Achromobacter seleniivolatilans sp. nov. and Buttiauxella selenatireducens sp. nov., isolated from the rhizosphere of selenium hyperaccumulator Cardamine hupingshanesis.

Two Gram-stain-negative bacterial strains, R39T and R73T, were isolated from the rhizosphere soil of the selenium hyperaccumulator Cardamine hupingshanesis in China. Strain R39T transformed selenite into elemental and volatile selenium, whereas strain R73T transformed both selenate and selenite into elemental selenium. Phylogenetic and phylogenomic analyses indicated that strain R39T belonged to the genus Achromobacter, while strain R73T belonged to the genus Buttiauxella. Strain R39T (genome size, 6.68 Mb; G+C content, 61.6 mol%) showed the closest relationship to Achromobacter marplatensis LMG 26219T and Achromobacter kerstersii LMG 3441T, with average nucleotide identity (ANI) values of 83.6 and 83.4 %, respectively. Strain R73T (genome size, 5.22 Mb; G+C content, 50.3 mol%) was most closely related to Buttiauxella ferragutiae ATCC 51602T with an ANI value of 86.4 %. Furthermore, strain A111 from the GenBank database was found to cluster with strain R73T within the genus Buttiauxella through phylogenomic analyses. The ANI and digital DNA-DNA hybridization values between strains R73T and A111 were 97.5 and 80.0% respectively, indicating that they belong to the same species. Phenotypic characteristics also differentiated strain R39T and strain R73T from their closely related species. Based on the polyphasic analyses, strain R39T and strain R73T represent novel species of the genera Achromobacter and Buttiauxella, respectively, for which the names Achromobacter seleniivolatilans sp. nov. (type strain R39T=GDMCC 1.3843T=JCM 36009T) and Buttiauxella selenatireducens sp. nov. (type strain R73T=GDMCC 1.3636T=JCM 35850T) are proposed.

Nitrate reductase involves in selenite reduction in Rahnella aquatilis HX2 and the characterization and anticancer activity of the biogenic selenium nanoparticles.

BACKGROUND: Biogenic selenium nanoparticles (SeNPs) show numerous advantages including their high stability, low toxicity, and high bioactivity. While metabolism of SeNPs remains not well studied and need more investigation to reveal the process. PURPOSE: The objective of the study was to investigate the relationship between nitrate reductase and selenite reduction in Rahnella aquatilis HX2, characterize the properties of HX2 produced SeNPs, and explore their potential applications, particularly their anticancer activity. PROCEDURES: Selenium species were measured by high-performance liquid chromatography coupled to inductively coupled plasma - Mass spectrometry (HPLC-ICP-MS). Transcription level of nitrate reductase was determined by Real-time quantitative PCR. Morphology, particle size, crystal structure and surface chemistry of SeNPs were determined by electron microscopy, dynamic light scattering method, Raman scattering, X-ray photoelectron spectroscopy, respectively. Anti cancer cell activity was measured by CCK-8 assay. MAIN FINDINGS: SeNP production in R. aquatilis HX2 was correlated with the cell growth. The products of selenite reduction in HX2 detected by HPLC-ICP-MS included SeNPs, selenocysteine (SeCys), Se-Methylselenocysteine (MeSeCys), and 7 unknown compounds. Nitrate addition experiments suggested the involvement of nitrate reductase in selenite reduction in HX2. Both the cellular membrane and cytoplasm of HX2 exhibited selenite-reducing ability, indicating that membrane-associated nitrate reductase was not the sole selenite reductase in HX2. Characterization of the biogenic SeNPs revealed a spherical morphology and amorphous structure of them. Surface chemistry analysis implicated the binding of extracellular polymeric substances to the biogenic SeNPs, and the presence of Se0, Se2-, and electron-rich Se atoms on the surface of SeNPs. Finally, the IC50 values of the biogenic SeNPs were 36.49 µM for HepG2 and 3.70 µM for HeLa cells. CONCLUSIONS: The study first revealed that the nitrate reductase is involving in selenite reduction in R. aquatilis HX2. The biogenic SeNPs coordinated with organic substances in the surface. And SeNPs produced by R. aquatilis HX2 showed excellent anticancer activities on HepG2 and HeLa cells.

