The ability of headwater bed and suspended sediments to mitigate non-point agricultural phosphorus (P) loads to the lower Great Lakes is recognized, but the specific biogeochemical processes promoting sediment P retention or internal P release remain poorly understood. To elucidate these mechanisms, three headwater segments located within priority watersheds of Southern Ontario, Canada, were sampled through the growing season of 2018-2020. The study employed equilibrium P assays along with novel assessments of legacy watershed nutrients, nitrogen (N) concentrations, sediment redox, and microbial community composition. 20-year data revealed elevated total P (TP) and total Nitrogen (TN) at an inorganic fertilizer and manure fertilizer-impacted site, respectively. Overall, sampled sites acted as P sinks; however, agricultural sediments exhibited significantly lower buffering capacity compared to a reference forested watershed. Collection of fine suspended sediment (<63 µm) through time-integrated sampling showed the suspended load at the inorganic-fertilized site was saturated with P, indicating a greater potential for P release into surface waters compared to bed sediments. Through vertical microsensor profiling and DNA sequencing of the sediment microbial community, site-specific factors associated with a distinct P-source event were identified. These included rapid depletion of dissolved oxygen (DO) across the sediment water interface (SWI), as well as the presence of nitrate-reducing bacterial and ammonia-oxidizing archaeal (AOA) genera. This research provides valuable insights into the dynamics of P in headwaters, shedding light on P retention and release. Understanding these processes is crucial for effective management strategies aimed at mitigating P pollution to the lower Great Lakes.

The pyruvate oxidases from Escherichia coli (EcPOX) and Lactobacillus plantarum (LpPOX) are both thiamin-dependent flavoenzymes. Their sequence and structure are closely related, and they catalyse similar reactions-but they differ in their activity pattern: LpPOX is always highly active, EcPOX only when activated by lipids or limited proteolysis, both involving the protein\'s C-terminal 23 residues (the \'α-peptide\'). Here, we relate the redox-induced infrared (IR) difference spectrum of EcPOX to its unusual activation mechanism. The IR difference spectrum of EcPOX is marked by contributions from the protein backbone, reflecting major conformational changes. A rare sulfhydryl (-SH) difference signal indicates changes in the vicinity of cysteines. We could pin the Cys-SH difference signal to Cys88 and Cys494, both being remote from the moving α-peptide and the redox-active flavin cofactor. Yet, when the α-peptide is proteolytically removed, the Cys-SH difference signal disappears, together with several difference signals in the amide range. The remaining IR signature of the permanently activated EcPOXΔ23 is strikingly similar to the simpler signature of LpPOX. The loss of the α-peptide \'transforms\' the catalytically complex EcPOX into the catalytically \'simpler\' LpPOX.

Cryopreservation has several advantages over other ex situ conservation methods, and indeed is the only viable storage method for the long term conservation of most plant species. However, despite many advances in this field, it is increasingly clear that some species are ill-equipped to overcome the intense stress imposed by the cryopreservation process, making protocol development incredibly difficult using traditional trial and error methods. Cryobiotechnology approaches have been recently recognised as a strategic way forward, utilising intimate understanding of biological systems to inform development of more effective cryopreservation protocols. Mitochondrial function is a model candidate for a cryobiotechnological approach, as it underpins not only energy provision, but also several other key determinants of germplasm outcome, including stress response, reduction-oxidation status, and programmed cell death. Extensive research in animal cell and tissue cryopreservation has established a clear link between mitochondrial health and cryopreservation survival, but also indicates that mitochondria are routinely subject to damage from multiple aspects of the cryopreservation process. Evidence is already emerging that mitochondrial dysfunction may also occur in plant cryopreservation, and this research can be greatly expanded by using considered applications of innovative technologies. A range of mitochondria-targeted prophylactic and therapeutic interventions already exist with potential to improve cryopreservation outcomes through mitochondrial function.

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