Activity-Based Protein Profiling of RHBDL4 Reveals Proteolysis of the Enzyme and a Distinct Inhibitor Profile.

Rhomboid proteases have fascinated scientists by virtue of their membrane-embedded active sites and proposed involvement in physiological and disease pathways. The human rhomboid protease RHBDL4 has generated particular interest due to its role in endoplasmic reticulum-associated protein degradation and upregulation in several cancers; however, chemical tools for studying this enzyme are currently lacking. Here, we describe the development of an activity-based protein profiling (ABPP) assay for RHBDL4. We have employed this assay to determine that human RHBDL4 undergoes proteolytic processing in cells to produce multiple active proteoforms with truncated C-termini. We have also used this assay to identify chemical scaffolds capable of inhibiting RHBDL4 activity and have observed distinct inhibitor preferences between RHBDL4 and a second human rhomboid protease PARL. Our work demonstrates the power of ABPP technology to characterize active forms of enzymes that might otherwise elude detection and the potential to achieve selective inhibition among the human rhomboid proteases.

Assessing the technical efficiency performance of Chinese ports logistics: Evidence from the DEA and fsQCA.

Ports are critical centers of international trade and global logistics now that economic globalization has taken hold. The efficiency performance of port logistics is crucial to building an emerging pattern of development in which domestic and foreign dual cycles are complementary for China. This paper examines the efficiency performance of 19 ports within five major economic circles in China. It explores how their efficiency is distributed, and the configurations of efficiency improvement during the new normal of China's economy. First, the DEA-BCC model is employed to calculate the technical efficiency performance and distribution of each port from 2011 to 2020. Then, fuzzy-set qualitative comparative analysis (fsQCA) was applied to integrate and analyze the influencing factors. The results show as follows: (1) Each port group performed differently on efficiency rankings, as well as regional distributions. Among these, the port groups of the Bohai Rim region, the Yangtze River Delta region, and the Bohai Rim region continue to rank highly. (2) From the perspective of configuration analysis, the results suggest that government support is not necessary for port logistics with better economic endowments. However, it is critical for backward ones. (3) A rational industrial structure can enhance levels of infrastructure, openness, and information technology, improving port performance. The findings can provide theoretical and practical references for better promoting the development of Chinese port management.al references for better promoting the development of Chinese port management.

The impact of SARS-Cov-2 Omicron infection on short-term outcomes after elective surgery in patients with gastrointestinal cancer.

With the emergence of novel variants, Omicron variant caused a different clinical picture than the previous variants and little evidence was reported regarding perioperative outcomes after Omicron variants. The aim of the study was to evaluate the postoperative outcomes of gastrointestinal cancer patients following Omicron variants infection and also to determine the timing of surgery after infection recovery. A total of 124 patients who underwent gastrointestinal cancer surgery with prior SARS-CoV-2 infection between December 2022 and February 2023 were retrospectively reviewed. 174 cases underwent the same operation during December 2018 and February 2019 as control group. SARS-CoV-2-infected patients were further categorized into three groups based on infected time (1-3 weeks; 4-6 weeks; and ≥ 7 weeks). 90.3% of SARS-CoV-2-infected patients had mild symptoms. The COVID-19 vaccination rate was 71.0%, with a full vaccination rate of 48.4%. There were no significant differences in 30-day morbidity and mortality. There was also no significant difference in pulmonary complications, cardiovascular complications, and surgical complications between the three different diagnosis time groups. In conclusion, reducing waiting time for elective surgery was safe for gastrointestinal cancer patients in the context of an increased transmissibility and milder illness severity with Omicron variant.

Genome-wide identification, stress- and hormone-responsive expression characteristics, and regulatory pattern analysis of Scutellaria baicalensis SbSPLs.

