Disproportionation Products Research Articles

Regulation of Airway Epithelial-Derived Alarmins in Asthma: Perspectives for Therapeutic Targets.

Asthma is a chronic respiratory condition predominantly driven by a type 2 immune response. Epithelial-derived alarmins such as thymic stromal lymphopoietin (TSLP), interleukin (IL)-33, and IL-25 orchestrate the activation of downstream Th2 cells and group 2 innate lymphoid cells (ILC2s), along with other immune effector cells. While these alarmins are produced in response to inhaled triggers, such as allergens, respiratory pathogens or particulate matter, disproportionate alarmin production by airway epithelial cells can lead to asthma exacerbations. With alarmins produced upstream of the type 2 inflammatory cascade, understanding the pathways by which these alarmins are regulated and expressed is critical to further explore new therapeutics for the treatment of asthmatic patients. This review emphasizes the critical role of airway epithelium and epithelial-derived alarmins in asthma pathogenesis and highlights the potential of targeting alarmins as a promising therapeutic to improve outcomes for asthma patients.

Hydrazine Oxidation in Aqueous Solutions II: N4H4 Decomposition

AbstractThe reaction mechanism for the N2H4 homogeneous oxidation in aqueous solutions is more complex than its heterogeneous electrochemical oxidation on the electrode surfaces. Homogenous oxidation of a mixture of non‐labeled (14N2H4) and 15N‐labeled (15N2H4) hydrazine in aqueous solutions produces 14N15N, indicating the intermediate existence of N4H6 or N4H4 intermediates with subsequent hydrogen transfers and splitting lateral N─N bonds. To explain the key part of the hydrazine oxidation reaction, the structures, thermodynamics, and electron characteristics of N4H4 in aqueous solution are investigated. Unlike N4H6, we have not found any spontaneous splitting of the bond between the lateral nitrogens in N4H4. The most probable products of N4H4 disproportionation are H2N─NH2 and N2, which are obtained by splitting the bond between the central nitrogen atoms, and so only 15N2 and 14N2 molecules are formed. Additionally, the formation of H3N─NH and N2 products is also preferred to structures without N─N fissions. The formation of H2N═N and HN═NH is energetically less advantageous. Cyclo‐N4H4 structures are stable, without any N─N fissions, but their energies indicate their vanishing abundance in aqueous solution, so their involvement in hydrazine oxidation is highly improbable. Unlike N4H6, the oxidation of hydrazine to 14N15N molecules cannot be explained by N4H4 intermediates.

AXDND1 is required to balance spermatogonial commitment and for sperm tail formation in mice and humans

Dynein complexes are large, multi-unit assemblies involved in many biological processes via their critical roles in protein transport and axoneme motility. Using next-generation sequencing of infertile men presenting with low or no sperm in their ejaculates, we identified damaging variants in the dynein-related gene AXDND1. We thus hypothesised that AXDND1 is a critical regulator of male fertility. To test this hypothesis, we produced a knockout mouse model. Axdnd1−/− males were sterile at all ages but presented with an evolving testis phenotype wherein they could undergo one round of histologically replete spermatogenesis followed by a rapid depletion of the seminiferous epithelium. Marker experiments identified a role for AXDND1 in maintaining the balance between differentiation-committed and self-renewing spermatogonial populations, resulting in disproportionate production of differentiating cells in the absence of AXDND1 and increased sperm production during initial spermatogenic waves. Moreover, long-term spermatogonial maintenance in the Axdnd1 knockout was compromised, ultimately leading to catastrophic germ cell loss, destruction of blood–testis barrier integrity and immune cell infiltration. In addition, sperm produced during the first wave of spermatogenesis were immotile due to abnormal axoneme structure, including the presence of ectopic vesicles and abnormalities in outer dense fibres and microtubule doublet structures. Sperm output was additionally compromised by a severe spermiation defect and abnormal sperm individualisation. Collectively these data identify AXDND1 as an atypical dynein complex-related protein with a role in protein/vesicle transport of relevance to spermatogonial function and sperm tail formation in mice and humans. This study underscores the importance of studying the consequences of gene loss-of-function on both the establishment and maintenance of male fertility.