Amorphous structure and crystal stability determine the bioavailability of selenium nanoparticles.

Microorganisms play a critical role in the biogeochemical cycling of selenium, often reducing selenite/selenate to elemental selenium nanoparticles (SeNPs). These SeNPs typically exist in an amorphous structure but can transform into a trigonal allotrope. However, the crystal structural transition process and its impact on selenium bioavailability have not been well studied. To shed light on this, we prepared chemosynthetic and biogenic SeNPs and investigated the stability of their crystal structure. We found that biogenic SeNPs exhibited a highly stable amorphous structure in various conditions, such as lyophilization, washing, and laser irradiation, whereas chemosynthetic SeNPs transformed into a trigonal structure in the same conditions. Additionally, a core-shell structure was observed in biogenic SeNPs after electron beam irradiation. Further analysis revealed that biogenic SeNPs showed a coordination reaction between Se atoms and surface binding biomacromolecules, indicating that the outer layer of Se-biomacromolecules complex prevented the SeNPs from crystallizing. We also investigated the effects of SeNPs crystal structures on the bioavailability in bacteria, yeast, and plants, finding that the amorphous structure of SeNPs determined Se bioavailability.

Shiga toxin 2 A-subunit induces mitochondrial damage, mitophagy and apoptosis via the interaction of Tom20 in Caco-2 cells.

Shiga toxin type 2 (Stx2) is the primary virulence factor produced by Shiga toxin-producing enterohemorrhagic Escherichia coli (STEC), which causes epidemic outbreaks of gastrointestinal sickness and potentially fatal sequela hemolytic uremic syndrome (HUS). Most studies on Stx2-induced apoptosis have been performed with holotoxins, but the mechanism of how the A and B subunits of Stx2 cause apoptosis in cells is not clear. Here, we found that Stx2 A-subunit (Stx2A) induced mitochondrial damage, PINK1/Parkin-dependent mitophagy and apoptosis in Caco-2 cells. PINK1/Parkin-dependent mitophagy caused by Stx2A reduced apoptosis by decreasing the accumulation of reactive oxidative species (ROS). Mechanistically, Stx2A interacts with Tom20 on mitochondria to initiate the translocation of Bax to mitochondria, leading to mitochondrial damage and apoptosis. Overall, these data suggested that Stx2A induces mitochondrial damage, mitophagy and apoptosis via the interaction of Tom20 in Caco-2 cells and that mitophagy caused by Stx2A ameliorates apoptosis by eliminating damaged mitochondria. These findings provide evidence for the potential use of Tom20 inhibition as an anti-Shiga toxin therapy.

A novel biocontrol agent Bacillus velezensis K01 for management of gray mold caused by Botrytis cinerea.

Gray mold is a destructive plant disease caused by a fungal pathogen Botrytis cinerea. The use of plant growth promoting rhizobacteria (PGPR) has proven to be a promising method to control this disease. Bacillus velezensis K01 was isolated from the rhizosphere of planting tomatoes. Strain K01 has a range of roles, including the ability to solubilize phytate phosphorus, stimulate resistant response, and produce indoleacetic acid (IAA), protease, cellulase, and antimicrobial substances. Strain K01 was found to inhibit 12 phytopathogenic fungi and 5 phytopathogenic bacteria. Specially, strain K01 demonstrated a biocontrol efficiency of over 78% against gray mold caused by B. cinerea on the leaves and fruits of tomato and pepper. Additionally, K01 was found to promote the growth of maize seedlings. Further genomic analysis revealed that K01 belongs to B. velezensis, which is consistent with phylogenetic analysis, average nucleotide polymorphism (ANI), and digital DNA-DNA hybridization (dDDH). The genome of strain K01 had a size of 3,927,799 bp and deduced 3866 predicted genes, with an average guanine-cytosine (GC) content of 46.5%. Based on the analyses of genomic secondary metabolites, over 18.4% of the genome was annotated to 12 gene clusters related to antimicrobial metabolite synthesis. Additionally, genome annotation and comparative genomics identified several genes associated with plant growth promotion and environmental adaption. These findings suggest that B. velezensis K01 has the potential to serve as a new biocontrol agent for management of gray mold on tomato and pepper.

