Preservation effect of Lactobacillus plantarum O2 fermentation supernatant on postharvest pepper and its induced resistance to Phytophthora capsici.

Research of lactic acid bacteria and its metabolites on biological preservatives becomes a hot topic. Lactobacillus plantarum O2, with good inhibition on Phytophthora capsici (P. capsici), was isolated from the pickle. In this study, the effects of L. plantarum O2 fermentation supernatant (FS) on pepper postharvest preservation and its induced resistance to P. capsici were studied. Results showed that weight loss rate, rot index, respiration rate, relative electrical conductivity, loss of chlorophyll content and VC of pepper in FS treatment group were decreased by 18 %, 64 %, 15 %, 26 %, 33 % and 20 % compared with blank control (BC) after 20 d storage. L* and b*-value of pepper in FS group were lower than those in the BC group. In addition, the damage-induced resistance test found that the infection rate in the FS group was reduced by 39 %, compared with CK2 after 12 d storage. Moreover, phenylalanine ammonia-lyase activity, peroxidase activity, polyphenol oxidase activity, proline content, total phenol content and flavonoid content increased by 14 %, 9 %, 30 %, 8 %, 8 % and 9 %, respectively, while malondialdehyde content decreased by 13 %. These results indicated that FS treatment showed good fresh-keeping effects on postharvest pepper. It could enhance the tolerance of pepper under stress by improving defensive enzyme activities, slowing down the damage caused by P. capsici, and inducing pepper resistance to P. capsici. Therefore, FS can be used as a microbial source bio-preservative for postharvest pepper.

Unveiling the duality of Pantoea dispersa: A mini review.

Pantoea dispersa is a Gram-negative bacterium that exists in a variety of environments and has potential in many commercial and agricultural applications, such as biotechnology, environmental protection, soil bioremediation, and plant growth stimulation. However, P. dispersa is also a harmful pathogen to both humans and plants. This "double-edged sword" phenomenon is not uncommon in nature. To ensure survival, microorganisms respond to both environmental and biological stimuli, which could be beneficial or detrimental to other species. Therefore, to harness the full potential of P. dispersa, while minimizing potential harm, it is imperative to unravel its genetic makeup, understand its ecological interactions and underlying mechanisms. This review aims to provide a comprehensive and up-to-date overview of the genetic and biological characteristics of P. dispersa, in addition to potential impacts on plants and humans, as well as to provide insights into potential applications.

Effects of Rhapontigenin as a Novel Quorum-Sensing Inhibitor on Exoenzymes and Biofilm Formation of Pectobacterium carotovorum subsp. carotovorum and Its Application in Vegetables.

The aim of this study was to devise a method to protect Chinese cabbage (Brassica chinensis) and lettuce (Lactuca sativa) from bacterial-disease-induced damage during storage. Thus, the potential of rhapontigenin as a quorum sensing (QS) inhibitor against Pectobacterium carotovorum subsp. carotovorum (P. carotovorum) was evaluated. The QS inhibitory effects of rhapontigenin were confirmed by significant inhibition of the production of violacein in Chromobacterium violaceum CV026 (C. violaceum, CV026). The inhibitory effects of rhapontigenin on the motility, exopolysaccharide (EPS) production, biofilm formation and virulence−exoenzyme synthesis of P. carotovorum were investigated. Acyl-homoserine lactones (AHLs) were quantified using liquid chromatography−mass spectrometry (LC−MS). The inhibitory effects of rhapontigenin on the development of biofilms were observed using fluorescence microscopy and scanning electron microscopy (SEM). A direct-inoculation assay was performed to investigate the QS inhibitory effects of rhapontigenin on P. carotovorum in Chinese cabbage and lettuce. Our results demonstrated that rhapontigenin exhibited significant inhibition (p < 0.05) of the motility, EPS production, biofilm formation, virulence−exoenzyme synthesis and AHL production of P. carotovorum. Additionally, the result of the direct-inoculation assay revealed that rhapontigenin might provide vegetables with significant shelf-life extension and prevent quality loss by controlling the spread of soft-rot symptoms. Consequently, the study provided a significant insight into the potential of rhapontigenin as a QS inhibitor against P. carotovorum.

