The mud-dwelling clam Meretrix petechialis secretes endogenously synthesized erythromycin.

Although lacking an adaptive immune system and often living in habitats with dense and diverse bacterial populations, marine invertebrates thrive in the presence of potentially challenging microbial pathogens. However, the mechanisms underlying this resistance remain largely unexplored and promise to reveal novel strategies of microbial resistance. Here, we provide evidence that a mud-dwelling clam, Meretrix petechialis, synthesizes, stores, and secretes the antibiotic erythromycin. Liquid chromatography coupled with mass spectrometry, immunocytochemistry, fluorescence in situ hybridization, RNA interference, and enzyme-linked immunosorbent assay revealed that this potent macrolide antimicrobial, thought to be synthesized only by microorganisms, is produced by specific mucus-rich cells beneath the clam's mantle epithelium, which interfaces directly with the bacteria-rich environment. The antibacterial activity was confirmed by bacteriostatic assay. Genetic, ontogenetic, phylogenetic and genomic evidence, including genotypic segregation ratios in a family of full siblings, gene expression in clam larvae, phylogenetic tree, and synteny conservation in the related genome region further revealed that the genes responsible for erythromycin production are of animal origin. The detection of this antibiotic in another clam species showed that the production of this macrolide is not exclusive to M. petechialis and may be a common strategy among marine invertebrates. The finding of erythromycin production by a marine invertebrate offers a striking example of convergent evolution in secondary metabolite synthesis between the animal and bacterial domains. These findings open the possibility of engineering-animal tissues for the localized production of an antibacterial secondary metabolite.

Clinical nurses' legal roles, challenges, and responses to enabling legislation in China: a qualitative study.

BACKGROUND: With the surge in China's registered nurse population, defining their rights and responsibilities is crucial for ensuring the quality of medical services. However, challenges such as unresolved medical disputes and unclear duties persist due to the inadequacy and lack of transparency in current nursing laws and policies. This study evaluated nurses' legal awareness, legislative needs, and views on laws and policies affecting their practice, providing insights for future improvements in nursing legislation. METHODS: This study employed a descriptive qualitative approach, utilizing purposive sampling to select 16 nurses for in-depth exploration of their experiences. Semi-structured interviews were conducted between December 2023 and March 2024. Data analysis was performed using directed content analysis. RESULTS: A total of 16 nurses with various positions and titles were interviewed. The analysis revealed three main themes and nine sub-themes, focusing on existing issues in the nursing environment, legal training needs, and attitudes towards legislative empowerment. CONCLUSIONS: In China, there is a gap in legal knowledge and training among nurses. Enhancing their legal literacy is crucial for elevating their professional status and the quality of their work. Our findings underscore strong support for the enactment of the Nurse Act with a focus on practice conditions, rights protection, and career development. National authorities and experts must expedite this legislation to safeguard the rights of nurses, bolster their professional confidence.

Molecular cloning, tissue distribution, and pharmacologic function of melanocortin-3 receptor in common carp (Cyprinus carpio).

Melanocortin-3 receptor (MC3R) not only regulates energy homeostasis in animals, but also is an important regulator of inflammation. As one of the most widely farmed freshwater fish, common carp has attracted great interest for its feeding and inflammation regulation. In this study, we cloned the coding sequence (CDS) of common carp Mc3r (ccMc3r), examined its tissue expression profile, and investigated the function of this receptor in mediating downstream signaling pathways. The results showed that the CDS of ccMc3r was 975 bp, encoding a putative protein of 324 amino acids. Homology, phylogeny, and chromosomal synteny analyses revealed that ccMc3r is evolutionarily close to the orthologs of cyprinids. Quantitative real-time PCR (qPCR) indicated that ccMc3r was highly expressed in the brain and intestine. The luciferase reporter systems showed that four ligands, ACTH (1-24), α-MSH, ß-MSH, and NDP-MSH, were able to activate the cAMP and MAPK/ERK signaling pathways downstream of ccMc3r with different potencies. For the cAMP signaling pathway, ACTH (1-24) had the highest activation potency; while for the MAPK/ERK signaling pathway, ß-MSH had the greatest activation effect. In addition, we found that the four agonists were able to inhibit TNF-α-induced NF-κB signaling in approximately the same order of potency as cAMP signaling activation. This study may facilitate future studies on the role of Mc3r in common carp feed efficiency and immune regulation.