MicroRNA-31 induced by Fusobacterium nucleatum infection promotes colorectal cancer tumorigenesis.

Persistent Fusobacterium nucleatum infection is associated with the development of human colorectal cancer (CRC) and promotes tumorigenicity, but the underlying mechanisms remain unclear. Here, we reported that F. nucleatum promoted the tumorigenicity of CRC, which was associated with F. nucleatum-induced microRNA-31 (miR-31) expression in CRC tissues and cells. F. nucleatum infection inhibited autophagic flux by miR-31 through inhibiting syntaxin-12 (STX12) and was associated with the increased intracellular survival of F. nucleatum. Overexpression of miR-31 in CRC cells promoted their tumorigenicity by targeting eukaryotic initiation factor 4F-binding protein 1/2 (eIF4EBP1/2), whereas miR-31 knockout mice were resistant to the formation of colorectal tumors. In conclusion, F. nucleatum, miR-31, and STX12 form a closed loop in the autophagy pathway, and continuous F. nucleatum-induced miR-31 expression promotes the tumorigenicity of CRC cells by targeting eIF4EBP1/2. These findings reveal miR-31 as a potential diagnostic biomarker and therapeutic target in CRC patients with F. nucleatum infection.

Germacrane Sesquiterpene Dilactones from Mikania micrantha and Their Antibacterial and Cytotoxic Activity.

Four new germacrane sesquiterpene dilactones, 2ß-hydroxyl-11ß,13-dihydrodeoxymikanolide (1), 3ß-hydroxyl-11ß,13-dihydrodeoxymikanolide (2), 1α,3ß-dihydroxy-4,9-germacradiene-12,8:15,6-diolide (3), and (11ß,13-dihydrodeoxymikanolide-13-yl)-adenine (4), together with five known ones (5-9) were isolated from the aerial parts of Mikania micrantha. Their structures were elucidated on the basis of extensive spectroscopic analysis. Compound 4 is featured with an adenine moiety in the molecule, which is the first nitrogen-containing sesquiterpenoid so far isolated from this plant species. These compounds were evaluated for their in vitro antibacterial activity against four Gram-(+) bacteria of Staphyloccocus aureus (SA), methicillin-resistant Staphylococcus aureus (MRSA), Bacillus cereus (BC) and Curtobacterium. flaccumfaciens (CF), and three Gram-(-) bacteria of Escherichia coli (EC), Salmonella. typhimurium (SA), and Pseudomonas Solanacearum (PS). Compounds 4 and 7-9 were found to show strong in vitro antibacterial activity toward all the tested bacteria with the MIC values ranging from 1.56 to 12.5 µg/mL. Notably, compounds 4 and 9 showed significant antibacterial activity against the drug-resistant bacterium of MRSA with MIC value 6.25 µg/mL, which was close to reference compound vancomycin (MIC 3.125 µg/mL). Compounds 4 and 7-9 were further revealed to show in vitro cytotoxic activity toward human tumor A549, HepG2, MCF-7, and HeLa cell lines, with IC50 values ranging from 8.97 to 27.39 µM. No antibacterial and cytotoxic activity were displayed for the other compounds. The present research provided new data to support that M. micrantha is rich in structurally diverse bioactive compounds worthy of further development for pharmaceutical applications and for crop protection in agricultural fields.

Uptake of Selenite by Rahnella aquatilis HX2 Involves the Aquaporin AqpZ and Na+/H+ Antiporter NhaA.