Standardization of Private Aircraft: Implications of Climate Change

Aviation being at the heart of the highest form of travel contributing to greenhouse emissions, has raised concern regarding climate change as aviation has evolved to become a major method of transportation in today’s era. The rise of demand for the privatization of aircraft for personal use has simultaneously increased. Whilst commercial aircraft still produce emissions, privatized aircraft emit much larger emissions, causing a disproportionate production of emissions per passenger on board. The lack of legislation on using private aircraft at the national and international levels has left the disproportionate emissions production unregulated. Within this paper, the necessity of policies to minimize the effects of aviation on private aircraft will be further discussed.

MnO2/Mn2+ chemistry: Charging protocol and electrolyte regulation

Aqueous rechargeable Zn-MnO2 batteries based on the dissolution/deposition mechanism of MnO2/Mn2+are gaining increasing attention due to their high capacity and structural simplicity. One of the major concerns is the Mn2+/Mn3+side reaction, which hampers the coulombic efficiency (CE) due to Mn3+(aq) disproportionation. However, factors affecting Mn3+ formation have not been systematically investigated. In this study, we utilized in situ optical microscopy and Scanning Electron Microscopy (SEM) to evaluate the formation of Mn3+ by observing its disproportionation product: the randomly deposited MnO2. We found that an excessively high charging voltage and a low electrolyte pH (pH<4.2) were shown to adversely accelerate Mn3+ formation. Most reports on the Mn2+/MnO2 cathode indicate a coulombic efficiency of only 80 % on carbon felt (thickness: 2.5 mm) at 2 mAh/cm2 due to the inherently low electrical conductivity of MnO2. Here with the optimized charging protocol and the utilization of the anode-friendly, methanesulfonic acid (MSA)-containing electrolyte, we achieved a CE of nearly 100 % for up to 200 cycles at 2 mAh/cm2. This work gives guidelines on the electrolyte design and charging protocol optimization towards high-performance MnO2/Mn2+cathodes.

Catalytic ozonation of dissolved acetaminophen with iron-doped graphitic carbon nitride in plasma-liquid system

Iron-based materials have been widely employed for initiating Fenton-like reactions and catalytic ozonation in plasma-liquid interactions. However, there is still a lack of consensus about the reaction’s selectivity and catalytic mechanism. Herein, elemental iron-doped graphitic carbon nitride (Fe/g-C3N4) is prepared and utilized to enhance the plasma oxidation of acetaminophen via selective catalysis of ozone. Unlike traditional heterogeneous catalytic ozonation, the superoxide anion is identified as the primary derivative species by electron paramagnetic resonance experiments and a kinetic analysis of quenching experiments. The singlet oxygen as a disproportionation product of superoxide anion is also involved in the degradation of acetaminophen, with the generation of additional hydrogen peroxide. Additionally, degradation pathways of acetaminophen involving multiple reactive species and optical emission are proposed. These findings provide novel insight into the mechanism of heterogeneous catalytic ozonation with Fe/g-C3N4 in plasma-liquid interactions for organic contaminant removal from water.

Photochemical transformations of AgCl in the context of its eventual photocatalytic applications

Ag/AgCl structures with specific morphology were synthesized via solvothermal method in ethylene glycol. Structures were characterized by SEM, EDS, XRD and DRS techniques and their photochemical and photoelectrochemical properties were examined. For the first time, the indirect method of chlorine disproportionation products sensing was applied together with reactions specific to hydroxyl radicals and hypochlorite ions to establish which reactive species are photogenerated in aqueous suspensions of the examined material. The results showed that the main species produced during irradiation are hypochlorous acid and hydrochloric acid. Moreover, the activity of silver chloride structures in the spectral range of visible light was confirmed. Photocurrent response reveals the material photoactivity up to 550 nm. The collected data indicate, that the photoactivity of Ag/AgCl should be considered as its photochemical transformations (photocorrosion) rather than photocatalytic processes.

Germline selection of PTPN11 (HGNC:9644) variants make a major contribution to both Noonan syndrome's high birth rate and the transmission of sporadic cancer variants resulting in fetal abnormality.

