The low efficiency of extracellular electron transfer (EET) is a major bottleneck for Shewanella oneidensis MR-1 acting as an electroactive biocatalyst in bioelectrochemical systems. Although it is well established that a periplasmic c-type cytochrome (c-Cyt) network plays a critical role in regulating EET efficiency, the understanding of the network in terms of structure and electron transfer activity is obscure and partial. In this work, we attempted to systematically investigate the impacts of the network components on EET in their absence and overproduction individually in microbial fuel cell (MFC). We found that overexpression of c-Cyt CctA leads to accelerated electron transfer between CymA and the Mtr system, which function as the primary quinol oxidase and the outer-membrane (OM) electron hub in EET. In contrast, NapB, FccA, and TsdB in excess severely impaired EET, reducing EET capacity in MFC by more than 50%. Based on the results from both strategies, a series of engineered strains lacking FccA, NapB, and TsdB in combination while overproducing CctA were tested for a maximally optimized c-Cyt network. A strain depleted of all NapB, FccA, and TsdB with CctA overproduction achieved the highest maximum power density in MFCs (436.5 mW/m2), ∼3.62-fold higher than that of wild type (WT). By revealing that optimization of periplasmic c-Cyt composition is a practical strategy for improving EET efficiency, our work underscores the importance in understanding physiological and electrochemical characteristics of c-Cyts involved in EET.

Summary Thiosulfate, an important form of sulfur compounds, can serve as both electron donor and acceptor in various microorganisms. In Shewanella oneidensis, a bacterium renowned for respiratory versatility, thiosulfate reduction has long been recognized but whether it can catalyse thiosulfate oxidation remains elusive. In this study, we discovered that S. oneidensis is capable of thiosulfate oxidation, a process specifically catalysed by two periplasmic cytochrome c (cyt c) proteins, TsdA and TsdB, which act as the catalytic subunit and the electron transfer subunit respectively. In the presence of oxygen, oxidation of thiosulfate has priority over reduction. Intriguingly, thiosulfate oxidation negatively regulates the cyt c content in S. oneidensis cells, largely by reducing intracellular levels of cAMP, which as the cofactor modulates activity of global regulator Crp required for transcription of many cyt c genes. This unexpected finding provides an additional dimension to interplays between the respiration regulator and the respiratory pathways in S. oneidensis. Moreover, the data presented here identified S. oneidensis as the first bacterium known to date owning both functional thiosulfate reductase and dehydrogenase, and importantly, genomics analyses suggested that the number of bacterial species possessing this feature is rather limited.

Zearalenone (ZEN, ZEA) contamination in various foods and feeds is a significant global problem. Similar to deoxynivalenol (DON) and other mycotoxins, ZEN in feed mainly enters the body of animals through absorption in the small intestine, resulting in estrogen-like toxicity. In this study, the gene encoding Oxa, a ZEN-degrading enzyme isolated from Acinetobacter SM04, was cloned into Lactobacillus acidophilus ATCC4356, a parthenogenic anaerobic gut probiotic, and the 38 kDa sized Oxa protein was expressed to detoxify ZEN intestinally. The transformed strain L. acidophilus pMG-Oxa acquired the capacity to degrade ZEN, with a degradation rate of 42.95% at 12 h (initial amount: 20 μg/mL). The probiotic properties of L. acidophilus pMG-Oxa (e.g., acid tolerance, bile salt tolerance, and adhesion properties) were not affected by the insertion and intracellular expression of Oxa. Considering the low amount of Oxa expressed by L. acidophilus pMG-Oxa and the damage to enzyme activity by digestive juices, Oxa was immobilized with 3.5% sodium alginate, 3.0% chitosan, and 0.2 M CaCl2 to improve the ZEN degradation efficiency (from 42.95% to 48.65%) and protect it from digestive juices. The activity of immobilized Oxa was 32–41% higher than that of the free crude enzyme at different temperatures (20–80 °C), pH values (2.0–12.0), storage conditions (4 °C and 25 °C), and gastrointestinal simulated digestion conditions. Accordingly, immobilized Oxa could be resistant to adverse environmental conditions. Owing to the colonization, efficient degradation performance, and probiotic functionality of L. acidophilus, it is an ideal host for detoxifying residual ZEN in vivo, demonstrating great potential for application in the feed industry.

One art, two generations of perseverance, director Wu Tianming took materials from local folk art, combined with the inheritance and memory of Suona art, to create a musical art fi lm work - "A Hundred Birds and Phoenixes". Taking Suona, a traditional folk art, as the main line, the director carefully carved out every detail when making the fi lm, so that the overall style and detail treatment of the fi lm have intriguing meaning. At the same time, focusing on the musical characteristics of Suona, the director starts from a unique aesthetic perspective, organically integrates traditional aesthetics with local culture, and enhances the aesthetic value of the fi lm. Based on this, this paper analyzes the evolution and development of Suona Qu "A Hundred Birds to the Phoenix", studies the aesthetic symbols of Suona in the movie "A Hundred Birds to the Phoenix", and discusses the aesthetic expression of Suona in the movie from the three-dimensional dimensions of space, life and emotion.