An atypical GdpP enzyme linking cyclic nucleotide metabolism to osmotic tolerance and gene regulation in Mycoplasma bovis

Nucleotide second messengers play an important role in bacterial adaptation to environmental changes. Recent evidence suggests that some of these regulatory molecular pathways were conserved upon the degenerative evolution of the wall-less mycoplasmas. We have recently reported the occurrence of a phosphodiesterase (PDE) in the ruminant pathogen Mycoplasma bovis, which was involved in c-di-AMP metabolism. In the present study, we demonstrate that the genome of this mycoplasma species encodes a PDE of the GdpP family with atypical DHH domains. Characterization of M. bovis GdpP (MbovGdpP) revealed a multifunctional PDE with unusual nanoRNase and single-stranded DNase activities. The alarmone ppGpp was found unable to inhibit c-di-NMP degradation by MbovGdpP but efficiently blocked its nanoRNase activity. Remarkably, MbovGdpP was found critical for the osmotic tolerance of M. bovis under K+ and Na+ conditions. Transcriptomic analyses further revealed the biological importance of MbovGdpP in tRNA biosynthesis, pyruvate metabolism, and several steps in genetic information processing. This study is an important step in understanding the role of PDE and nucleotide second messengers in the biology of a minimal bacterial pathogen

HIV-associated neurocognitive disorder: key implications of the microbiota-gut-brain axis

HIV-associated neurocognitive disorder (HAND) is now recognized to be relatively common in people living with HIV (PLWH), and remains a common cause of cognitive impairment. Unfortunately, the fundamental pathogenic processes underlying this specific outcome of HIV infection have not as yet been fully elucidated. With increased interest in research related to the microbiota-gut-brain axis, the gut-brain axis has been shown to play critical roles in regulating central nervous system disorders such as Alzheimer’s disease and Parkinson’s disease. PLWH are characterized by a particular affliction, referred to as gut-associated dysbiosis syndrome, which provokes an alteration in microbial composition and diversity, and of their associated metabolite composition within the gut. Interestingly, the gut microbiota has also been recognized as a key element, which both positively and negatively influences human brain health, including the functioning and development of the central nervous system (CNS). In this review, based on published evidence, we critically discuss the relevant interactions between the microbiota-gut-brain axis and the pathogenesis of HAND in the context of HIV infection. It is likely that HAND manifestation in PLWH mainly results from (i) gut-associated dysbiosis syndrome and a leaky gut on the one hand and (ii) inflammation on the other hand. In other words, the preceding features of HIV infection negatively alter the composition of the gut microbiota (microbes and their associated metabolites) and promote proinflammatory immune responses which singularly or in tandem damage neurons and/or induce inadequate neuronal signaling. Thus, HAND is fairly prevalent in PLWH. This work aims to demonstrate that in the quest to prevent and possibly treat HAND, the gut microbiota may ultimately represent a therapeutically targetable “host factor.

Comparative Geno-Plasticity Analysis of Mycoplasma bovis HB0801 (Chinese Isolate)

Mycoplasma bovis pneumonia in cattle has been epidemic in China since 2008. To investigate M. bovis pathogenesis, we completed genome sequencing of strain HB0801 isolated from a lesioned bovine lung from Hubei, China. The genomic plasticity was determined by comparing HB0801 with M. bovis strain ATCC® 25523™/PG45 from cow mastitis milk, Chinese strain Hubei-1 from lesioned lung tissue, and 16 other Mycoplasmas species. Compared to PG45, the genome size of HB0801 was reduced by 11.7 kb. Furthermore, a large chromosome inversion (580 kb) was confirmed in all Chinese isolates including HB0801, HB1007, a strain from cow mastitis milk, and Hubei-1. In addition, the variable surface lipoproteins (vsp) gene cluster existed in HB0801, but contained less than half of the genes, and had poor identity to that in PG45, but they had conserved structures. Further inter-strain comparisons revealed other mechanisms of gene acquisition and loss in HB0801 that primarily involved insertion sequence (IS) elements, integrative conjugative element, restriction and modification systems, and some lipoproteins and transmembrane proteins. Subsequently, PG45 and HB0801 virulence in cattle was compared. Results indicated that both strains were pathogenic to cattle. The scores of gross pathological assessment for the control group, and the PG45- and HB0801-infected groups were 3, 13 and 9, respectively. Meanwhile the scores of lung lesion for these three groups were 36, 70, and 69, respectively. In addition, immunohistochemistry detection demonstrated that both strains were similarly distributed in lungs and lymph nodes. Although PG45 showed slightly higher virulence in calves than HB0801, there was no statistical difference between the strains (P>0.05). Compared to Hubei-1, a total of 122 SNP loci were disclosed in HB0801. In conclusion, although genomic plasticity was thought to be an evolutionary advantage, it did not apparently affect virulence of M. bovis strains in cattle

