Linking biodiversity and ecological function through extensive microeukaryotic movement across different habitats in six urban parks

Invasive apple snails with their core microbes are underestimated hotspots for disseminating antibiotic resistance genes and virulence factors in aquatic habitats

Antibiotic resistance in pathogens is a threat to human health. The invasive apple snail (Pomacea canaliculata), widely distributed and linked to human activities, is a potential vector for human pathogens. However, its role in spreading antibiotic resistance genes (ARGs) is poorly understood. This study assessed the microbiological risk of this snail by sampling from five interconnected habitats: feces of invasive apple snails and native snails, ditch water, sediment, and soil. Using metagenomic and 16S rRNA sequencing, we analyzed the microbial communities and quantified the ARGs and virulence factors (VFs). Results showed that invasive apple snails carried significantly higher levels of ARGs and VFs compared with the native snails and environmental samples. ARGs and VFs were primarily found co-occurring in Aeromonas and Citrobacter freundii, with Aeromonas identified as the core microbe selected by invasive apple snails. Furthermore, the abundance and community dissimilarity of Aeromonas positively correlated with those of ARGs and VFs, both directly and indirectly through mobile genetic elements. This suggests Aeromonas may play a key role in disseminating ARGs and VFs across habitats. Overall, this study highlights the invasive apple snail as a significant vector for ARGs and virulent pathogens, providing critical insights for risk assessment and targeted management within the One Health framework.

Bacterial community assembly processes mediate soil functioning under cadmium stress in the agroecosystem

Elucidating the effects of community assembly processes on soil functioning represents a crucial challenge in theoretical ecology, particularly under cadmium (Cd) stress, where our understanding remains limited. In this study, we therefore used amplicon sequencing and a quantitative-PCR-based chip to analyze the changes in bacterial community characteristics, soil functioning and their interrelationships in agroecosystems under different levels of Cd stress. The results indicated that Cd stress led to a decline in community diversity (Z-score), network complexity and stability, an increase in species turnover, and a regulation of community structure. Cd stress significantly increased the relative importance of dispersal limitation and homogeneous selection, reducing community drift and rendering the community more deterministic. Finally, Cd stress significantly reduced soil functional potential (Z-score) and soil functional stability (Z-score), impairing soil carbon, nitrogen, phosphorus, and sulfur cycling. It is noteworthy that correlation and random forest analyses revealed significant effects of specific community assembly processes, including dispersal limitation, homogeneous selection, drift (and others), on changes in soil functional potential (Z-score). The results emphasize the pivotal role of community assembly processes in dictating soil functioning under Cd stress, thereby offering novel insights into the comprehension of microbial-driven mechanisms governing soil functioning.

Relationships between soil health and dynamics of soil potential pathogenic microbiota in functional domains of Xi'an urban greenspaces, China

Soil potential pathogenic microbiota exacerbate the environment and human health through invading normal tissues of the human body, but their distributions and interactions across functional domains in urban greenspaces are poorly understood. Herein, we collected soil samples from parkland and residential land to explore the relationships between soil health and the dynamics of soil potential pathogenic microbiota. Soil organic matter-associated properties, soil multifunctionality and health were significantly about 30 % higher in parkland, but soil stoichiometry including C/N, C/P, and C/N/P were lower in parkland. Alpha diversity of soil pathogenic bacterial communities was higher than for fungal communities in residential land. The relative abundances of the dominant genera Mycobacterium, Metarhizium, and Cladosporium that may cause chronic lung and gastrointestinal diseases in humans were greater for residential land. Potential connected networks including soil pathogenic bacterial and fungal phylotypes were more complicated and stable in residential land, based on higher total and positive connections and higher robustness. Meanwhile, bacterial phylotypes belonging to the genus Shigella were identified as keystone species in parkland network, all of which were chronic pathogens. Soil total nitrogen and phosphorus as dominant properties had greater total effects on soil health in parkland and residential land, respectively. In general, soil health was mostly affected by soil multifunctionality in parkland, but was subject to higher explanation in residential land. These findings underscore intimate relationships between soil health and the dynamics of soil potential pathogenic microbiota in urban greenspaces, which has implications for human daily outdoor routines and urban habitability.

