent a novel PET hydrolases class. The present work suggests that extreme carbon-poor environments may harbour a diverse range of known and novel PET hydrolases for carbon acquisition as an environmental adaptation mechanism.

Atmospheric trace gases support primary production in Antarctic desert surface soil.

Cultivation-independent surveys have shown that the desert soils of Antarctica harbour surprisingly rich microbial communities. Given that phototroph abundance varies across these Antarctic soils, an enduring question is what supports life in those communities with low photosynthetic capacity. Here we provide evidence that atmospheric trace gases are the primary energy sources of two Antarctic surface soil communities. We reconstructed 23 draft genomes from metagenomic reads, including genomes from the candidate bacterial phyla WPS-2 and AD3. The dominant community members encoded and expressed high-affinity hydrogenases, carbon monoxide dehydrogenases, and a RuBisCO lineage known to support chemosynthetic carbon fixation. Soil microcosms aerobically scavenged atmospheric H2 and CO at rates sufficient to sustain their theoretical maintenance energy and mediated substantial levels of chemosynthetic but not photosynthetic CO2 fixation. We propose that atmospheric H2, CO2 and CO provide dependable sources of energy and carbon to support these communities, which suggests that atmospheric energy sources can provide an alternative basis for ecosystem function to solar or geological energy sources. Although more extensive sampling is required to verify whether this process is widespread in terrestrial Antarctica and other oligotrophic habitats, our results provide new understanding of the minimal nutritional requirements for life and open the possibility that atmospheric gases support life on other planets.

Similar heterotrophic communities but distinct interactions supported by red and green-snow algae in the Antarctic Peninsula.

Snow algae are predicted to expand in polar regions due to climate warming, which can accelerate snowmelt by reducing albedo. Green snow frequently occurs near penguin colonies, and red snow distributes widely along ocean shores. However, the mechanisms underpinning the assemblage of algae and heterotrophs in colored snow remain poorly characterized. We investigated algal, bacterial, and fungal communities and their interactions in red and green snows in the Antarctic Peninsula using a high-throughput sequencing method. We found distinct algal community structure in red and green snows, and the relative abundance of dominant taxa varied, potentially due to nutrient status differences. Contrastingly, red and green snows exhibited similar heterotrophic communities (bacteria and fungi), whereas the relative abundance of fungal pathogens was substantially higher in red snow by 3.8-fold. Red snow exhibited a higher network complexity, indicated by a higher number of nodes and edges. Red snow exhibited a higher proportion of negative correlations among heterotrophs (62.2% vs 3.4%) and stronger network stability, suggesting the red-snow network is more resistant to external disturbance. Our study revealed that the red snow microbiome exhibits a more stable microbial network than the green snow microbiome.

Grazing greatly reduces the temporal stability of soil cellulolytic fungal community in a steppe on the Tibetan Plateau.

Excessive livestock grazing degrades grasslands ecosystem stability and sustainability by reducing soil organic matter and plant productivity. However, the effects of grazing on soil cellulolytic fungi, an important indicator of the degradation process for soil organic matter, remain less well understood. Using T-RFLP and sequencing methods, we investigated the effects of grazing on the temporal changes of cellulolytic fungal abundance and community structure in dry steppe soils during the growing months from May to September, on the Tibetan Plateau using T-RFLP and sequencing methods. The results demonstrated that the abundance of soil cellulolytic fungi under grazing treatment changed significantly from month to month, and was positively correlated with dissolved organic carbon (DOC) and soil temperature, but negatively correlated with soil pH. Contrastingly, cellulolytic fungal abundance did not change within the fencing treatment (ungrazed conditions). Cellulolytic fungal community structure changed significantly in the growing months in grazed soils, but did not change in fenced soils. Grazing played a key role in determining the community structure of soil cellulolytic fungi by explaining 8.1% of the variation, while pH and DOC explained 4.1% and 4.0%, respectively. Phylogenetically, the cellulolytic fungi were primarily affiliated with Ascomycota (69.65% in relative abundance) and Basidiomycota (30.35%). Therefore, grazing substantially reduced the stability of soil cellulolytic fungal abundance and community structure, as compared with the fencing treatment. Our finding provides a new insight into the responses of organic matter-decomposing microbes for grassland managements.

