Unveiling the regulatory mechanism of poly-γ-glutamic acid on soil characteristics under drought stress through integrated metagenomics and metabolomics analysis.

It is of utmost importance to understand the characteristics and regulatory mechanisms of soil in order to optimize soil management and enhance crop yield. Poly-γ-glutamic acid (γ-PGA), a stress-resistant amino acid polymer, plays a crucial role in plant drought stress resistance. However, little is known about the effects of γ-PGA on soil characteristics during drought treatments. In this study, the effects of different forms of γ-PGA on soil texture and basic physical and chemical properties under short-term drought conditions were investigated. Furthermore, the impact of γ-PGA on the microbial community and metabolic function of maize was analyzed. Under drought conditions, the introduction of γ-PGA into the soil resulted in notable improvements in the mechanical composition ratio and infiltration capacity of the soil. Concurrently, this led to a reduction in soil bulk density and improved soil organic matter content and fertility. Additionally, metagenomic analysis revealed that under drought conditions, the incorporation of γ-PGA into the soil enhanced the soil microbiota structure. This shift led to the predominance of bacteria that are crucial for carbon, nitrogen, and phosphorus cycles in the soil. Metabolomics analysis revealed that under drought treatment, γ-PGA affected soil metabolic patterns, with a particular focus on alterations in amino acid and vitamin metabolism pathways. Correlation analysis between the soil metagenome and metabolites showed that microorganisms played a significant role in metabolite accumulation. These results demonstrated that γ-PGA could improve soil characteristics under drought conditions and play an important role in soil microorganisms and microbial metabolism, providing further insights into the changes in soil characteristics under drought conditions.

HetI-Like Phosphopantetheinyl Transferase Posttranslationally Modifies Acyl Carrier Proteins in Xanthomonas spp.

In Xanthomonas spp., the biosynthesis of the yellow pigment xanthomonadin and fatty acids originates in the type II polyketide synthase (PKS II) and fatty acid synthase (FAS) pathways, respectively. The acyl carrier protein (ACP) is the central component of PKS II and FAS and requires posttranslational phosphopantetheinylation to initiate these pathways. In this study, for the first time, we demonstrate that the posttranslational modification of ACPs in X. campestris pv. campestris is performed by an essential 4'-phosphopantetheinyl transferase (PPTase), XcHetI (encoded by Xc_4132). X. campestris pv. campestris strain XchetI could not be deleted from the X. campestris pv. campestris genome unless another PPTase-encoding gene such as Escherichia coli acpS or Pseudomonas aeruginosa pcpS was present. Compared with wild-type strain X. campestris pv. campestris 8004 and mutant XchetI::PapcpS, strain XchetI::EcacpS failed to generate xanthomonadin pigments and displayed reduced pathogenicity for the host plant, Brassica oleracea. Further experiments showed that the expression of XchetI restored the growth of E. coli acpS mutant HT253 and, when a plasmid bearing XchetI was introduced into P. aeruginosa, pcpS, which encodes the sole PPTase in P. aeruginosa, could be deleted. In in vitro enzymatic assays, XcHetI catalyzed the transformation of 4'-phosphopantetheine from coenzyme A to two X. campestris pv. campestris apo-acyl carrier proteins, XcAcpP and XcAcpC. All of these findings indicate that XcHetI is a surfactin PPTase-like PPTase with a broad substrate preference. Moreover, the HetI-like PPTase is ubiquitously conserved in Xanthomonas spp., making it a potential new drug target for the prevention of plant diseases caused by Xanthomonas.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

[Mechanism of inhibitory effect of catalpol on TNF-α induced HAECs cell damage].

Catalpol is an iridoid glycoside extracted from the root of Rehmannia glutinosa. It has been reported to have antioxidant stress effects. Adenosine 5' monophosphate-activated protein kinase( AMPK) plays an important role in inhibiting oxidative stress. This study was designed to investigate the protective effects of catalpol on TNF-α-exposed human aorta epithelial cells( HAECs) via inhibit oxidative stress,and the relationship between catalpol and AMPK was detected by RNA interference technique. Levels of superoxide dismutase( SOD),malonaldehyde( MDA),glutathione( GSH) and lactate dehydrogenase( LDH) were measured with a colorimetric assay kit. The level of ROS was measured with FACS calibur. Western blot was employed to detect the protein expression of AMPK,phosphorylated-AMPK and NOX4. Finally,RNA interference technique was used to investigate the role of AMPK in catalpol-induced protective effects. TNF-α treatment decreased the expression of phosphorylated-AMPK protein level,however,catalpol could reverse the decreased phosphorylated-AMPK level. Catalpol could inhibit NOX4 protein expression and decrease ROS overproduction. After using AMPK siRNA that effects of catalpol on ROS overproduction and NOX4 protein expression inhibition were attenuated. The above results suggest that catalpol inhibits oxidative stress in TNF-α-exposed HAECs by activating AMPK.

[Research on structure of MC-nylon 6/aramid composites by spectroanalysis method].