SQUAMOSA PROMOTER BINDING PROTEIN-LIKEs (SPLs) encode plant-specific transcription factors that regulate plant growth and development, stress response, and metabolite accumulation. However, there is limited information on Scutellaria baicalensis SPLs. In this study, 14 SbSPLs were identified and divided into 8 groups based on phylogenetic relationships. SbSPLs in the same group had similar structures. Abscisic acid-responsive (ABRE) and MYB binding site (MBS) cis-acting elements were found in the promoters of 8 and 6 SbSPLs. Segmental duplications and transposable duplications were the main causes of SbSPL expansion. Expression analysis based on transcriptional profiling showed that SbSPL1, SbSPL10, and SbSPL13 were highly expressed in roots, stems, and flowers, respectively. Expression analysis based on quantitative real-time polymerase chain reaction (RT‒qPCR) showed that most SbSPLs responded to low temperature, drought, abscisic acid (ABA) and salicylic acid (SA), among which the expression levels of SbSPL7/9/10/12 were significantly upregulated in response to abiotic stress. These results indicate that SbSPLs are involved in the growth, development and stress response of S. baicalensis. In addition, 8 Sba-miR156/157 s were identified, and SbSPL1-5 was a potential target of Sba-miR156/157 s. The results of target gene prediction and coexpression analysis together indicated that SbSPLs may be involved in the regulation of L-phenylalanine (L-Phe), lignin and jasmonic acid (JA) biosynthesis. In summary, the identification and characterization of the SbSPL gene family lays the foundation for functional research and provides a reference for improved breeding of S. baicalensis stress resistance and quality traits.

Integration of machine learning for developing a prognostic signature related to programmed cell death in colorectal cancer.

BACKGROUND: Colorectal cancer (CRC) presents a significant global health burden, characterized by a heterogeneous molecular landscape and various genetic and epigenetic alterations. Programmed cell death (PCD) plays a critical role in CRC, offering potential targets for therapy by regulating cell elimination processes that can suppress tumor growth or trigger cancer cell resistance. Understanding the complex interplay between PCD mechanisms and CRC pathogenesis is crucial. This study aims to construct a PCD-related prognostic signature in CRC using machine learning integration, enhancing the precision of CRC prognosis prediction. METHOD: We retrieved expression data and clinical information from the Cancer Genome Atlas and Gene Expression Omnibus (GEO) datasets. Fifteen forms of PCD were identified, and corresponding gene sets were compiled. Machine learning algorithms, including Lasso, Ridge, Enet, StepCox, survivalSVM, CoxBoost, SuperPC, plsRcox, random survival forest (RSF), and gradient boosting machine, were integrated for model construction. The models were validated using six GEO datasets, and the programmed cell death score (PCDS) was established. Further, the model's effectiveness was compared with 109 transcriptome-based CRC prognostic models. RESULT: Our integrated model successfully identified differentially expressed PCD-related genes and stratified CRC samples into four subtypes with distinct prognostic implications. The optimal combination of machine learning models, RSF + Ridge, showed superior performance compared with traditional methods. The PCDS effectively stratified patients into high-risk and low-risk groups, with significant survival differences. Further analysis revealed the prognostic relevance of immune cell types and pathways associated with CRC subtypes. The model also identified hub genes and drug sensitivities relevant to CRC prognosis. CONCLUSION: The current study highlights the potential of integrating machine learning models to enhance the prediction of CRC prognosis. The developed prognostic signature, which is related to PCD, holds promise for personalized and effective therapeutic interventions in CRC.

Coarse particles compensate for missing daytime sources of nitrous acid and enhance atmospheric oxidation capacity in a coastal atmosphere.