Lipopeptides against COVID-19 RNA-dependent RNA polymerase using molecular docking.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is caused by a novel virus that is responsible for the largest pandemic in recent times. Although numerous studies have explored methods to cope with COVID-19 and targeted drugs and vaccines have been developed, the spread of disease remains rapid due to the high infectivity and mutation capability of SARS-CoV-2, the causative virus of COVID-19. Therefore, there is an urgent necessity to seek more efficient treatments and approaches to combat the disease. METHODS: In this study, molecular docking was used to predict the binding of different lipopeptides, which exhibit significant biological functions, to the RNA-dependent RNA polymerase (also known as nsp12) of SARS-CoV-2, the central component of coronaviral replication and transcription machinery. RESULTS: The results showed that seven lipopeptides bound to nsp12 at the same location as the FDA-approved drug remdesivir, with higher affinities. Notably, iron-chelating ferrocin A (ferrocin A-iron complex [FAC]) bound to nsp12 most tightly, releasing up to 9.1 kcal mol-1 of free energy. Protein-ligand interaction analysis revealed that FAC formed four hydrogen bonds, two hydrophobic interactions, and three salt bridges with nsp12. These active amino acids are mainly distributed in the fingers and thumb subdomains of nsp12 and are highly conserved. CONCLUSIONS: Our findings suggest that the abovementioned lipopeptides can tightly bind to nsp12, and thus represent promising drug candidates for anti-coronaviral treatments with the potential to fight SARS-CoV-2.

Improvement of antifungal activity of a culture filtrate of endophytic Bacillus amyloliquefaciens isolated from kiwifruit and its effect on postharvest quality of kiwifruit.

This study reports the optimization of culture conditions and medium components of M9, an endophytic strain of Bacillus amyloliquefaciens, which we had previously isolated from kiwifruit, and evaluation of its effect on kiwifruit postharvest protection against soft rot. The method of one-factor-at-a-time was used to determine the optimum culture conditions, and response surface methodology was applied to optimize the medium constituents. After optimization, a high rate of antifungal activity (73.12% decrease in decay rate) by M9 culture filtrate against the soft rot fungal pathogen, Botryosphaeria dothidea, was obtained. Compared with the initial culture conditions, the antifungal activity of M9 culture filtrate was increased by 19.5%. Furthermore, a postharvest storage experiment on kiwifruit showed that M9 culture filtrate could maintain the quality of stored kiwifruit, delay fruit senescence, and significantly enhance the storability of kiwifruit. Using liquid chromatography-mass spectrometry, we found that the antifungal activity of M9 was associated with the presence of the C12-surfactin A lipopeptide. PRACTICAL APPLICATIONS: Soft rot caused by Botryosphaeria dothidea is one of the most important diseases of kiwifruit, causing postharvest fruit rot. The disease progresses rapidly and is difficult to control, posing a great threat to the kiwifruit industry. In this study, the culture conditions and medium composition for culture of the strain M9 (kiwifruit endophytic Bacillus amyloliquefaciens) were optimized to maximize the inhibition of B. dothidea. A postharvest storage experiment showed that M9 culture filtrate could improve the disease resistance of kiwifruits, delay the senescence of the fruits, and maintain the quality of kiwifruit during storage. Because M9 is a natural endophyte of kiwifruit, the strategy used in this study was both effective and safe. This work will contribute to the exploitation of B. amyloliquefaciens in controlling the pathogens of kiwifruit and the development of safer and more advanced strategies for the postharvest protection of kiwifruits.

Changes in volatile flavor compounds of peppers during hot air drying process based on headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS).

