Unveiling cold Code: Acinetobacter calcoaceticus TY1's adaptation strategies and applications in nitrogen treatment.

Overcoming low nitrogen removal efficiency at low temperatures is a challenge in biological treatment. This study investigated the cold-tolerant heterotrophic nitrification-aerobic denitrification by Acinetobacter calcoaceticus TY1. Transcriptomic and biochemical analyses indicated that strain TY1 upregulated genes for energy production, assimilation, cell motility, and antioxidant enzyme production under cold stress, maintaining functions such as energy supply, nitrogen utilization, and oxidative defense. Increasing the synthesis of extracellular polysaccharides, unsaturated fatty acids, and medium-chain fatty acids and secreting large amounts of antioxidant enzymes ensured cell membrane flexibility while enhancing the antioxidant system. Immobilization experiments showed that biofilms accelerated the removal of nitrogen pollutants and demonstrated good stability, with carriers being reusable to five times, maintaining high ammonia nitrogen (63.90 %) and total nitrogen (50.66 %) removal rates. These findings reveal the cold tolerance mechanisms of strain TY1 and its excellent practical potential as a candidate for wastewater treatment in cold regions.

Regulation of nitrite-dependent anaerobic methane oxidation bacteria by available phosphorus and microbial communities in lake sediments of cold and arid regions.

As global anthropogenic nitrogen inputs continue to rise, nitrite-dependent anaerobic methane oxidation (N-DAMO) plays an increasingly significant role in CH4 consumption in lake sediments. However, there is a dearth of knowledge regarding the effects of anthropogenic activities on N-DAMO bacteria in lakes in the cold and arid regions. Sediment samples were collected from five sampling areas in Lake Ulansuhai at varying depth ranges (0-20, 20-40, and 40-60 cm). The ecological characterization and niche differentiation of N-DAMO bacteria were investigated using bioinformatics and molecular biology techniques. Quantitative PCR confirmed the presence of N-DAMO bacteria in Lake Ulansuhai sediments, with 16S rRNA gene abundances ranging from 1.72 × 104 to 5.75 × 105 copies·g-1 dry sediment. The highest abundance was observed at the farmland drainage outlet with high available phosphorus (AP). Anthropogenic disturbances led to a significant increase in the abundance of N-DAMO bacteria, though their diversity remained unaffected. The heterogeneous community of N-DAMO bacteria was affected by interactions among various environmental characteristics, with AP and oxidation-reduction potential identified as the key drivers in this study. The Mantel test indicated that the N-DAMO bacterial abundance was more readily influenced by the presence of the denitrification genes (nirS and nirK). Network analysis revealed that the community structure of N-DAMO bacteria generated numerous links (especially positive links) with microbial taxa involved in carbon and nitrogen cycles, such as methanogens and nitrifying bacteria. In summary, N-DAMO bacteria exhibited sensitivity to both environmental and microbial factors under various human disturbances. This study provides valuable insights into the distribution patterns of N-DAMO bacteria and their roles in nitrogen and carbon cycling within lake ecosystems.