The biocontrol potentials of rhizospheric bacterium Bacillus velezensis K0T24 against mulberry bacterial wilt disease.

Mulberry bacterial wilt disease, caused by Ralstonia pseudosolanacearum, is a devastating soil-borne disease in the silk-mulberry-related industry. In this study, through high-throughput sequencing, we compared the rhizosphere bacterial composition of the mulberry-resistant cultivar (K10) and susceptible cultivar (G12), confirming Bacillus as a genus-level biomarker for K10. Next, twelve Bacillus spp. isolates, derived from the rhizosphere of K10, were screened for their antagonistic activity against R. pseudosolanacearum. The isolate showing strong antagonism was identified as B. velezensis K0T24 and selected for further analysis. The fermentation supernatant of B. velezensis K0T24 significantly inhibited the growth of R. pseudosolanacearum (82.47%) and the expression of its pathogenic genes. Using B. velezensis K0T24 in mulberry seedlings also increased defense enzyme activities and achieved a control efficacy of up to 55.17% against mulberry bacterial wilt disease. Collectively, our findings demonstrate the potential of B. velezensis K0T24 in suppressing mulberry bacterial wilt disease.

Tuning energetic properties through co-crystallisation - a high-pressure experimental and computational study of nitrotriazolone: 4,4'-bipyridine.

We report the preparation of a co-crystal formed between the energetic molecule 3-nitro-1,2,4-triazol-5-one (NTO) and 4,4'-bipyridine (BIPY), that has been structurally characterised by high-pressure single crystal and neutron powder diffraction data up to 5.93 GPa. No phase transitions or proton transfer were observed up to this pressure. At higher pressures the crystal quality degraded and the X-ray diffraction patterns showed severe twinning, with the appearance of multiple crystalline domains. Computational modelling indicates that the colour changes observed on application of pressure can be attributed to compression of the unit cell that cause heightened band dispersion and band gap narrowing that coincides with a shortening of the BIPY π⋯π stacking distance. Modelling also suggests that the application of pressure induces proton migration along an N-H⋯N intermolecular hydrogen bond. Impact-sensitivity measurements show that the co-crystal is less sensitive to initiation than NTO, whereas computational modelling suggests that the impact sensitivities of NTO and the co-crystal are broadly similar.

High-pressure structural studies and pressure-induced sensitisation of 3,4,5-trinitro-1H-pyrazole.

Herein we report the first high-pressure study of the energetic material 3,4,5-trinitro-1H-pyrazole (3,4,5-TNP) using neutron powder diffraction and single-crystal X-ray diffraction. A new high-pressure phase, termed Form II, was first identified through a substantial change in the neutron powder diffraction patterns recorded over the range 4.6-5.3 GPa, and was characterised further by compression of a single crystal to 5.3 GPa in a diamond-anvil cell using X-ray diffraction. 3,4,5-TNP was found to be sensitive to initiation under pressure, as demonstrated by its unexpected and violent decomposition at elevated pressures in successive powder diffraction experiments. Initiation coincided with the sluggish phase transition from Form I to Form II. Using a vibrational up-pumping model, its increased sensitivity under pressure can be explained by pressure-induced mode hardening. These findings have potential implications for the safe handling of 3,4,5-TNP, on the basis that shock- or pressure-loading may lead to significantly increased sensitivity to initiation.

Study on the Potential for Stimulating Mulberry Growth and Drought Tolerance of Plant Growth-Promoting Fungi.

Drought stress often leads to heavy losses in mulberry planting, especially for fruits and leaves. Application of plant growth-promoting fungi (PGPF) endows various plant beneficial traits to overcome adverse environmental conditions, but little is known about the effects on mulberry under drought stress. In the present study, we isolated 64 fungi from well-growing mulberry trees surviving periodical drought stress, and Talaromyces sp. GS1, Pseudeurotium sp. GRs12, Penicillium sp. GR19, and Trichoderma sp. GR21 were screened out due to their strong potential in plant growth promotion. Co-cultivation assay revealed that PGPF stimulated mulberry growth, exhibiting increased biomass and length of stems and roots. Exogenous application of PGPF could alter fungal community structures in the rhizosphere soils, wherein Talaromyces was obviously enhanced after inoculation of Talaromyces sp. GS1, and Peziza was increased in the other treatments. Moreover, PGPF could promote iron and phosphorus absorption of mulberry as well. Additionally, the mixed suspensions of PGPF induced the production of catalase, soluble sugar, and chlorophyll, which in turn enhanced the drought tolerance of mulberry and accelerated their growth recovery after drought. Collectively, these findings might provide new insights into improving mulberry drought tolerance and further boosting mulberry fruit yields by exploiting interactions between hosts and PGPF.