BACKGROUND: Flavor plays a critical role in defining sensory and consumer acceptance of dried pepper, and it can be affected by temperature and moisture content during hot air drying (HAD). Thus, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was used to analyze changes in volatile compounds of pepper during the HAD process with different drying temperatures. RESULTS: A total of 45 volatile flavor compounds were identified, including 11 esters, 11 aldehydes, nine alcohols, five ketones, three furans, three acids, two pyrazines, and one ether. The results showed that with the loss of moisture during drying, aldehydes and alcohols decreased, esters initially increased and then decreased. However, propyl acetate, 2,3-butanediol, 2-acetylfuran, and 2-methylpyrazine increased. Moreover, drying temperature was closely related to the change of volatile flavor compounds. Aldehydes, alcohols, and some other volatile flavor compounds (methyl salicylate, ethyl acetate, 2-methylpyrazine, dipropyl disulfide) decreased with an increase of temperature (60-80 °C) at the same moisture content, while high temperature could promote the formation of ethyl octanoate, methyl octanoate, benzaldehyde, furfurol, acetal, 5-methylfurfural, and 2-acetylfuran. Based on principal components analysis and heat map clustering analysis, peppers dried at 70 or 80 °C presented similar composition, and the loss of volatile flavor compounds was more than samples died at 60 °C during the HAD process. CONCLUSION: Overall, the flavor quality of peppers dried at 60 °C was better than that of other treatments during the HAD process. HS-GC-IMS was a reliable and effective means of analyzing volatile flavor compounds in peppers during the drying process. © 2020 Society of Chemical Industry.

Conjugation of the CRM197-inulin conjugate significantly increases the immunogenicity of Mycobacterium tuberculosis CFP10-TB10.4 fusion protein.

Mycobacterium tuberculosis (Mtb) is a serious fatal pathogen that causes tuberculosis (TB). Effective vaccination is urgently needed to deal with the serious threat from TB. Mtb-secreted protein antigens are important virulence determinants of Mtb with poor immunogenicity. Adjuvants and antigen delivery systems are thus highly desired to improve the immunogenicity of protein antigens. Inulin is a biocompatible polysaccharide (PS) adjuvant that can stimulate a strong cellular and humoral immunity. Bacterial capsular PS and haptens have been conjugated with cross-reacting material 197 (CRM197) to improve their immunogenicity. CFP10 and TB10.4 were two Mtb-secreted immunodominant protein antigens. A CFP10-TB10.4 fusion protein (CT) was used as the antigen for covalent conjugation with the CRM197-inulin conjugate (CRM-inu). The resultant conjugate (CT-CRM-inu) elicited high CT-specific IgG titers, stimulated splenocyte proliferation and provoked the secretion of Th1-type and Th2-type cytokines. Conjugation with CRM-inu significantly prolonged the systemic circulation of CT and exposure to the immune system. Moreover, CT-CRM-inu showed no apparent toxicity to cardiac, hepatic and renal functions. Thus, conjugation of CT with CRM-inu provided an effective strategy for development of protein-based vaccines against Mtb infection.

Repression of Biotin-Related Proteins by Benzo[a]Pyrene-Induced Epigenetic Modifications in Human Bronchial Epithelial Cells.

Benzo[a]pyrene (B[a]P) exposure has been associated with the alteration in epigenetic marks that are involved in cancer development. Biotinidase (BTD) and holocarboxylase synthetase (HCS) are 2 major enzymes involved in maintaining the homeostasis of biotinylation, and the deregulation of this pathway has been associated with a number of cancers. However, the link between B[a]P exposure and the dysregulation of BTD/HCS in B[a]P-associated tumorigenesis is unknown. Here we showed that the expression of both BTD and HCS was significantly decreased upon B[a]P treatment in human bronchial epithelial (16HBE) cells. Benzo[a]pyrene exposure led to the global loss of DNA methylation by immunofluorescence, which coincided with the reduction in acetylation levels on histones H3 and H4 in 16HBE cells. Consistent with decreased histone acetylation, histone deacetylases (HDACs) HDAC2 and HDAC3 were significantly upregulated in a dosage-dependent manner. When DNA methylation or HDAC activity was inhibited, we found that the reduction in BTD and HCS was separately regulated through distinct epigenetic mechanisms. Together, our results suggested the potential link between B[a]P toxicity and deregulation of biotin homeostasis pathway in B[a]P-associated cancer development.

Inhibition of migration and induction of apoptosis in LoVo human colon cancer cells by polysaccharides from Ganoderma lucidum.

