A novel alkane monooxygenase evolved from a broken piece of ribonucleotide reductase in Geobacillus kaustophilus HTA426 isolated from Mariana Trench.

We have accidentally found that a thermophilic Geobacillus kaustophilus HTA426 is capable of degrading alkanes although it has no alkane oxygenating enzyme genes. Our experimental results revealed that a putative ribonucleotide reductase small subunit GkR2loxI (GK2771) gene encodes a novel heterodinuclear Mn-Fe alkane monooxygenase/hydroxylase. GkR2loxI protein can perform two-electron oxidations similar to homonuclear diiron bacterial multicomponent soluble methane monooxygenases. This finding not only answers a long-standing question about the substrate of the R2lox protein clade, but also expands our understanding of the vast diversity and new evolutionary lineage of the bacterial alkane monooxygenase/hydroxylase family.

Duckweed-associated bacteria as plant growth-promotor to enhance growth of Spirodela polyrhiza in wastewater effluent from a poultry farm.

Duckweed has been highlighted as an invaluable resource because of its abilities to remove nitrogen and phosphorus from wastewater coupling with the production of high starch/protein-containing plant biomass. Duckweed recruits microbes and particularly forms a stable "core" bacterial microbiota, which greatly reduces the colonization efficiency of plant growth-promoting bacteria (PGPB). In this study, natural duckweeds were enriched in a sterilized-partially treated wastewater effluent from a poultry farm. After 24 days of cultivation, the duckweed-associated bacteria (DAB) were isolated and evaluated for their plant growth-promoting (PGP) potentials by co-cultivation with axenic Spirodela polyrhiza. Ten species were found in more than one location and could be considered candidates for the stable "core" DAB. Among them, all isolates of Acinetobacter soli, Acidovorax kalamii, Brevundimonas vesicularis, Pseudomonas toyotomiensis, and Shinella curvata increased duckweed growth in Hoagland medium. The highest PGP ability was observed in Sh. curvata W12-8 (with EPG value of 208.72%), followed by Paracoccus marcusii W7-16 (171.31%), Novosphingobium subterraneum W5-13 (156.96%), and Ac. kalamii W7-18 (156.96%). However, the highest growth promotion in the wastewater was observed when co-cultured with W7-16, which was able to increase biomass dry weight and root length of duckweed by 3.17 and 2.26 folds, respectively.

Growth Promotion of Giant Duckweed Spirodela polyrhiza (Lemnaceae) by Ensifer sp. SP4 Through Enhancement of Nitrogen Metabolism and Photosynthesis.

Duckweeds (Lemnaceae) are representative producers in fresh aquatic ecosystems and also yield sustainable biomass for animal feeds, human foods, and biofuels, and contribute toward effective wastewater treatment; thus, enhancing duckweed productivity is a critical challenge. Plant-growth-promoting bacteria (PGPB) can improve the productivity of terrestrial plants; however, duckweed-PGPB interactions remain unclear and no previous study has investigated the molecular mechanisms underlying duckweed-PGPB interaction. Herein, a PGPB, Ensifer sp. strain SP4, was newly isolated from giant duckweed (Spirodela polyrhiza), and the interactions between S. polyrhiza and SP4 were investigated through physiological, biochemical, and metabolomic analyses. In S. polyrhiza and SP4 coculture, SP4 increased the nitrogen (N), chlorophyll, and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) contents and the photosynthesis rate of S. polyrhiza by 2.5-, 2.5-, 2.7-, and 2.4-fold, respectively. Elevated photosynthesis increased the relative growth rate and biomass productivity of S. polyrhiza by 1.5- and 2.7-fold, respectively. Strain SP4 significantly altered the metabolomic profile of S. polyrhiza, especially its amino acid profile. N stable isotope analysis revealed that organic N compounds were transferred from SP4 to S. polyrhiza. These N compounds, particularly glutamic acid, possibly triggered the increase in photosynthetic and growth activities. Accordingly, we propose a new model for the molecular mechanism underlying S. polyrhiza growth promotion by its associated bacteria Ensifer sp. SP4, which occurs through enhanced N compound metabolism and photosynthesis. Our findings show that Ensifer sp. SP4 is a promising PGPB for increasing biomass yield, wastewater purification activity, and CO2 capture of S. polyrhiza.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Nostosin G and Spiroidesin B from the Cyanobacterium Dolichospermum sp. NIES-1697.