Cyanobacterial blooms specifically alter the dispersal-mediated taxonomic and functional vertical similarity of microbial communities in a subtropical reservoir

Harmful cyanobacterial blooms, including Raphidiopsis raciborskii (basionym Cylindrospermopsis raciborskii), are an increasing environmental concern in freshwater ecosystems globally. However, the ecological consequences of cyanobacterial blooms for the vertical similarity of microbial community structure have yet to be thoroughly investigated, especially in deep waters. Here, we explored the taxonomic and functional similarity of microbial communities at different depths in a subtropical reservoir over a 7-year period following multiple R. raciborskii blooms. Our results showed that vertical microbial dispersal, rather than ecological niche, is the main process determining vertical similarity. Both particle-attached (PA) and free-living (FL) bacteria from the surface water were able to reach the deep water, particle size being a contributing factor to their vertical dispersal. Cyanobacterial blooms enhanced the vertical microbial transport of PA, impacting the composition and biogeochemical processes of deep microbial communities. During the mixing period, microbial taxonomic and functional similarities between the different water layers were high whereas they were minimal across the oxycline during the stratification period, suggesting a bottleneck in microbial vertical dispersal. In the deep water layers, the abundances of specific taxa, such as those of Burkholderiales and Desulfomonilales in PA and FL fractions respectively in stratification periods, increased during blooms. Additionally, cyanobacterial blooms enhanced sulfur compound respiration in both PA and FL fractions and suppressed nitrification in PA bacteria and denitrification in FL bacteria, simultaneously reducing light-utilization capacity in PA bacteria and altering organic matter degradation. Several mechanisms are proposed to drive variations in microbial vertical connectivity by cyanobacteria, including ecological niche shifts and alterations of physicochemical properties and nutrient dynamics. Overall, our results reveal complex effects of cyanobacterial blooms on microbial taxonomic and functional vertical similarity and highlight the contribution of surface communities to the biodiversity and biogeography of deep communities.

Sequential decline in cyanobacterial, total prokaryotic, and eukaryotic responses to backward flow in a river connected to Lake Taihu

River ecosystems face escalating challenges due to altered flow regimes from human activities, such as urbanization with hydrological modifications. Understanding the role of microbial communities for ecosystems with changing flow regimes is still incomplete and remains at the frontier of aquatic microbial ecology. In particular, influences of riverine backward flow on the aquatic biota remain largely unknown. Therefore, we examined the impact of backward flow on the cyanobacterial, total prokaryotic, and eukaryotic communities in the Changdougang River, which naturally flows into Lake Taihu, through environmental DNA metabarcoding. We analyzed the differences in community diversity, assembly, and ecological network stability among groups under backward, weak, and forward flow direction conditions. Non-metric multidimensional scaling showed higher variations in communities of groups across flow direction conditions than seasonal groups. Variations in alpha and beta diversity showed that cyanobacterial and total prokaryotic communities experienced strong homogenization under backward flow conditions, whereas the ecological uniqueness of the eukaryotic community decreased. Assembly of the three flow-related communities was primarily governed by drift and dispersal limitation in stochastic processes. However, in the cyanobacterial community, homogeneous selection in deterministic processes increased from 22.79 % to 42.86 % under backward flow, aligning with trends observed in the checkerboard score (C-score). More importantly, the topological properties of ecological networks and the degree of average variation revealed higher stability in the cyanobacterial community compared to total prokaryotic and eukaryotic communities. Considering the variations in cohesion, the network stability in the cyanobacterial community decreased under backward flow. Our findings emphasize the distinct and sequentially diminishing responses of cyanobacterial, total prokaryotic, and eukaryotic communities to backward flowing rivers. This knowledge is crucial for maintaining ecological health of rivers, assessing the complex ecological impacts on hydrological engineering, and formulating sustainable water management strategies.