Volatile-mediated antagonism of soil bacterial communities against fungi.

Competition is a major type of interaction between fungi and bacteria in soil and is also an important factor in suppression of plant diseases caused by soil-borne fungal pathogens. There is increasing attention for the possible role of volatiles in competitive interactions between bacteria and fungi. However, knowledge on the actual role of bacterial volatiles in interactions with fungi within soil microbial communities is lacking. Here, we examined colonization of sterile agricultural soils by fungi and bacteria from non-sterile soil inoculums during exposure to volatiles emitted by soil-derived bacterial communities. We found that colonization of soil by fungi was negatively affected by exposure to volatiles emitted by bacterial communities whereas that of bacteria was barely changed. Furthermore, there were strong effects of bacterial community volatiles on the assembly of fungal soil colonizers. Identification of volatile composition produced by bacterial communities revealed several compounds with known fungistatic activity. Our results are the first to reveal a collective volatile-mediated antagonism of soil bacteria against fungi. Given the better exploration abilities of filamentous fungi in unsaturated soils, this may be an important strategy for bacteria to defend occupied nutrient patches against invading fungi. Another implication of our research is that bacterial volatiles in soil atmospheres can have a major contribution to soil fungistasis.

LncRNA SNHG6 enhances the radioresistance and promotes the growth of cervical cancer cells by sponging miR-485-3p.

BACKGROUND: Cervical cancer (CC) is the one of most common malignant gynecological tumors, which is characterized with the high mortality and recurrence rate. Previous studies have elucidated the oncogenic role of small nucleolar RNA host gene 6 (SNHG6) in some types of human cancers, whereas it is unclear whether it functions as an oncogene in CC. This study was aimed at unveiling the role of SNHG6 in CC. METHODS: qRT-PCR analysis was implemented to evaluate the expression levels of SNHG6, miR-485-3p and STYX in CC cells. RNA pull down assay and luciferase reporter assay were conducted to verify the interaction between miR-485-3p and SNHG6 or STYX. Functional assays, such as colony formation assay, JC-1 assay and TUNEL assay were applied to detect the biological behaviors of CC cells. The resistance of CC cells to radiation was evaluated by colony formation assay. RESULTS: SNHG6 was expressed at a high level in CC cells. Silenced SNHG6 suppressed cell proliferation but promoted cell apoptosis. Additionally, silenced SNHG6 could sensitize CC cells to radiation treatment. miR-485-3p could bind to both SNHG6 and STYX. Knockdown of miR-485-3p or overexpression of STYX could abolish the effects of SNHG6 silencing on CC cell growth. CONCLUSIONS: LncRNA SNHG6 enhances the radioresistance of CC cells and promotes CC cell growth by sponging miR-485-3p to release STYX.

Experimental and simulation study of the high-pressure behavior of squalane and poly-α-olefins.

The equation of state, dynamical properties, and molecular-scale structure of squalane and mixtures of poly-α-olefins at room temperature are studied with a combination of state-of-the-art, high-pressure experiments and molecular-dynamics simulations. Diamond-anvil cell experiments indicate that both materials are non-hydrostatic media at pressures above ∼1 GPa. The equation of state does not exhibit any sign of a first-order phase transition. High-pressure x-ray diffraction experiments on squalane show that there are no Bragg peaks, and hence, the apparent solidification occurs without crystallization. These observations are complemented by a survey of the equation of state and dynamical properties using simulations. The results show that molecular diffusion is essentially arrested above about 1 GPa, which supports the hypothesis that the samples are kinetically trapped in metastable amorphous-solid states. The shear viscosity becomes extremely large at very high pressures, and the coefficient governing its increase from ambient pressure is in good agreement with the available literature data. Finally, simulated radial distribution functions are used to explore the evolution of the molecular-scale structure with increasing pressure. Subtle changes in the short-range real-space correlations are related to a collapse of the molecular conformations with increasing pressure, while the evolution of the static structure factor shows excellent correlation with the available x-ray diffraction data. These results are of indirect relevance to oil-based lubricants, as the pressures involved are comparable to those found in engines, and hence, the ability of lubricating thin films to act as load-bearing media can be linked to the solidification phenomena studied in this work.

