Dysregulation of the Gut Microbiota Contributes to Sevoflurane-Induced Cognitive Dysfunction in Aged Mice by Activating the NLRP3 Inflammasome.

Postoperative cognitive dysfunction (POCD), a common complication in elderly patients after surgery, seriously affects patients' quality of life. Long-term or repeated inhalation of sevoflurane can cause neuroinflammation, which is a risk factor for POCD. However, the underlying mechanism needs to be further explored. Recent research had revealed a correlation between neurological disorders and changes in the gut microbiota. Dysfunction of the gut microbiota is involved in the occurrence and development of central nervous system diseases. Here, we found that cognitive dysfunction in aged mice induced by sevoflurane exposure (3%, 2 hours daily, for 3 days) was related to gut microbiota dysbiosis, while probiotics improved cognitive function by alleviating dysbiosis. Sevoflurane caused a significant decrease in the abundance of Akkermansia (P<0.05), while probiotics restored the abundance of Akkermansia. Compared to those in the control group, sevoflurane significantly increased the expression of NLRP3 inflammasome-associated proteins in the gut and brain in the sevoflurane-exposed group, thus causing neuroinflammation and synaptic damage, which probiotics can mitigate (con vs. sev, P < 0.01; p+sev vs. sev, P < 0.05). In conclusion, for the first time, our study revealed that dysbiosis of the gut microbiota caused by sevoflurane anesthesia contributes to the NLRP3 inflammasome-mediated neuroinflammation and cognitive dysfunction from the perspective of the gut-brain axis. Perhaps postoperative cognitive impairment in elderly patients can be alleviated or even prevented by regulating the gut microbiota. This study provides new insights and methods for the prevention and treatment of cognitive impairment induced by sevoflurane.

Mitochondrial quality control alterations and placenta-related disorders.

Mitochondria are ubiquitous in eukaryotic cells. Normal maintenance of function is the premise and basis for various physiological activities. Mitochondrial dysfunction is commonly observed in a wide range of pathological conditions, such as neurodegenerative, metabolic, cardiovascular, and various diseases related to foetal growth and development. The placenta is a highly energy-dependent organ that acts as an intermediary between the mother and foetus and functions to maintain foetal growth and development. Recent studies have demonstrated that mitochondrial dysfunction is associated with placental disorders. Defects in mitochondrial quality control mechanisms may lead to preeclampsia and foetal growth restriction. In this review, we address the quality control mechanisms of mitochondria and the relevant pathologies of mitochondrial dysfunction in placenta-related diseases, such as preeclampsia and foetal growth restriction. This review also investigates the relation between mitochondrial dysfunction and placental disorders.

The effects of Eisenia fetida and Metaphire guillelmi on the soil micro-food web in a microcosm experiment.

Numerous studies have shown that the function of earthworms may depend on their ecotype and density, which affects how they impact soil microbial and nematode communities. However, it is unclear how different earthworm species and densities alter the composition of soil microbial and nematode communities and how these modifications impact the soil micro-food web. The structural equation model (SEM) is a more accurate tool for identifying the intricate relationships between various trophic levels in the soil micro-food webs than the widely used bivariate data analysis. In order to ascertain the effects of earthworm species, including epigeic earthworm Eisenia fetida and anecic earthworm Metaphire guillelmi, as well as varying densities on the composition of main microbial groups, soil nematodes and their relationships, a microcosm experiment was conducted in a greenhouse. After nine weeks of observation, compared with the control treatments, Eisenia fetida increased the biomasses of total microorganism and bacteria, whereas Metaphire guillelmi decreased the biomasses of total microorganism, bacteria, and gram-positive bacteria, but showed an increase in AMF biomass. Additionally, both two earthworm species decreased the abundance of total soil nematode, bacterivores, and omnivore-predators, which is in contrast with the control treatments. The SEM results indicated that the addition of Eisenia fetida at different densities had indirect negative effects on the abundance of omnivore-predators, as it significantly increased the content of soil organic carbon, ammonium nitrogen, and nitrate nitrogen. The bottom-up effects were found to be the dominant forces, which promoted bacterial-dominated decomposition channels. The addition of Metaphire guillelmi with different density had direct negative impact on bacterivores and fungivores. Moreover, it had indirect negative effects on omnivore-predators by altering the soil properties. The dominant forces were still the bottom-up effects. Our study suggests that different earthworm species have distinct mechanisms that affect the soil micro-food web in different ways.