A 7–13 GHz 10 W High-Efficiency MMIC Power Amplifier in 0.25 µm GaN HEMT Process

With the increase in applications of the millimeter wave spectrum for phased array radar systems, mobile 7–13 communication systems, and satellite systems, the demand for a wideband, high-efficiency, high-power monolithic microwave integrated circuit (MMIC) power amplifier (PA) is increasing. In this paper, a 7–13 GHz 10 W high-efficiency MMIC PA is designed. This amplifier consists of a two-stage circuit structure with two high electron mobility transistor (HEMT) cells for the driver stage and four HEMT cells for the power stage. To ensure high efficiency and a certain output power (Pout), both the driver–stage and power–stage transistors use a deep Class–AB bias. At the same time, in order to further improve the efficiency, low-loss and second–harmonic tuning techniques are used in the output and inter-stage matching networks, respectively. Finally, the electromagnetic simulation results show that within a frequency of 7–13 GHz, the amplifier achieves an average saturated continuous wave (CW) Pout of 40 dBm, a small signal gain of 14.5–15.5 dB, a power-added efficiency (PAE) of 30–46%, and the input and output return loss are better than 5 dB and 8 dB, respectively

A 7–13 GHz 10 W High-Efficiency MMIC Power Amplifier in 0.25 µm GaN HEMT Process

With the increase in applications of the millimeter wave spectrum for phased array radar systems, mobile 7–13 communication systems, and satellite systems, the demand for a wideband, high-efficiency, high-power monolithic microwave integrated circuit (MMIC) power amplifier (PA) is increasing. In this paper, a 7–13 GHz 10 W high-efficiency MMIC PA is designed. This amplifier consists of a two-stage circuit structure with two high electron mobility transistor (HEMT) cells for the driver stage and four HEMT cells for the power stage. To ensure high efficiency and a certain output power (Pout), both the driver–stage and power–stage transistors use a deep Class–AB bias. At the same time, in order to further improve the efficiency, low-loss and second–harmonic tuning techniques are used in the output and inter-stage matching networks, respectively. Finally, the electromagnetic simulation results show that within a frequency of 7–13 GHz, the amplifier achieves an average saturated continuous wave (CW) Pout of 40 dBm, a small signal gain of 14.5–15.5 dB, a power-added efficiency (PAE) of 30–46%, and the input and output return loss are better than 5 dB and 8 dB, respectively

Measurement and Correlation of Solubility on Reactive Crystallization of Methyl D‑(−)-4-Hydroxy-phenylglycinate

In this paper, the solubility of methyl D-(−)-4-hydroxy-phenylglycinate was measured under the different pH levels, pure solvents, mixed solvents, ionic strength, and impurities in the temperature range from 283 to 323 about 5 K intervals by using laser method at atmospheric pressure. The results reveal that the solubility of methyl D-(−)-4-hydroxy-phenylglycinate increases with increasing temperature in all selected solvents, which decreases with increasing mole fraction composition of water in the mixed solvents. The solubility curve of methyl D-(−)-4-hydroxy-phenylglycinate in the aqueous solution at different pH is “U” shape and the solubility of methyl D-(−)-4-hydroxy-phenylglycinate increases with concentrations of ammonium chloride and has no obvious changes when its concentration increases up to 1.25 mol/kg. It is beneficial to maximize the reaction conversion rate of D-4-hydroxyphenylglycine methyl ester hydrochloride and reduce the residual D-4-hydroxyphenylglycine methyl ester hydrochloride on reactive crystallization of methyl D-(−)-4-hydroxy-phenylglycinate. Furthermore, the modified Apelblat equation and <i>C</i>_T = <i>C</i>₀(α_H⁺/<i>k</i>₁ + <i>k</i>₂/α_H⁺ + 1) type correlation regression model have made good correlation of the experimental solubility in pure solvents, mixed solvents, and the aqueous solution at different pH, respectively

MbovP0725, a secreted serine/threonine phosphatase, inhibits the host inflammatory response and affects metabolism in Mycoplasma bovis