Soil acidification amendments change the rhizosphere bacterial community of tobacco in a bacterial wilt affected field.

Application of soil amendments has been wildly used to increase soil pH and control bacterial wilt. However, little is known about causal shifts in the rhizosphere microbial community of crops, especially when the field naturally harbors the disease of bacterial wilt to tobacco for many years due to long-term continuous cropping and soil acidification. In this study, biochar (CP), lime (LM), oyster shell powder (OS) and no soil amendment additions (Control; CK) were assessed for their abilities to improve the soil acidification, change the composition of rhizosphere soil bacterial communities and thus control tobacco bacterial wilt. The results showed that oyster shell powder significantly increased soil pH by 0.77 and reduced the incidence of tobacco bacterial wilt by 36.67% compared to the control. The Illumina sequencing -based community analysis showed that soil amendment applications affected the composition of rhizosphere bacterial community and increased the richness and diversity. In contrast, the richness and diversity correlated negatively to disease incidence. Using LEfSe analyses, 11 taxa were found to be closely related with disease suppression, in which Saccharibacteria, Aeromicrobium, and Pseudoxanthomonas could be potential indicators of disease suppression. Our results suggested that the suppression of bacterial wilt after the application of soil amendments (especially oyster shell powder) was attributed to the improved soil pH and increased bacterial richness and diversity.

Purification and characterization of a novel bacteriocin produced by Lactobacillus crustorum MN047 isolated from koumiss from Xinjiang, China.

The growing emergence of antibiotic-resistant bacteria in the food industry needs to be controlled with effective antimicrobials. In this study, bacteriocin MN047 A (BMA) was found to have antibacterial activity against multidrug-resistant bacteria. It was produced by Lactobacillus crustorum MN047, which was first isolated from koumiss, a traditional fermented dairy product from Xinjiang Autonomous Region, China. It was purified by ammonium sulfate precipitation, ion-exchange chromatography, and reversed-phase chromatography. It had a low molecular mass of 1,770.89 Da according to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and the sequence was identified as QLPWQILGIVAGMFQA by liquid chromatography-tandem mass spectrometry analysis and MASCOT searching. It was proteinaceous in nature: the bacteriocin was digested by protease but not by α-amylase or lipase. It showed broad pH toleration (pH 2-11), good thermostability, and good storage stability. It had a broad inhibitory spectrum, including both gram-positive and gram-negative bacteria. Growth curve and time-kill kinetics indicated that it was bactericidal to the indicator strains, and this finding was verified by scanning electron microscope and transmission electron microscope after treatment with BMA. As well, BMA halted the growth of Staphylococcus aureus and Escherichia coli in the G1 and G2/M phases according to cell-cycle analysis by flow cytometry, indicating that BMA had comprehensive inhibitory effects against foodborne pathogens.

The effects of oxygen flow ratio on the properties of Ag x O thin films grown by radio frequency magnetron sputtering.

The Ag x O thin film with various oxygen flow ratios (R[O2]%) deposited by radio frequency magnetron sputtering (RFM-SPT) has been studied. While adjusting R[O2]% from 0% to 30%, the Ag x O thin film transitioned from metal to semiconductor and/or insulator with different transparent appearances on the surface observed using X-ray diffraction (XRD) and transmittance measurement. At high oxygen flow ratios, the Ag x O film is multi-phased as a mixture of Ag(II)O and Ag2 (III)O3. In addition, the work function (ϕ) of those samples changes from 4.7 eV to 5.6 eV as measured by photoelectron yield spectroscopy (PYS). The compositional and chemical state changes that occur at the Ag x O surface during the increments of R[O2]% are evaluated by the relative peak intensities and binding energy shifts in X-ray photoelectron spectroscopy (XPS). With the incorporation of more electrons in chemical bonding, the oxygen-induced band forms. And combining all the results from transmittance (band gap confirmation), PYS (work function confirmation), and XPS (valence band position confirmation), the estimated band diagrams are given for the oxidation state of Ag x O with various oxygen flow ratios.