Some spontaneous germline gain-of-function mutations promote spermatogonial stem cell clonal expansion and disproportionate variant sperm production leading to unexpectedly high transmission rates for some human genetic conditions. To measure the frequency and spatial distribution of de novo mutations we divided three testes into 192 pieces each and used error-corrected deep-sequencing on each piece. We focused on PTPN11 (HGNC:9644) Exon 3 that contains 30 different PTPN11 Noonan syndrome (NS) mutation sites. We found 14 of these variants formed clusters among the testes; one testis had 11 different variant clusters. The mutation frequencies of these different clusters were not correlated with their case-recurrence rates nor were case recurrence rates of PTPN11 variants correlated with their tyrosine phosphatase levels thereby confusing PTPN11's role in germline clonal expansion. Six of the PTPN11 exon 3 de novo variants associated with somatic mutation-induced sporadic cancers (but not NS) also formed testis clusters. Further, three of these six variants were observed among fetuses that underwent prenatal ultrasound screening for NS-like features. Mathematical modeling showed that germline selection can explain both the mutation clusters and the high incidence of NS (1/1000-1/2500).

Labor advantages drive the greater productivity of faculty at elite universities.

Faculty at prestigious institutions dominate scientific discourse, producing a disproportionate share of all research publications. Environmental prestige can drive such epistemic disparity, but the mechanisms by which it causes increased faculty productivity remain unknown. Here, we combine employment, publication, and federal survey data for 78,802 tenure-track faculty at 262 PhD-granting institutions in the American university system to show through multiple lines of evidence that the greater availability of funded graduate and postdoctoral labor at more prestigious institutions drives the environmental effect of prestige on productivity. In particular, greater environmental prestige leads to larger faculty-led research groups, which drive higher faculty productivity, primarily in disciplines with group collaboration norms. In contrast, productivity does not increase substantially with prestige for faculty publications without group members or for group members themselves. The disproportionate scientific productivity of elite researchers can be largely explained by their substantial labor advantage rather than inherent differences in talent.

Peculiarities of conventional HDDR process in (Nd,Pr)-Fe-B alloy powders under low hydrogen pressure

The relationship between the temperature of the start, peak and finish of conventional disproportionation and recombination, in hydrogen, reactions and the low starting hydrogen pressure of 10, 20, 30, 40, 50, 60, 70 and 80 kPa and maximum processing temperature of 950–1015 °C was studied by DTA and X-ray diffraction measurements for 10 g of (Nd,Pr)-Fe-B ferromagnetic powder batches. It was shown that the starting temperature of the disproportionation reaction increases when hydrogen pressure decreases. A similar dependence took place for finishing temperature of the disproportionation when pressure was in the range of 40–80 kPa. At a hydrogen pressure of 10–30 kPa, finishing temperature of the disproportionation decreased with decreasing of pressure. The temperature of the recombination reaction in hydrogen increased with increasing of the hydrogen pressure. The non-equilibrium pressure–composition–temperature schema with four zones for the (Nd,Pr)-Fe-B alloy–hydrogen system was built. The remnants of the (Nd,Pr)2Fe14B phase and disproportionation products – (Nd,Pr)H2±x, α-Fe and Fe2B were in zone I – zone of the disproportionation reaction and in zone II – interstitial zone. The recombined (Nd,Pr)2Fe14B phase, (Nd,Pr)H0–2±x, α-Fe and Fe2B phases were in the zone III – zone of the recombination reaction. And the (Nd,Pr)2Fe14B phase, recombined in hydrogen, existed in the zone IV – zone of the existence of (Nd,Pr)2Fe14B phase.

C-methylation of Organic Substrates: A Comprehensive Overview; Methanol as a Methylating Agent: A Case of Catalysis Versatility (Part III)#