Ganoderma lucidum polysaccharides (GLPs), which were purified from the medicinal herb G. lucidum followed by ethanol precipitation, protein depletion using the Sevage assay, purification using DEAE­cellulose (DE-52), dialysis and the use of ultrafiltration membranes, are used as an ingredient in traditional anticancer treatments in China. The aim of the current study was to evaluate the anticancer effects and investigate the underlying molecular mechanisms of GLPs on LoVo human colon cancer cells. The results demonstrated that the GLP­mediated anticancer effect in LoVo cells was characterized by cytotoxicity, migration inhibition, enhanced DNA fragmentation, morphological alterations and increased lactate dehydrogenase release. Furthermore, the activation of caspases­3, ­8 and ­9 was involved in GLP­stimulated apoptosis. Additionally, treatment with GLPs promoted the expression of Fas and caspase­3 proteins, whilst reducing the expression of cleaved poly(ADP­ribose) polymerase. These data indicate that GLPs demonstrate potential antitumor activity in human colon cancer cells, predominantly through the inhibition of migration and induction of apoptosis. Furthermore, activation of the Fas/caspase-dependent apoptosis pathway is involved in the cytotoxicity of GLPs.

Ganoderma lucidum polysaccharides target a Fas/caspase dependent pathway to induce apoptosis in human colon cancer cells.

Ganoderma lucidum polysaccharides (GLP) extracted from Ganoderma lucidum have been shown to induce cell death in some kinds of cancer cells. This study investigated the cytotoxic and apoptotic effect of GLP on HCT-116 human colon cancer cells and the molecular mechanisms involved. Cell proliferation, cell migration, lactate dehydrogenase (LDH) levels and intracellular free calcium levels ([Ca(2+)]i) were determined by MTT, wound-healing, LDH release and fluorescence assays, respectively. Cell apoptosis was observed by scanning and transmission electron microscopy. For the mechanism studies, caspase-8 activation, and Fas and caspase-3 expression were evaluated. Treatment of HCT-116 cells with various concentrations of GLP (0.625-5 mg/mL) resulted in a significant decrease in cell viability (P< 0.01). This study showed that the antitumor activity of GLP was related to cell migration inhibition, cell morphology changes, intracellular Ca(2+) elevation and LDH release. Also, increase in the levels of caspase-8 activity was involved in GLP-induced apoptosis. Western blotting indicated that Fas and caspase-3 protein expression was up-regulated after exposure to GLP. This investigation demonstrated for the first time that GLP shows prominent anticancer activities against the HCT-116 human colon cancer cell line through triggering intracellular calcium release and the death receptor pathway.

Chemical characterization and antitumor activities of polysaccharide extracted from Ganoderma lucidum.

Ganoderma lucidum polysaccharide (GLP) is a biologically active substance reported to possess anti-tumor ability. Nonetheless, the mechanisms of GLP-stimulated apoptosis are still unclear. This study aims to determine the inhibitory and apoptosis-inducing effects of GLP on HCT-116 cells. We found that GLP reduced cell viability on HCT-116 cells in a time- and dose-dependent manner, which in turn, induced cell apoptosis. The observed apoptosis was characterized by morphological changes, DNA fragmentation, mitochondrial membrane potential decrease, S phase population increase, and caspase-3 and -9 activation. Furthermore, inhibition of c-Jun N-terminal kinase (JNK) by SP600125 led to a dramatic decrease of the GLP-induced apoptosis. Western blot analysis unveiled that GLP up-regulated the expression of Bax/Bcl-2, caspase-3 and poly (ADP-ribose) polymerase (PARP). These results demonstrate that apoptosis stimulated by GLP in human colorectal cancer cells is associated with activation of mitochondrial and mitogen-activated protein kinase (MAPK) pathways.

[Study the rudimentary immunoregulatory mechanisms of Ganoderma Spore oil on immunocompromized mice].

OBJECTIVE: To study the rudimentary immunoregulatory mechanisms of Ganoderma spore oil on immunocompromized mice model. METHODS: Thrity KM mice were randomly selected and assigned into three groups (ten animals per group): the model control group, Ganoderma Lucidum spores oil group and the normal control group. The model control group and Ganoderma Lucidum spores oil group were injected intraperitoneally with cyclophosphamide at 40 mg x kg(-1) d to generate a immunocompromized mice model. The normal control group were administered with 0.9% NaCl solution 0.1 ml/10 g BW as placebo. All agents were given orally once a day, given for consecutive 30 days, Ganoderma Lucidum spores oil group 150 mg/kg, the others given maize 0.1 ml/10 g BW. The serum TNF-alpha , IFN-gamma content of the mice through ELISA kit and the expression levels of IL-2, IL-10, IL-12, IL-4, IFN-gamma, TNF-alpha mRNA in mouse spleen and thymus were examined by RT-PCR to rudimentary study its immunoregulatory mechanisms. RESULTS: Ganoderma spore oil can significantly increased the content of TNF-alpha and IFN-gamma in the serum and the expression levels of IL-2, IL-10, IL-12, IL-4, IFN-gamma, TNF-alpha mRNA in spleen and thymus, with obvious difference from the model control (P < or = 0.05). CONCLUSION: Ganoderma spore oil can be able to improve the above cytokine ion expression to immunoregulate the immunocompromized mice.