Chemical investigation of the cyanobacterium Dolichospermum sp. NIES-1697 afforded nostosin G (1), a linear tripeptide, spiroidesin B (2), and two known compounds, anabaenopeptins I (3) and J (4). Planar structures and absolute configurations for 1 and 2 were determined by 2D NMR, HRMS, Marfey's methodology, chiral-phase HPLC, and enzymatic degradation. Nostosin G (1) is a unique example of a linear peptide containing three subunits, 4-hydroxyphenyllactic acid (Hpla), homotyrosine (Hty), and argininal, with potent trypsin inhibitory properties. The biosynthetic gene clusters for nostosin G (1) and spiroidesin B (2) were investigated based on the genome sequence of Dolichospermum sp. NIES-1697.

Light-Triggered, Non-Centrosymmetric Self-Assembly of Aqueous Arylazopyrazoles at the Air-Water Interface and Switching of Second-Harmonic Generation.

Trans-p-methoxy arylazopyrazole spontaneously forms non-centrosymmetric polar crystals, which reversibly undergo liquefaction upon photoisomerization to the cis-isomer. This liquid cis-isomer has a large electric dipole moment and is highly soluble in water (solubility up to ≈58 mM), which is remarkably higher than that of the trans-isomer (690 µM). Vis-light illumination of the aqueous cis-isomer generates macroscopically oriented, non-centrosymmetric crystals at the air-water interface. Polar crystals are also formed in sandwich glass cells (spacing, 20 µm) upon photo-induced crystallization of the liquid cis-isomer. The trans-crystals thus formed showed second harmonic generation (SHG) whose intensity is switched on/off in response to the photo-induced phase transition.

Enhanced Electric Polarization and Polar Switching of Dipolar Aromatic Liquids Confined in Supramolecular Gel Networks.

Dipolar aromatic liquids confined in the interstitial domains of chiral organogels show significantly enhanced electric polarization, as compared with those of pure liquids alone or organogels formed with nonpolar liquids. Intriguingly, nitrobenzene gels showed a supramolecular polar switching phenomenon; i.e., hysteresis in the polarization (P)-electric field (E) curves was observed for the gel above the melting point of the solvent. This indicates that the nitrobenzene molecules confined in the chiral nanofibrous gel networks exert macroscopic polarization whose direction is inversed depending on the direction of the external electric field. The anomalously enhanced electric polarization and polar switching phenomenon of supramolecular gels in varied solvents are scrutinized by the positive-up-negative-down (PUND) measurements, and the interactions between the gel nanofibers and the polar solvent molecules play crucial roles for the emergence of the polar switching phenomenon. This work presents for the first time that dipolar liquid molecules filling the interstitial space of supramolecular gels exhibit a significant confinement effect. It provides a new perspective to design electric-field-responsive soft materials based on the functional liquid domains confined in their porous networks.

Biosurfactants from Marine Cyanobacteria Collected in Sabah, Malaysia.

Chemical investigation of the organic extract from Moorea bouillonii, collected in Sabah, Malaysia, led to the isolation of three new chlorinated fatty acid amides, columbamides F (1), G (2), and H (3). The planar structures of 1-3 were established by a combination of mass spectrometric and NMR spectroscopic analyses. The absolute configuration of 1 was determined by Marfey's analysis of its hydrolysate and chiral-phase HPLC analysis after conversion and esterification with Ohrui's acid, (1S,2S)-2-(anthracene-2,3-dicarboximido)cyclohexanecarboxylic acid. Compound 1 showed biosurfactant activity by an oil displacement assay. Related known fatty acid amides columbamide D and serinolamide C exhibited biosurfactant activity with critical micelle concentrations of about 0.34 and 0.78 mM, respectively.