The Kevlar fiber, treated with toluene-2,4-diisocyanate and caprolactam, was used to reinforce MC nylon 6. XPS showed the change in chemical components and spectra after fiber was treated. IR showed that the spectra of Kevlar fiber and MC-nylon 6 were incorporated purely when they were mixed, while the treated Kevlar fiber provided the activation in the ring-opening polymerization of caprolactam, and the amide groups of graft chains could form strong hydrogen bonds with matrix. These graft chains and hydrogen bonds would contribute to improving interfacial bonding between MC-nylon 6 and Kevlar fiber. XRD indicated that the induction of Kevlar fiber had no effect on the cryastalline style of MC-nylon 6 obviously, however, the crystals had better seasonal structure. The crystals of MC-nylon 6/Kevlar fiber composites were more perfect than that of MC-nylon 6/Kevlar untreated fiber composites with the same amount of Kevlar fiber. The increase of Kevlar fiber contributed to forming perfect a spherulite when the mass concentration of Kevlar fiber was less than 2%, however, the more the Kevlar fiber, the less the content of a spherulite when the mass concentration of Kevlar fiber was more than 2%.

[FTIR research on the modification of plant oil pitch binders by polyester waste].

Various plant oil pitchs (cottonseed pitch, bean oil pitch, and mixed plant oil pitch) were used to prepare the plant oil pitch binders for casting. They were treated by polyester waste and processed by several technics such as esterifying. In the mean time, FTIR and TG were adopted to learn the structure, property, and sclerous mechanism of the binders. From the comparison with synthetic fat binder, the authors can see that the treated binders have similar components. They also have many excellent properties such as higher dry tensile strength and slower deflation velocity, which equal to or even exceed the properties of synthetic fat binder. Therefore, the treated binders, which were cheaper, can be used to make class I mold and core binders.

[Research on the modification of Kevlar fiber by polypropylene glycol and cis-2-butene-1,4-diol].

The mechanism of the modification of Kevlar fiber by polypropylene glycol(PPG) and cis-2-butene-1, 4-diol was studied in the paper, the authors learned the esterification of toluene-2, 4-diisocyanate (TDI) onto Kevlar fiber by infrared spectrum. In the mean time, the infrared spectrograms of the productions which steadily disposed by PPG and butendiol were analysed respectively, the result showed that the intensity of the bands was reinforced at about 1700-1720 cm(-1) after the samples were steadily disposed, that is to say, the group of --NCO has been stabilized into --NHCO group, the effect of steady disposal was obvious; but the disposal effect of butendiol was apparently better than PPG's at the same condition. Finally, the authors compared the influence of different mol rates between TDI and butendiol on the productions. Based onthe consequence, excessive butendiol would prevent the Kevlar fiber from farther reaction, therefore, the mol rate between TDI and butendiol should approach 1:1.

[Surface grafting modification and stabilization of Kevlar fiber].

Chemical disposal was used to bring the activity group onto the surface of Kevlar fiber for the purpose of surface grafting modification. The interfacial constitution of the grafting of toluene-2,4-diisocyanate (TDI) onto Kevlar fiber was determined by Fourier transform infrared spectroscopy. In the mean time, hexyl-lactam stabilization and poly-glycol (400, PEG) stabilization on the grafted product were also studied. The effects of different nTDI:nPEG ratios on the production's interfacial constitution was analysed. It is concluded that the stabilization took place on the surface. The intensity of the bands relented at about 3300 cm(-1) and was reinforced at about 1700-1720 cm(-1) when the ratio of nTDI:nPEG = 1:3, but when the ratio is 1:1 and 1:2, the bands at about 3 300 and 1700-1720 cm(-1) are almost the same.

[Research of FTIR and XRD study on the organic modification of bentonites].

Organobentonites were prepared to improve the compatibility between bentonites and organic phase. The change of lamellar structure after organic modification was observed. Na+ -bentonites and octadecylamine were used to exchange the Na+ which is in the layers of bentonites, and the organobentonites were obtained. Both FTIR and DTA-TG proved that octadecylamine entered the layers of bentonites, and XRD showed that the lamellar distance increased from 1.4 nm to 4.3 nm. Based on the experiment, most of the properties of Na+ -bentonites such as the ethylene blue adsorbed by bentonites, cation exchange capacity and the like are better than Ca2+ -bentonites'. The bentonites modified by octadecylamine improved the hydrophobic ability and widened the lamellar distance of bentonites, which contributes to enhancing the whole properties of composites.

[Study on the modification of short chain phoshate ammonium salt of bentonites].

The Organobentonites were synthesized by means of the ionexchange reaction of Na+ between tetramethylammonium chloride and tetrabutylammonium chloride quaternary ammonium salts, and sodium base bentonites. The authors used FTIR, X-ray diffraction diagram and DSC thermograms to characterize the structure of the modified bentonites, and discussed the effect of different quaternary ammonium salt on the properties of organobentonites. The results showed that ions of the surfactants had entered into the chip layer of the bentonites, changed the hydrophilic environment of the chip layer into a hydrophobic environment, increased the distance among the chip layers, and improved the compatibility between montmorillonite andthe organic phases. All of these have laid a base for the preparation of nanometer composite material of high polymer/bentonite.

[The research on the surfacial modification of organic high-performance Kevlar fiber].

In the paper the authors tried to use chemical disposal to bring the activity mass onto the surface of Kevlar fiber with the purpose of surface graft modification. In the paper the authors used the FTIR spectra to discuss the graft of toluene-2, 4-diisocyanate onto Kevlar fiber. The authors studied and analysed the effect of hydrolytic time on the content of -O-H group of the production, and the effect of hydrolyzation and hexyl-lactam steadily disposing on the graft reaction. The result showed that the content of -O-H group increased after hydrolyzation, it's helpful for the graft reaction, and hexyl-lactam steadily disposing made the graf product more stable. Through the research the authors came to the conclusion that by bringing some activity masses onto the fiber surface the authors can improve the interface of fiber/resin effectively.