ABSTRACT Peroxy natural products, including endoperoxides, acyclic peroxides, and hydroperoxides, are widely distributed across all domains of life, with many, such as artemisinin and prostaglandins, serving as clinically important agents. However, the enzymatic mechanisms by which nature installs O─O bonds have largely remained elusive. To date, only a limited number of endoperoxide‐forming enzymes have been identified, while the enzymatic basis for acyclic peroxide assembly remains unknown. Here, we identify two homologous flavin‐dependent enzymes, OxaJ and OtnJ, that catalyze enantioselective acyclic peroxide formation in the biosynthesis of oxanthromicin natural products. A conserved structural motif acts as a redox gate by blocking NADPH access to the active site, thereby promoting peroxide installation. Removal of this motif permits NADPH binding and redirects the enzyme's activity toward hydroxylation. This work establishes the first example of peroxide formation by a flavin‐dependent enzyme and introduces redox gating as a previously unrecognized strategy for controlling oxidative divergence in enzymatic catalysis.

Holo-omics provide a novel opportunity to study the interactions among fungi from different functional guilds in host plants in field conditions. We address the entangled responses of plant pathogenic and endophytic fungi associated with sorghum when droughted through the assembly of the most abundant fungal, endophyte genome from rhizospheric metagenomic sequences followed by a comparison of its metatranscriptome with the host plant metabolome and transcriptome. The rise in relative abundance of endophytic Acremonium persicinum (operational taxonomic unit 5 (OTU5)) in drought co-occurs with a rise in fungal membrane dynamics and plant metabolites, led by ethanolamine, a key phospholipid membrane component. The negative association between endophytic A. persicinum (OTU5) and plant pathogenic fungi co-occurs with a rise in expression of the endophyte's biosynthetic gene clusters coding for secondary compounds. Endophytic A. persicinum (OTU5) and plant pathogenic fungi are negatively associated under preflowering drought but not under postflowering drought, likely a consequence of variation in fungal fitness responses to changes in the availability of water and niche space caused by plant maturation over the growing season. Our findings suggest that the dynamic biotic interactions among host, beneficial and harmful microbiota in a changing environment can be disentangled by a blending of field observation, laboratory validation, holo-omics and ecological modelling.

Correct usage and maintenance of the enteral nutrition feeding pump system is always a challenge in nutrition support for patients with colorectal cancer (CRC). However, there are few studies on the sustained accuracy improvement of the enteral nutrition feeding system in discharged CRC patients. Here, we established a seven-month quality control circle (QCC) activity with the theme of improving the performance of home enteral feeding pumps (EFP) and examined the effect of QCC activity on the nutritional state and quality of life in discharged CRC patients. We enrolled 100 discharged CRC patients treated with home enteral nutrition from Zhejiang Cancer Hospital between March 2020 and December 2021. The patients were randomly split into two research groups: one participated in the QCC activity (n = 50) and the other did not (n = 50). QCC analysis indicated that the top 3 causes of EFP inaccurate usage are the simple and boring contents of training, various types of pumps, no examination rules, and lack of management. Furthermore, both intra- and inter-group comparisons showed that QCC significantly improved the patients’ pass rate of nutrition pump operation from 52 to 70% after 1-month of activity, which gradually improved and got the highest (90%) after 3 months (p < 0.05). Interestingly, the established QCC activity significantly increased the patient-generated subjective global assessment (PG-SGA) and Barthel index (BI) scores, body fat mass (BFM) and superior longitudinal muscle (SLM) by intra- and inter-group comparisons. In this study, we clarified the main causes of inaccurate EFP usage and established a QCC process to improve the pass rate of EFP usage. It finally leads to the improvement of nutritional state and quality of life in CRC patients.

ABSTRACT The human fungal pathogen Candida albicans colonizes and infects various host sites with diverse environmental pH. Adaptation to these diverse pH conditions plays a crucial role in its success as a commensal and pathogen. The conserved Rim101 pH sensing pathway is responsible for neutral–alkaline pH responses in C. albicans. In this study, we identified a novel Rfg1-Bcr1 regulatory pathway that governs acidic pH responses and regulates filamentation in C. albicans. A null mutant library was screened, and we have identified Rfg1 and Bcr1 as key regulators of filamentation under acidic pH conditions. Rfg1 directly binds to the promoter region of Bcr1 to regulate its transcriptional expression, which in turn suppresses the filamentation of C. albicans. PHR1, an alkaline pH response gene, is significantly activated by the absence of Rfg1, indicating that Rfg1 regulates acidic pH response through the Rim101-Phr1 pathway. Moreover, the cAMP signaling pathway, transcription factors Efg1 and Flo8, and the hyphal-specific G1 cyclin Hgc1 play critical roles in the regulation. Our findings provide new insights into the mechanisms underlying the acidic pH response of C. albicans, which reflects its elaborate regulatory control of environmental adaptation. IMPORTANCE Candida albicans is a human commensal and frequent pathogen that encounters a wide range of pH stresses. The ability of C. albicans to adapt to changes in extracellular pH is crucial for its success in colonization and pathogenesis. The Rim101 pH sensing pathway is well known to govern neutral–alkaline pH responses in this pathogen. Here, we report a novel Rfg1-Bcr1 regulatory pathway that governs acidic pH responses and regulates filamentous growth in C. albicans. In addition, the Rim101-Phr1 pathway, cAMP signaling pathway, transcription factors Efg1 and Flo8, and hyphal-specific G1 cyclin Hgc1 cooperate with this regulation. Our findings provide new insights into the regulatory mechanism of acidic pH response in C. albicans.

