Ultraplankton plays an important role in the biogeochemical cycles of aquatic ecosystems. Based on 16S rRNA gene sequencing technology, the community structure composition of prokaryotic ultraplankton and its relationship with environmental factors were analyzed. The results showed that Cihu Lake was experiencing eutrophication and that Xiandao Lake was in the process of changing from mesotrophic to oligotrophic conditions. Cihu Lake and Xiandao Lake were regulated primarily by nitrogen nutrients. Proteobacteria, Bacteroidota, Cyanobacteria, and Actinobacteriota were the major phyla of prokaryotic ultraplankton in both lakes. Among them, Cyanobacteria dominate in the summer in Cihu Lake, which can have seasonal cyanobacterial blooms. Seasonal variation significantly affects the diversity and community structure of prokaryotic ultraplankton in the lakes, with temperature and dissolved oxygen being the key environmental factors determining plankton community composition. The PICRUSt functional prediction analysis indicated a higher water purification and exogenous pollution remediation capacity of the microbial communities of Xiandao Lake, as well as in the spring samples of Cihu Lake. In this study, the diversity and spatial–temporal succession patterns of prokaryotic ultraplankton in Cihu Lake and Xiandao Lake were elucidated, providing a useful reference for the lake environmental protection and water eutrophication management in Cihu Lake and Xiandao Lake.

Hyriopsis cumingii is an important economic freshwater shellfish in China and there is a need to understand changes in the microbial community structure resulting in multidimensional quality degradation when the fish is stored at different temperatures. This study integrated 16S rRNA full-length sequencing with multidimensional quality indicators to investigate the temperature-regulated bacterial community shifts and quality deterioration mechanisms in stored H. cumingii meat. The results showed that bacterial richness (Chao1 index) decreased progressively with both refrigerated (4 °C) and room-temperature (25 °C) storage. Community composition underwent significant restructuring, with Bacteroidota decreasing at 25 °C while Bacillota increased compared to 4 °C storage. Additionally, the refrigerated group showed enrichment of Delftia turuhatensis and Chryseobacterium indologenes compared to the room-temperature storage group. Temperature significantly restructured bacterial communities, with notably higher pathogenic bacteria under refrigeration and spoilage bacteria dominance at room temperature. Metagenomic functional profiling revealed temperature-driven metabolic pathway divergence, indicating distinct spoilage mechanism. Predictable quality changes in H. cumingii correlated with temperature-imposed microbial composition.

Background: The JinEr mushroom results from the heterogeneous symbiosis of Naematelia aurantialba and Stereum hirsutum, with low-temperature storage being key for postharvest quality preservation. However, the species-specific low-temperature response patterns remain unclear. Methods: An integrated approach combining metabolomics, transcriptomics (dual-genome alignment), and spatially resolved enzyme assays was used to dissect responses at 0 °C and 4 °C. Results: The two fungi displayed distinct stress response tendencies under the studied conditions. N. aurantialba showed enhanced stress defense (DNA repair, antioxidant pathways) with defense-related enzyme activities concentrated in its apical/middle enrichment regions. S. hirsutum was observed to maintain overall metabolic activity at the pathway level, and its metabolic enzyme activities were predominant in the basal region. The symbiotic system exhibited temperature-dependent plasticity stress responses. Storage at 0 °C induced a survival-oriented response with slower crude polysaccharide degradation. In contrast, storage at 4 °C supported active metabolic defense coordination but more pronounced polysaccharide loss. Conclusions: These observed defense- and metabolism-biased differential responses suggest a cold stress-specific coordination working model within the symbiotic system under postharvest cold stress. A temperature of 0 °C is more suitable for enabling JinEr mushroom postharvest storage to retain polysaccharides. This study advances our understanding of heterogeneous symbiotic fungi’s postharvest biology and provides a temperature-targeted theoretical basis for storage optimization.