Adaptation of protein phosphatases in Oryza sativa and Cucumis sativus to microcystins.

Microcystins (MCs) in irrigation water could inhibit crop growth and yield. Protein phosphatases (PPs) play an important role in regulating physiological mechanisms in plants to adapt abiotic stresses. To clarify the adaptation mechanism in plants to MCs stress, we compared PPs in rice and cucumber leaves by analyzing PPs total activity, protein phosphatase-2A (PP2A) activity and expression, as well as related growth and gas exchange parameters. After 7-day exposure of MCs (5 ~ 100 µg/L) and 7-day recovery without MCs, rice showed higher tolerance to MCs by analyzing dry weight and gas exchange parameters. Both crops may regulate PPs activity to adapt MCs stress by increasing the expression of genes encoding PPs. Among them, PP2A activity in two crops showed more sensitivity to MCs than total PPs activity. In addition, the higher expressions of PP2A catalytic and regulatory subunits and lower decrease PP2A activity were observed in rice leaves compared to cucumber. All results suggest that the expression levels of PP2A subunits could play a role in maintaining the activity of PP2A to regulating plant tolerance to MCs stress.

Lower grip strength and insufficient physical activity can increase depressive symptoms among middle-aged and older European adults: a longitudinal study.

OBJECTIVES: The present study aimed to identify the gender-specific trajectories of grip strength using group-based trajectories, explore the interaction between grip strength and physical activity on depression, and investigate the association of physical activity with the change in depression by different grip strength groups among middle-aged and older European adults. METHODS: A total of 14,098 participants aged 50 years or older from the Survey of Health, Ageing and Retirement in Europe 2007-2019 were included in this study. Group-based trajectory modeling was used to identify the low, middle and high group of grip strength by gender. Generalized estimated equations were fitted to analyze the interaction effect. The data of wave 2-wave 5 and wave 2-wave 7 were chosen to conduct sensitivity analyses. RESULTS: Significant interactions between grip strength group and physical inactivity were found (x2 interaction = 11.16, P = 0.004). Significant interactions between physical inactivity and time on depression were identified in low (x2 interaction = 27.83, P < 0.001) and moderate (x2 interaction = 23.67, P < 0.001) grip strength, but a similar result was not found in high grip strength (x2 interaction = 4.39, P = 0.495). Participants in the physical inactivity group had higher depression scores in the low and moderate grip strength groups. Sensitivity analyses yield almost similar results. CONCLUSIONS: Grip strength and physical inactivity interact with depression. Lower grip strength and insufficient physical activity can increase depressive symptoms. People with lower grip strength and physical inactivity should pay special attention to the prevention of depression.

A Modified Microscopic-Endoscopic Bilateral Transseptal Approach for Pituitary Adenomas: Comparisons of Nasal Outcome and Quality of Life Using the Microscopic Transnasal Approach.

OBJECTIVES: In this study, we introduced a novel modified microscopic-endoscopic bilateral transseptal approach for pituitary adenoma resection to minimize surgery-related nasal injury. We also retrospectively compared comprehensive nasal outcomes and quality of life between the microscopic transnasal approaches. METHODS: Patients with pituitary adenomas who underwent modified microscopic-endoscopic bilateral transseptal or microscopic transnasal approaches were assessed for olfactory function and quality of life using the Sniffin' Sticks test, the Sino-Nasal Outcome Test-22 (SNOT-22), the SF-36, the anterior skull base (ASK) nasal inventory, and the subjective visual analog scale (VAS) before and 1 and 3 months after surgery. A nasal endoscopy procedure was also performed to evaluate structure abnormalities at 1 and 3 months after surgery. RESULTS: Fifty-eight patients who underwent either modified microscopic-endoscopic bilateral transseptal (35 patients) or microscopic transnasal (23 patients) surgery were consecutively enrolled. Patients who underwent either transnasal approach experienced similar surgical complications, except for intraoperative cerebrospinal fluid leakage (43.5% vs 14.3% for modified microscopic-endoscopic bilateral transseptal or microscopic transnasal approach, respectively; p = 0.013). Patients who underwent the two approaches fully recovered according to the SF-36, SNOT-22, VAS, and Sniffin' Sticks surveys, but not ASK scores, 3 months post-operatively. There was no significant difference in nasal endoscopy outcome at 3 months follow-up between the two approaches. CONCLUSIONS: The modified microscopic-endoscopic bilateral transseptal approach showed largely similar nasal mucosa protective outcomes to those of the microscopic transnasal approach for pituitary adenoma surgery. After pituitary adenoma resection using the modified approach, patients' postoperative olfactory function, nasal structure, and quality of life can be restored to preoperative status within 3 months.