[Effect of L-arabinose on glucose and lipid metabolism in type 2 diabetic rats].

OBJECTIVE: To investigate the effect of L-arabinose on glucose and Organ and islet in type 2 diabetic rats. METHODS: Male Wistar rats were fed high-sugar and high-fat diet after 8 weeks, then inject streptozotocin intraperitoneally according to 25 mg/kgbw dose to establish animal models of type 2 diabetes, and fed L-arabinose according to a low dose (50 mg/kgbw ), medium dose (150 mg/kgbw) and high dose (500 mg/kgbw) ,the animal be fed acarbose (20 mg/kgbw) as a positive control, the use of L-arabinose and acarbose were prepared in the dextrin (0.36 g/ml) and sucrose (0.04 g/ml) of the suspension, free to eat water. OGTT after 4 weeks, After animal death, rat liver, epididymal fat and cecum were weighed and calculate the ratio of organ weight. Results compared with model group, low, animals with L-arabinose-intervention those blood glucose response had a significant impact, 30 min, 60 min, 120 min blood glucose values and AUC were significantly lower than the model group (P < 0.05), of which medium dose is most significant (P < 0.01). L-arabinose intervention increased cecal weight and showed protective effect on beta-cell. CONCLUSION: L-arabinose long-term intervention can improve glucose tolerance in type 2 diabetic rats, this effect may be related to L-arabinose inhibition of digestive enzymes and the protective effect on beta-cell.

[Isolation, identification and field control efficacy of an endophytic strain against tobacco bacterial wilt (Ralstonia solanacarum)].

In this paper, an endophytic strain B-001 against tobacco bacterial wilt (Ralstonia solanacarum) was isolated from the stem of healthy tobacco in R. solanacarum-infected fields, which had a stronger inhibitory effect on some kinds of gram-positive bacteria, gram-negative bacteria, and pathogenic fungi. This strain belonged to Bacillus, and its 16S rDNA after PCR and sequencing had an accession of GenBank being DQ444283. The 16S rDNA phylogenetic tree was constructed with MEGA3, and compared with the published 16S rDNA sequences of relative bacteria species. B-001 had a 99.2% sequence similarity with Bacillus subtilis (DQ415893). According to the morphological, physiological and biochemical characteristics, and based on phylogenetic analysis, B-001 was identified as a strain of B. subtilis. Field experiments in Guiyang and Ningxiang counties of Hunan Province showed that in 2005 and 2006, the control efficacy of B-001 on R. solanacarum ranged from 40.03% to 78. 14%, better than that of Streptomycini.

Synthesis and antifungal activity of 5,8-quinazolinedione derivatives modified at positions 6 and 7.

5,8-Quinazolinediones modified at positions 6 and 7 were synthesized and tested for in vitro antifungal activities against Candida species and Aspergillus niger. Most of 5,8-quinazolinediones 3-5 generally exhibited potent antifungal activity. 6-Arylamino-7-chloro-5,8-quinazolinediones (3) generally showed more potent antifungal activity than 7-arylthio-5,8-quinzolinediones (4) and 6,7-bis-(arylthio)-5,8-quinazolinediones (5).

6-Arylamino-7-chloro-quinazoline-5,8-diones as novel cytotoxic and DNA topoisomerase inhibitory agents.

A series of 6-arylamino-7-chloro-quinazoline-5,8-diones were prepared and evaluated for their in vitro cytotoxicity in cultured human cancer cell lines A549 (lung cancer), Col2 (colon cancer), and SNU-638 (stomach cancer). The preliminary structure-activity relationship has been described for providing further development of potent antitumor agents. To further investigate the cytotoxic mechanism, the effects of test compounds on DNA topoisomerase I and II activities have been assessed.