Cystatin C and eGFRCKD-EPI-CysC: novel biomarkers for renal impairment diagnosis and two-year progression-free survival in multiple myeloma.

To evaluate cystatin C (CysC) and estimation of glomerular filtration rate (GFR) calculated using the formula, CKD-EPI-CysC (eGFRCKD-EPI-CysC) for renal impairment diagnosis and predicting the prognosis of patients with multiple myeloma (MM). One hundred-fourteen patients with MM and 38 healthy individuals were recruited for the study. Data on clinical characteristics and renal function-related biochemical indicators were collected and analyzed. Patients with MM had increased levels of CysC (1.25 (0.97-2.31) vs. 0.84 (0.80-0.92), respectively, p < 0.001) and decreased levels of eGFRCKD-EPI-CysC (53.0 (24.4-81.1) vs. 97.2 (87.0-104.5), respectively, p < 0.001), compared with healthy individuals. There were significantly more patients with elevated CysC levels than with elevated sCr levels (64.9% vs. 41.2%, respectively, p < 0.001). The CKD-EPI-CysC formula detected more patients with eGFR < 60 ml/(min × 1.73 m2) than the CKD-EPI-sCr formula (52.63% vs. 37.72%, respectively, p < 0.001). Correlation analysis found that only CysC, eGFRCKD-EPI-CysC, and eGFRCKD-EPI-sCr-CysC strongly correlated with ß2-microglobulin in group ISS-I. Logistic regression analysis was used to screen CysC (OR = 1.495, 95% CI = 1.097-2.038, p = 0.011) and eGFRCKD-EPI-CysC (OR = 0.980, 95% CI = 0.967-0.993, p = 0.003) as independent prognostic indicators for 2-year-progression-free survival (PFS) of patients with MM. Receiver operating characteristic curve analysis found that CysC values >1.70 mg/L had 67.6% sensitivity and 65.2% specificity and eGFRCKD-EPI-CysC values <38.62 ml/(min × 1.73 m2) had 65.2% sensitivity and 67.6% specificity for 2-year PFS of patients with MM. In summary, CysC and eGFRCKD-EPI-CysC were more sensitive than sCr and eGFRCKD-EPI-sCr for predicting renal impairment in patients newly diagnosed with MM. Increased CysC and decreased eGFRCKD-EPI-CysC levels were effective predictors of 2-year PFS of patients with MM.

Epidemiology and Association Rules Analysis for Pulmonary Tuberculosis Cases with Extrapulmonary Tuberculosis from Age and Gender Perspective: A Large-Scale Retrospective Multicenter Observational Study in China.

Background: Tuberculosis (TB), a multisystemic disease with protean presentation, remains a major global health problem. Although concurrent pulmonary tuberculosis (PTB) and extrapulmonary tuberculosis (EPTB) cases are commonly observed clinically, knowledge regarding concurrent PTB-EPTB is limited. Here, a large-scale multicenter observational study conducted in China aimed to study the epidemiology of concurrent PTB-EPTB cases by diagnostically defining TB types and then implementing association rules analysis. Methods: The retrospective study was conducted at 21 hospitals in 15 provinces in China and included all inpatients with confirmed TB diagnoses admitted from Jan 2011 to Dec 2017. Association rules analysis was conducted for cases with concurrent PTB and various types of EPTB using the Apriori algorithm. Results: Evaluation of 438,979TB inpatients indicated PTB was the most commonly diagnosed (82.05%) followed by tuberculous pleurisy (23.62%). Concurrent PTB-EPTB was found in 129,422 cases (29.48%) of which tuberculous pleurisy was the most common concurrent EPTB type observed. The multivariable logistic regression models demonstrated that odds ratios of concurrent PTB-EPTB cases varied by gender and age group. For PTB cases with concurrent EPTB, the strongest association was found between PTB and concurrent bronchial tuberculosis (lift = 1.09). For EPTB cases with concurrent PTB, the strongest association was found between pharyngeal/laryngeal tuberculosis and concurrent PTB (lift = 1.11). Confidence and lift values of concurrent PTB-EPTB cases varied with gender and age. Conclusions: Numerous concurrent PTB-EPTB case types were observed, with confidence and lift values varying with gender and age. Clinicians should screen for concurrent PTB-EPTB in order to improve treatment outcomes.

Predictive models for sepsis in children with Staphylococcus aureus bloodstream infections: a retrospective cohort study.