Microbial transformation of selenite [Se(IV)] to elemental selenium nanoparticles (SeNPs) is known to be an important process for removing toxic soluble selenium (Se) oxyanions and recovery of Se from the environment as valuable nanoparticles. However, the mechanism of selenite uptake by microorganisms, the first step through which Se exerts its cellular function, remains not well studied. In this study, the effects of selenite concentration, time, pH, metabolic inhibitors, and anionic analogues on selenite uptake in Rahnella aquatilis HX2 were investigated. Selenite uptake by R. aquatilis HX2 was concentration- and time-dependent, and its transport activity was significantly dependent on pH. In addition, selenite uptake in R. aquatilis HX2 was significantly inhibited by the aquaporin inhibitor AgNO3 and sulfite (SO32-), and partially inhibited by carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and 2,4-dinitrophenol (2,4-DNP) treatments. Three mutants with in-frame deletions of aqpZ, glpF, and nhaA genes were constructed. The transport assay showed that the water channel protein AqpZ, and not GlpF, was a key channel of selenite uptake by R. aquatilis HX2, and sulfite and selenite had a common uptake pathway. In addition, the Na+/H+ antiporter NhaA is also involved in selenite uptake in R. aquatilis HX2.

Isolation of Fusobacterium nucleatum from human feces using immunomagnetic separation coupled with fastidious anaerobe agar.

AIM: Fusobacterium nucleatum (F. nucleatum) is associated with the initiation, development, and metastasis of colorectal cancer. However, it is difficult to isolate F. nucleatum from clinical specimens. In this study, we aimed to develop an effective and rapid method for isolating F. nucleatum from human feces using polyclonal antibody (PAB)-coated immunomagnetic beads (IMBs) with selective media. METHODS AND RESULTS: IMBs conjugated with PAB were prepared and used to isolate F. nucleatum from human feces, and the bacteria were cultured with selective culture media (fastidious anaerobe agar + nalidixic acid + vancomycin). Under optimized experimental conditions, IMBs could selectively recover F. nucleatum from fecal microbiota samples spiked with Peptostreptococcus or Bacteroides fragilis. In artificial fecal samples, the detection sensitivity of IMBs for F. nucleatum was 103 CFU mL-1. In addition, IMBs combined with selective media could rapidly isolate F. nucleatum from human feces. CONCLUSIONS: This study successfully established an effective method for the rapid isolation of F. nucleatum from human feces by IMBs. The whole procedure requires 2-3 days, and has a sensitivity of 103 CFU mL-1 feces.

Ustiloxin A inhibits proliferation of renal tubular epithelial cells in vitro and induces renal injury in mice by disrupting structure and respiratory function of mitochondria.

Recently, we found that Ustiloxin A (UA, a mycotoxin) was widely detected in paddy environment and rice samples from several countries, and was also detected in human urine samples from China. However, the current knowledge about the health risks of UA are limited. In this research, the cytotoxicity of UA in mice renal tubular epithelial cells (mRTECs) was evaluated, and the results indicated that UA arrested cell cycle in G2/M phase via altering cellular morphology and microtubule, and inhibited the proliferation and division of mRTECs. Furthermore, UA could inhibit mitochondrial respiration via binding to the CoQ-binding site in dihydro-orotate dehydrogenase (DHODH) protein, and resulted in mitochondrial damage. These adverse effects of UA on mitochondria might be responsible for the cytotoxicity observed in vitro. In vivo, UA at concentrations that were comparable to the realistic concentrations of human exposure induced renal insufficiency in mice, and this might be associated with the renal mitochondrial damage in mice. However, exposure to UA at those realistic concentrations did not promote the progression from renal insufficiency to renal fibrosis and chronic kidney disease was not observed in mice.

Pollution Risk Assessment and Sources Analysis of Heavy Metal in Soil from Bamboo Shoots.

In order to investigate the pollution situation and sources analysis of heavy metals in bamboo shoot soil in Guangdong Province, a total of 175 soil samples were collected at 46 sites. Atomic fluorescence spectrophotometer and inductively coupled plasma mass spectrometry were used to determine the content of five heavy metals: lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg), and chromium (Cr). In addition, the soil environmental quality was evaluated through different index methods, including single-factor pollution, Nemeiro comprehensive pollution, geoaccumulation, and potential ecological risk. Furthermore, the correlation coefficients were also discussed. The results showed that the soils collected were acidic or slight alkaline. The maximum content of Pb and As from some areas exceeded the standard limit value. The coefficient of variation value from six areas exceeded 100%. The index method mentioned above confirmed that the soil within study areas was divided into three pollution levels: no, slightly, and mild. Additionally, there was a very significant correlation between pH and Pb, Hg; the correlation between heavy metal As and Pb, Cr also reached a very significant level. The principal component analysis results show that PC1 accounts for 39.60% of the total variance, which includes Pb, Cd, and As. PC2 mainly includes Hg and Cr.

