Small RNA AvrA Regulates IscR to Increase the Stress Tolerances in SmpB Deficiency of Aeromonas veronii

The superbacteria Aeromonas veronii displays not only a strong pathogenicity but also the resistance to nine kinds of antibiotics, resulting in the economic losses and health hazards. Small Protein B (SmpB) plays an important role in protein quality control, virulence, and stress reactions. Transcriptomic data revealed that expressions of the type IV pilus assembly and type VI secretion system (T6SS) proteins were downregulated in SmpB deficiency, indicating that the virulence of A. veronii might be attenuated. Although SmpB deletion decreased colonization in the mouse spleen and liver, LD50 of the smpB mutant was not altered as expected, compared with the wild type. Further, the transcriptomic and quantitative RT-PCR analyses showed that the combination of the downregulated AvrA and the upregulated iron-sulfur protein activator IscR, mediated the oxidative tolerance in smpB deletion. Next a reporter plasmid was constructed in which the promoter of iscR was applied to control the expression of the enhanced green fluorescent protein (eGFP) gene. When the reporter plasmid was co-expressed with the AvrA expression into E. coli, the relative fluorescence intensity was decreased significantly, suggesting that AvrA bound to iscR mRNA by base pairing, which in turn relieved the inhibition of iscR and intensified the downstream iron-sulfur proteins. Collectively, the smpB mutant exhibited an attenuated virulence in mice and enhanced tolerances to oxidative stress. This study demonstrates the complexity of gene regulation networks mediated by sRNA in systems biology, and also reflects the strong adaptability of superbacteria A. veronii in the process of evolution

Antifungal activity of an artificial peptide aptamer SNP-D4 against Fusarium oxysporum

Fusarium oxysporum f. sp. cubense (FOC4) is a pathogen of banana fusarium wilt, which is a serious problem that has plagued the tropical banana industry for many years. The pathogenic mechanism is complex and unclear, so the prevention and control in agricultural production applications is ineffective. SNP-D4, an artificial peptide aptamer, was identified and specifically inhibited FOC4. To evaluate the efficacy of SNP-D4, FoC4 spores were treated with purified SNP-D4 to calculate the germination and fungicide rates. Damage of FOC4 spores was observed by staining with propidium iodide (PI). Eight proteins of FOC4 were identified to have high affinity for SNP-D4 by a pull-down method combined with Q-Exactive mass spectrometry. Of these eight proteins, A0A5C6SPC6, the aldehyde dehydrogenase of FOC4, was selected as an example to scrutinize the interaction sites with SNP-D4. Molecular docking revealed that Thr66 on the peptide loop of SNP-D4 bound with Tyr437 near the catalytic center of A0A5C6SPC6. Subsequently 42 spore proteins which exhibited associations with the eight proteins were retrieved for protein-protein interaction analysis, demonstrating that SNP-D4 interfered with pathways including ‘translation’, ‘folding, sorting and degradation’, ‘transcription’, ‘signal transduction’ and ‘cell growth and death’, eventually causing the inhibition of growth of FOC4. This study not only investigated the possible pathogenic mechanism of FOC4, but also provided a potential antifungal agent SNP-D4 for use in the control of banana wilt disease

Genome-wide DNA N6-methyladenosine in Aeromonas veronii and Helicobacter pylori

Abstract Background DNA N6-methyladenosine (6mA), as an important epigenetic modification, widely exists in bacterial genomes and participates in the regulation of toxicity, antibiotic resistance, and antioxidant. With the continuous development of sequencing technology, more 6mA sites have been identified in bacterial genomes, but few studies have focused on the distribution characteristics of 6mA at the whole-genome level and its association with gene expression and function. Results This study conducted an in-depth analysis of the 6mA in the genomes of two pathogenic bacteria, Aeromonas veronii and Helicobacter pylori. The results showed that the 6mA was widely distributed in both strains. In A. veronii, 6mA sites were enriched at 3’ end of protein-coding genes, exhibiting a certain inhibitory effect on gene expression. Genes with low 6mA density were associated with cell motility. While in H. pylori, 6mA sites were enriched at 5’ end of protein-coding genes, potentially enhancing gene expression. Genes with low 6mA density were closely related to defense mechanism. Conclusions This study elucidated the distribution characteristics of 6mA in A. veronii and H. pylori, highlighting the effects of 6mA on gene expression and function. These findings provide valuable insights into the epigenetic regulation and functional characteristics of A. veronii and H. pylori

Preparation of novel Ti–Y/ZrO2 ceramic by two-step of mechanical alloying and microwave-assisted sintering process