Fate of glacier surface snow-originating bacteria in the glacier-fed hydrologic continuums.

Glaciers represent important biomes of Earth and are recognized as key species pools for downstream aquatic environments. Worldwide, rapidly receding glaciers are driving shifts in hydrology, species distributions and threatening microbial diversity in glacier-fed aquatic ecosystems. However, the impact of glacier surface snow-originating taxa on the microbial diversity in downstream aquatic environments has been little explored. To elucidate the contribution of glacier surface snow-originating taxa to bacterial diversity in downstream aquatic environments, we collected samples from glacier surface snows, downstream streams and lakes along three glacier-fed hydrologic continuums on the Tibetan Plateau. Our results showed that glacier stream acts as recipients and vectors of bacteria originating from the glacier environments. The contributions of glacier surface snow-originating taxa to downstream bacterial communities decrease from the streams to lakes, which was consistently observed in three geographically separated glacier-fed ecosystems. Our results also revealed that some rare snow-originating bacteria can thrive along the hydrologic continuums and become dominant in downstream habitats. Finally, our results indicated that the dispersal patterns of bacterial communities are largely determined by mass effects and increasingly subjected to local sorting of species along the glacier-fed hydrologic continuums. Collectively, this study provides insights into the fate of bacterial assemblages in glacier surface snow following snow melt and how bacterial communities in aquatic environments are affected by the influx of glacier snow-originating bacteria.

Distinct assembly mechanisms underlie similar biogeographical patterns of rare and abundant bacteria in Tibetan Plateau grassland soils.

Rare biosphere represents the majority of Earth's biodiversity and performs vital ecological functions, yet little is known about its biogeographical patterns and community assembly processes in terrestrial ecosystems. Herein, we investigated the community composition and phylogeny of rare (relative abundance <0.1%) and abundant (>1%) bacteria in dryland grassland soils on the Tibetan Plateau. Results revealed similar biogeographical patterns of rare and abundant bacteria at both compositional and phylogenetic levels, but rare subcommunity was more heavily influenced by stochasticity (72%) than the abundant (57%). The compositional variation of rare bacteria was less explained by environmental factors (41%) than that of the abundant (80%), while the phylogeny of rare bacteria (36%) was more explained than that of the abundant (29%). The phylogeny of rare bacteria was equally explained by local factors (soil and vegetation) and geospatial distance (11.5% and 11.9% respectively), while that of the abundant was more explained by geospatial distance (22.1%) than local factors (11.3%). Furthermore, a substantially tighter connection between the community phylogeny and composition was observed in rare (R2 = 0.65) than in abundant bacteria (R2 = 0.08). Our study provides novel insights into the assembly processes and biographical patterns of rare and abundant bacteria in dryland soils.

Izhakiella australiensis sp. nov. isolated from an Australian desert soil.

A Gram-stain-negative, rod-shaped, non-motile bacterium, designated D4N98T, was isolated from a desert soil near Glendambo, Australia. The taxonomic position of strain D4N98T was investigated using a polyphasic approach. Strain D4N98T shared 97 % 16S rRNA gene sequence similarity with the only reference strain of the genus Izhakiella (Izhakiella capsodis N6PO6T), and less than 96 % similarity with other species of genera in the family Enterobacteriaceae with validly published names. Phylogenetic analysis, based on 16S rRNA, rpoB, atpD, gyrB genes and a concatenated sequence comprising 37 single copy marker genes, as well as chemotaxonomic data (major polar lipids: phosphatidyl ethanolamine, phosphatidylglycerol, diphosphatidylglycerol, a neutral lipid, and a glycolipid. Major fatty acids (>10 %): C16 : 0, C17 : 0 cyclo, summed feature 2 (C14 : 0 3-OH and/or iso-C16 : 1 I), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) support the affiliation of this strain to the genus Izhakiella. The results of in silico DNA-DNA hybridisation plus physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain D4N98T from the other species of the genus Izhakiellawith validly published names. Therefore, strain D4N98T represents a novel species, for which the name Izhakiella australiensis sp. nov. is proposed. The type strain is D4N98T (LMG 30066T=DSM 105030T).

Geological connectivity drives microbial community structure and connectivity in polar, terrestrial ecosystems.