MiR-186-5p Dysregulation Leads to Depression-like Behavior by De-repressing SERPINF1 in Hippocampus.

Diagnosis of major depressive disorder (MDD) is perplexing due to its multifactorial etiologies. Here, we isolated exosomes from the peripheral blood of MDD patients and healthy control subjects for mass spectrometry-based label-free quantitative proteomics. We identified that SERPINF1 is significantly diminished in the peripheral blood-derived exosomes of MDD patients compared to the healthy control subjects. Through RNA immunoprecipitation and luciferase reporter assays, we validated that SERPINF1 is a target of miR-186-5p that is upregulated in MDD patients' blood. In vivo studies in the chronic unpredictable mild stress (CUMS) mice further demonstrated that SERPINF1 in hippocampus is suppressed by miR-186-5p. Inhibiting the microRNA significantly restores the hippocampal SERPINF1 mRNA and protein expression, and ameliorates the depressive-like behaviors including sucrose preference and extended immobility time in the forced swim test. Instead, overexpressing miR-186-5p through tail intravenous injection of the mimics molecularly and behaviorally phenocopies the CUMS mice in wild-type mice. Our results indicate that the exosomal SERPINF1 in peripheral blood could serve as a reliable biomarker indicating MDD development, and miR-186-5p is a potential therapeutic target for the disease.

Long Noncoding RNA LINC00899/miR-944/ESR1 Axis Regulates Cervical Cancer Cell Proliferation, Migration, and Invasion.

Cervical cancer (CC) is a common malignancy in women. Long noncoding RNA LINC00899 plays a role in cancer, but its effects in CC are unknown. Our experiment aims to investigate the specific effects of LINC00899 in CC. LINC00899 was lowly expressed in CC tissues and cells, and overexpressed LINC0089 inhibited the viability, proliferation, migration, and invasion of CC cells, whereas silencing of LINC00899 had the opposite effect. There is a targeting relationship between LINC0089 and miR-944. It was found that miR-944 could competitively bind with LINC00899, and LINC00899 in turn, could downregulate expression of miR-944. Moreover, estrogen receptor 1 (ESR1) was the target gene of miR-944. Overexpressed miR-944 inhibited ESR1 expression, yet enhanced the migration and invasion of CC cells and promoted the expression levels of N-cadherin and Vimentin while inhibiting the expression of E-cadherin. However, overexpressed ESR1 reversed the effect of miR-944 overexpression on CC cells. LINC00899/miR-944/ESR1 axis regulates the proliferation, migration, and invasion of CC cells by regulating the expression levels of related proteins.

Differential circular RNA expression profiles in umbilical cord blood exosomes from preeclampsia patients.

BACKGROUND: Exosomal circular RNAs (circRNAs) are emerging as important regulators of physiological development and disease pathogenesis. However, the roles of exosomal circRNAs from umbilical cord blood in preeclampsia (PE) occurrence remains poorly understood. METHODS: We used microarray technology to establish the differential circRNA expression profiles in umbilical cord blood exosomes from PE patients compared with normal controls. Bioinformatics analysis was conducted to further predict the potential effects of the differentially expressed circRNAs and their interactions with miRNAs. RESULTS: According to the microarray data, we identified 143 significantly up-regulated circRNAs and 161 significantly down-regulated circRNAs in umbilical cord blood exosomes of PE patients compared with controls. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathway analyses showed that circRNA parental genes involved in the regulation of metabolic process, trophoblast growth and invasion were significantly enriched, which play important roles in PE development. Moreover, pathway network was constructed to reveal the key pathways in PE, such as PI3K-Akt signaling pathway. Further circRNA/miRNA interactions analysis demonstrated that most exosomal circRNAs had miRNA binding sites, and some miRNAs were associated with PE. CONCLUSIONS: Our results highlight the importance of exosomal circRNAs in the pathogenesis of PE and lay a foundation for extensive studies on the role of exosomal circRNAs in PE development.