Abstract: The present account surveys the results of a myriad of works on the C-methylation of organic substrates with methanol as an eco-friendly methylating agent. The innumerable reports on this issue reveal the widespread use of a set of solid catalysts such as molecular sieves, zeolites, metal phosphates, metal oxides and transition metal complexes to accomplish such methylation. One related facet was the impact of the numbers of Brønstëd acid sites, Lewis acid sites, and Lewis base sites present in solid catalysts, such as zeolites, their ratios, and strengths that affect the distribution of the methylation products and their selectivities. Moreover, specific surface area and porosity of some solid catalysts, such as zeolites, play additional roles in the overall reaction. Not only do these catalyst properties influence the methylation outcome, the temperature, space velocity (WHSV, LHSV, GSHV), weight of catalyst per reactant flow rate (W/F), time of stream (TOS), and methanol/ substrate molar ratio also do. The treated substrates herein discussed were aromatic hydrocarbons (benzene, biphenyls, naphthalenes, toluene, xylenes), alkenes, phenolics (phenol, cresols, anisole), Nheteroarenes, carbonyls, alcohols, and nitriles. Methylation of benzene affords not only toluene as the main product but also polymethylated benzenes (xylenes, pseudocumene, hexamethylenebenzene, and also ethylbenzene as a side-chain product). Furthermore, toluene is sensitive to the reaction conditions, giving rise to ring methylation and to side-chain one (ethylbenzene and styrene), besides the formation of benzene as a disproportionation product. A number of results from the methylation of phenolic compounds bear witness to the interest of different investigators in this special research. With respect to these phenolics, concurrent O-methylation inevitably parallels the C-methylation, and the selectivity of the latter one remains dependent on the above-cited factors; ortho-cresol and 2,6-xylenol have been the main C-ring methylated phenols. Methylation of olefins with methanol over solid catalysts, leading to higher olefins, is of great interest. The chemistry involved in the methylation of N-heteroarenes, such as pyridines, indoles, and pyrroles, is significant. Application of the methylation protocols, using methanol as a reagent and transition of metal complexes as catalysts to ketones, esters, aldehydes, nitriles, and alcohols, ends up with some important molecules, such as acrylonitrile (a monomer) and isobutanol (a biofuel).

Assessing star value: The influence of prior performance and visibility on compensation strategy

AbstractThe greatest competition among rivals in many industries is not for market share but human capital. In the so‐called talent war, organisations compete aggressively to attract star employees—individuals with disproportionate productivity and external visibility—in pursuit of competitive advantage. Building on human capital and resource‐based view theories, we argue that firms' compensation strategies are influenced by the intangible assets that define stars. With data from Major League Baseball, we find that organisations are likely to pay higher wages to stars based on their prior performance and visibility. Furthermore, our data indicate that firm competitive position influences which of these intangible assets holds greater value for managers. We discuss the implications of these findings for organisations waging a war for talent and suggest directions for future research on a matter that is far from over.

Reversible C-C Bond Formation, Halide Abstraction, and Electromers in Complexes of Iron Containing Redox-Noninnocent Pyridine-imine Ligands.

The exploration of pyridine-imine (PI) iron complexes that exhibit redox noninnocence (RNI) led to several interesting discoveries. The reduction of (PI)FeX2 species afforded disproportionation products such as (dmpPI)2FeX (dmp = 2,6-Me2-C6H3, X = Cl, Br; 8-X) and (dippPI)2FeX (dipp = 2,6-iPr2-C6H3, X = Cl, Br; 9-X), which were independently prepared by reductions of (PI)FeX2 in the presence of PI. The crystal structure of 8-Br possessed an asymmetric unit with two distinct electromers, species with different electronic GSs: a low-spin (S = 1/2) configuration derived from an intermediate-spin S = 1 core antiferromagnetically (AF) coupled to an S = 1/2 PI ligand, and an S = 3/2 center resulting from a high-spin S = 2 core AF-coupled to an S = 1/2 PI ligand. Calculations were used to energetically compare plausible ground states. Polydentate diazepane-PI (DHPI) ligands were applied to the synthesis of monomeric dihalides (DHPI)FeX2 (X = Cl, 1-Cl2; X = Br, 1-Br2); reduction generated the highly distorted bioctahedral dimers (DHPA)2Fe2X2 ((3-X)2) containing a C-C bond formed from imine coupling; the monomers 1-X2 could be regenerated upon Ph3CX oxidation. Dihalides and their reduced counterparts were subjected to various alkyl halides and methyl methacrylate (MMA), generating polymers with little to no molecular weight control, indicative of simple radical-initiated polymerization.

