Microbial Ecology最新文献

Delftia acidovorans, a Gram-negative bacterium commonly found in diverse environments, can occasionally cause infections in immunocompromised individuals. Despite its environmental prevalence and clinical relevance, there is a notable lack of studies on the cellular ultrastructure of D. acidovorans. Characterizing this aspect is essential for understanding the bacterium aggregation behavior, which significantly influences biofilm formation, environmental adaptability, and potential pathogenicity in clinical contexts. This study employs cryo-electron tomography to investigate the cellular ultrastructure of Delftia acidovorans. Our observations of D. acidovorans revealed a supercoiling pattern in flagellar filaments and diverse outer membrane projections. Our major finding was the observation of cytoplasmic membrane invaginations resembling mesosomes seen in Gram-positive bacteria, offering new insights into the cellular architecture and potential functions of these structures in Gram-negative bacteria. Together, these ultrastructural insights reveal adaptations potentially linked to environmental persistence and interspecies aggregation.

The invasive vine Mikania micrantha H. B. K. poses severe threats to biodiversity and ecosystem stability in tropical and subtropical regions, calling for sustainable ecological approaches. This study explores how the native legume Pueraria lobata var. thomsonii Benth displaces M. micrantha in the field, with a focus on the synergistic roles of light capture advantage and rhizosphere potassium (K) dynamics driven by specialized bacteria. In competitive ecotones, P. lobata demonstrated superior growth and photosynthetic performance relative to M. micrantha. Its main stem length was 1.31 times greater, while net photosynthetic rate, stomatal conductance, and chlorophyll content were 80%, 110.7%, and 21.4% higher, respectively. Soils associated with P. lobata contained significantly higher available K, correlated with enhanced enzyme activities, indicating a "microbe-enzyme-K" activation cascade. P. lobata specifically enriched efficient potassium‑solubilizing bacteria (KSB), such as Pseudomonas and Acinetobacter. Isolated KSB strains exhibited K‑solubilizing and plant‑growth‑promoting capacities and increased the competitive balance index of P. lobata in inoculation assays. Partial least‑squares discriminant analysis confirmed that KSB‑mediated K mobilization boosted stem elongation primarily by improving photosynthetic potassium use efficiency (PKUE), forming a reinforcing "light-K-microbe" loop that drives competitive displacement. This work establishes a "microbe‑mediated invasion suppression" framework, demonstrating how a native plant can couple superior light‑use efficiency with a specialized rhizosphere microbiome to outcompete an invasive species. We propose that managing potassium‑solubilizing microbiomes offers a sustainable strategy for ecological restoration in K‑limited ecosystems.

Desertification is a global concern, reducing vegetation cover and soil fertility. Arbuscular mycorrhizal symbiosis (AM), the most common plant-fungi association, can enhance plant fitness and stress tolerance. Despite its significance, comprehensive data on community-wide patterns and drivers of plant AM traits are limited in the Mediterranean, one of the regions most vulnerable to desertification. We examined four traits: colonization frequency, intensity, arbuscule abundance, and spore density in the rhizosphere of 20 plant species across ten agroecosystems in desertification-prone areas of Italy, Spain, and Portugal. We analysed whether these traits varied across Raunkiær's plant life forms and were affected by vegetation cover, soil properties, precipitation, and temperature, both overall and regionally, to explore potential context-dependency. All plants showed a high frequency of AMF colonization, with an average intensity of 54%, indicating obligate AMF interactions, and arbuscule abundance was significantly correlated with spore density. These traits were significantly higher in microhabitats dominated by trees and shrubs compared to those dominated by herbaceous plants. Phanerophytes (perennials) presented lower trait values than therophytes (annuals), while the highest values were found in hemicryptophytes. Lampedusa, a region with hotter and drier climate conditions in Southern Europe, had significantly lower AMF trait levels, though Spanish site values resembled those in Sicily more than Portugal. Soil organic carbon, nitrogen, and the overall positive interaction between precipitation and temperature significantly influenced all AMF traits. However, the magnitude and direction of soil and climate related effects differed among regions, indicating strong context dependency. Our study contributes to better define indicators for monitoring desertification and evaluating restoration efforts while highlighting the need of site-specific evaluations and careful interpretation of broad generalisations.

