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A facile alkyne-based multicomponent polymerization route was developed for the construction of solution-processable fluoropolymers with multiple functionalities. The palladium-catalyzed one-pot po...

The development of efficient multi-component polymerizations from handy monomers to synthesize multifunctional polymers with complicated structures is an attractive but challenging research topic. In this work, a facile, one-pot, three-component polymerization route for in situ generation of polymers with aggregation-induced emission (AIE) characteristics has been developed. Under the catalysis of NiCl2, polycoupling of dihaloarenes, internal diynes, and Grignard reagents proceeded efficiently, generating poly(tetraarylethene)s (PTAEs) with high number average molecular weights (Mn up to 16 800) in high yields (up to 93%) in only three hours. The obtained PTAEs show typical AIE characteristics due to the in situ-generated AIEgen units, tetraphenylethene, in the polymer backbone. Utilizing the AIE property, aggregate-state PTAE could serve as an efficient fluorescent chemosensor for picric acid and Ru3+ with amplified sensitivity, and the quenching constants reached 2.33 × 106 L mol−1 and 6.85 × 104 L mol−1, respectively. Furthermore, the polymer thin films showed modulable refractive indices under UV irradiation in the wide wavelength region of 400–900 nm, presenting great potential in optical fiber applications. Well-resolved 2D fluorescent patterns can also be generated by photo-oxidation of the thin films of PTAEs under UV irradiation through a copper photomask. This work provides another successful example of an in situ generation strategy for functional AIE polymers, broadening the scope of the monomer library.

Diabetic nephropathy (DN) is the most common chronic microvascular complication of diabetes. Therefore, it is of great significance to effectively prevent and treat DN. Licochalcone A (LicA) is a flavonoid found in licorice; previous studies have shown that LicA can reduce blood glucose, blood lipids and improve insulin resistance. There has been no research on whether LicA can prevent and treat DN. In this study, an animal model of type 2 diabetes mellitus (T2DM) mice induced by high fat diet/streptozotocin was established, and the intervention of LicA was applied to investigate the protective effect of LicA on the kidneys of DN mice. After 4 weeks of intervention, LicA could effectively reduce blood glucose and alleviate the phenomenon of weight loss in mice. Meanwhile, the levels of MDA, SOD and GSH-Px in the kidney tissue and serum were recovered to different degrees. Besides, LicA decreased the levels of TC, TG and LDL-C in the kidney tissue and increased the level of HDL-C in the kidney tissue. The 24 h urinary protein, blood urea nitrogen (BUN) and serum creatinine (SCr) levels of mice in the treatment group of LicA were significantly lower than those in the model group. Furthermore, HE staining, PAS staining and Masson staining indicated that LicA improved the pathological damage of kidneys, and the kidney index of mice also decreased. Western blotting results indicated that LicA could significantly down-regulate the protein expression of AGEs/RAGE, TGF-β1, HIF-1α and GLUT1, and up-regulate the protein expression of Nrf2. It provides a theoretical basis for the further development and utilization of LicA.

A strain of porcine epidemic diarrhoea virus (PEDV), namely HLJBY, was isolated in Heilongjiang province, China. To provide insight into the understanding of the phylogenetic and the current epidemiological status of PEDV, PEDV HLJBY was compared with CV777 and other PEDV strains deposited in the GenBank. The homology between the entire genomic nucleotide sequences of PEDV HLJBY and CV777 was 97.7%. The homology of M gene was the highest (99.0%). However, the homology of ORF3 gene was 97.7%, and protein of ORF3 was 90.1%. In addition, HLJBY showed the highest nucleotide identity (99.9%) with PEDV‐SX/China/2017 strain and lowest similarity (91.2%) to PEDV/Belgorod/dom/2008 strain. We analysed the changes in S gene and its protein of PEDV HLJBY with 65 historic PEDV strains. The highest nucleotide identity was 99.9% compared with PEDV‐SX/China/2017 strain, and the lowest nucleotide identity was 60.0% compared with PEDV/Belgorod/dom/2008 strain. The length of deduced amino acid sequences of S proteins varied from 1,372 to 1,390 amino acids (aa). Compared with most aa sequences of S proteins, HLJBY exhibited 5 aa deletions (position 55, 59–61, 144). Analysis and comparison of open reading frame 3 (ORF3) proteins between HLJBY strain and other PEDV strains were also focused in this study. We revealed that the length of deduced amino acid sequences of ORF3 proteins was 80–224 aa among tested strains and the identity of HLJBY ORF3 amino acids with other PEDV strains was 71.4%–98.9%. ORF3 protein of both HLJBY strain and PEDV‐SX/China/2017 strain consists of 91 aa, with 133 aa deletions at their C' end in relation to the other tested PEDV strains. The phylogenetic tree based on different proteins or genes resulted in different phylogenetic groups. For pathogenicity evaluation of PEDV HLJBY strain, colostrum deprivation piglets were challenged with PEDV HLJBY, and PEDV reference strain CV777 as a control, the results showed that animals challenged with either of these PEDV strains developed diarrhoea, and histopathological examination of small intestines of challenged animals showed acute viral enteritis with villous atrophy in either PEDV HLJBY‐P10 or PEDV CV777‐P8 inoculated piglets.

