Assessment of the Safety and Exopolysaccharide Synthesis Capabilities of Bacillus amyloliquefaciens D189 Based on Complete Genome and Phenotype Analysis.

Exopolysaccharides (EPS) are natural macromolecular carbohydrates with good functional activity and physiological activities, which can be utilized as an emulsifier, viscosity enhancer, stabilizer, gelling agent, and water retention agent in a wide range of food products. In this study, the whole genome of Bacillus amyloliquefaciens D189, an EPS-producing bacteria, was sequenced. The result showed that D189 contains a single, circular chromosome of 3,963,356 bp with an average GC content of 45.74% and 3996 coding genes. The gene annotation results showed that D189 is a potentially safe strain and confirmed to be safe associated with hemolytic assay, and antibiotic resistance test. Meanwhile, D189 genome possessed 240 genes related to carbohydrate metabolism. More importantly, D189 could transport 9 sugars and contained a complete biosynthetic pathway for 8 nucleotide sugars. Based on the validation experiments, strain D189 could metabolize 8 sugars (glucose, sucrose, trehalose, fructose, cellobiose, maltose, mannitol, and N-acetyl-D-glucosamine) to produce EPS, with the highest yield of 1.212 g/L when sucrose was the carbon source. Therefore, the whole genome sequencing preliminarily elucidated the physiological mechanism of EPS, providing several pathways for engineering D189 to further enhance the yield of EPS.

BmPGPR-L4 is a negative regulator of the humoral immune response in the silkworm Bombyx mori.

Toll, immune deficiency and prophenoloxidase cascade represent vital immune signaling pathways in insects. Peptidoglycan recognition proteins (PGRPs) are innate immune receptors that activate and regulate the immune signaling pathways. Previously, we reported that BmPGPR-L4 was induced in the silkworm Bombyx mori larvae by bacteria and peptidoglycan challenges. Here, we focused on the function of BmPGRP-L4 in regulating the expression of antimicrobial peptides (AMPs). The hemolymph from BmPGRP-L4-silenced larvae exhibited an enhanced inhibitory effect on the growth of Escherichia coli, either by growth curve or inhibitory zone experiments. Coincidentally, most of the AMP genes were upregulated after RNAi of BmPGRP-L4. Oral administration of heat-inactivated E. coli and Staphylococcus aureus after RNAi of BmPGRP-L4 resulted in the increased expression of BmPGRP-L4 in different tissues of the silkworm larvae, revealing an auto-regulatory mechanism. By contrast, the expression of most AMP genes was downregulated by oral bacterial administration after RNAi of BmPGRP-L4. The above results demonstrate that BmPGRP-L4 recognizes bacterial pathogen-associated molecular patterns and negatively regulates AMP expression to achieve immunological homeostasis. As a negative regulator, BmPGPR-L4 is proposed to be involved in the feedback regulation of the immune signaling pathways of the silkworm to prevent excessive activation of the immune response.

Structural, electronic, and optical properties of three types Ca3N2 from first-principles study.

CONTEXT: To find the potential value of Ca3N2 in the field of optoelectronics, the physical properties of Ca3N2 will be analyzed. It can be concluded from the electronic properties that the Ca-N bonds of α-Ca3N2 are more stable than those of δ-Ca3N2 and ε-Ca3N2. The dielectric function, reflectivity function, and absorption function of three types of Ca3N2 were accurately calculated, and it was concluded that α-Ca3N2, δ-Ca3N2, and ε-Ca3N2 have greater transmittance for visible light and exhibit optical transparency in the near-infrared frequency domain. Combined with the high hardness, strong bonding, high melting point, and wear resistance of Ca3N2, Ca3N2 can be used as a new generation of window heat-resistant materials. The α-Ca3N2, δ-Ca3N2, and ε-Ca3N2 are indirect, direct, and indirect narrow bandgap compounds, respectively, that is, δ-Ca3N2 is more suitable for luminescent materials than α-Ca3N2 and ε-Ca3N2. α-Ca3N2 and δ-Ca3N2 have high reflective properties in the ultraviolet region and can be used as UV protective coatings. All three Ca3N2 materials can be used industrially to synthesize photovoltaic devices that operate in the ultraviolet region. METHODS: Based on the first-principles of density functional theory calculations, the structures, electronic properties, and optical properties of α-Ca3N2, δ-Ca3N2, and ε-Ca3N2 were calculated. The calculation results show that although the α-Ca3N2, δ-Ca3N2, and ε-Ca3N2 have similar electronic structures, some phases have better properties in some aspects.

Estimation of leaf nutrition status in degraded vegetation based on field survey and hyperspectral data.

Timely monitoring of global plant biogeochemical processes demands fast and highly accurate estimation of plant nutrition status, which is often estimated based on hyperspectral data. However, few such studies have been conducted on degraded vegetation. In this study, complete combinations of either original reflectance or first-order derivative spectra have been developed to quantify leaf nitrogen (N), phosphorus (P), and potassium (K) contents of tree, shrub, and grass species using hyperspectral datasets from light, moderate, and severely degraded vegetation sites in Helin County, China. Leaf N, P, and K contents were correlated to identify suitable combinations. The most effective combinations were those of reflectance difference (Dij), normalized differences (ND), first-order derivative (FD), and first-order derivative difference (FD(D)). Linear regression analysis was used to further optimize sensitive band-based combinations, which were compared with 43 frequently used empirical spectral indices. The proposed hyperspectral indices were shown to effectively quantify leaf N, P, and K content (R2 > 0.5, p < 0.05), confirming that hyperspectral data can be potentially used for fine scale monitoring of degraded vegetation.

Immobilization of Anions on Polymer Matrices for Gel Electrolytes with High Conductivity and Stability in Lithium Ion Batteries.

This study reports on a high ionic-conductivity gel polymer electrolyte (GPE), which is supported by a TiO2 nanoparticle-decorated polymer framework comprising poly(acrylonitrile-co-vinyl acetate) blended with poly(methyl methacrylate), i.e. , PAVM: TiO2. High conductivity GPE-PAVM: TiO2 is achieved by causing the PAVM:TiO2 polymer framework to swell in 1 M LiPF6 in carbonate solvent. Raman analysis results demonstrate that the poly(acrylonitrile) (PAN) segments and TiO2 nanoparticles strongly adsorb PF6(-) anions, thereby generating 3D percolative space-charge pathways surrounding the polymer framework for Li(+)-ion transport. The ionic conductivity of GPE-PAVM: TiO2 is nearly 1 order of magnitude higher than that of commercial separator-supported liquid electrolyte (SLE). GPE-PAVM: TiO2 has a high Li(+) transference number (0.7), indicating that most of the PF6(-) anions are stationary, which suppresses PF6(-) decomposition and substantially enlarges the voltage that can be applied to GPE-PAVM: TiO2 (to 6.5 V vs Li/Li(+)). Immobilization of PF6(-) anions also leads to the formation of stable solid-electrolyte interface (SEI) layers in a full-cell graphite|electrolyte|LiFePO4 battery, which exhibits low SEI and overall resistances. The graphite|electrolyte|LiFePO4 battery delivers high capacity of 84 mAh g(-1) even at 20 C and presents 90% and 71% capacity retention after 100 and 1000 charge-discharge cycles, respectively. This study demonstrates a GPE architecture comprising 3D space charge pathways for Li(+) ions and suppresses anion decomposition to improve the stability and lifespan of the resulting LIBs.