Gastrointestinal manifestations of critical ill heatstroke patients and their associations with outcomes: A multicentre, retrospective, observational study.

BACKGROUND: Extreme heat exposure is a growing health problem, and the effects of heat on the gastrointestinal (GI) tract is unknown. This study aimed to assess the incidence of GI symptoms associated with heatstroke and its impact on outcomes. AIM: To assess the incidence of GI symptoms associated with heatstroke and its impact on outcomes. METHODS: Patients admitted to the intensive care unit (ICU) due to heatstroke were included from 83 centres. Patient history, laboratory results, and clinically relevant outcomes were recorded at ICU admission and daily until up to day 15, ICU discharge, or death. GI symptoms, including nausea/vomiting, diarrhoea, flatulence, and bloody stools, were recorded. The characteristics of patients with heatstroke concomitant with GI symptoms were described. Multivariable regression analyses were performed to determine significant predictors of GI symptoms. RESULTS: A total of 713 patients were included in the final analysis, of whom 132 (18.5%) patients had at least one GI symptom during their ICU stay, while 26 (3.6%) suffered from more than one symptom. Patients with GI symptoms had a significantly higher ICU stay compared with those without. The mortality of patients who had two or more GI symptoms simultaneously was significantly higher than that in those with one GI symptom. Multivariable logistic regression analysis revealed that older patients with a lower GCS score on admission were more likely to experience GI symptoms. CONCLUSION: The GI manifestations of heatstroke are common and appear to impact clinically relevant hospitalization outcomes.

Disruption of precise regulation of αPKC expression and cellular localization is associated with cervical cancer progression.

PURPOSE: To understand the pathogenesis of cervical cancer (CC) associated with polarity protein αPKC and the potential roles of αPKC in clinical management of CC. METHODS: Tissue samples were collected from women who received colposcopy biopsy or hysterectomy surgery, including 9 CIN1, 8 CIN2, 15 CIN3, and 12 invasive cervical squamous cancer (ICC). 16 normal controls were from the normal region of tumor samples, HE and immunofluorescence staining of αPKC were performed on these samples. ANOVA and Kruslal-wallis test were used to quantitate the abnormal distribution and expression level of αPKC among different cervical lesions. RESULTS: Disruption of polarized apical localization and increased cytoplasmic accumulation of αPKC were identified in cervical lesions. In normal cervical epithelium, αPKC was detected on the apical membrane of endocervical columnar epithelial cells and of exocervical epithelial cells located at basal layer of squamous epithelium. While in squamous metaplasia, a precancerous lesion of cervical neoplasia, the polarized apical membrane localization of αPKC was disrupted, and intensed cytoplasmic accumulation was identified in the immature squamous metaplastic cells. Compared with normal cervix, number of epithelial cells with abnormal αPKC distribution was progressively increased in CINs and ICC (P < 0.05), and cytoplasmic accumulation of αPKC was increased in CIN2, CIN3, and ICC compared with CIN1 (P < 0.05). CONCLUSIONS: Disruption of polarized apical localization and increased cytoplasmic accumulation of αPKC were associated with CC progression, indicating that precise regulation of αPKC may play important roles in CC progression, and αPKC may be a potential molecular target for clinical diagnoses and treatment of CC.

MiR-223-3p overexpressed adipose mesenchymal stem cell-derived exosomes promote wound healing via targeting MAPK10.