BACKGROUND: The presence of Staphylococcus aureus in the bloodstream can lead to the development of sepsis; however, the severity and risk factors of the systemic inflammatory response to Staphylococcus aureus bloodstream infections were unclear. This study is aimed to build a model to predict the risk of sepsis in children with Staphylococcus aureus bloodstream infections. METHODS: A retrospective analysis of hospitalized pediatric patients diagnosed with Staphylococcus aureus bloodstream infections was performed between January 2013 and December 2019. Each patient was assessed using the pediatric version of the Sequential Organ Failure Assessment score (pSOFA) within 24 h of blood culture collection. A nomogram based on logistic regression models was constructed to predict the risk factors for sepsis in children with Staphylococcus aureus bloodstream infections. It was validated using the area under the receiver-operating characteristic curve (AUC). RESULTS: Of the 94 patients included in the study, 35 cases (37.2%) developed sepsis. The pSOFA scores ranged from 0 to 8, with 35 patients having a pSOFA score of ≥ 2. Six children (6.4%) died within 30 days, who were all from the sepsis group and had different pSOFA scores. The most common organs involved in sepsis in children with staphylococcal bloodstream infections were the neurologic system (68.6%), respiratory system (48.6%), and coagulation system (45.7%). Hospital-acquired infections (adjusted odds ratio [aOR], 3.0; 95% confidence interval [CI], 1.3-7.2), implanted catheters (aOR, 10.4; 95% CI, 3.8-28.4), procalcitonin level ≥ 1.7 ng/mL (aOR, 15.4; 95% CI, 2.7-87.1), and underlying diseases, especially gastrointestinal malformations (aOR, 14.0; 95% CI, 2.9-66.7) were associated with Staphylococcus aureus sepsis. However, methicillin-resistant Staphylococcus aureus infection was not a risk factor for sepsis. The nomogram had high predictive accuracy for the estimation of sepsis risk, with an AUC of 0.85. CONCLUSIONS: We developed a predictive model for sepsis in children with Staphylococcus aureus infection.

A new l-serine binding orphan SerBP affects indole synthesis in Pantoea ananatis.

Indole is traditionally known as a metabolite of l-tryptophan and now as an important signaling molecule in bacteria, however, the understanding of its upstream synthesis regulation is very limited. Pantoea ananatis YJ76, a predominant diazotrophic endophyte isolated from rice (Oryza sativa), can produce indole to regulate various physiological and biochemical behaviors. We constructed a mutant library of YJ76 using the mTn5 transposon insertion mutation method, from which an indole-deficient mutant was screened out. Via high-efficiency thermal asymmetric interlaced PCR (hiTAIL-PCR), the transposon was determined to be inserted in a gene (RefSeq: WP014605468.1) of unknown function that is highly conserved at the intraspecific level. Bioinformatics analysis implied that the protein (Protein ID: WP089517194.1) encoded by the mutant gene is most likely to be a new orphan substrate-binding protein (SBP) for amino acid ABC transporters. Amino acid supplement cultivation experiments and surface plasmon resonance revealed that the protein could bind to l-serine (KD = 6.149 × 10-5 M). Therefore, the SBP was named as SerBP. This is the first case that a SBP responds to l-serine ABC transports. As a precursor of indole synthesis, the transmembrane transported l-serine was directly correlated with indole signal production and the mutation of serBP gene weakened the resistance of YJ76 to antibiotics, alkali, heavy metals, and starvation. This study provided a new paradigm for exploring the upstream regulatory pathway for indole synthesis of bacteria.

Molecular cloning and functional characterization of melanocortin-3 receptor in grass carp (Ctenopharyngodon idella).

The melanocortin-3-receptor (MC3R) plays an important role in mammals' food intake and energy homeostasis. However, its physiological role in bony fishes, such as grass carp, has not been well understood. This study reports the molecular cloning, tissue distribution, and pharmacological characterization of grass carp melanocortin-3-receptor (ciMC3R). Phylogenetic and chromosomal synteny analyses indicated that ciMC3R was closest to cyprinid fishes in evolution. Quantitative PCR experiments revealed that the mRNA of ciMC3R was highly expressed in the brain of grass carp. The cytological function of ciMC3R was investigated by the co-transfection of pcDNA3.1-ciMC3R and the signal-pathway-specific luciferase into the HEK293T cells. Results revealed that the four agonists, α-MSH, ß-MSH, ACTH, and NDP-MSH, potentiate the activation of ciMC3R and further increase the production of cAMP and upregulate the MAPK/ERK signaling, respectively. Our study will provide basic data for exploring the physiological functions of grass carp MC3R, especially in energy homeostasis and food intake.