Flotation response of cerussite after hydrothermal treatment with sulfur and the sulfidation mechanism

Hydrothermal sulfidation followed by flotation is well known as a promising technology for recovery of valuable metals from refractory non-ferrous ores. Cerussite (PbCO3), as one of the most representative lead oxide minerals, was selected as the research object in this paper. Hydrothermal sulfidation performances were directly characterized by flotation tests and the sulfidation mechanism was further revealed by XRD, XPS and EPMA–EDS. Flotation tests results showed that flotation recovery of cerussite reached approximately 80% at a suitable S/PbCO3 mole ratio and pH. XRD analyses results confirmed that the cerussite was transformed into mainly PbS and PbSO4 after hydrothermal sulfidation. XPS analyses results indicated that more lead-bearing species including PbSn and PbO·PbSO4, besides mainly PbS and PbSO4, were generated at the surface. EPMA–EDS results showed that the core part of particle remained lead carbonate, but the out layer of particle was completely converted into sulfur-bearing compounds. A reaction model of hydrothermal sulfidation of cerussite with sulfur was designed and the sulfidation process can be divided into five steps: disproportionation of sulfur, adsorption of disproportionation products, dissolution of carbonate ion, formation of lead sulfide precipitate and diffusion of carbonate ion. These findings can lay a good theoretical foundation for optimizing the hydrothermal sulfidation process to recover cerussite and even other non-ferrous metals oxide materials by using the hydrothermal sulfidation–flotation processes.

Multiphase-field modeling of disproportionation performance of ZrCo alloy during hydrogen absorption

This work attempts to develop a multiphase field model to study ZrCoHy, ZrH2, and ZrCo2 phase formation paths in the ZrCoH0.5 matrix. Interestingly, one conserved phase-field variable (c) and four non-conserved phase-field variables (ϕi) are utilized to construct free energy function, where c represents the hydrogen concentration and ϕi stands for the ZrCoHx, ZrCoHy, ZrH2, and ZrCo2 phase. Some valuable material parameters, such as the Gibbs formation enthalpy, are also taken into account. Importantly, the system energy fluctuation is taken as the driving force of phase evolution, and then, governing equations are solved by self-programming complied with the Fortran language. The results demonstrate that disproportionation products are most likely to be derived from the initial ZrCoHy. The presence of ZrH2 and ZrCo2 promotes the nucleation incubation of disproportionation products. Besides, ZrCoHy is more prone to generate ZrH2 and ZrCo2 in comparison with ZrCoHx, which is attributed to the fact that the crystal structure of ZrCoHy is closer to that of ZrCo2. Because ZrCoHy could be regarded as the transition state when ZrCoHx is transformed into ZrCo2, ZrCoHy is easy to be produced in advance during the ZrCoHx disproportionation process, instead of ZrH2 and ZrCo2 directly generated by the ZrCoHx disproportionation.

Thermal Cycling of a MOF-Based NO Disproportionation Catalyst.

The metal-organic framework CuI-MFU-4l reacts with NO, initially forming a copper(I)-nitrosyl at low pressure, and subsequently generates NO disproportionation products CuII-NO2 and N2O. The thermal stability of MFU-4l allows NOx to be released from the framework at temperatures greater than 200 °C. This treatment regenerates the original CuI-MFU-4l, which can engage in subsequent cycles of NO disproportionation.

Contribution to the Management of Abnormal Insulin Secretion in Diabetes of Pregnancy using Antidiabetic Medicinal Plants in Cameroon

Abnormal insulin secretion occurs during hypoinsulinism and hyperinsulinism. Hypoinsulinism is absolute or relative insulin insufficiency which produces a very common clinical sickness called diabetes mellitus. Hyperinsulinism designs an overhead normal level of insulin in a patient’s blood. Hyperinsulinism is the disproportionate production of insulin by tumors of the pancreatic β cells. Patients who suffer from hyperinsulinism disorder undergo hypoglycemic crises, weakness, intense perspiring, and vertigo. This alteration is not known by people of surrounding areas of developing countries like Cameroon. To identify previous work used to write this article a systematical search was done using engines including: “Antidiabetic plants help to control the hyperinsulism in pregnant diabetic women or animals” and “Toxicity of a given recorded plant name” used to verify the harmlessness of recorded plants. Plants that caught our attention are plants already used by hinterlands diabetic women in Cameroon. An increase in insulin secretion by fetal pancreas and placenta coincides with an increased number of insulin-producing B-cells to lower glucose levels in the bloodstream and promote the storage of glucose in adipose and muscle tissue, liver and other body tissues. It was demonstrated that insulin released from the liver stimulate also glucose uptake and naturally maternal insulin does not cross the placenta. Well controlled healthy pregnant women have a good chance of having a normal pregnancy and birth. But in developing countries diabetes is not generally well controlled during pregnancy in many hinterland areas and still affecting maternal and baby health. At the time of birth newborns diabetic mothers are still often larger, and after birth their vagina is harder and may upsurge the risk for nerve injuries and other trauma during birth. Also many risk including birth defect of the lower spine, birth defect of the brain, and limb result from pre-existing diabetes. Screening of all pregnancy for insulin resistance and early intervention may help to reduce these connected complications. Do antidiabetic plants more economical and available, taken by indigenous gestational diabetics control GDM?