Enhanced lipid productivity of Chlamydomonas reinhardtii with combination of NaCl and CaCl2 stresses.

Salinity (NaCl) stress treatment is a strategy to induce lipid accumulation in microalgae. This study aimed to investigate the effect of a combination of two salts (NaCl/CaCl2) on lipid productivity of Chlamydomonas reinhardtii. C. reinhardtii was cultured in a two-stage culture comprising 9-day active growth in C medium followed by 3-day salt stress in C medium with various concentrations of NaCl (50‒200 mM)/CaCl2 (100 mM). In salt stress stage, NaCl (200 mM), CaCl2 (100 mM), and the NaCl/CaCl2 mixture inhibited growth but increased the lipid content in C. reinhardtii in comparison with NaCl (0, 50, and 100 mM) conditions. Combinatorial treatment with 100 mM NaCl/100 mM CaCl2 resulted in the highest lipid content (73.4%) and lipid productivity (10.9 mg/L/days), being 3.5- and 2.1-fold, respectively, in salt-free control conditions, and 1.8- and 1.5-folds, respectively, with 200 mM NaCl. Furthermore, 100 mM NaCl/100 mM CaCl2 treatment markedly upregulated glycerol-3-phosphate dehydrogenase (GPDH), lysophosphatidic acid acyltransferase (LPAAT), and diacylglycerol acyltransferase (DAGAT), which are involved in lipid accumulation in C. reinhardtii. The upregulation of these genes with 100 mM NaCl/100 mM CaCl2 resulted in the highest lipid content in C. reinhardtii. Therefore, stress treatment using two salts, 100 mM NaCl/100 mM CaCl2, is a potentially promising strategy to enhance lipid productivity in microalgae.

Colonization and Competition Dynamics of Plant Growth-Promoting/Inhibiting Bacteria in the Phytosphere of the Duckweed Lemna minor.

Despite the considerable role of aquatic plant-associated bacteria in host plant growth and nutrient cycling in aquatic environments, the mode of their plant colonization has hardly been understood. This study examined the colonization and competition dynamics of a plant growth-promoting bacterium (PGPB) and two plant growth-inhibiting bacteria (PGIB) in the aquatic plant Lemna minor (common duckweed). When inoculated separately to L. minor, each bacterial strain quickly colonized at approximately 106 cells per milligram (plant fresh weight) and kept similar populations throughout the 7-day cultivation time. The results of two-membered co-inoculation assays revealed that the PGPB strain Aquitalea magnusonii H3 consistently competitively excluded the PGIB strain Acinetobacter ursingii M3, and strain H3 co-existed at almost 1:1 proportion with another PGIB strain, Asticcacaulis excentricus M6, regardless of the inoculation ratios (99:1-1:99) and inoculation order. We also found that A. magnusonii H3 exerted its growth-promoting effect over the negative effects of the two PGIB strains even when only a small amount was inoculated, probably due to its excellent competitive colonization ability. These experimental results demonstrate that there is a constant ecological equilibrium state involved in the bacterial colonization of aquatic plants.

Hierarchical Hybrid Metal-Organic Frameworks: Tuning the Visible/Near-Infrared Optical Properties by a Combination of Porphyrin and Its Isomer Units.