The interaction of MC3R and MC4R with MRAP2a in rainbow trout (Oncorhynchus mykiss).

Melanocortin 3 and 4 receptors are two important neural G protein-coupled receptors that regulate energy homeostasis in vertebrates. Melanocortin receptor accessory protein 2 (MRAP2) is also involved in the regulation of food intake and body weight as a variable regulator of melanocortin receptors. Rainbow trout (Oncorhynchus mykiss) is a valuable cold-water fish cultured worldwide. In the rainbow trout model, we cloned and identified mrap2a, a paralog of mrap2. Rainbow trout mrap2a consisted of a 690 bp ORF and was expected to encode a putative protein of 229 amino acids. The qPCR results showed that rainbow trout mrap2a was expressed at high levels in brain tissue similar to mc3r and mc4r. In addition, co-immunoprecipitation verified that MRAP2a interacts with MC3R and MC4R in vitro and that MRAP2a is involved in and regulates the constitutive activity and signaling of MC3R and MC4R. MRAP2a reduced constitutive and agonist-stimulated cAMP levels of MC3R; furthermore, MRAP2a increased constitutive ERK1/2 activation but reduced ligand-induced stimulation at high levels of expression. For MC4R, MRAP2a showed decreased cAMP basal activity but increased agonist-stimulated cAMP signaling and increased ACTH ligand sensitivity. However, MRAP2a failed to affect MC4R constitutive activity and agonist-induced ERK1/2 signaling. Undoubtedly, our study will have great significance for revealing the conserved role of MC4R and MC3R signaling in teleost fish, especially in cold-water fish growth and energy homeostasis.

NMDA receptor antagonists engender neuroprotection against gp120-induced cognitive dysfunction in rats through modulation of PKR activation, oxidative stress, ER stress and IRE1α signal pathway.

It is widely accepted that the surface glycoprotein (gp120) of human immunodeficiency virus-1 (HIV-1) plays an important role in HIV-1-induced nerve damage and pathogenesis of HIV-associated neurocognitive disorders (HAND). Our previous work has demonstrated that gp120 enhanced excitatory postsynaptic currents (EPSCs) mediated by N-methyl-d-aspartate receptors (NMDARs) and caused neural injury. However, the relationship between gp120, NMDARs and HAND is still unclear. Several lines of evidence indicate that double-stranded RNA-activated protein kinase (PKR) is involved in NMDA-induced cerebral ischaemia and retinal damage, but because its role in neuropathology is still debated, we examined whether PKR links oxidative stress and endoplasmic reticulum (ER) stress to exert a deleterious role in the rat model with gp120-induced dementia. In this study, we found that NMDAR antagonist memantine or PKR inhibitor C16 improved gp120-induced learning and memory impairment and inhibited gp120-induced PKR activity. Furthermore, memantine or C16 was found to attenuate gp120-induced neuroinflammation, oxidative stress, ER stress and its downstream IRE1α/JNK pathway. Additionally, memantine or C16 evidently inhibited apoptotic pathways by reducing the Bax and caspase-3, -8, -9 expressions and increasing Bcl-2 expression. So the NMDA receptor antagonists could alleviate HIV/gp120-induced dementia in the rat model by altering PKR level. In conclusion, this study demonstrates that NMDARs play a key role in HIV/gp120-induced hippocampal damage and cognitive dysfunction through PKR-mediated oxidative stress, ER stress, and IRE1α/JNK signalling pathway in rats, and implicating PKR inhibitors could provide a novel neuroprotective strategy for HAND via inhibiting ER stress and its downstream IRE1α signalling pathway.

A Facile machine learning multi-classification model for Streptococcus agalactiae clonal complexes.