Arctic regions are inhabited by terrestrial ectotherms that have adapted to an extreme environment where food resources are limited. The host associated microbiome may partly explain their ability to live under these conditions, but very little is known about the microbiome of Arctic ectotherms. We investigate how the bacterial community of the Greenlandic seed bug (Nysius groenlandicus) and damsel bug (Nabis flavomarginatus) is affected by different abiotic and biotic factors (time, acclimation temperature, humidity, and diet) under both field and laboratory conditions. We found large differences in the bacterial composition and diversity between the two species including species-specific presence of potentially symbiotic bacteria. The bacterial community of both species changed across the season, which may be explained by the changing climatic conditions, such as temperature and humidity. This was further supported by results from the laboratory experiments. We also found that diet changed the bacterial composition in both species and that bacteria could be transferred from prey to predator. Together, these results show that the bacterial community of some Arctic insects are highly dynamic and modulated by different abiotic and biotic factors, suggesting that the microbiome plays an important role for these organisms to persist in an extreme and resource-limited Arctic environment.

The growing global population increases the demand for protein, while organic waste management has become more challenging. Alternative protein sources are essential to mitigate the environmental impact of food production. The black soldier fly (BSF; Hermetia illucens) has emerged as an alternative to traditional protein sources (e.g., soybean meal, fishmeal) due to its ability to convert diverse organic waste, addressing both issues simultaneously. This makes the BSF a promising candidate for industrial rearing, with its successful development closely tied to microbial influences on growth and behaviour, particularly bacterial influences on oviposition. In this study, we focus on the microbiota throughout insect development with a special focus on egg surface microbiota and their origin. We analysed the microbiota in the haemolymph and gut of larvae raised on sterilized and non-sterilized feed, pupal cell pulp, the wash of the ovipositor, eggs directly collected after oviposition, ovarian eggs, the empty female abdomen, eggs exposed to adult BSF, and surface-sterilized eggs. Our analysis revealed distinct bacterial community profiles across life stages, indicating a transition from larval dominance of Enterobacteriaceae to Burkholderiaceae on all analysed eggs. At the genus level, larval stages were characterized by Morganella, Escherichia, and Proteus, transitioning to less diverse communities in egg samples predominated by Burkholderia-Caballeronia-Paraburkholderia. Our study reveals that while predominant microbiota persist throughout all life stages, microbial community composition transforms progressively during maturation, particularly before oviposition. Understanding egg surface microbiota and the cues guiding oviposition has the potential to boost egg production and simplify mass harvesting of BSF larvae.

Cadmium (Cd) contamination in soil is a growing problem, posing a significant threat to soil microorganisms and plant growth. Understanding how Cd exposure disrupts the evolution of soil microbial communities and the mechanisms underlying community remodeling requires further investigation. In this study, the rice rhizosphere treated with 0 (CK), 2.5 (LC), 5 (MC), and 15 (HC) mg kg^-1 Cd was used as a model and combined with 16S rRNA gene sequencing to systematically evaluate the response patterns of rice rhizosphere microbial communities under Cd gradient treatments. The study found that rice rhizosphere microbial communities responded to Cd exposure with a unimodal pattern of "low-promotion and high-suppression". LC treatment significantly increased the alpha diversity of rare fungal taxa and significantly enriched rare genera such as Candidatus Solibacter and Penicillium. Network analysis further confirmed that LC treatment significantly enhanced symbiotic relationships within and across rare taxa. The assembly of abundant bacterial and fungal taxa was consistently dominated by stochastic diffusional constraints, while rare taxa were primarily driven by deterministic homogeneous selection. In summary, rice rhizosphere microbial communities showed specific response patterns under Cd gradient treatment. Rare fungal taxa, as core members, actively responded to Cd exposure, made prominent contributions to shaping the community composition, and played a crucial role in maintaining the complexity and stability of the microbial network.

Hydro- and xerohalophytes withstand stress thanks to the resistance traits they have, complemented with the functions of their associated microbiota. Besides, given a higher exposition of the phyllosphere to environmental conditions compared to roots, their endospheric bacteria should be more resistant to stress. In this study, we analysed the composition and functional traits of the bacterial leaf endosphere of six xero- and hydrohalophytes species in two seasons. We sequenced their endospheric metagenomes by shotgun and annotated genes related with Plant-Growth-Promoting (PGP) properties. We showed that the composition, structure and functions of the bacterial endosphere are mainly influenced by host plant species, followed by functional type. Moreover, plant species and functional type promoted a different relative abundance of, respectively, 62 and 6 PGP properties. This study shows that not only the composition but also the functionality of the bacterial leaf endosphere of halophytes is more influenced by host species than functional type. Moreover, the leaf endosphere of the different plant species and functional type could be an important source of bacteria with diverse PGP properties.