Impact of the Coronavirus Disease 2019 Pandemic on Authorship Gender in The Journal of Pediatrics: Disproportionate Productivity by International Male Researchers

To assess the impact of the coronavirus disease 2019 (COVID-19) pandemic on authorship gender in articles submitted to The Journal of Pediatrics. Using gender-labeling algorithms and human inspection, we inferred the gender of corresponding authors of original articles submitted in January-February and April-May of 2019 and 2020 noting those articles related to the COVID-19 pandemic. We used Pearson χ2 tests to determine differences in gender proportions during the selected periods in the US and internationally. We analyzed 1521 original articles. Submissions increased 10.9% from January-February 2019 to January-February 2020 and 61.6% from April-May 2019 to April-May 2020. Women accounted for 56.0% of original articles in April-May 2019 but only 49.8% of original articles in April-May 2020. Original articles focused on COVID-19 represented a small percentage of additional articles submitted in January-February 2020 (1/33 or 3.0%) and (53/199 or 26.6%) in April-May 2020 compared with the number of submissions in the same months in 2019. International male corresponding authors submitted a significantly larger proportion of original articles compared with international female corresponding authors in April-May 2020 compared to April-May 2019 (P=.043). There was no difference in corresponding author gender proportion in the US (US in April-May of 2020 vs April-May of 2019; P=.95). There was no significant difference in final dispositions based on corresponding author gender for original articles from 2019 and 2020 (P=.17). Original article submissions to The Journal increased in April-May 2020, with the greatest increase by international male corresponding authors. The majority of the submission growth was not related to COVID-19.

Enhanced coercivity in SmCo5 magnet subjected to hydrogen treatment

The relations between the phase recombination conditions and phase content, microstructure, and magnetic properties of sintered SmCo5-based permanent magnets, subjected to hydrogen treatment, were studied by X-ray diffraction, scanning electron microscopy, and magnetic hysteresis loop measurements. Recombination of the disproportionation products, SmH2±x, Co, and remains of SmCo5 phase, was carried out by heating the alloy in a vacuum to 850 °C with and without holding it for 1 h, and by heating it to 950 °С. It was shown that after recombination, the coercivity of the magnet, μ0Hc, reached the value of 4.90–4.97 T. The remnant magnetization increased from 27.7 to 43.5, and to 46.7 Am2/kg with increasing holding time during recombination from 0 to 1 h at a temperature of 850 °С, and with increased recombination temperature to 950 °C. The hysteresis loop rectangularity changed from 77 to 74.6, and to 78.8% under the same conditions.

Hydroxylamine metabolism of Ca. Kuenenia stuttgartiensis

Hydroxylamine is a key intermediate in several biological reactions of the global nitrogen cycle. However, the role of hydroxylamine in anammox is still not fully understood. In this work, the impact of hydroxylamine (also in combination with other substrates) on the metabolism of a planktonic enrichment culture of the anammox species Ca. Kuenenia stuttgartiensis was studied. Anammox bacteria were observed to produce ammonium both from hydroxylamine and hydrazine, and hydroxylamine was consumed simultaneously with nitrite. Hydrazine accumulation - signature for the presence of anammox bacteria - strongly depended on the available substrates, being higher with ammonium and lower with nitrite. Furthermore, the results presented here indicate that hydrazine accumulation is not the result of the inhibition of hydrazine dehydrogenase, as commonly assumed, but the product of hydroxylamine disproportionation. All kinetic parameters for the identified reactions were estimated by mathematical modelling. Moreover, the simultaneous consumption and growth on ammonium, nitrite and hydroxylamine of anammox bacteria was demonstrated, this was accompanied by a reduction in the nitrate production. Ultimately, this study advances the fundamental understanding of the metabolic versatility of anammox bacteria, and highlights the potential role played by metabolic intermediates (i.e. hydroxylamine, hydrazine) in shaping natural and engineered microbial communities.