BACKGROUND: The clinical significance of group B streptococcus (GBS) was different among different clonal complexes (CCs), accurate strain typing of GBS would facilitate clinical prognostic evaluation, epidemiological investigation and infection control. The aim of this study was to construct a practical and facile CCs prediction model for S. agalactiae. METHODS: A total of 325 non-duplicated GBS strains were collected from clinical samples in Xinhua Hospital, Shanghai, China. Multilocus sequence typing (MLST) method was used for molecular classification, the results were analyzed to derive CCs by Bionumeric 8.0 software. Antibiotic susceptibility test was performed using Vitek-2 Compact system combined with K-B method. Multiplex PCR method was used for serotype identification. A total of 45 virulence genes associated with adhesion, invasion, immune evasion were detected by PCR method and electrophoresis. Three types of features, including antibiotic susceptibility (A), serotypes (S) and virulence genes (V) tests, and XGBoost algorithm was established to develop multi-class CCs identification models. The performance of proposed models was evaluated by the receiver operating characteristic curve (ROC). RESULTS: The 325 GBS were divided into 47 STs, and then calculated into 7 major CCs, including CC1, CC10, CC12, CC17, CC19, CC23, CC24. A total of 18 features in three kinds of tests (A, S, V) were significantly different from each CC. The model based on all the features (S&A&V) performed best with AUC 0.9536. The model based on serotype and antibiotic resistance (S&A) only enrolled 5 weighed features, performed well in predicting CCs with mean AUC 0.9212, and had no statistical difference in predicting CC10, CC12, CC17, CC19, CC23 and CC24 when compared with S&A&V model (all p > 0.05). CONCLUSIONS: The S&A model requires least parameters while maintaining a high accuracy and predictive power of CCs prediction. The established model could be used as a promising tool to classify the GBS molecular types, and suggests a substantive improvement in clinical application and epidemiology surveillance in GBS phenotyping.

The Association of Peripheral T Lymphocyte Subsets Disseminated Infection by Mycobacterium Tuberculosis in HIV-Negative Patients: A Retrospective Observational Study.

Background and Objective: This study was performed to investigate the association of peripheral T lymphocyte subsets with disseminated infection (DI) by Mycobacterium tuberculosis (MTB) in HIV-negative patients. Methods and Materials: The study included 587 HIV-negative tuberculosis (TB) patients. Results: In TB patients with DI, the proportion of CD4+ T cells decreased, the proportion of CD8+ T cells increased, and the ratio of CD4+/CD8+ T cells decreased. According to univariate analysis, smoking, alcohol consumption, rifampicin-resistance, retreatment, and high sputum bacterial load were linked to lower likelihood of developing MTB dissemination. Multivariate analysis indicated that after adjustment for alcohol use, smoking, retreatment, smear, culture, rifampicin-resistance, and CD4+/CD8+, the proportion of CD8+ T cells (but not CD4+ T cells) was independently and positively associated with the prevalence of DI in HIV-negative pulmonary TB (PTB) patients. Conclusions: Examining T lymphocyte subsets is of great value for evaluating the immune function of HIV-negative TB patients, and an increase in the CD8+ T cell proportion may be a critical clue regarding the cause of DI in such patients.

The prevalence and risks of major comorbidities among inpatients with pulmonary tuberculosis in China from a gender and age perspective: a large-scale multicenter observational study.

In clinical practice, PTB patients have concurrent many types of comorbidities such as pneumonia, liver disorder, diabetes mellitus, hematological disorder, and malnutrition. Detecting and treating specific comorbidities and preventing their development are important for PTB patients. However, the prevalence of most comorbid conditions in patients with PTB is not well described. We conducted a large-scale, multicenter, observational study to elucidate and illustrate the prevalence rates of major comorbidities in inpatients at 21 hospitals in China. The 19 specific comorbidities were selected for analysis in this patient cohort, and stratified the inpatient cohort according to age and gender. A total of 355,929 PTB inpatients were included, with a male:female ratio of 1.98 and the proportion of ≥ 65 years PTB inpatients was the most. Approximately 70% of PTB inpatients had at least one defined type of comorbidity. The prevalence of 19 specific comorbidities in inpatients with PTB was analyzed, with pneumonia being the most common comorbidity. The prevalence of most comorbidities was higher in males with PTB except thyroid disorders, mental health disorders, etc. The prevalence of defined most comorbidities in patients with PTB tended to increase with increasing age, although some specific comorbidities tended to increase initially then decrease with increasing age. Our study describes multiple clinically important comorbidities among PTB inpatients, and their prevalence between different gender and age groups. The results will enhance the clinical aptitude of physicians who treat patients with PTB to recognize, diagnose, and treat PTB comorbidities early.

Green synthesis of orange emissive carbon dots for the detection of Ag+and their application via solid-phase sensing and security ink.