Quality of Life in Patients with Acromegaly before and after Transsphenoidal Surgical Resection.

OBJECTIVE: We aimed to determine the perioperative changes in the quality of life (QoL) in patients with acromegaly and to reveal the relationship between biochemical indicators and quality of life change after tumor resection. METHODS: Patients with acromegaly were enrolled from a tertiary pituitary center. SF-36 scale and AcroQoL scale were used to determine the QoL before and after surgery. We analyzed changes in QoL using a generalized linear model for repeated measurements. We compared the changes in QoL among three groups (remission, active, and discordant group) based on postoperative growth hormone (GH) and insulin-like growth factor-1. RESULTS: 151 patients (75 males and 76 females) diagnosed with acromegaly were included. The average age was 43.9 ± 12.3 years. The median total SF-36 scale was 65.3% (IQR: 63.2%-69.2%). Overall AcroQoL score at baseline was 59.1% (IQR: 51.8%-71.8%). Nadir GH levels (coefficient -0.08, p=0.047), T3 levels (coefficient 2.8, p=0.001), and testosterone levels (coefficient -0.20, p=0.033) in males were independent predictive factors of the total SF-36 score. During the follow-up, the median overall SF-36 score increased to 66.1% at 3 months and 75.3% at 6 months (p < 0.001) after surgery. The median overall AcroQoL score increased to 74.5% at 3 months and 77.3% at 6 months (p < 0.001) after surgery. At 6-month follow-up, median scores were still less than 70% in appearance, vitality, and mental health dimensions. The QoL after surgery were similar among the three groups, although higher GH and more preoperative somatostatin analogs usage were observed in the active group. CONCLUSION: In conclusion, acromegalic patients were associated with low QoL, which could be reversed partially by surgery. The improvement was independent of the endocrine remission. Appearance, vitality, and mental health were three major aspects that warrant further attention from physicians and caregivers after surgery.

Responses of antioxidative enzymes and gene expression in Oryza sativa L and Cucumis sativus L seedlings to microcystins stress.

Microcystins (MCs) have become an important global environmental issue, causing oxidative stress, which is an important toxic mechanism for MCs in plants. However, the regulating mechanism of antioxidative enzymes in plants in adapting to MCs stress remains unclear. We studied the dynamic effects of MCs at different concentrations (5, 10, 50 and 100 µg/L) in rice and cucumber seedlings on relative growth rate (RGR), and reactive oxygen species and malondialdehyde (MDA) content, and antioxidative enzyme activities, during a stress period (MCs exposed for 1, 3, 5 and 7 d) and recovery period (7 d). During the stress period, MCs at 5 µg/L inhibited RGR in cucumber and promoted RGR in rice. The contents of superoxide anion (O2·-), hydrogen peroxide (H2O2) and MDA increased and RGR declined in both crops with time and intensity of MCs stress. For cucumber, all these parameters responded earlier to MCs stress, and O2·-, MDA and RGR were more responsive to MCs stress than in rice. Moreover, catalase (CAT) and peroxidase (POD), and the relative expressions of CAT genes increased in both crops at 5-100 µg/L MCs, whereas relative expression of POD genes increased only in cucumber. Diversely, superoxide dismutase (SOD) response to MCs in cucumber leaves was later than for rice. MCs at 100 µg/L decreased the relative expression of SOD genes in cucumber but did not change SOD activity. During the recovery period, all the above indicators in both crops were higher than the control and lower than in the stress period. Conversely, RGR was lower than in the control and higher than in the stress period, except for cucumber which was lower, and MDA content higher than the stress period at 100 µg/L MCs. Overall, these results indicated that cucumber was more sensitive to MCs than rice, and SOD, CAT and POD play an important role in plant response to MCs stress.

miR-30-5p-mediated ferroptosis of trophoblasts is implicated in the pathogenesis of preeclampsia.