Large missing sources of daytime atmospheric nitrous acid (HONO), a vital source of hydroxyl radicals (OH) through its photolysis, frequently exist in global coastal regions. In this study, ambient HONO and relevant species were measured at a coastal site in the Pearl River Delta (PRD), China, during October 2019. Relatively high concentrations (0.32 ± 0.19 ppbv) and daytime peaks at approximately 13:00 of HONO were observed, and HONO photolysis was found to be the dominant (55.5 %) source of the primary OH production. A budget analysis of HONO based on traditional sources suggested large unknown sources during the daytime (66.4 %), which had a significant correlation with the mass of coarse particles (PM2.5-10) and photolysis frequency (J(NO2)). When incorporating photolysis of the abundant nitrate measured in coarse particles with a reasonable enhancement factor relative to fine particles due to favorable aerosol conditions, the missing daytime sources of HONO could be fully compensated by coarse particles serving as the largest source at this coastal site. Our study revealed great potential of coarse particles as a strong daytime HONO source, which has been ignored before but can efficiently promote NOx recycling and thus significantly enhance atmospheric oxidation capacity.

Aletrisguangxiensis (Nartheciaceae), a new species from Guangxi, China.

Aletrisguangxiensis Y. Nong & Y. F. Huang (Nartheciaceae), a new species from Guangxi, China, is described and illustrated. This new species is most similar to A.scopulorum, but it can be easily distinguished by its sparsely glandular, 5-18 cm long scape, glandular inflorescence axis, distinctly pedicellate flowers, sparsely glandular, 5-10 mm long pedicel, bract borne at base of pedicel, glabrous perianth divided to the base, strongly recurved or revolute perianth lobes and turbinate, obovoid to oblong-obovoid capsule. An identification key for 24 species and 1 hybrid of Aletris is also provided.

Supervised Manifold Learning Based on Multi-Feature Information Discriminative Fusion within an Adaptive Nearest Neighbor Strategy Applied to Rolling Bearing Fault Diagnosis.

Rolling bearings are a key component for ensuring the safe and smooth operation of rotating machinery and are very prone to failure. Therefore, intelligent fault diagnosis research on rolling bearings has become a crucial task in the field of mechanical fault diagnosis. This paper proposes research on the fault diagnosis of rolling bearings based on an adaptive nearest neighbor strategy and the discriminative fusion of multi-feature information using supervised manifold learning (AN-MFIDFS-Isomap). Firstly, an adaptive nearest neighbor strategy is proposed using the Euclidean distance and cosine similarity to optimize the selection of neighboring points. Secondly, three feature space transformation and feature information extraction methods are proposed, among which an innovative exponential linear kernel function is introduced to provide new feature information descriptions for the data, enhancing feature sensitivity. Finally, under the adaptive nearest neighbor strategy, a novel AN-MFIDFS-Isomap algorithm is proposed for rolling bearing fault diagnosis by fusing various feature information and classifiers through discriminative fusion with label information. The proposed AN-MFIDFS-Isomap algorithm is validated on the CWRU open dataset and our experimental dataset. The experiments show that the proposed method outperforms other traditional manifold learning methods in terms of data clustering and fault diagnosis.

Walsuraguangxiensis (Meliaceae), a new species from Guangxi, China.

Walsuraguangxiensis (Meliaceae), a new species from Guangxi, China, is here described and illustrated. The new species is easily distinguishable from the other two Chinese members of the genus by its petals being pale yellow, filaments being connate into tubes above the middle, the berry being oval and glabrous. An identification key of Walsura for 17 species is also provided.

Lysimachiacavicola (Primulaceae), a new species from Guangxi, China.

Lysimachiacavicola (Subgen. Idiophyton, Primulaceae), a new species from Guangxi, China, is here described and illustrated based on morphological data. Although it shares similarities with L.microcarpa, L.fooningensis, and L.capillipes, there are distinguishing characteristics that set it apart. These include erect stems either solitary or in clusters of 1 to 2, herbaceous, terete, and densely glandular hairy. The leaves are either ovate or elliptical lanceolate, with inconspicuously reticulate veins. The petiole measures 2-4 mm in length covered with minute glandular hairy. The corolla is deeply parted, measuring 6-8 mm in length, with narrowly elliptic or narrowly oblong lobes that are 1-2 mm wide. The capsule is globose, measuring 2-3 × 2-3 mm, and possesses a chalky, brittle texture, which splits into 5-valved segments. The calyx of the plant appears yellowish-white during fruiting. This newly discovered species is endemic to limestone areas in Fengshan County, Guangxi, China.

