Microbial Ecology最新文献

Phytomyxea (SAR: Rhizaria: Endomyxa) is a group of obligate biotrophic parasitic protists comprised of two orders: Plasmodiophorida, found in terrestrial or freshwater environments, and Phagomyxida, found in marine environments. While Plasmodiophorida has been extensively studied due to its economic importance as plant pathogens, Phagomyxida remains poorly investigated despite its ecological significance in marine ecosystems. During intensive sampling along the Korean coast from April to December 2023, novel parasitoids infecting dinoflagellates were discovered in seawater collected at 10 coastal stations. A total of 23 isolates were successfully established in culture, and the morphology of infected host cells resembled that of known Phagomyxa infections. The newly identified parasitoid exhibits a life cycle that includes zoospore penetration, multinucleate plasmodium development, and formation of a sporangiosorus composed of numerous zoosporangia. Each zoosporangium produces three biflagellate zoospores, and no resting spores were observed. A key morphological feature distinguishing this parasitoid from Phagomyxa species is the presence of a sporangiosorus wall enclosing the zoosporangia. Phylogenetic analysis based on small subunit (SSU) ribosomal DNA (rDNA) revealed that this parasitoid forms a distinct clade with Marinomyxa and the environmental sequence TAGIRI-5, suggesting a disparity between its morphological similarity to Phagomyxa and its molecular phylogenetic position. The SSU rRNA gene sequence of the new parasitoid showed 99.87% identity to the TAGIRI-5 sequence obtained from an anoxic sediment in Kagoshima Bay, Japan. Cross-infection experiments demonstrated that infections occurred only in five dinoflagellate genera among the taxa tested. Based on morphological and molecular data obtained in this study, we propose a new genus and species, Dinopallor comventus n. gen., n. sp., for this newly discovered parasitoid.

Acantholyda posticalis (Matsumura) is a globally significant forest pest that inflicts substantial economic losses through its feeding activity on Pinus species. As an oligophagous insect, A. posticalis relies critically on its gut microbiota to overcome the defensive secondary metabolites of pine needles, particularly α- and β-pinene terpenoids. This study investigated the dynamic compositional changes of gut bacterial communities across different developmental stages of A. posticalis and characterized their functional roles in host adaptation. Through traditional culturing methods, two pinene-degrading bacterial strains-Klebsiella variicola and Enterobacter hormaechei-were isolated from the larval gut. In vitro assays demonstrated their significant capacity to degrade the two pinenes. High-throughput 16S rRNA sequencing revealed stage-specific bacterial enrichment patterns. Functional prediction suggested these microbial communities participate in critical metabolic processes, including phosphotransferase systems, GST activity, and detoxification pathways. This work advances understanding of insect-microbe symbiosis in oligophagous systems and proposes novel strategies for ecologically sustainable A. posticalis control through manipulation of its gut microbiota.

Spatial differences in microbial community structure and function were examined across polynyas, sea ice zones (SIZ), and ice-free waters of the Amundsen Sea, Southern Ocean, using 16 S and 18 S rRNA gene-based eDNA metabarcoding and quantitative PCR targeting nitrogen cycling and dimethylsulfoniopropionate (DMSP) degradation genes. The SIZ exhibited enrichment of psychrophilic bacteria (Colwellia spp.) and dominant eukaryotic taxa such as Diatomea and Prymnesiophyceae, likely linked to sea-ice-driven shifts in nutrient stoichiometry (elevated N: P and positive N*). Network analysis revealed interactions among primary producers, bacteria, and zooplankton, highlighting complementary roles in trophic energy transfer and nutrient recycling. Metabolic pathway predictions implied active bacterial processes related to sulfur and nitrogen cycling in the SIZ, particularly dissimilatory nitrate reduction and DMSP demethylation, suggesting coupling between carbon, nitrogen, and sulfur pathways. Quantitative PCR showed higher copy numbers of nitrogen cycling genes and DMSP degradation genes in the SIZ than in other regions, consistent with enhanced microbial denitrification, nitrogen fixation, and sulfur cycling under cold conditions shaped by sea-ice-driven nutrient dynamics. These findings demonstrate that environmental variation in Antarctic waters influences microbial diversity, reshapes ecological interactions, and modulates biogeochemical functions, with implications for nutrient cycling, food web dynamics, and ecosystem resilience in this climate-sensitive region.

Alternaria spp. is one of the fungal genera affecting olive cultivation, and its temporal dynamics are influenced by climatic variations occurring throughout the crop's vegetative cycle. The aim of this study was to determine the presence of Alternaria spp. in an olive-growing area in northwestern Spain and to examine the relationship between its airborne concentrations and meteorological variables, in order to preliminarily predict its presence in the atmosphere during the olive tree's phenological cycle. To achieve this, a phenological, aeromycological, and meteorological study was conducted from 2021 to 2024. Alternaria spp. conidia were detected in the air throughout all major phenological stages, with peak concentrations occurring mainly during fruit development. The highest percentages of spores were recorded between 11:00 and 22:00, primarily influenced by temperature and sunlight. During the maturity of fruit stages in 2023 and 2024, isolates from the Alternaria section Alternaria were identified as the cause of olive rot. A predictive model was obtained that estimates the atmospheric concentrations of this type of fungus in the study area, based on average temperature values and hours of sunshine. This study constitutes the first report of Alternaria spp. in an olive-growing area of northwestern Spain and provides models that preliminarily predict its presence. These models can inform growers of the pathogen's presence in the air before visible symptoms appear, thereby reducing the likelihood of infection in susceptible plants when environmental conditions favor its development.