Exposure to tris(1,3-dichloro-2-propyl) phosphate for two generations aggravates the adverse effects on survival and growth of zebrafish at environmentally relevant concentrations.

It was reported that tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) could inhibit the growth of F0-generation fish. However, multi-generation effects of TDCIPP on survival and growth of fish remain unknown. In this study, the effects of TDCIPP on survival and growth in F1 generation zebrafish were evaluated after two-generation exposure. Results demonstrated that TDCIPP inhibited the survival and growth of F1-generation zebrafish at 96 hpf and 30 dpf. Moreover, compared with the F0 generation, two-generation exposure resulted in a greater accumulation of TDCIPP in F1 generation zebrafish, and strongly down-regulated the expression of genes related to the GH/IGF axis (gh, igf1, igf2b) and HPT axis (tshß). Taken together, for the first time, this study revealed that exposure to TDCIPP for two generations at environmentally relevant concentrations aggravated the adverse effects on growth and survival in zebrafish.

Fusobacterium nucleatum induces excess methyltransferase-like 3-mediated microRNA-4717-3p maturation to promote colorectal cancer cell proliferation.

Fusobacterium nucleatum infection plays vital roles in colorectal cancer (CRC) progression. Overexpression of microRNA-4717-3p (miR-4717) was reported to be upregulated in F. nucleatum positive CRC tissues, however, the underlying mechanism is unknown. In this study, we found that miR-4717 promoted CRC cell proliferation in vitro and growth of CRC in vivo following F. nucleatum infection. MicroRNA-4717 suppressed the expression of mitogen-activated protein kinase kinase 4 (MAP2K4), a tumor suppressor, by directly targeting its 3'-UTR. Furthermore, we confirmed that methyltransferase-like 3 (METTL3)-dependent m6 A methylation could methylate primary (pri)-miR-4717, which further promoted the maturation of pri-miR-4717, and METTL3 positively regulated CRC cell proliferation through miR-4717/MAP2K4 pathways. In conclusion, F. nucleatum-induced miR-4717 excessive maturation through METTL3-dependent m6 A modification promotes CRC cell proliferation, which provides a potential therapeutic target and diagnostic biomarker for CRC.

Long non-coding RNA EVADR induced by Fusobacterium nucleatum infection promotes colorectal cancer metastasis.

Both Fusobacterium nucleatum (F. nucleatum) and long non-coding RNA (lncRNA) EVADR are associated with colorectal cancer (CRC), but their relationship with CRC metastasis and the mechanisms by which EVADR promotes CRC metastasis are poorly understood. Here, we report that F. nucleatum promotes colorectal cancer cell metastasis to the liver and lung and that it can be detected in CRC-metastasis colonization in mouse models. Furthermore, F. nucleatum upregulates the expression of EVADR, which can increase the metastatic ability of CRC cells in vivo and in vitro. Mechanistically, elevated EVADR serves as a modular scaffold for the Y-box binding protein 1 (YBX1) to directly enhance the translation of epithelial-mesenchymal transition (EMT)-related factors, such as Snail, Slug, and Zeb1. These findings suggest that EVADR induced by F. nucleatum promotes colorectal cancer metastasis through YBX1-dependent translation. The EVADR-YBX1 axis may be useful for the prevention and treatment of patients with F. nucleatum-associated CRC metastasis.

Radical Multicomponent Alkyl Alkynylation of Propellane via Synergistic Photoredox and Copper Catalysis.