Urban parks affect soil macroinvertebrate communities: The case of Tehran, Iran

Land use change represents a significant environmental transformation on a global scale, profoundly impacting natural ecosystems. The conversion of rangelands into urban parks can adversely affect soil characteristics and biodiversity. This transformation may lead to alterations in soil properties and invertebrate communities, subsequently influencing ecosystem functioning and resilience. This study aims to investigate the diversity of soil macroinvertebrates and examine the impacts of land use changes on their communities. Therefore, sampling was conducted at three locations in Tehran (Chitgar, Lavizan, and Darakeh), where rangelands surround by urban parks. Two sites were selected within each region, and 72 quadrats surveyed the study area. In total, 1517 samples were collected and classified into 267 morphological operational taxonomic units (MorphOTUs). Our findings indicate that the total abundance of macroinvertebrates is higher in rangeland habitats, with a count of 872, compared to 645 in urban parks. Additionally, rangelands demonstrate a greater diversity of MorphOTUs than urban parks. Specifically, Chitgar, Lavizan, and Darakeh reported 162, 141, and 190 MorphOTUs, respectively, while urban parks reported 152, 122, and 118. Univariate and multivariate statistical analyses were employed on abundance, diversity, and macroinvertebrate communities to examine the impacts of changing rangelands to urban parks. Our research indicates that land use change from rangelands to urban parks can significantly (p-value < 0.05) affect the abundance and community composition of macroinvertebrates, as these groups are sensitive to land use changes. Beta diversity analysis indicated turnover happened between them (Chitgar = 0.986; Lavizan = 0.983; Darakeh = 0.983). The SIMPER analysis showed that several MorphOTUs have contributed to this dissimilarity in every location. Furthermore, the Shannon-Wiener diversity index values for Araneae, Hemiptera, and Orthoptera were slightly higher in the rangeland than in the urban park. Our results also exhibited a diverse range of species in urban parks highlighting their important role in supporting biodiversity. Given that these parks have been established for many years, they have had ample opportunity to recover and enhance their ecological value. This study emphasizes that attention to soil organisms is essential for addressing conservation issues. Therefore, studying macroinvertebrate groups as biological indicators can assist in monitoring the effects of land use changes and will contribute to ecosystem management.

Species pool and soil properties in mangrove habitats influence the species-immigration process of diazotrophic communities across southern China

Microbial immigration is an ecological process in natural environments; however, the ecological trade-off mechanisms that govern the balance between species extinction and migration are still lacking. In this study, we investigated the mechanisms underlying the migration of diazotrophic communities from soil to leaves across six natural mangrove habitats in southern China. The results showed that the diazotrophic alpha and beta diversity exhibited significant regional and locational variations. The diazotrophic species pool gradually increased from the leaves to nonrhizosphere soil at each site, exhibiting a vertical distribution pattern. Mantel test analyses suggested that climate factors, particularly mean annual temperature, significantly influenced the structure of the diazotrophic community. The diazotrophic community assembly was mainly governed by dispersal limitation in soil and root samples, whereas dispersal limitation and ecological drift were dominant in leaves. Partial least squares path modeling revealed that the species pool and soil properties, particularly the oxidation-reduction potential and pH, were closely linked to the species-immigration ratio of diazotrophic communities. Our study provides novel insights for understanding the ecological trait diversity patterns and spread pathways of functional microbial communities between below- and aboveground habitats in natural ecosystems.IMPORTANCEEnvironmental selection plays key roles in microbial transmission. In this study, we have provided a comprehensive framework to elucidate the driving patterns of the ecological trade-offs in diazotrophic communities across large-scale mangrove habitats. Our research revealed that Bradyrhizobium japonicum, Marinobacterium lutimaris, and Agrobacterium tumefaciens were more abundant in root-associated soil than in leaves by internal and external pathways. The nonrhizospheric and rhizospheric soil samples harbored the most core amplicon sequence variants, indicating that these dominant diazotrophs could adapt to broader ecological niches. Correlation analysis indicated that the diversities of the diazotrophic community were regulated by biotic and abiotic factors. Furthermore, this study found a lower species immigration ratio in the soil than in the leaves. Both species pool and soil properties regulate the species-immigration mechanisms of the diazotrophic community. These results suggest that substantial species immigration is a widespread ecological process, leading to alterations in local community diversity across diverse host environments.

Submerged macrophyte restoration enhanced microbial carbon utilization in shallow lakes

Submerged macrophytes are integral to the functioning of shallow lakes through their interaction with microorganisms. However, we have a limited understanding of how microbial communities in shallow lakes respond when macrophytes are restored after being historically extirpated. Here, we explored the interactions between prokaryotic communities and carbon utilization in two lakes where submerged macrophytes were restored. We found restoration reduced total carbon in sediment by 8.9 %-27.9 % and total organic carbon by 16.7 %-36.9 % relative to control treatment, but had no effects on carbon content in the overlying water. Sediment microbial communities were more sensitive to restoration than planktonic microbes and showed enhanced utilization of simple carbon substrates, such as Tween 40, after restoration. The increase in carbon utilization was attributed to declines in the relative abundance of some genera, such as Saccharicenans and Desertimonas, which were found weakly associated with the utilization of different carbon substrates. These genera likely competed with microbes with high carbon utilization in restored areas, such as Lubomirskia. Our findings highlight how restoring submerged macrophytes can enhance microbial carbon utilization and provide guidance to improve the carbon sequestration capacity of restored shallow lakes.