Fluorescent carbon dots (CDs) have attracted considerable interest due to their superior optical properties and facile preparation. In this work, O-phenylenediamine and melamine were used as precursors for the one-step hydrothermal synthesis of novel orange emissive CDs (O-CDs) in an aqueous solution. The fluorescence intensity (580 nm) of the O-CDs exhibited a good linear relationship with Ag+in the range of 0.0-50.0µM with the detection limit of 0.289µM. Moreover, the O-CDs were successfully used to determine Ag+in biological samples (Hela cells) because of their low cytotoxicity, and good biocompatibility. Besides, the O-CDs-doped solid-phase detection materials (test paper and hydrogel) were employed to monitor Ag+qualitatively and quantitatively, indicated that the O-CDs had a great capacity for the detection of Ag+in biological and environmental areas. Based on their extraordinary fluorescence property, the O-CDs could also be used as security ink. Overall, based on their excellent fluorescent performance, the CDs in this study have significant potential for practical application toward solid-phase sensing and security ink.

Polarity Umpolung Strategy for the Radical Alkylation of Alkenes.

Free radical mediated alkylation of alkenes is a challenging and largely unmet goal. Disclosed here is a conceptually novel "polarity umpolung" strategy for radical alkylation of alkenes using a portfolio of easily accessed, difunctional alkylating reagents. This strategy is achieved by substituting inherently nucleophilic alkyl radicals with electrophilic sulfone-bearing surrogates, thus inverting the usual mode of reactivity. Along with alkylation, either an heteroaryl or oximino group is concurrently incorporated into the alkenes by a consecutive docking and migration process, leading to valuable products. The reaction displays a broad functional-group tolerance under mild reaction conditions. The protocol opens new vistas for the late-stage modification of complex natural products and drug molecules containing alkene moieties.

Mating-type loci of Ustilago esculenta are essential for mating and development.

Ustilago esculenta is closely related to the smut fungus Ustilago maydis and, in an endophytic-like life in the plant Zizania latifolia, only infects host stems and causes swollen stems to form edible galls called Jiaobai in China. In order to study its different modes of invasion and sites of symptom development from other smut fungi at the molecular level, we first characterized the a and b mating-type loci of U. esculenta. The a loci contained three a mating-type alleles, encoding two pheromones and one pheromone receptor per allele. The pheromone/receptor system controlled the conjugation formation, the initial step of mating, in which each pheromone was specific for recognition by only one mating partner. In addition, there are at least three b alleles identified in U. esculenta, encoding two subunits of heterodimeric homeodomain transcription factors bE and bW, responsible for hyphal growth and invasiveness. Hyphal formation, elongation and invasion after mating of two compatible partners occurred, only when a heterodimer complex was formed by the bE and bW proteins derived from different alleles. We also demonstrated that even with only one paired pheromone-pheromone receptor, the active b locus heterodimer triggered hyphal growth and infection.

Molecular Dynamics Simulation of Heat Transport through Solid-Liquid Interface during Argon Droplet Evaporation on Heated Substrates.

This paper presents a series of molecular dynamics simulations of the evaporating process of an argon droplet on heated substrates and the energy transport mechanism through the solid-liquid interface. Results indicate that the mass density through the liquid-vapor interface decreases sharply when the evaporation is in the steady state. Meanwhile, there is an adsorption layer in the form of clusters at the solid-liquid interface, which has a higher mass density than the droplet inside. Furthermore, the wetting property of the solid substrate is related to the system's initial temperature and the solid-liquid potential energy parameter. The contact angle decreases with the increase of initial temperature and solid-liquid potential energy parameter. During the accelerated evaporation process, small part of energy transports into the liquid in the perpendicular direction to the solid-liquid interface and most of the energy transports along the parallel direction to the solid-liquid interface in the adsorption layer to the three-phase contact line. The heat-transfer process from the solid substrate to the droplet inside is hindered by the Kapitza resistance at the solid-liquid interface, no matter the solid substrate is hydrophilic or hydrophobic. Meanwhile, the Kapitza resistance gradually increases with the increase of the initial temperature and decreases with the increase of the solid-liquid energy parameter.

Gill symbionts of the cold-seep mussel Bathymodiolus platifrons: Composition, environmental dependency and immune control.