Hybrid metal-organic frameworks (MOFs) with core/shell-like hierarchical structure comprised of zirconium metal and porphyrin (e.g., TPP) and its isomer, N-confused porphyrin (NCP), were synthesized through a seed-mediated reaction. The hierarchical structures of hybrid MOFs were characterized by the microscopic image analyses (e.g., scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectrometry, and confocal laser scanning microscope (CLSM)). Taking advantage of the intrinsic light-harvesting properties of the porphyrin dye and the N-confused isomer, changing the core/shell layer structures of hybrid MOFs allows for tuning of the visible-to-near-infrared (NIR) absorption/emission characters, excited-state energy migrations, and photosensitization capabilities. The Förster energy transfer event occurring in the bulk MOF samples by photoexcitation enabled us to control the photoinduced singlet oxygen generation through the comprehensive light-harvesting ability of these hybrid porphyrinic MOFs. Therefore, implementation of a precisely designed porphyrin "substitute" into the MOF-based materials indeed provides a new mimic of the photosynthetic pigment system and should be potentially applicable for solar-light-driven devices.

Simple and Versatile Platform for Air-Tolerant Photon Upconverting Hydrogels by Biopolymer-Surfactant-Chromophore Co-assembly.

Exploration of triplet-triplet annihilation based photon upconversion (TTA-UC) in aqueous environments faces difficulty such as chromophores insolubility and deactivation of excited triplets by dissolved oxygen molecules. We propose a new strategy of biopolymer-surfactant-chromophore coassembly to overcome these issues. Air-stable TTA-UC with a high upconversion efficiency of 13.5% was achieved in hydrogel coassembled from gelatin, Triton X-100 and upconverting chromophores (triplet sensitizer and emitter). This is comparable to the highest UC efficiency observed to date for air-saturated aqueous UC systems. Moreover, this is the first example of air-stable TTA-UC in the form of hydrogels, widening the applicability of TTA-UC in biological applications. The keys are two-fold. First, gelatin and the surfactant self-assemble in water to give a developed hierarchical structure with hydrophobic domains which accommodate chromophores up to high concentrations. Second, thick hydrogen-bonding networks of gelatin backbone prevent O2 inflow to the hydrophobic interior, as evidenced by long acceptor triplet lifetime of 4.9 ms. Air-stable TTA-UC was also achieved for gelatin with other nonionic surfactants (Tween 80 and Pluronic f127) and Triton X-100 with other gelling biopolymers (sodium alginate and agarose), demonstrating the versatility of current strategy.

Photoresponsive Nanosheets of Polyoxometalates Formed by Controlled Self-Assembly Pathways.

Anionic Keggin polyoxometalates (POMs) and ether linkage-enriched ammonium ions spontaneously self-assemble into rectangular ultrathin nanosheets in aqueous media. The structural flexibility of the cation is essential to form oriented nanosheets; as demonstrated by single-crystal X-ray diffraction measurements. The difference in initial conditions exerts significant influence on selecting for self-assembly pathways in the energy landscape. Photoillumination of the POM sheets in pure water causes dissolution of reduced POMs, which allowed site-specific etching of nanosheets using laser scanning microscopy. By contrast, photoetching was suppressed in aqueous AgNO3 and site-selective deposition of silver nanoparticles occurred as a consequence of electron transfer from the photoreduced POMs to Ag+ ions on the nanosheet surface.

Ferroelectric Coordination Polymers Self-Assembled from Mesogenic Zinc(II) Porphyrin and Dipolar Bridging Ligands.

A new class of ferroelectric coordination-based polymers has been developed by the self-assembly of lipophilic zinc porphyrin (ZnP) and ditopic bridging ligands. The ligands contain dipolar benzothiadiazole or fluorobenzene units, which are axially coordinated to ZnP with the dipole moments oriented perpendicular to the coordination axes. The coordination-based polymers show ferroelectric characteristics in the liquid crystalline state, as revealed by distinctive hysteresis in the polarization-electric field (P-E) loops and inversion current peaks in current-voltage (I-V) loops. The observed ferroelectric properties are explainable by flip-flop rotation of the dipolar axle ligands induced by the applied electric field, as demonstrated by the positive-up-negative-down (PUND) measurements. The present system provides a new operating principle in supramolecular ferroelectrics.