ABSTRACTMycoplasma species are able to produce and release secreted proteins, such as toxins, adhesins, and virulence-related enzymes, involved in bacteria adhesion, invasion, and immune evasion between the pathogen and host. Here, we investigated a novel secreted protein, MbovP0725, from Mycoplasma bovis encoding a putative haloacid dehalogenase (HAD) hydrolase function of a key serine/threonine phosphatase depending on Mg2+ for the dephosphorylation of its substrate pNPP, and it was most active at pH 8 to 9 and temperatures around 40°C. A transposon insertion mutant strain of M. bovis HB0801 that lacked the protein MbovP0725 induced a stronger inflammatory response but with a partial reduction of adhesion ability. Using transcriptome sequencing and quantitative reverse transcription polymerase chain reaction analysis, we found that the mutant was upregulated by the mRNA expression of genes from the glycolysis pathway, while downregulated by the genes enriched in ABC transporters and acetate kinase–phosphate acetyltransferase pathway. Untargeted metabolomics showed that the disruption of the Mbov_0725 gene caused the accumulation of 9-hydroxyoctadecadienoic acids and the consumption of cytidine 5′-monophosphate, uridine monophosphate, and adenosine monophosphate. Both the exogenous and endogenous MbvoP0725 protein created by purification and transfection inhibited lipopolysaccharide (LPS)-induced IL-1β, IL-6, and TNF-α mRNA production and could also attenuate the activation of MAPK-associated pathways after LPS treatment. A pull-down assay identified MAPK p38 and ERK as potential substrates for MbovP0725. These findings define metabolism- and virulence-related roles for a HAD family phosphatase and reveal its ability to inhibit the host pro-inflammatory response.IMPORTANCEMycoplasma bovis (M. bovis) infection is characterized by chronic pneumonia, otitis, arthritis, and mastitis, among others, and tends to involve the suppression of the immune response via multiple strategies to avoid host cell immune clearance. This study found that MbovP0725, a haloacid dehalogenase (HAD) family phosphatase secreted by M. bovis, had the ability to inhibit the host pro-inflammatory response induced by lipopolysaccharide. Transcriptomic and metabolomic analyses were used to identify MbovP0725 as an important phosphatase involved in glycolysis and nucleotide metabolism. The M. bovis transposon mutant strain T8.66 lacking MbovP0725 induced a higher inflammatory response and exhibited weaker adhesion to host cells. Additionally, T8.66 attenuated the phosphorylation of MAPK P38 and ERK and interacted with the two targets. These results suggested that MbovP0725 had the virulence- and metabolism-related role of a HAD family phosphatase, performing an anti-inflammatory response during M. bovis infection

Design of 2–16 GHz Non-Uniform Distributed GaN HEMT MMIC Power Amplifier with Harmonic Suppression Network

In this paper, an ultra-wideband (UWB) power amplifier (PA) on a 0.25 μm gallium-nitride (GaN) on silicon carbide (SiC) high-electron-mobility transistor (HEMT) process, operating in Ku-band, is presented. The broadband PA design is based on the four-stage non-uniform distributed amplifier structure. In order to improve the efficiency of the PA, a harmonic suppression network is added at the output of the drain artificial transmission line. At the same time, a capacitor is connected in series at the input of the gate, which is used to compensate for the phase offset of the gate and increase the cut-off frequency of the PA. The final gate width of the first stage is 0.56 μm, and the other three-stage gate widths are all 0.32 μm. Over the frequency range of 2–16 GHz, the simulated results of this NDPA exhibit a power-added efficiency (PAE) of 16.6–27%, a saturated continuous wave (CW) output power of 35–37 dBm, a small signal gain of 9.1–11.6 dB, and output return losses of 5–15 dB

Design of 2&ndash;16 GHz Non-Uniform Distributed GaN HEMT MMIC Power Amplifier with Harmonic Suppression Network

In this paper, an ultra-wideband (UWB) power amplifier (PA) on a 0.25 &mu;m gallium-nitride (GaN) on silicon carbide (SiC) high-electron-mobility transistor (HEMT) process, operating in Ku-band, is presented. The broadband PA design is based on the four-stage non-uniform distributed amplifier structure. In order to improve the efficiency of the PA, a harmonic suppression network is added at the output of the drain artificial transmission line. At the same time, a capacitor is connected in series at the input of the gate, which is used to compensate for the phase offset of the gate and increase the cut-off frequency of the PA. The final gate width of the first stage is 0.56 &mu;m, and the other three-stage gate widths are all 0.32 &mu;m. Over the frequency range of 2&ndash;16 GHz, the simulated results of this NDPA exhibit a power-added efficiency (PAE) of 16.6&ndash;27%, a saturated continuous wave (CW) output power of 35&ndash;37 dBm, a small signal gain of 9.1&ndash;11.6 dB, and output return losses of 5&ndash;15 dB