Deep-sea Bathymodiolus mussels depend on the organic carbon supplied by symbionts inside their gills. In this study, optimized methods of quantitative real-time PCR and fluorescence in situ hybridization targeted to both mRNA and 16S rRNA were used to investigate the gill symbionts of the cold-seep mussel Bathymodiolus platifrons, including species composition, environmental dependency and immune control by the host. Our results showed that methanotrophs were the major symbiotic bacteria in the gills of B. platifrons, while thiotrophs were scarce. In the mussels freshly collected from the deep sea, methanotrophs were housed in bacteriocytes in a unique circular pattern, and a lysosome-related gene (VAMP) encoding a vesicle-associated membrane protein was expressed at a high level and presented exactly where the methanotrophs occurred. After the mussels were reared for three months in aquaria without methane supply, the abundance of methanotrophs decreased significantly and their circle-shaped distribution pattern disappeared; in addition, the expression of VAMP decreased significantly. These results suggest that the symbiosis between B. platifrons and methanotrophs is influenced by the environment and that the lysosomal system plays an important immune role in controlling the abundance of endosymbionts in host. This study provides a reliable method for investigating symbionts in deep-sea mussels and enriches the knowledge about symbionts in B. platifrons.

Dynamic immune and metabolism response of clam Meretrix petechialis to Vibrio challenge revealed by a time series of transcriptome analysis.

Meretrix petechialis is an important commercial aquaculture species in China. During the clam culture period, mass mortality events often occurred due to the Vibrio infection. In this paper, M. petechialis were challenged with Vibrio parahaemolyticus immersion to simulate a natural infection, and the infection process were divided into four phases including latency, prodrome, onset and recovery phases based on the clam mortality data. Then, the dynamic response of clams to Vibrio infection at different infection phases were investigated by transcriptome analysis. A total of 38,067 differentially expressed genes (DEGs) were identified at different infection phases. DEG annotations showed that immune-related and metabolism-related signaling pathways were enriched, indicating that immune defense and metabolism process play key roles during bacterial infection. Three kinds of expression pattern were classified by cluster analysis, including U-shape, L-shape and inverted V-shape. Anabolism and cellular growth proliferation related signaling pathways were repressed (long-lasting or transient) during bacterial infection. However, the immune related signaling pathways with different immune functions showed induction expression or repression expression against bacterial infection, which indicated that immune system take different strategies against bacterial infection. Furthermore, some signaling pathways such as PI3K-Akt signaling pathway both involved in immune defense and cell metabolism. This study provides a sight that the dynamic immunity and metabolic responses may be integrated to improve the host survival and shift more energy for immune defense.

p38 MAPK is involved in the immune response to pathogenic Vibrio in the clam Meretrix petechialis.

p38 mitogen-activated protein kinases (MAPKs) are involved in the response to various extracellular stimuli via regulating gene expression. In the present study, a p38 MAPK gene (MpP38) was identified from the clam Meretrix petechialis. The full-length cDNA of MpP38 measures 1,720 bp, consisting of a 134-bp 5'-UTR, a 1,095-bp ORF and a 491-bp 3'-UTR. Both the mRNA and protein expression levels of MpP38 increased after Vibrio challenge, implying that MpP38 is involved in clam immunity. Based on our previous study, a transcription factor activated by p38 MAPK, i.e. microphthalmia-associated transcription factor (MITF), participated in clam immunity by regulating the expression of phenoloxidase (PO). Coupled with other related reports, the mechanism underlying the involvement of MpP38 in clam immunity is most likely that pathogen stimuli induce the phosphorylation of p38 MAPK and thus activate MITF to regulate the expression of the immune-related gene PO. The results obtained in this study support this mechanism. First, we found that the MpP38 phosphorylation level increased in response to Vibrio challenge. Second, as revealed by a yeast two-hybrid assay, there was a direct interaction between MpP38 and MITF. Meanwhile, inhibiting the phosphorylation of MpP38 decreased the phosphorylation level of MpMITF, implying that MpP38 phosphorylation is required for MpMITF activation. Additionally, our results showed that there was a regulatory relationship between MpP38 phosphorylation level and PO expression level. With increased MpP38 phosphorylation level, the PO expression level was also increased after Vibrio challenge; when MpP38 phosphorylation was inhibited, the PO expression level was significantly decreased. This study describes the immune function of p38 MAPK in the clam for the first time and analyses its potential underlying mechanism, which will help to elucidate the immune mechanism in the clam M. petechialis.