New insights of bacterial and eukaryotic phenotypes on the plastics collected from the typical natural habitat of the endangered crocodile lizard

Although accumulating evidence indicates that endangered animals suffer from plastic pollution, this has been largely overlooked. Here, we explored the bacteria and eukaryotes living in the plastics gathered from the natural habitat of the highly endangered crocodile lizard. The results demonstrated that the bacterial and eukaryotic communities on plastics formed a unique ecosystem that exhibited lower diversity than those in the surrounding water and soil. However, microbes displayed a more complex and stable network on plastic than that in water or soil, implying unique mechanisms of stabilization. These mechanisms enhanced their resilience and contributed to the provision of stable ecological services. Eukaryotes formed a simpler and smaller network than bacteria, indicating different survival strategies. The bacteria residing on the plastics played a significant role in carbon transformation and sequestration, which likely impacted carbon cycling in the habitat. Furthermore, microbial exchange between plastics and the crocodile lizard was observed, suggesting that plastisphere serves as a mobile gene bank for the exchange of information, including potentially harmful substances. Overall, microbes on plastic appear to significantly impact the crocodile lizard and its natural habitat via various pathways. These results provided novel insights into risks evaluation of plastic pollution and valuable guidance for government efforts in plastic pollutant control in nature reserves.

Ecological and evolutionary processes involved in shaping microbial habitat generalists and specialists in urban park ecosystems

Microbiomes are integral to ecological health and human well-being; however, their ecological and evolutionary drivers have not been systematically investigated, especially in urban park ecosystems. As microbes have different levels of tolerance to environmental changes and habitat preferences, they can be categorized into habitat generalists and specialists. Here, we explored the ecological and evolutionary characteristics of both prokaryotic and microeukaryotic habitat generalists and specialists from six urban parks across five habitat types, including moss, soil, tree hole, water, and sediment. Our results revealed that different ecological and evolutionary processes maintained and regulated microbial diversity in urban park ecosystems. Under ecological perspective, community assembly of microbial communities was mainly driven by stochastic processes; however, deterministic processes were higher for habitat specialists than generalists. Microbial interactions were highly dynamic among habitats, and habitat specialists played key roles as module hubs in intradomain networks. In aquatic interdomain networks, microeukaryotic habitat specialists and prokaryotic habitat specialists played crucial roles as module hubs and connectors, respectively. Furthermore, analyzing evolutionary characteristics, our results revealed that habitat specialists had a much higher diversification potential than generalists, while generalists showed shorter phylogenetic branch lengths as well as larger genomes than specialists. This study broadens our understanding of the ecological and evolutionary features of microbial habitat generalists and specialists in urban park ecosystems across multi-habitat.

IMPORTANCE

Urban parks, as an important urban greenspace, play essential roles in ecosystem services and are important hotspots for microbes. Microbial diversity is driven by different ecological and evolutionary processes, while little is currently known about the distinct roles of ecological and evolutionary features in shaping microbial diversity in urban park ecosystems. We explored the ecological and evolutionary characteristics of prokaryotic and microeukaryotic habitat generalists and specialists in urban park ecosystems based on a representative set of different habitats. We found that different ecological and evolutionary drivers jointly maintained and regulated microbial diversity in urban park microbiomes through analyzing the community assembly process, ecological roles in hierarchical interaction, and species diversification potential. These findings significantly advance our understanding regarding the mechanisms governing microbial diversity in urban park ecosystems.

Primer selection impacts the evaluation of microecological patterns in environmental microbiomes

This study revealed that primer selection substantially influences the taxonomic and predicted functional composition and the characterization of microecological patterns, which was not alleviated by close-reference clustering. Biases were relatively consistent across different habitats in community profiling but not in microecological patterns. These primer biases could be attributed to multiple aspects, including taxa specificity, regional hypervariability, and amplification efficiency.