With the intensification of human activities, large amounts of antibiotics, heavy metals, and disinfectants enter lakes, exerting continuous selective pressure and driving the enrichment and dissemination of ARGs and VFs in aquatic microbial communities. Previous studies have primarily focused on the occurrence and abundance of ARGs in extreme plateau environments. However, the diversity and abundance of ARGs and VFs in eutrophic plateau lakes under different seasons and environmental pressures remain underexplored. In this study, we analyzed the presence of ARGs and VFs in the eutrophic plateau lake Qilu Lake across different seasons. From the perspective of hydrology and water quality, there is no inflow into the lake during the dry season, while the wet season sees an inflow of 28.1724 million cubic meters. Organic matter and metal ions are significantly higher in the dry season, whereas total nitrogen and pH levels rise notably in the wet season. We found 29 types of ARGs and 601 types of VFs in the dry season, compared to 45 types of ARGs and 637 types of VFs in the wet season. In both seasons, glycopeptide antibiotic resistance genes were the most abundant ARGs. LPS was the most abundant VFs in the dry season, while Type IV pili dominated in the wet season. The primary microbial-driven resistance mechanism strategy in both seasons was Antibiotic target alteration. The microorganism with the highest abundance of ARGs and VFs in both seasons was Pseudomonadota. Correlation analysis showed a positive relationship between the abundance of ARGs and VFs in both seasons, with this relationship being more pronounced in the dry season. Our findings indicate that the increased diversity and abundance of ARGs during the wet season may be directly linked to the heightened input of exogenous antibiotic-resistant bacteria and the promotion of plasmid conjugation transfer by hydraulic disturbances. Although VFs diversity was higher in the wet season, the low-water concentration effect and metal ion stress during the dry season significantly elevated the relative abundance of core VFs (e.g., type IV pili), resulting in the abundance of VFs per unit volume surpassing that of the wet season.

Egg hatching success in sea turtle nests can be influenced by multiple abiotic and biotic factors. Although interest in nest microbiota as a determinant of embryo development and viability is increasing, its role has not yet been fully elucidated. In this study, we profiled the bacterial communities of four Caretta caretta nests on Lampedusa Island: Cala Pisana (P1 and P2) and Spiaggia dei Conigli (C1 and C2), which showed different hatching success rates (P1 = 85.2%, P2 = 1.1%, C1 = 1.1%, C2 = 0.0%). Using 16S rRNA gene (V3-V4) sequencing, we analyzed different sample types, including sand from inside and outside the nest chamber, eggshells, and inner membranes. Alpha diversity was highest in sand and lower in eggshells and inner membranes. β-diversity clearly separated the only successful nest (P1) from the others (P2, C1, and C2) (PERMANOVA p < 0.001). Across all nests, the dominant phyla were Proteobacteria, Firmicutes, Actinobacteriota, and Bacteroidota; notably, the Firmicutes/Bacteroidota (F/B) ratio was lowest in P1 compared with P2, C1, and C2. Nests with low hatching success were Firmicutes-dominated, enriched in Bacillus and Pseudomonas, and harbored hydrocarbon-degrading genera (Pseudoxanthomonas and Devosia), suggesting environmental influences. Opportunistic pathogens (Ochrobactrum and Simkaniaceae), likely associated with vertical transmission, were detected exclusively in C1 and C2 nests. Overall, our findings highlight the potentially critical role of nest microbiota in reproductive success. Both vertical (maternal) and horizontal (environmental and anthropogenic) transmission appear to shape microbial composition, potentially affecting hatchling viability and offering useful insights for conservation monitoring.

Glacial ecosystems of Central Asia represent extreme environments where microbial communities are shaped by both physicochemical conditions and hydrological dynamics. In this study, we analysed 21 surface and meltwater samples collected in September 2023 from a lake, river, glacier, glacial river, and sedimentary lake in the Zhongar Alatau National Park (Kazakhstan, 1 040-3 360 m a.s.l.). Bacterial community structure was assessed using ARISA profiling, while spectrometric methods determined concentrations of chemical elements. Alpha diversity indices revealed the highest richness and diversity in lake and sedimentary lake samples, moderate diversity in river samples, and the lowest values in glacier samples. The glacial river samples showed the strongest variability among the samples. Unique operational taxonomic units (OTUs) were most abundant in the lake, but the glacier exhibited the highest relative proportion of habitat-specific OTUs. Principal component analysis revealed that DNA yield, along with heavy metals and other elements (Rb, Fe, Mn, K, Ba), covaried along the major axes, primarily reflecting differences driven by habitat. Overall, our results demonstrate that glacial valley habitats host distinct bacterial assemblages and that the chemical environment is consistent with the observed spatial structuring of microbial communities. These findings highlight the vulnerability and sensitivity of mountain freshwater ecosystems to glacier retreat and associated changes in water chemistry.