Landscape heterogeneity impacts community assembly in animals and plants, but it is not clear if this ecological concept extends to microbes. To examine this question, we chose to investigate polar soil environments from the Antarctic and Arctic, where microbes often form the major component of biomass. We examined soil environments that ranged in connectivity from relatively well-connected slopes to patchy, fragmented landforms that comprised isolated frost boils. We found landscape connectedness to have a significant correlation with microbial community structure and connectivity, as measured by co-occurrence networks. Soils from within fragmented landforms appeared to exhibit less local environmental heterogeneity, harboured more similar communities, but fewer biological associations than connected landforms. This effect was observed at both poles, despite the geographical distances and ecological differences between them. We suggest that microbial communities inhabiting well-connected landscape elements respond consistently to regional-scale gradients in biotic and edaphic factors. Conversely, the repeated freeze thaw cycles that characterize fragmented landscapes create barriers within the landscape and act to homogenize the soil environment within individual frost boils and consequently the microbial communities. We propose that lower microbial connectivity in the fragmented landforms is a function of smaller patch size and continual disturbances following soil mixing.

High hydrostatic pressure stimulates microbial nitrate reduction in hadal trench sediments under oxic conditions.

Hadal trenches are extreme environments situated over 6000 m below sea surface, where enormous hydrostatic pressure affects the biochemical cycling of elements. Recent studies have indicated that hadal trenches may represent a previously overlooked source of fixed nitrogen loss; however, the mechanisms and role of hydrostatic pressure in this process are still being debated. To this end, we investigate the effects of hydrostatic pressure (0.1 to 115 MPa) on the chemical profile, microbial community structure and functions of surface sediments from the Mariana Trench using a Deep Ocean Experimental Simulator supplied with nitrate and oxygen. We observe enhanced denitrification activity at high hydrostatic pressure under oxic conditions, while the anaerobic ammonium oxidation - a previously recognized dominant nitrogen loss pathway - is not detected. Additionally, we further confirm the simultaneous occurrence of nitrate reduction and aerobic respiration using a metatranscriptomic dataset from in situ RNA-fixed sediments in the Mariana Trench. Taken together, our findings demonstrate that hydrostatic pressure can influence microbial contributions to nitrogen cycling and that the hadal trenches are a potential nitrogen loss hotspot. Knowledge of the influence of hydrostatic pressure on anaerobic processes in oxygenated surface sediments can greatly broaden our understanding of element cycling in hadal trenches.

Bacterial diversity in a continuum from supraglacial habitats to a proglacial lake on the Tibetan Plateau.

Mountain glaciers are frequently assessed for their hydrological connectivity from glaciers to proglacial lakes. Ecological process on glacier surfaces and downstream ecosystems have often been investigated separately, but few studies have focused on the connectivity between the different glacial habitats. Therefore, it remains a limited understanding of bacterial community assembly across different habitats along the glacier hydrological continuum. In this study, we sampled along a glacial catchment from supraglacial snow, cryoconite holes, supraglacial runoff, ice-marginal moraine and proglacial lake on the Tibetan Plateau. The bacterial communities in these habitats were analyzed using high-throughput DNA sequencing of the 16S rRNA gene to determine the bacterial composition and assembly. Our results showed that each habitat hosted unique bacterial communities, with higher bacterial α-diversity in transitional habitats (e.g. runoff and ice-marginal moraine). Null model analysis indicated that deterministic processes predominantly shaped bacterial assembly in snow, cryoconite holes and lake, while stochastic process dominantly governed bacterial community in transitional habitats. Collectively, our findings suggest that local environment play a critical role in filtering bacterial community composition within glacier habitats. This study enhances our understanding of microbial assembly process in glacier environments and provides valuable insights into the factors governing bacterial community compositions across different habitats along the glacial hydrological continuum.

Anthropogenic impact on airborne bacteria of the Tibetan Plateau.