BACKGROUND: Adipose mesenchymal stem cell (AMSC)-derived exosomes are promising novel factors for wound repair and regeneration. This study aimed to explore the potential roles and underlying mechanisms of specific miRNA in wound healing using AMSC-derived exosomes as carriers. METHODS: The expression profiles of GSE197840 were downloaded to screen for differentially expressed miRNAs (DEmiRNAs), and the corresponding genes of the identified miRNAs were predicted. Next, miRNA-mRNA co-expression networks were constructed and the genes in these networks were subjected to functional analysis. miR-223-3p overexpressed AMSCs were then established to isolate exosomes, and the effects of AMSC-derived exosomes carrying miR-223-3p on wound healing and the related potential mechanisms were further investigated in vivo. RESULTS: 35 DEmiRNAs were identified and a co-expression network containing 22 miRNAs and 91 target genes was constructed. Based on the network, miR-223-3p was the hub node and the genes were significantly enriched in 15 GO terms of biological processes and 14 KEGG pathways, including cAMP, PI3K-Akt, cGMP-PKG, neurotrophin signaling pathway, and dopaminergic synapse. Then, miR-223-3p overexpressed AMSCs-derived exosomes were successfully extracted, and miR-223-3p was found to directly bind with MAPK10. In vivo experiments validated that AMSCs-derived exosomal miR-223-3p could promote wound healing, and up-regulated α-SMA, CD31, COL1A1, COL2A1, COL3A1, and down-regulated MAPK10, TNF-α, IL-ß, and IL-6. CONCLUSIONS: AMSC-derived exosomal miR-223-3p may accelerate wound healing by targeting MAPK10.

Statins on Spontaneous Intracerebral Hemorrhage: A Meta-Analysis.

Objective: In order to explore whether the application of statins can improve the prognosis of patients with intracerebral hemorrhage. Methods: Studies of patients with intracerebral hemorrhage taking statins published in English until December 2021 were searched based on limited search terms, the retrieved literature was screened out based on inclusion and exclusion criteria, and the quality assessment and data extraction were carried out independently by two investigators. The extracted clinical data were then meta-analyzed. Results: A total of 17 literatures were included in this study, with a sample size of 16,988 cases, including 3,001 cases in the statin group and 13,487 cases in the control group. MRS score of mortality was used as the prognostic index to evaluate cerebral hemorrhage. According to the Newcastle-Ottawa Scale (NOS), the score of literature quality evaluation scale was 6-8, indicating good literature quality. Meta-analysis of clinical data extracted from the literature showed that the statin group reduced overall mortality after intracerebral hemorrhage compared with the nonstatin group (P < 0.01). In terms of improving functional prognosis, the statin group improved functional prognosis 90 days after intracerebral hemorrhage (P=0.01). There was no significant difference between the statin and nonstatin groups in reducing the number of intracerebral hematomas. Conclusions: Statins can reduce the total mortality after ICH and improve the survival rate (90 d), without increasing the amount of hematoma.

Mechanisms of DNA opening revealed in AAA+ transcription complex structures.

Gene transcription is carried out by RNA polymerase (RNAP) and requires the conversion of the initial closed promoter complex, where DNA is double stranded, to a transcription-competent open promoter complex, where DNA is opened up. In bacteria, RNAP relies on σ factors for its promoter specificities. Using a special form of sigma factor (σ54), which forms a stable closed complex and requires its activator that belongs to the AAA+ ATPases (ATPases associated with diverse cellular activities), we obtained cryo-electron microscopy structures of transcription initiation complexes that reveal a previously unidentified process of DNA melting opening. The σ54 amino terminus threads through the locally opened up DNA and then becomes enclosed by the AAA+ hexameric ring in the activator-bound intermediate complex. Our structures suggest how ATP hydrolysis by the AAA+ activator could remove the σ54 inhibition while helping to open up DNA, using σ54 amino-terminal peptide as a pry bar.

Plant Allometric Growth Enhanced by the Change in Soil Stoichiometric Characteristics With Depth in an Alpine Meadow Under Climate Warming.