Photon Upconversion and Molecular Solar Energy Storage by Maximizing the Potential of Molecular Self-Assembly.

The self-assembly of functional molecules into ordered molecular assemblies and the fulfillment of potentials unique to their nanotomesoscopic structures have been one of the central challenges in chemistry. This Feature Article provides an overview of recent progress in the field of molecular self-assembly with the focus on the triplet-triplet annihilation-based photon upconversion (TTA-UC) and supramolecular storage of photon energy. On the basis of the integration of molecular self-assembly and photon energy harvesting, triplet energy migration-based TTA-UC has been achieved in varied molecular systems. Interestingly, some molecular self-assemblies dispersed in solution or organogels revealed oxygen barrier properties, which allowed TTA-UC even under aerated conditions. The elements of molecular self-assembly were also introduced to the field of molecular solar thermal fuel, where reversible photoliquefaction of ionic crystals to ionic liquids was found to double the molecular storage capacity with the simultaneous pursuit of switching ionic conductivity. A future prospect in terms of innovating molecular self-assembly toward molecular systems chemistry is also discussed.

Hierarchical Self-Assembly of Luminescent Tartrate-Bridged Chiral Binuclear Tb(III) Complexes in Ethanol.

A new family of supramolecular metalloamphiphiles carrying two metal centers is developed. They are formed by bridging two coordinatively unsaturated lipophilic Tb3+ complexes (TbL+) with chiral dicarboxylate anions. The formation of bridging coordination bonds is confirmed using UV spectroscopy, induced circular dichroism (ICD), increased luminescence intensity of TbL+, and electrospray ionization mass spectrometry (ESIMS) analysis. These supramolecular metalloamphiphiles hierarchically self-assemble in ethanol to give luminescent nanospheres, as observed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The two hydroxyl groups introduced in the bridging ligands of [TbL]2(d-/l-tartrate) significantly promote self-assembly by increasing coherent forces via intermolecular hydrogen bonding. The observed self-assembly in ethanol also merits mention because such polar alcoholic media have been unfavorable for conventional molecular self-assemblies. The present approach offers a new molecular design strategy for composable metalloamphiphiles.

Wewakazole B, a Cytotoxic Cyanobactin from the Cyanobacterium Moorea producens Collected in the Red Sea.

A mass spectrometry (MS)-guided isolation has led to the purification of a new cyanobactin, wewakazole B (1), along with the known compound curacin D from a Red Sea Moorea producens. The planar structure of 1 was elucidated using a combination of NMR and MS techniques. After ozonolysis and acid hydrolysis, the absolute configurations of the amino acid components of 1 were determined by chiral-phase LC-MS and HPLC analyses. Notably, compound 1 exhibited cytotoxic activity toward human MCF7 breast cancer cells (IC50 = 0.58 µM) and human H460 lung cancer cells (IC50 = 1.0 µM) and was also found to be inactive in a siderophore assay.

Isolation and characterization of an early colonizing Rhizobium sp. R8 from a household toilet bowl.

The bacterial community structure was compared between the third days', one week', and three weeks' biofilm samples from the surface of a household toilet bowl. It was found that the PCR-DGGE band pattern of 16S rRNA gene was dramatically changed after the third day and was not further changed until three weeks. This result suggests that there are early and late colonizing bacterial groups. One of the early colonizers isolated from the third days' sample was Rhizobium sp. R8, a closest relative to Rhizobium giardinii, which exhibited the highest biofilm formation activity in an artificial urine condition. R8 produced extracellular polysaccharides containing galactose, glucose, and mannose at the molar ratio of 8:1:1, which were probably responsible for the biofilm formation. Its excelled biofilm formation and urease activities together with the lack of nodulation and nitrogen fixing genes in R8 suggest that this strain has been specifically adapted to urine condition in a toilet bowl.

Photoliquefiable ionic crystals: a phase crossover approach for photon energy storage materials with functional multiplicity.