The Tibetan Plateau is a pristine environment with limited human disturbance, with its aerosol microbiome being primarily influenced by the monsoon and westerly circulations. Additionally, the diversity and abundance of airborne microorganisms are also affected by anthropogenic activities, such as animal farming, agriculture, and tourism, which can lead to increased risks to the ecosystem and human health. However, the impact of anthropogenic activities on airborne microbes on the Tibetan Plateau has been rarely studied. In this work, we investigated the airborne bacteria of areas with weak (rural glacier) and strong human disturbance (urban building), and found that anthropogenic activities increased the diversity of airborne bacteria, and the concentration of potential airborne pathogens. Moreover, airborne bacteria in rural aerosols demonstrated significant differences in their community structure during monsoon- and westerly-affected seasons, while this pattern was weakened in urban aerosols. Additionally, urban aerosols enriched Lactobacillus sp. (member of genus Lactobacillus), which are potential pathogens from anthropogenic sources, whereas rural aerosols enriched A. calcoaceticus (member of genus Acinetobacter) and E. thailandicus (member of genus Enterococcus), which are both speculated to be sourced from surrounding animal farming. This study evaluated the impact of human activities on airborne bacteria in the Tibetan Plateau and contributed to understanding the enrichment of airborne pathogens in natural and anthropogenic background.

Genomic basis of environmental adaptation in the widespread poly-extremophilic Exiguobacterium group.

Delineating cohesive ecological units and determining the genetic basis for their environmental adaptation are among the most important objectives in microbiology. In the last decade, many studies have been devoted to characterizing the genetic diversity in microbial populations to address these issues. However, the impact of extreme environmental conditions, such as temperature and salinity, on microbial ecology and evolution remains unclear so far. In order to better understand the mechanisms of adaptation, we studied the (pan)genome of Exiguobacterium, a poly-extremophile bacterium able to grow in a wide range of environments, from permafrost to hot springs. To have the genome for all known Exiguobacterium type strains, we first sequenced those that were not yet available. Using a reverse-ecology approach, we showed how the integration of phylogenomic information, genomic features, gene and pathway enrichment data, regulatory element analyses, protein amino acid composition, and protein structure analyses of the entire Exiguobacterium pangenome allows to sharply delineate ecological units consisting of mesophilic, psychrophilic, halophilic-mesophilic, and halophilic-thermophilic ecotypes. This in-depth study clarified the genetic basis of the defined ecotypes and identified some key mechanisms driving the environmental adaptation to extreme environments. Our study points the way to organizing the vast microbial diversity into meaningful ecologically units, which, in turn, provides insight into how microbial communities adapt and respond to different environmental conditions in a changing world.

Radiation impacts gene redundancy and biofilm regulation of cryoconite microbiomes in Northern Hemisphere glaciers.

BACKGROUND: Glaciers harbor diverse microorganisms adapted to extreme conditions with high radiation, fluctuating temperature, and low nutrient availability. In glacial ecosystems, cryoconite granules are hotspots of microbial metabolic activity and could influences the biogeochemical cycle on glacier surface. Climate change could influence glacier dynamics by changing regional meteorological factors (e.g., radiation, precipitation, temperature, wind, and evaporation). Moreover, meteorological factors not only influence glacier dynamics but also directly or indirectly influence cryoconite microbiomes. However, the relationship of the meteorological factors and cryoconite microbiome are poorly understood. RESULTS: Here, we collected 88 metagenomes from 26 glaciers distributed in the Northern Hemisphere with corresponding public meteorological data to reveal the relationship between meteorological factors and variation of cryoconite microbiome. Our results showed significant differences in taxonomic and genomic characteristics between cryoconite generalists and specialists. Additionally, we found that the biogeography of both generalists and specialists was influenced by solar radiation. Specialists with smaller genome size and lower gene redundancy were more abundant under high radiation stress, implying that streamlined genomes are more adapted to high radiation conditions. Network analysis revealed that biofilm regulation is a ubiquitous function in response to radiation stress, and hub genes were associated with the formation and dispersion of biofilms. CONCLUSION: These findings enhance our understanding of glacier cryoconite microbiome variation on a hemispheric scale and indicate the response mechanisms to radiation stress, which will support forecasts of the ecological consequences of future climate change. Video Abstract.

Monsoon affects the distribution of antibiotic resistome in Tibetan glaciers.