Chemoproteomic strategy identified p120-catenin glutathionylation regulates E-cadherin degradation and cell migration.

Identification of cysteines with high oxidation susceptibility is important for understanding redox-mediated biological processes. In this report, we report a chemical proteomic strategy that finds cysteines with high susceptibility to S-glutathionylation. Our proteomic strategy, named clickable glutathione-based isotope-coded affinity tag (G-ICAT), identified 1,518 glutathionylated cysteines while determining their relative levels of glutathionylated and reduced forms upon adding hydrogen peroxide. Among identified cysteines, we demonstrated that CTNND1 (p120) C692 has high susceptibility to glutathionylation. Also, p120 wild type (WT), compared to C692S, induces its dissociation from E-cadherin under oxidative stress, such as glucose depletion. p120 and E-cadherin dissociation correlated with E-cadherin destabilization via its proteasomal degradation. Lastly, we showed that p120 WT, compared to C692S, increases migration and invasion of MCF7 cells under glucose depletion, supporting a model that p120 C692 glutathionylation increases cell migration and invasion by destabilization of E-cadherin, a core player in cell-cell adhesion.

Evaluation of virulence of Klebsiella pneumoniae using zebrafish behavior as a biological indicator.

INTRODUCTION: Klebsiella pneumoniae is one of the common pathogenic bacteria that can cause infections in hospitals and communities and can cause respiratory, urinary, and other multi-system infections. In recent years, the emergence of highly virulent and drug-resistant Klebsiella pneumoniae has greatly increased the difficulty of treatment for infection. Clinically, it is very important to accurately judge the virulence of isolated Klebsiella pneumoniae for treatment, but there is no better method to evaluate its virulence. METHODS: In this study, zebrafish were used as a model organism, and the swimming distance was used as a detection index to identify clinically isolated Klebsiella pneumoniae. In this study, we selected two different strains of Klebsiella pneumoniae, i.e., NTUH-K2044 and ATCC BAA-1705, with known high and low virulence, respectively, to infect zebrafish juveniles and evaluated their behavioral ability according to different bacterial concentrations and different developmental times. RESULTS: It was found that highly virulent Klebsiella pneumoniae caused a significant decrease in the behavioral ability of zebrafish larvae, while low-virulence Klebsiella pneumoniae had relatively little effect. CONCLUSIONS: These results indicate that it is entirely feasible to assess the virulence of Klebsiella pneumoniae based on behavioral ability.

Application of a New Retraction Method in Laparoscopic Gastrectomy for Gastric Cancer.

BACKGROUND: Better exposition is important for lymph node dissection in the suprapancreatic region and lesser curvature region of the stomach, and digestive tract reconstruction, especially without excellent assistants. PATIENTS AND METHODS: We developed a new laparoscopic retraction method with the use of two internal retractors (TIRs) punctured along with suture. Clinicopathological data, surgical data, and postoperative outcomes were assessed. RESULTS: Of the 143 patients included, 51 underwent surgery with the double-sling suture method and 92 underwent surgery with the TIRs method. Laparoscopic radical gastrectomy was successfully performed in all patients. There were no significant differences in patient characteristics or preoperative data in the 2 groups. The operative time was significantly shorter in the TIR group, but the amount of bleeding did not differ. No retraction-related complications both in clipped tissue and liver occurred in all patients. CONCLUSIONS: Our new retraction technique provided an optimal surgical field and make surgery lower requirements for assistants.

Revealing the interfacial water structure on a p-nitrobenzoic acid specifically adsorbed Au(111) surface.