Ionic crystals (ICs) of the azobenzene derivatives show photoinduced IC-ionic liquid (IL) phase transition (photoliquefaction) upon UV-irradiation, and the resulting cis-azobenzene ILs are reversibly photocrystallized by illumination with visible light. The photoliquefaction of ICs is accompanied by a significant increase in ionic conductivity at ambient temperature. The photoliquefaction also brings the azobenzene ICs further significance as photon energy storage materials. The cis-IL shows thermally induced crystallization to the trans-IC phase. This transition is accompanied by exothermic peaks with a total ΔH of 97.1 kJ mol(-1) , which is almost double the conformational energy stored in cis-azobenzene chromophores. Thus, the integration of photoresponsive ILs and self-assembly pushes the limit of solar thermal batteries.

Self-assembly of azobenzene bilayer membranes in binary ionic liquid-water nanostructured media.

Anionic azobenzene-containing amphiphile 1 (sodium 4-[4-(N-methyl-N-dodecylamino)phenylazo]benzenesulfonate) forms ordered bilayer membranes in binary ionic liquid (1-ethyl-3-methylimidazolium ethyl sulfate, [C2mim][C2OSO3])-water mixtures. The binary [C2mim][C2OSO3]-water mixture is macroscopically homogeneous at any mixing ratio; however, it possesses fluctuating nanodomains of [C2mim][C2OSO3] molecules as observed by dynamic light scattering (DLS). These nanodomains show reversible heat-induced mixing behavior with water. Although the amphiphile 1 is substantially insoluble in pure water, it is dispersible in the [C2mim][C2OSO3]-water mixtures. The concentration of [C2mim][C2OSO3] and temperature exert significant influences on the self-assembling characteristics of 1 in the binary media, as shown by DLS, transmission electron microscopy (TEM), UV-vis spectroscopy, and zeta-potential measurements. Bilayer membranes with rod- or dotlike nanostructures were formed at a lower content of [C2mim][C2OSO3] (2-30 v/v %), in which azobenzene chromophores adopt parallel molecular orientation regardless of temperature. In contrast, when the content of [C2mim][C2OSO3] is increased above 60 v/v %, azobenzene bilayers showed thermally reversible gel-to-liquid crystalline phase transition. The self-assembly of azobenzene amphiphiles is tunable depending on the volume fraction of [C2mim][C2OSO3] and temperature, which are associated with the solvation by nanoclusters in the binary [C2mim][C2OSO3]-water media. These observations clearly indicate that mixtures of water-soluble ionic liquids and water provide unique and valiant environments for ordered molecular self-assembly.

Cloning and expression of three ladA-type alkane monooxygenase genes from an extremely thermophilic alkane-degrading bacterium Geobacillus thermoleovorans B23.

An extremely thermophilic bacterium, Geobacillus thermoleovorans B23, is capable of degrading a broad range of alkanes (with carbon chain lengths ranging between C11 and C32) at 70 °C. Whole-genome sequence analysis revealed that unlike most alkane-degrading bacteria, strain B23 does not possess an alkB-type alkane monooxygenase gene. Instead, it possesses a cluster of three ladA-type genes, ladAαB23, ladAßB23, and ladB B23, on its chromosome, whose protein products share significant amino acid sequence identities, 49.8, 34.4, and 22.7 %, respectively, with that of ladA alkane monooxygenase gene found on a plasmid of Geobacillus thermodetrificans NG 80-2. Each of the three genes, ladAαB23, ladAßB23, and ladB B23, was heterologously expressed individually in an alkB1 deletion mutant strain, Pseudomonas fluorescens KOB2Δ1. It was found that all three genes were functional in P. fluorescens KOB2Δ1, and partially restored alkane degradation activity. In this study, we suggest that G. thermoleovorans B23 utilizes multiple LadA-type alkane monooxygenases for the degradation of a broad range of alkanes.