Antibiotic-resistance gene (ARG) is a biological pollutant and is globally distributed due to increased anthropogenic activities. ARGs in the cryosphere have received increased attention due to global warming, and ARGs in glaciers are predicted to be released into downstream ecosystems during glacier melting. In this study, ARG distribution and influential factors were investigated in 85 samples from 21 Tibetan glaciers, covering snow, ice, and cryoconite habitats. The results revealed ARGs against 29 antibiotics in Tibetan glaciers, dominated by tetracycline, bacitracin, macrolide, and fluoroquinolone resistance. ARGs in snow exhibited biogeographic patterns influenced by atmospheric circulation. Specifically, monsoon-dominated glaciers exhibited a significantly higher abundance of ARGs than the westerly-dominated glaciers, which could be associated with higher antibiotic usage in the Indian subcontinent. Of the 3241 metagenome-assembled genomes obtained, 36.8% of which were identified as ARG hosts and 33.8% were multidrug-resistant. In addition, 90 ARGs were linked to mobile genetic elements (MGEs). 90.9% and 9.1% of MGEs were identified as plasmid and phage in 45 MAGs carrying both ARGs and MGEs. Our study suggests a greater risk of ARGs being released from the monsoon-dominated glaciers, which were the glaciers that melt at high rates and thus need to be carefully monitored.

Plant colonization mediates the microbial community dynamics in glacier forelands of the Tibetan Plateau.

It has long been recognized that pH mediates community structure changes in glacier foreland soils. Here, we showed that pH changes resulted from plant colonization. Plant colonization reduced pH and increased soil organic carbon, which increased bacterial diversity, changed the community structure of both bacteria and fungi, enhanced environmental filtering, and improved microbial network disturbance resistance.

Diversity and function of mountain and polar supraglacial DNA viruses.

Mountain and polar glaciers cover 10% of the Earth's surface and are typically extreme environments that challenge life of all forms. Viruses are abundant and active in supraglacial ecosystems and play a crucial role in controlling the supraglacial microbial communities. However, our understanding of virus ecology on glacier surfaces and their potential impacts on downstream ecosystems remains limited. Here, we present the supraglacial virus genome (SgVG) catalog, a 15-fold expanded genomic inventory of 10,840 DNA-virus species from 38 mountain and polar glaciers, spanning habitats such as snow, ice, meltwater, and cryoconite. Supraglacial DNA-viruses were highly specific compared to viruses in other ecosystems yet exhibited low public health risks. Supraglacial viral communities were primarily constrained by habitat, with cryoconite displaying the highest viral activity levels. We observed a prevalence of lytic viruses in all habitats, especially in cryoconite, but a high level of lysogenic viruses in snow and ice. Additionally, we found that supraglacial viruses could be linked to ∼83% of obtained prokaryotic phyla/classes and possessed the genetic potential to promote metabolism and increase cold adaptation, cell mobility, and phenolic carbon use of hosts in hostile environmental conditions using diverse auxiliary metabolic genes. Our results provide the first systematic characterization of the diversity, function, and public health risks evaluation of mountain and polar supraglacial DNA viruses. This understanding of glacial viruses is crucial for function assessments and ecological modeling of glacier ecosystems, especially for the Tibetan Plateau's Mountain glaciers, which support ∼20% of the human populations on Earth.

Variation of High and Low Nucleic Acid-Content Bacteria in Tibetan Ice Cores and Their Relationship to Black Carbon.

Nutrient enrichment caused by black carbon (BC) is a major ecological crisis in glacial ecosystems. The microbiological effects of BC were assessed in this study by using fluorescent fingerprinting assay based on flow cytometry (FCM) of bacterial communities with low (LNA) and high (HNA) nucleic acid-content bacteria. Here, we investigated a high-resolution temporal variation of bacterial abundance and LNA/HNA ratio in Tibetan ice cores. Our results revealed that bacterial abundance was proportional to the atmospheric BC on the glaciers. The shift of LNA functional groups to HNA functional groups in glaciers suggested BC emissions increased the proportion of highly active cells. In addition, distinct number of LNA and HNA functional groups was identified between the monsoon and non-monsoon seasons. Westerly winds with high amounts of BC accounted for high ratio of HNA functional groups during the non-monsoon season. In comparison, high moisture during the monsoon season decreased atmospheric BC loading, which increases the ratio of LNA functional groups. Correlations between BC and functional groups were very strong, showing that two functional groups may serve as early-warning indicators of microbiological effects of BC at low trophic level. Our approach provides a potential early-warning framework to study the influences of atmospheric BC on the glaciological community.