The effects of global warming have warmed the climate of the Qinghai-Tibetan Plateau (QTP) leading to changes in plant growth and soil nutrients in the alpine meadows. However, few studies have addressed the effects of warming on plant allometric growth and soil stoichiometry in these meadows on a long-term scale. Therefore, the effects of soil stoichiometry on plant allometric growth remain unclear under long-term warming in the alpine meadows. This study adopted infrared radiators to conduct an 8-year warming experiment in a permafrost region on the QTP starting in 2010, and surveyed growth indices of the plant community during the growing season. Soil organic carbon (C), total nitrogen (N), and total phosphorus (P) in an alpine meadow were measured. We initially learned that the aboveground part of the alpine meadow vegetation in the warming treatment changed from an isometric to an allometric growth pattern while the allometric growth pattern of the belowground part was further strengthened. Second, the contents of soil C, N, and P decreased at the 0-20 cm depth and increased at the 20-30 cm depth in warming. The ratios of soil C:N, C:P, and N:P showed increasing trends at different soil depths with artificial warming, and their amplitudes increased with soil depths. Warming promoted the migration of soil stoichiometric characteristics of C, N, and P to deep soil. Finally, the correlations of plant growth with soil stoichiometric characteristics were weakened by warming, demonstrating that the downward migration of soil stoichiometric characteristics to deep soil in warming had effects on the growth of vegetation in the alpine meadow. It concludes that the change in soil stoichiometric characteristics with soil depths promotes plant allometric growth in the alpine meadow under climate warming.

Alleviating Soil Acidification Could Increase Disease Suppression of Bacterial Wilt by Recruiting Potentially Beneficial Rhizobacteria.

Bacterial wilt is accompanied by microbial communities shift and soil acidification. However, the relationship between the changes of bacterial communities and bacterial wilt under the influence of different acidification levels has not been fully elucidated. Here, we analyzed the abundance of Ralstonia solanacearum, rhizosphere bacterial communities and carbon metabolism at differently acidic levels (pH 6.45, pH 5.60, pH 5.35, pH 4.90 and pH 4.45) and soil amendment treatment (CaO). The results indicated that both the abundance of R. solanacearum and the incidence of bacterial wilt showed a significant trend of first increasing and then decreasing with the increase of soil pH. The Firmicutes phylum and potentially beneficial genera Bacillus, Paenibacillus, Flavobacterium and Pseudomonas were significantly enriched at pH 6.45. The metabolic ability in response to the l-arginine and 4-hydroxybenzoic acid was significantly increased at pH 6.45. After using CaO to increase the pH of diseased soil from 5.45 to 6.05, the abundance of R. solanacearum and the incidence of bacterial wilt were significantly reduced, the Firmicutes and potentially beneficial genera Bacillus and Pseudomonas were significantly enriched. Overall, alleviating soil acidification to a slightly acidic level (pH 6.0-6.5) could suppress bacterial wilt by suppressing the growth of R. solanacearum and enriching the rhizosphere potentially beneficial bacteria, and further emphasized the importance of increasing soil pH in biological control of bacterial wilt. IMPORTANCE The rhizosphere microbiota and soil acidification have been shown to have impacts on bacterial wilt. However, the influence of different acidification levels on the rhizosphere communities and bacterial wilt has not been fully studied. In this study, the potentially beneficial bacteria (Bacillus and Pseudomonas) were significantly enriched in the slightly acidic soil (pH 6.45), leading to the increase of the metabolism of 4-hydroxybenzoic acid and the decrease of pathogenic R. solanacearum, thereby alleviating the occurrence of bacterial wilt. The changes of potentially beneficial bacteria and pathogenic R. solanacearum in strongly acidic soil (pH 5.35) with the highest incidence of bacterial wilt were just the opposite. These findings help clarify the mechanisms by which soil bacteria exert influence on bacterial wilt outbreak under different soil acidification levels.

Soil conditions on bacterial wilt disease affect bacterial and fungal assemblage in the rhizosphere.