Oxidative stress is a major cause of adverse outcomes in preeclampsia (PE). Ferroptosis, i.e. programmed cell death from iron-dependent lipid peroxidation, likely mediates PE pathogenesis. We evaluated specific markers for ferroptosis in normal and PE placental tissues, using in vitro (trophoblasts) and in vivo (rat) models. Increase in malondialdehyde content and total Fe2+ along with reduced the glutathione content and glutathione peroxidase activity was observed in PE placenta. While the trophoblasts experienced death under hypoxia, inhibitors of ferroptosis, apoptosis, autophagy, and necrosis increased the cell viability. Microarrays, bioinformatic analysis, and luciferase reporter assay revealed that upregulation of miR-30b-5p in PE models plays a pivotal role in ferroptosis, by downregulating Cys2/glutamate antiporter and PAX3 and decreasing ferroportin 1 (an iron exporter) expression, resulting in decreased GSH and increased labile Fe2+. Inhibition of miR-30b-5p expression and supplementation with ferroptosis inhibitors attenuated the PE symptoms in rat models, making miR-30b-5p a potential therapeutic target for PE.

[Effect of Ozonation on Microorganism in the Biological Activated Carbon and Disinfection By-Products in the Effluent].

This study was carried out in the ozone (O3) and biological activated carbon (BAC) section of a drinking water plant to investigate the effects of O3 on microbial and effluent disinfection by-products (DBPs) in BAC during drinking water treatment. The water quality, dissolved organic matter (DOM) characteristics, microbial activity, and DBPs formation at different O3 concentrations were analyzed. Results showed that the effect of O3 on microorganisms is mainly that it increased the utilization efficiency of DOM. However, excessive O3 increased the amount of organic matter such as protein and microbial metabolites (SMPs) in the effluent. When the O3 concentration increased from 0 mg·L-1 to 2.0 mg·L-1, the survival rate of microorganisms in the BAC decreased from 95.10% to 62.60%. However, since O3 transforms organic matter into a biodegradable substance, we found that microbial activity increased by 62.52% and that the biofiltration of the BAC was enhanced. When the O3 concentration was further increased to 4.0 mg·L-1, the microbial survival rate decreased to 49.9% and the protein and SMPs produced by the microorganisms increased. This resulted in an increased formation of carbon-containing DBPs (C-DBPs) and nitrogen-containing DBPs (N-DBPs) by 41.93% and 7.18%, respectively. In summary, an appropriate dosage of O3 was beneficial for removing DOM by O3-BAC, but we found that an excessive O3 concentration caused the formation of new DBPs precursors.

Effects of Earthworms and Agricultural Plant Species on the Soil Nematode Community in a Microcosm Experiment.

Both earthworms and plants may affect the soil nematode community. However, the effects of earthworms and plant species interactions on soil nematode community are poorly understood. We explored how an epigeic earthworm Eisenia fetida affects the soil nematode community in systems with three representative plants (wheat, cotton and cabbage) which were grown in pots with or without added earthworms under greenhouse conditions. Earthworm presence decreased the abundance of total nematode and all four nematode trophic groups, except for the fungivore and predator/omnivore nematodes in wheat systems, but increased the genus richness of nematode in all treatments. Due to plant identity and different root exudates, plants had significant effects on soil nematode abundance. Compared with the no plant and without earthworm treatment, wheat and cabbage had the higher stimulation of the abundance of total nematode, bacterivores and fungivores, and cotton had the higher stimulation of the abundance of fungivores and predators-omnivores; whereas earthworm presence mostly weakened the stimulation effects of plant species on soil nematode abundance which indicated earthworms had the enhanced effects in the presence of plants. The interaction affected soil nematode abundance (total nematodes, bacterivore, fungivore and omnivore-predators) and community diversity indices (diversity index H', evenness index J', community maturity index ∑MI, Simpson dominance index λ and nematode channel ratio NCR). Principal component analysis showed that plant species affected soil nematode community composition. Redundancy analysis indicated plant species and biomass accounted for 41.60% and 34.13% of the variation in soil nematode community structure, respectively; while earthworms explained only 6.13%. Overall, current study suggest that earthworm could inhibit nematode abundance; whereas, plants have exerted greater influences on nematode community structure than earthworm presence due to their species-specific effects on different trophic groups of nematodes.

miR-362-3p regulates cell proliferation, migration and invasion of trophoblastic cells under hypoxia through targeting Pax3.