The detailed structure of the water layer in the inner Helmholtz plane of a solid/aqueous solution interface is closely related to the electrochemical and catalytic performances of electrode materials. While the applied potential can have a great impact, specifically adsorbed species can also influence the interfacial water structure. With the specific adsorption of p-nitrobenzoic acid on the Au(111) surface, a protruding band above 3600 cm-1 appears in the electrochemical infrared spectra, indicating a distinct interfacial water structure as compared to that on bare metal surfaces, which displays a potential-dependent broad band in the range of 3400-3500 cm-1. Although three possible structures have been guessed for this protruding infrared band, the band assignment and interfacial water structure remain ambiguous in the past two decades. Herein, by combining surface-enhanced infrared absorption spectroscopy and our newly developed quantitative computational method for electrochemical infrared spectra, the protruding infrared band is clearly assigned to the surface-enhanced stretching mode of water molecules hydrogen-bonded to the adsorbed p-nitrobenzoate ions. Water molecules, meanwhile, are hydrogen-bonded with themselves to form chains of five-membered rings. Based on the reaction free energy diagram, we further demonstrate that both hydrogen-bonding interactions and coverages of specifically adsorbed p-nitrobenzoate play an important role in determining the structure of the water layer in the Au(111)/p-nitrobenzoic acid solution interface. Our work sheds light on structural studies of the inner Helmholtz plane under specific adsorptions, which advances the understanding of structure-property relationships in electrochemical and heterogeneous catalytic systems.

Comparison of [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/MRI in the Preoperative Diagnosis of Gastric Cancer.

Purpose: Our objective was to compare the value of positron emission tomography/magnetic resonance imaging (PET/MRI) with the new imaging agent [68Ga]Ga-DOTA-FAPI-04 and the traditional imaging agent [18F]FDG for the preoperative diagnosis of gastric cancer. Methods: Forty patients with gastric cancer diagnosed by gastroscopy in gastrointestinal surgery at our hospital from June 2020 to January 2021 were analyzed. All patients underwent simultaneous [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/MRI. The standard uptake value (SUV), fat removal standard uptake value (SUL), and diagnostic sensitivity, specificity, and accuracy for primary and metastatic lesions were compared, and their diagnostic value for different lymph node dissection stages was analyzed. Results: The median age of the patients in this cohort was 68 years. Twenty-nine patients underwent surgery, and 11 patients underwent gastroscopic biopsy. The SUVmax of primary lesions in the FDG group and the FAPI group was 5.74 ± 5.09 and 8.06 ± 4.88, respectively (P < 0.01); SULmax values were 3.52 ± 2.80 and 5.64 ± 3.25, respectively (P < 0.01). The SUVmax of metastases in the two groups was 3.81 ± 3.08 and 5.17 ± 2.80, respectively (P < 0.05). The diagnostic sensitivities for primary lesions in the FDG group and the FAPI group were 0.72 and 0.94, respectively (P < 0.05). Combined with postoperative pathological staging, there was no difference in diagnostic sensitivity and specificity of lymph node staging between the FDG and FAPI groups (P > 0.05). Conclusion: Compared with the traditional imaging agent, [68Ga]Ga-DOTA-FAPI-04 has better diagnostic efficiency but no substantial advantage for preoperative lymph node staging.

Advanced surface engineering of titanium materials for biomedical applications: From static modification to dynamic responsive regulation.

Titanium (Ti) and its alloys have been widely used as orthopedic implants, because of their favorable mechanical properties, corrosion resistance and biocompatibility. Despite their significant success in various clinical applications, the probability of failure, degradation and revision is undesirably high, especially for the patients with low bone density, insufficient quantity of bone or osteoporosis, which renders the studies on surface modification of Ti still active to further improve clinical results. It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants. Therefore, it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration. This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical, physical and chemical treatments based on the formation mechanism of the modified coatings. Such conventional methods are able to improve bioactivity of Ti implants, but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues. Hence, beyond traditional static design, dynamic responsive avenues are then emerging. The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers. In short, this review surveys recent developments in the surface engineering of Ti materials, with a specific emphasis on advances in static to dynamic functionality, which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

Assessment of Autologous Blood marker localIzation and intraoperative coLonoscopy localIzation in laparoscopic colorecTal cancer surgery (ABILITY): a randomized controlled trial.