Natural soil has the ability to suppress the soil-borne pathogen to a certain extent, and the assemblage of soil microbiome plays a crucial role in maintaining such ability. Long-term monoculture accelerates the forms of soil microbiome and leads to either disease conducive or suppressive soils. Here, we explored the impact of soil conditions on bacterial wilt disease (healthy or diseased) under long-term tobacco monoculture on the assemblage of bacterial and fungal communities in bulk and rhizosphere soils during the growth periods. With Illumina sequencing, we compared the bacterial and fungal composition of soil samples from tobacco bacterial wilt diseased fields and healthy fields in three growth periods. We found that Proteobacteria and Ascomycota were the most abundant phylum for bacteria and fungi, respectively. Factors of soil conditions and tobacco growth periods can significantly influence the microbial composition in bulk soil samples, while the factor of soil conditions mainly determined the microbial composition in rhizosphere soil samples. Next, rhizosphere samples were further analyzed with LEfSe to determine the discriminative taxa affected by the factor of soil conditions. For bacteria, the genus Ralstonia was found in the diseased soils, whereas the genus Flavobacterium was the only shared taxon in healthy soils; for fungi, the genus Chaetomium was the most significant taxon in healthy soils. Besides, network analysis confirmed that the topologies of networks of healthy soils were higher than that of diseased soils. Together, our results suggest that microbial assemblage in the rhizosphere will be largely affected by soil conditions especially after long-term monoculture.

Mutation in phcA Enhanced the Adaptation of Ralstonia solanacearum to Long-Term Acid Stress.

Bacterial wilt, caused by the plant pathogen Ralstonia solanacearum, occurs more severely in acidified soil according to previous reports. However, R. solanacearum cannot grow well in acidic environments under barren nutrient culture conditions, especially when the pH is lower than 5. With the worsening acidification of farmland, further determination of how R. solanacearum adapts to the long-term acidic environment is worthwhile. In this study, experimental evolution was applied to evaluate the adaptability and mechanism of the R. solanacearum experimental population responding to long-term acid stress. We chose the CQPS-1 strain as the ancestor, and minimal medium (MM medium) with different pH values as the culture environment to simulate poor soil. After 1500 generations of serial passage experiments in pH 4.9 MM, acid-adapted experimental strains (denoted as C49 strains) were obtained, showing significantly higher growth rates than the growth rates of control experimental strains (serial passage experiment in pH 6.5 MM, denoted as C65 strains). Competition experiments showed that the competitive indices (CIs) of all selected clones from C49 strains were superior to the ancestor in acidic environment competitiveness. Based on the genome variation analysis and functional verification, we confirmed that loss of function in the phcA gene was associated with the acid fitness gain of R. solanacearum, which meant that the inactivation of the PhcA regulator caused by gene mutation mediated the population expansion of R. solanacearum when growing in an acidic stress environment. Moreover, the swimming motility of acid evolution strains and the phcA deletion mutant was significantly enhanced compared to CQPS-1. This work provided evidence for understanding the adaptive strategy of R. solanacearum to the long-term acidic environment.

Effect of an Environment Friendly Heat and Relative Humidity Approach on γ-Aminobutyric Acid Accumulation in Different Highland Barley Cultivars.

In this study, heat and relative humidity (HRH) treatment was applied in highland barley for γ-aminobutyric acid (GABA) accumulation. Tibetan highland barley cultivars (25) were selected for comparison and analysis. HRH treatment could accumulate GABA in several hours with low moisture content and high temperature, and the grains were treated for 2.5 h at 65 °C in this study. The GABA content of processed grains under HRH optimal condition ranged from 26.91 to 76.28 mg·100 g−1, which was significantly higher than the initial content (12.78−43.00 mg·100 g−1). The highest GABA accumulation capacity was observed in two-row yellow cultivars (YT1), increasing from 36.52 to 76.28 mg·100 g−1. Correlation analysis showed that the accumulation of GABA after HRH treatment was positively and significantly (p < 0.05) correlated with the contents of protein (0.52), total free amino acids (0.68), threonine (0.53), serine (0.51), glutamate (0.69), glycine (0.49), alanine (0.46), cysteine (0.57), tyrosine (0.50), lysine (0.53), proline (0.40), and glutamate decarboxylase (GAD) activity (0.62), which were closely related to GABA-shunt pathway. The polyamines contents, diamine oxidase (DAO) and polyamine oxidase (PAO) activities, as the substrates and critical enzymes of polyamine degradation pathway, showed no significant correlation with GABA accumulation. The results suggested that the main pathway of GABA accumulation in highland barley under HRH treatment was GABA-shunt pathway.