Preeclampsia (PE), a common obstetrical disorder, is one of the leading causes of pregnancy associated death. PE is closely linked with impaired migration and invasion ability of trophoblastic cells. miR-362-3p recently received our particular attention due not only to its aberrant expression in the placentas of patients with PE, but also to its important roles in regulating migration and invasion of various cells. This study was thus conducted to investigate the roles of miR-362-3p in PE and the related mechanism. The expression of miR-362-3p and Pax3 was examined in placentas of patients with PE and in normal placentas. HTR8/SVneo cells were cultured under hypoxia and transfected with miR-362-3p mimics, miR-362-3p inhibitors or Pax3 over-expression vectors. Results showed up-regulation of miR-362-3p but down-regulation of Pax3 in placentas of preeclamptic pregnancies. Luciferase report assay confirmed that Pax3 is a direct target of miR-362-3p. Although Pax3 was predicted to be targeted by miR-30a-3p and miR-181a-5p as well, their expression either had no difference between placentas of PE patients and normal placentas or showed less increment in placentas of PE patients than miR-362-3p. Exposure to hypoxia inhibited cell viability, migration and invasion of HTR8/SVneo cells. Increasing miR-362-3p by the mimics conferred improved effects on the inhibition. However, deletion of miR-362-3p or overexpression of Pax3 abolished the inhibiton. These results suggest that miR-362-3p/Pax3 axis regulates cell viability, migration and invasion of HTR8/SVneo cells under hypoxia. The present study adds to the further understanding of the pathogenesis of PE.

Monitoring cellular redox state under hypoxia using a fluorescent sensor based on eel fluorescent protein.

Genetically encoded fluorescent sensors are widely used to visualize secondary messengers, metabolites and dynamic events in living cells. However, almost all of these sensors are based on Aequorea GFPs or GFP-like proteins, which do not correctly maturate and fluoresce under hypoxia or anoxic conditions, greatly limiting their application in biomedical research. Herein, we provide a novel strategy for design of sensors and report a series of thiol redox-sensitive sensor based on a recently discovered oxygen-independent fluorescent protein UnaG from Japanese eel. These redox sensors have large dynamic range, rapid responsiveness, a flexible "switch", and pH-independence, are particularly compatible with hypoxia conditions, and therefore represent a substantial improvement for live-cell redox measurement. We further demonstrated the versatility of these redox sensors, by simultaneously monitoring redox changes and hypoxia state in living cells, thereby proving its capability as a powerful and flexible tool for indexing multidimensional metabolism data in the context of physiological stressors and pathological states. These redox sensors are not only the first case of UnaG-based functional sensors, but also the first case of functional sensors based on non GFP-like proteins. Based on this strategy, more oxygen-independent biosensors could be developed, hence, provide new opportunities for bioimaging.

A genetically encoded toolkit for tracking live-cell histidine dynamics in space and time.

High-resolution spatiotemporal imaging of histidine in single living mammalian cells faces technical challenges. Here, we developed a series of ratiometric, highly responsive, and single fluorescent protein-based histidine sensors of wide dynamic range. We used these sensors to quantify subcellular free-histidine concentrations in glucose-deprived cells and glucose-fed cells. Results showed that cytosolic free-histidine concentration was higher and more sensitive to the environment than free histidine in the mitochondria. Moreover, histidine was readily transported across the plasma membrane and mitochondrial inner membrane, which had almost similar transport rates and transport constants, and histidine transport was not influenced by cellular metabolic state. These sensors are potential tools for tracking histidine dynamics inside subcellular organelles, and they will open an avenue to explore complex histidine signaling.

Genetic Modulation of c-di-GMP Turnover Affects Multiple Virulence Traits and Bacterial Virulence in Rice Pathogen Dickeya zeae.