Zirconia composite ceramic materials are popular for their many excellent properties. In this study, nTi-3Y–ZrO2 composite ceramics were produced by the mechanical alloying-microwave sintering method with different Ti-doping amounts and microwave sintering temperatures. The sample's phase composition, stability rate, lattice parameters, micromorphology, relative density, and grain size are characterized. The results showed that when the sintering temperature is 1200 °C, the samples with different doping amounts are mainly mixed crystalline structures with tetragonal and cubic phases, and the stability rate remains above 90 %. As TiO2 doping increases, the lattice parameters a(Å) and b(Å)first increase and then decrease, while the lattice parameter c (Å) shows an overall increasing trend. Raman data demonstrated that the increase in Ti content promoted the generation of tetragonal phase zirconia. The average grain size is 61.33 nm, 76.23 nm, 58.77 nm, 63.35 nm, and 68.99 nm, respectively. The increase in doping is also accompanied by a narrowing of the grain size distribution, which increases the sintering activity of the sample. In addition, the relative densities of the samples were 67.85 %, 73.94 %, 84.25 %, 84.87 %, and 77.54 %, respectively, showing a gradual increasing trend overall. When the microwave sintering temperature is 1200 °C, and the doping amount is 5Ti–3Y–92Zr, the performance of the sample is superior to other groups. The preparation of nTi-3Y–ZrO2 composite ceramics can provide certain ideas for preparing ceramic materials with excellent performance in various aspects

Genetic Selection of Peptide Aptamers That Interact and Inhibit Both Small Protein B and Alternative Ribosome-Rescue Factor A of Aeromonas veronii C4

Aeromonas veronii is a pathogenic gram-negative bacterium, which infects a variety of animals and results in mass mortality. The stalled-ribosome rescues are reported to ensure viability and virulence under stress conditions, of which primarily include trans-translation and alternative ribosome-rescue factor A (ArfA) in A. veronii. For identification of specific peptides that interact and inhibit the stalled-ribosome rescues, peptide aptamer library (pTRG-SN-peptides) was constructed using pTRG as vector and Staphylococcus aureus nuclease (SN) as scaffold protein, in which 16 random amino acids were introduced to form an exposed surface loop. In the meantime both Small Protein B (SmpB) which acts as one of the key components in trans-translation, and alternative ribosome-rescue factor A (ArfA) were inserted to pBT to constitute pBT-SmpB and pBT-ArfA, respectively. The peptide aptamer PA-2 was selected from pTRG-SN-peptides by bacterial two-hybrid system (B2H) employing pBT-SmpB or pBT-ArfA as baits. The conserved sites G133K134 and D138K139R140 of C-terminal SmpB were identified by interacting with N-terminal SN, and concurrently the residue K62 of ArfA was recognized by interacting with the surface loop of the specific peptide aptamer PA-2. The expression plasmids pN-SN or pN-PA-2, which combined the duplication origin of pRE112 with the neokanamycin promoter expressing SN or PA-2, were created and transformed into A. veronii C4, separately. The engineered A. veronii C4 which endowing SN or PA-2 expression impaired growth capabilities under stress conditions including temperatures, sucrose, glucose, potassium chloride (KCl) and antibiotics, and the stress-related genes rpoS and nhaP were down-regulated significantly by Quantitative Real-time PCR (qRT-PCR) when treating in 2.0% KCl. Thus，the engineered A. veronii C4 conferring PA-2 expression might be potentially attenuated vaccine, and also the peptide aptamer PA-2 could develop as anti-microbial drugs targeted to the ribosome rescued factors in A. veronii

Effect of microwave drying technology on drying kinetics of Al2O3–ZrO2 composite ceramic powder

Al2O3–ZrO2 composite ceramic is a significant structural material and functional material, and the preparation of high-quality Al2O3–ZrO2 powder is a key step to meeting practical application requirements. The major factor affecting the quality of Al2O3–ZrO2 powder is the drying effect. This paper uses modern microwave drying technology to dry Al2O3–ZrO2 powder. The result was indicative that the average drying rate increases with initial moisture content, initial mass, and microwave heating power. Four dynamic models were applied to fit the empirical data of Al2O3–ZrO2 powder under different pretreatment conditions, the Modified Page model can precisely delineate the Al2O3–ZrO2 microwave drying procedure. To evaluate the changes in samples before and post-drying, the specimens were characterized by Fourier transform infrared spectroscopy. These results demonstrate that microwaves can accelerate the drying of Al2O3–ZrO2 and improve its dispersion. Fick's second law calculates the effective diffusion coefficient. When the initial moisture content of Al2O3–ZrO2 was 5.6%, the microwave heating power is 560 W, and the initial quality is 15 g, the effective diffusion coefficient of Al2O3–ZrO2 is 0.006361 m2/s. Based on the relevance of the microwave power and activating energy, the activating energy of microwave drying Al2O3–ZrO2 was calculated, which is −34.80 g/W. This paper provides basic study data and theory instructions for microwave drying technology in drying Al2O3–ZrO2 even the drying process in green metallurgy

Open Access

Clinicopathological and prognostic significanc