BACKGROUND: Laparoscopic colorectal surgery has been proved to have similar oncological outcomes with open surgery. Due to the lack of tactile perception, surgeons may have misjudgments in laparoscopic colorectal surgery. Therefore, the accurate localization of a tumor before surgery is important, especially in the early stages of cancer. Autologous blood was thought a feasible and safe tattooing agent for preoperative endoscopic localization but its benefits remain controversial. We therefore proposed this randomized trial to the accuracy and safety of autogenous blood localization in small, serosa-negative lesion which will be resected by laparoscopic colectomy. METHODS: The current study is a single-center, open-label, non-inferiority, randomized controlled trial. Eligible participants would be aged 18-80 years and diagnosed with large lateral spreading tumors that could not be treated endoscopically, malignant polyps treated endoscopically that required additional colorectal resection, and serosa-negative malignant colorectal tumors (≤ cT3). A total of 220 patients would be randomly assigned (1:1) to autologous blood group or intraoperative colonoscopy group. The primary outcome is the localization accuracy. The secondary endpoint is adverse events related to endoscopic tattooing. DISCUSSION: This trial will investigate whether autologous blood marker achieves similar localization accuracy and safety in laparoscopic colorectal surgery compared to intraoperative colonoscopy. If our research hypothesis is statistically proved, the rational introduction of autologous blood tattooing in preoperative colonoscopy can help improve identification of the location of tumors for laparoscopic colorectal cancer surgery, performing an optimal resection, and minimizing unnecessary resections of normal tissues, thereby improving the patient's quality of life. Our research data will also provide high quality clinical evidence and data support for the conduction of multicenter phase III clinical trials. TRIAL REGISTRATION: This study is registered with ClinicalTrials.gov, NCT05597384. Registered 28 October 2022.

Gut Microbiota and Metabolites May Play a Crucial Role in Sea Cucumber Apostichopus japonicus Aestivation.

The constant increase in temperatures under global warming has led to a prolonged aestivation period for Apostichopus japonicus, resulting in considerable losses in production and economic benefits. However, the specific mechanism of aestivation has not been fully elucidated. In this study, we first tried to illustrate the biological mechanisms of aestivation from the perspective of the gut microbiota and metabolites. Significant differences were found in the gut microbiota of aestivating adult A. japonicus (AAJSD group) compared with nonaestivating adult A. japonicus (AAJRT group) and young A. japonicus (YAJRT and YAJSD groups) based on 16S rRNA gene high-throughput sequencing analysis. The abundances of Desulfobacterota, Myxococcota, Bdellovibrionota, and Firmicutes (4 phyla) in the AAJSD group significantly increased. Moreover, the levels of Pseudoalteromonas, Fusibacter, Labilibacter, Litorilituus, Flammeovirga, Polaribacter, Ferrimonas, PB19, and Blfdi19 genera were significantly higher in the AAJSD group than in the other three groups. Further analysis of the LDA effect size showed that species with significant variation in abundance in the AAJSD group, including the phylum Firmicutes and the genera Litorilituus, Fusibacter, and Abilibacter, might be important biomarkers for aestivating adult A. japonicus. In addition, the results of metabolomics analysis showed that there were three distinct metabolic pathways, namely biosynthesis of secondary metabolites, tryptophan metabolism, and sesquiterpenoid and triterpenoid biosynthesis in the AAJSD group compared with the other three groups. Notably, 5-hydroxytryptophan was significantly upregulated in the AAJSD group in the tryptophan metabolism pathway. Moreover, the genera Labilibacter, Litorilituus, Ferrimonas, Flammeovirga, Blfdi19, Fusibacter, Pseudoalteromonas, and PB19 with high abundance in the gut of aestivating adult A. japonicus were positively correlated with the metabolite 5-HTP. These findings suggest that there may be potential biological associations among the gut microbiota, metabolites, and aestivation in A. japonicus. This work may provide a new perspective for further understanding the aestivation mechanism of A. japonicus.