Blood-testis barrier (BTB) damage promotes spermatogenesis dysfunction, which is a critical cause of male infertility. Dyslipidemia has been correlated with male infertility, but the major hazardous lipid and the underlying mechanism remains unclear. In this study, we firstly discovered an elevation of palmitic acid (PA) and a decrease of inhibin B in patients with severe dyszoospermia, which leaded us to explore the effects of PA on Sertoli cells. We observed a damage of BTB by PA. PA penetration to endoplasmic reticulum (ER) and its damage to ER structures were exhibited by microimaging and dynamic observation, and consequent ER stress was proved to mediate PA-induced Sertoli cell barrier disruption. Remarkably, we demonstrated a critical role of aberrant protein palmitoylation in PA-induced Sertoli cell barrier dysfunction. An ER protein, Calnexin, was screened out and was demonstrated to participate in this process, and suppression of its palmitoylation showed an ameliorating effect. We also found that ω-3 poly-unsaturated fatty acids down-regulated Calnexin palmitoylation, and alleviated BTB dysfunction. Our results indicate that dysregulated palmitoylation induced by PA plays a pivotal role in BTB disruption and subsequent spermatogenesis dysfunction, suggesting that protein palmitoylation might be therapeutically targetable in male infertility.

This paper aims to explore the effects of chicken interferon-γ (ChIFN-γ) and interleukin-2 (ChIL-2) on type 1 helper (Th1) T lymphocyte differentiation. To be specific, ChIFN-γ and ChIL-2 were first expressed in Escherichiacoli competent cells and then purified by Ni-NTA affinity chromatography. Different concentration of ChIFN-γ and ChIL-2 were employed to stimulate the lymphocytes in chicken peripheral blood which had been activated by concanavalin A (Con A), and the mRNA levels of cytokines related to Th1 cell differentiation were detected by real-time quantitative PCR (RT-qPCR). The results showed that both ChIFN-γ and ChIL-2 can significantly up-regulate mRNA levels of cytokines related to Th1 cell differentiation and the optimal concentration was 12.5 μg/mL and 25.0 μg/mL, respectively. In addition, specific-pathogen-free (SPF) chickens were immunized with ChIL-2 or ChIFN-γ together with H9N2 vaccine, or H9N2 vaccine alone by oral administration or intramuscular injection, respectively. The mRNA levels of cytokines related to Th1 cell differentiation were detected after immunization. The results showed that ChIFN-γ and ChIL-2 significantly up-regulated the mRNA levels of cytokines related to Th1 cell differentiation induced by H9N2 vaccine compared with H9N2 vaccine alone, and that the intramuscular injection was better than oral administration. In this study, we verified that ChIFN-γ and ChIL-2 can significantly enhance mRNA levels of cytokines related to Th1 cell differentiation induced by ConA or H9N2 vaccine invitro and invivo. The results of this study can lay a theoretical basis for using ChIFN-γ and ChIL-2 as vaccine adjuvants.

Candida auris is an emerging pathogenic fungal species found worldwide. Since April 2016, C. auris colonization/infection cases have been found in a general hospital in Shenyang, China. The genome-based phylogenetic studies of these isolates remain undefined. In the current study, the microbiological characteristics and antifungal susceptibility of these C. auris isolates, which were collected in Shenyang during the three-year period (2016-2018), were investigated. Whole-genome sequencing was applied to investigate the genetic variation and molecular epidemiological characteristics. A total of 93 C. auris isolates, including 92 clinical isolates and 1 environmental screening isolate were identified. Among the investigated wards, the C. auris cases were the most prevalent (97.4%, 37/38) in four intensive care units (ICUs). The Shenyang isolates carrying the VF125AL mutation in the key drug-resistance gene ERG11 were mainly fluconazole resistant and formed a distinct subclade under the South African clade according to the phylogenetic and population structural analyses. In addition, the Shenyang subclade was found to be closely related to the British subclade in the aspect of genetic distance. As a conclusion, this study provides an important clue for revealing the origin of C. auris found in Shenyang and could also contribute to improve the understanding of the epidemiological characteristics of C. auris worldwide.

Fungal highly reducing polyketide synthases (HRPKSs) are highly programmed multidomain enzymes that synthesize reduced polyke-tide structures. Recent reports indicated salicylaldehydes are synthe-sized by HRPKS biosynthetic gene clusters, which are unexpected based on known enzymology of HRPKSs. Using genome mining of a Trichoderma virens HRPKS gene cluster that encodes a number of redox enzymes, we uncover the strategy used by HRPKS pathways in the biosynthesis of aromatic products such as salicylaldehyde 4, which can be oxidatively modified to the epoxycyclohexanol natural product trichoxide 1. We show selective -hydroxyl groups in the linear HRPKS product are individually reoxidized to -ketones by short-chain dehydrogenase/reductase (SDR) enzymes, which enabled in-tramolecular aldol condensation and aromatization. Our work ex-pands the chemical space of natural products accessible through HRPKS pathways.