The frequent outbreaks of rice foot rot disease caused by Dickeya zeae have become a significant concern in rice planting regions and countries, but the regulatory mechanisms that govern the virulence of this important pathogen remain vague. Given that the second messenger cyclic di-GMP (c-di-GMP) is associated with modulation of various virulence-related traits in various microorganisms, here we set to investigate the role of the genes encoding c-di-GMP metabolism in the regulation of the bacterial physiology and virulence by construction all in-frame deletion mutants targeting the annotated c-di-GMP turnover genes in D. zeae strain EC1. Phenotype analyses identified individual mutants showing altered production of exoenzymes and phytotoxins, biofilm formation and bacterial motilities. The results provide useful clues and a valuable toolkit for further characterization and dissection of the regulatory complex that modulates the pathogenesis and persistence of this important bacterial pathogen.

The complete genome sequence of Dickeya zeae EC1 reveals substantial divergence from other Dickeya strains and species.

BACKGROUND: Dickeya zeae is a bacterial species that infects monocotyledons and dicotyledons. Two antibiotic-like phytotoxins named zeamine and zeamine II were reported to play an important role in rice seed germination, and two genes associated with zeamines production, i.e., zmsA and zmsK, have been thoroughly characterized. However, other virulence factors and its molecular mechanisms of host specificity and pathogenesis are hardly known. RESULTS: The complete genome of D. zeae strain EC1 isolated from diseased rice plants was sequenced, annotated, and compared with the genomes of other Dickeya spp.. The pathogen contains a chromosome of 4,532,364 bp with 4,154 predicted protein-coding genes. Comparative genomics analysis indicates that D. zeae EC1 is most co-linear with D. chrysanthemi Ech1591, most conserved with D. zeae Ech586 and least similar to D. paradisiaca Ech703. Substantial genomic rearrangement was revealed by comparing EC1 with Ech586 and Ech703. Most virulence genes were well-conserved in Dickeya strains except Ech703. Significantly, the zms gene cluster involved in biosynthesis of zeamines, which were shown previously as key virulence determinants, is present in D. zeae strains isolated from rice, and some D. solani strains, but absent in other Dickeya species and the D. zeae strains isolated from other plants or sources. In addition, a DNA fragment containing 9 genes associated with fatty acid biosynthesis was found inserted in the fli gene cluster encoding flagellar biosynthesis of strain EC1 and other two rice isolates but not in other strains. This gene cluster shares a high protein similarity to the fatty acid genes from Pantoea ananatis. CONLUSION: Our findings delineate the genetic background of D. zeae EC1, which infects both dicotyledons and monocotyledons, and suggest that D. zeae strains isolated from rice could be grouped into a distinct pathovar, i.e., D. zeae subsp. oryzae. In addition, the results of this study also unveiled that the zms gene cluster presented in the genomes of D. zeae rice isolates and D. solani strains, and the fatty acid genes inserted in the fli gene cluster of strain EC1 were likely derived from horizontal gene transfer during later stage of bacterial evolution.

Production of novel antibiotics zeamines through optimizing Dickeya zeae fermentation conditions.

Dickeya zeae strain EC1 was recently shown to produce a new type of phytotoxins designated as zeamine and zeamine II, which are potent wide-spectrum antibiotics against Gram-positive and Gram-negative bacterial pathogens, suggesting their promising potential as clinical medicines. In this study, the optimized medium composition and culture conditions for biosynthesis of novel antibiotics zeamines have been established by using response surface methodology, largely increasing the yield of zeamines from original about 7.35 µg · mL(-1) in minimal medium to about 150 µg · mL(-1) in LS5 medium. The study identified the major factors contributing to zeamines production, which include nitrate, sucrose, asparaginate, mineral elements Mg2+ and K+, and optimized amount of phosphate. In addition, the results showed that overexpression of zmsK in D. zeae strain EC1 could further increase zeamines yield to about 180 µg · mL(-1) in LS5 medium. The findings from this study could facilitate further characterization and utilization of these two novel antibiotics, and also provide useful clues for understanding the regulatory mechanisms that govern D. zeae virulence.