Bicyclo[1.1.1]pentanes (BCPs) are important bioisosteres of aryl, tert-butyl groups, and internal alkynes that can impact key physicochemical properties on drug candidates. Herein, we describe a novel and efficient reaction to synthesize alkyl-alkynyl-substituted BCP derivatives by synergistic photoredox and copper catalysis at room temperature. The mild reaction conditions, simple protocol, broad functional group tolerance, and high efficiency of this procedure make it a valuable strategy for accessing alkynyl-substituted BCPs.

Polycyclic Phenol Derivatives from the Leaves of Spermacoce latifolia and Their Antibacterial and α-Glucosidase Inhibitory Activity.

Three new polycyclic phenol derivatives, 2-acetyl-4-hydroxy-6H-furo [2,3-g]chromen-6-one (1), 2-(1',2'-dihydroxypropan-2'-yl)-4-hydroxy-6H-furo [2,3-g][1]benzopyran-6-one (2) and 3,8,10-trihydroxy-4,9-dimethoxy-6H-benzo[c]chromen-6-one (8), along with seven known ones (3-7, 9 and 10) were isolated for the first time from the leaves of Spermacoce latifolia. Their structures were determined by spectroscopic analysis and comparison with literature-reported data. These compounds were tested for their in vitro antibacterial activity against four Gram-(+) bacteria: Staphyloccocus aureus (SA), methicillin-resistant Staphylococcus aureus (MRSA), Bacillus cereus (BC), Bacillus subtilis (BS), and the Gram-(-) bacterium Escherichia coli. Compounds 1, 2, 5 and 8 showed antibacterial activity toward SA, BC and BS with MIC values ranging from 7.8 to 62.5 µg/mL, but they were inactive to MRSA. Compound 4 not only showed the best antibacterial activity against SA, BC and BS, but it further displayed significant antibacterial activity against MRSA (MIC 1.95 µg/mL) even stronger than vancomycin (MIC 3.9 µg/mL). No compounds showed inhibitory activity toward E. coli. Further bioassay indicated that compounds 1, 4, 5, 6, 8 and 9 showed in vitro α-glucosidase inhibitory activity, among which compound 9 displayed the best α-glucosidase inhibitory activity with IC50 value (0.026 mM) about 15-fold stronger than the reference compound acarbose (IC50 0.408 mM). These results suggested that compounds 4, 8 and 9 were potentially highly valuable compounds worthy of consideration to be further developed as an effective anti-MRSA agent or effective α-glucosidase inhibitors, respectively. In addition, the obtained data also supported that S. latifolia was rich in structurally diverse bioactive compounds worthy of further investigation, at least in searching for potential antibiotics and α-glucosidase inhibitors.

Highly stable selenium nanoparticles: Assembly and stabilization via flagellin FliC and porin OmpF in Rahnella aquatilis HX2.

Microorganisms play a critical role in the reduction of the more toxic selenite and selenate to the less toxic elemental selenium. However, the assembly process and stability of selenium nanoparticles (SeNPs) remain understudied. The plant growth-promoting rhizobacterium Rahnella aquatilis HX2 can reduce selenite to biogenic SeNPs (BioSeNPs). Two main proteins, namely flagellin FliC and porin OmpF were identified in the BioSeNPs. The fliC and ompF gene mutation experiments demonstrated that the FliC and OmpF could control the assembly of BioSeNPs in vivo. At the same time, the expressed and purified FliC and OmpF could control the assembly of SeNPs in vitro. BioSeNPs produced by R. aquatilis HX2 exhibited high stability under various ionic strengths, while the chemically synthesized SeNPs (CheSeNPs) showed a high level of aggregation. The in vitro experiments verified that FliC and OmpF could prevent the aggregation of the CheSeNPs under various ionic strengths. This work reports the preparation of highly stable BioSeNPs produced by strain R. aquatilis HX2 and verifies that FliC and OmpF both could control the assembly and stability of BioSeNPs. BioSeNPs with high stability could be suitable as nutritional supplement to remedy selenium deficiency and in nanomedicine applications.

Thymol derivatives with antibacterial and cytotoxic activity from the aerial parts of Ageratina adenophora.