A systematic review, meta-analysis and meta-regression of the global prevalence of foodborne Vibrio spp. infection in fishes: A persistent public health concern.

Human vibriosis, caused by pathogenic Vibrio spp., such as Vibrio parahaemolyticus, Vibrio cholerae and Vibrio vulnificus, has been increasing worldwide, mediated by increasing consumption of seafood. The present study was conducted to examine the global prevalence of V. vulnificus, V. parahaemolyticus and V. cholerae in fishes. We searched PubMed, Web of Science, Scopus, and CNKI for peer-reviewed articles and dissertations prior to December 31, 2021. A total of 24,831 articles were retrieved, and 82 articles contained 61 fish families were included. The global pooled prevalence of V. cholerae, V. parahaemolyticus and V. vulnificus in fishes was 9.56 % (95 % CI: 2.12-20.92), 24.77 % (95 % CI: 17.40-32.93) and 5.29 % (95 % CI: 0.38-13.61), respectively. Subgroup and meta-regression analyses showed that study-level covariates, including temperature, country, continent, origin and detection methods partly explained the between-study heterogeneity. These heterogeneities were underpinned by differences of the three Vibrio spp. in fishes at geographical and climatic scales. These results reveal a high global prevalence of pathogenic Vibrio spp. in fishes and highlight the need for implementation of more effective prevention and control measures to reduce food-borne infection in humans.

The growth, lipid accumulation and adaptation mechanism in response to variation of temperature and nitrogen supply in psychrotrophic filamentous microalga Xanthonema hormidioides (Xanthophyceae).

BACKGROUND: Microalgae are promising feedstocks for production of renewable biofuels and value-added bioproducts. Temperature and nitrogen supply are important environmental and nutritional factors affecting the growth and metabolism of microalgae, respectively. In this study, the growth and lipid accumulation of filamentous microalgae Xanthonema hormidioides under different temperatures (5, 7, 10, 15, 20, 25, 27 and 30 °C) and initial nitrogen concentrations (3, 9, 18 mM) were investigated, and its adaptive mechanisms of tolerance to low temperature and nitrogen stress were analysis by proteomics. RESULTS: The optimum temperature range for the growth of X. hormidioides was between 15 and 20 °C, and the algal cells had slow growth rate at 5 °C and could not survive at 30 °C. The maximum biomass concentration was 11.73 g L-1 under the temperature of 20 °C, and the highest total lipid content was 56.63% of dry weight. Low temperature did not change the fatty acids profiles but promoted the accumulation of unsaturated fatty acids of X. hormidioides. The maximum contents of palmitoleic acid, eicosapentaenoic acid and total fatty acid were 23.64%, 2.49% and 41.14% of dry weight, respectively. Proteomics was performed under three temperature (7, 15, 25 °C), two nitrogen concentrations (3 and 18 mM) and two cultivation times (day 3 and 12). A total of 6503 proteins were identified. In the low temperature, photosynthesis-related proteins were down-regulated to protect the photosynthetic apparatus. The up-regulation of key enzymes DGAT and PDAT demonstrated the accumulation of TAGs under low nitrogen treatment. The proteins related to ribosome, phosphatidylinositol signaling system, antioxidant system and cold shock proteins (CSPs) in X. hormidioides were co-upregulated under the treatment of low temperature, which can alleviate the damages induced by temperature stress and maintain the normal growth and metabolism of algal cells. CONCLUSIONS: X. hormidioides is a psychrotolerant microalga. It is an oleaginous filamentous microalga containing hyper palmitoleic acid and a certain amount of eicosapentaenoic acid with great potential for biofuel development, as well as for applications in nutritional health products and other industries.