Three new thymol derivatives, 7-formyl-9-isobutyryloxy-8-hydroxythymol (1), 7,9-di-isobutyryloxy-8,10-dehydrothymol (2) and 2α-methoxyl-3ß-methyl-6-methylol-2,3-dihydrobenzofuran (3), along with five known ones (4-8), were isolated from the aerial parts of the invasive plant Ageratina adenophora. Their structures were elucidated by extensive spectroscopic analysis and they were all isolated from the aerial part of A. adenophora for the first time. These compounds, except 8, selectively showed in vitro antimicrobial activity against three Gram-(+) and two Gram-(-) bacterial strains. In particular, compounds 1 and 5 showed notable in vitro antimicrobial activity against all five bacterial strains with IC50 values ranging from 3.9 to 15.6 µg mL-1, as compared to reference compound kanamycin sulfate with a MIC value 1.9-3.9 µg mL-1. Compounds 1 and 5 were further revealed to show in vitro cytotoxic activity against three tested human tumor (MCF-7, NCI-H460 and HeLa) cell lines, with IC50 values ranging from 7.45 to 28.63 µM. Compounds 7 and 8 selectively showed slight but detectable in vitro cytotoxicity toward MCF-7 and NCI-H460 cell lines, with IC50 values 44.65-83.19 µM. No cytotoxic effects were detected in the bioassay of the other four thymol derivatives. The present results provide new data to support that the aerial parts of A. adenophora are a rich source of bioactive chemicals valuable in medicinal applications.

The small RNA chaperone Hfq is a critical regulator for bacterial biosynthesis of selenium nanoparticles and motility in Rahnella aquatilis.

The RNA chaperone, Hfq, is a global post-transcriptional regulator that plays an important role in regulating pleiotropic functions, such as cell growth and motility, stress tolerance, and virulence to host, in many Gram-negative bacteria. This study examined the functional roles of Hfq in Rahnella aquatilis HX2, a plant beneficial, selenium nanoparticles (SeNPs)-producing soil bacterium. A mutant HX2∆hfq with an in-frame deletion within the hfq gene in R. aquatilis HX2 was constructed and tested for various phenotypic features. Bacterial growth, motility, selenite reduction, and SeNPs production were compared between the mutant, the wild-type, and the complementation strain. The hfq gene deletion delayed the growth of strain HX2, with a lower bacterial population during the stationary phase, and significantly impaired the swimming motility of the bacterium, showing a smaller motility ring on the plate. The hfq mutation also dramatically declined microbial-induced reduction of selenite and SeNPs production in HX2, which was independent of cell growth. The introduction of a trans-expressed hfq gene into HX2∆hfq for complementation completely restored impacted phenotypes. In addition, reverse transcription real-time quantitative PCR (RT-qPCR) analysis revealed that the expression of ten genes involved in bacterial growth and survival, motility and chemotaxis, and selenite or seleno-compound metabolism were influenced by Hfq loss-of-function by at least two-fold. Six genes including two involved in SeNPs production were positively regulated by hfq, while other four genes were negatively regulated. Homolog search suggested that the rprA gene might encode a small RNA regulated by Hfq in R. aquatilis HX2. Overall, the present study provides novel information about the function of Hfq and the regulation of bacterial biosynthesis of SeNPs.

Anti-MRSA Sesquiterpenes from the Semi-Mangrove Plant Myoporum bontioides A. Gray.

The striking rise of methicillin-resistant Staphylococcus aureus (MRSA) infections has become a serious threat to public health worldwide. In an effort to search for new anti-MRSA agents from natural products, a bioassay-guided phytochemical study was conducted on the semi-mangrove plant Myoporum bontioides A. Gray, which led to the isolation of two new sesquiterpene alkaloids (1 and 2) and six known furanosesquiterpenes (3⁻8). Their structures were elucidated on the basis of extensive analysis of their 1D, 2D NMR and mass spectroscopic data. These two new alkaloids (1 and 2) displayed potent anti-MRSA activity with MIC value of 6.25 µg/mL. This is the first report of sesquiterpene alkaloids from the plants of Myoporum genus and their anti-MRSA activity.