A new synthetic route toward multifunctional poly(indazole)s (PIs) with an effect of monomer stoichiometry imbalance-promoted polymerization is described in this work. The palladium-catalyzed oxidative polyannulations of internal diynes and 1-methylpyrazole proceed smoothly in 1,4-dioxane at 120 °C with copper acetate monohydrate functioning as the oxidant. A series of PIs with high molecular weights (Mw up to 35 800) are generated in good yields (up to 84.0%) under monomer non-stoichiometric conditions. These polymers exhibit high thermal stability, losing merely 5% of their weights at high temperatures of 321–353 °C. The solid thin films of these PIs show high and UV-tunable refractive indices (n = 1.8870–1.6051) in a wide wavelength range of 400–900 nm. The tetraphenylethene-containing PI shows obvious solid-state emission properties and good photosensitivity. Its thin film was successfully fabricated into a well-defined two-dimensional fluorescent photopattern with sharp edges.

Type 2 diabetes mellitus (T2DM) is a type of metabolic illness based on relatively insufficient insulin secretion and insulin resistance (IR) as pathophysiological bases. Currently, it is the main type of diabetes. Hypoglycemic and hypolipidemic effects of licochalcone A (LicA) on high-fat diet and streptozocin-caused T2DM were studied. LicA can remarkably decline the IR index and blood glucose and serum lipid levels. Also, the treatment of LicA can improve the "three more and one less" phenomenon in T2DM mice, such as excessive drinking, eating, urine, and weight loss. In addition, LicA can improve oral glucose tolerance, pancreatic injury, and liver enlargement in T2DM mice. Network pharmacology analysis demonstrated that the observed pharmacological effects were mediated by regulating the insulin signal transduction pathway. Therefore, the PI3K/Akt-signaling pathway was selected for verification; it was demonstrated that LicA could improve the insulin-signaling pathway, protect islet cells, improve IR, reduce blood glucose levels, and alleviate lipid metabolism disorder. Its mechanism of influence may be closely related to LicA up-regulating the liver and pancreas IRS-2/PI3K/AKT-signaling pathway. Among them, the high-dose group of LicA had the best effect, which provided an idea for the use of LicA as a nutritional agent in the cure of T2DM.

Development of new methodologies for synthesizing polymers with novel structures and unique properties is a fundamentally important area in polymer science. Herein, a novel synthetic strategy to conjugated poly(p-arylene dihalodiene)s (PADs) with high regio- and stereoselectivity was developed. In the presence of PdBr2 and CuBr2, the polymerizations of terminal alkynes proceeded smoothly in air without heating to generate PADs in high yields (up to 95.3%) with high molecular weights (Mw up to 915 900). Low-cost inorganic CuBr2 played dual roles as cocatalyst and comonomer. The PADs possessed good solubility and film-forming ability. Their thin films exhibited high refractive indices (1.7149–1.7245) and would be fabricated into well-resolved fluorescent photopatterns by photolithography. Thanks to the vinyl bromine functionality, the PADs could undergo efficient postmodification to afford polymers with more sophisticated structures and applications.

Licorice residues are rich in flavonoids and are considered to be valuable reusable resources with broad applications and a high economic value. In view of above, the ultrasound-assisted adsorption/desorption of licorice flavonoids (LFs) on HPD-100 resins was studied. This process was studied at different temperatures (20–30 ℃) using ultrasound at different power densities (0.2, 0.35, 0.5 W/cm2). The higher ultrasonic power density (0.5 W/cm2) and lower temperature (20 ℃) facilitated the adsorption process. The ultrasonic power density of 0.5 W/cm2 and the temperature of 30 ℃ were favorable for the desorption process. The adsorption behavior can be well described by the pseudo second-order kinetic model. It was illustrated that the ultrasonic power density was 0.5 W/cm2, the recovery of ultrasonic assisted adsorption/desorption of LFs was 9.99 % higher than that without ultrasonic treatment. Interestingly, licochalcone A (LicA) had the highest adsorption capacities, while the desorption capacities of liquiritigenin was the highest. In addition, it was worth mentioning that the activities of LFs were increased with the enhancement of the ultrasonic power density. Furthermore, it was demonstrated that LFs had a protective effect on the injury and apoptosis of H9c2 cardiomyocytes induced by H2O2. The underlying mechanism may be interrelated with the activation of Nrf2/HO-1 pathway.

Polymers containing rich chalcogen elements are rarely reported due to the lack of facile synthesis methods. Herein, a novel multicomponent polymerization route toward chalcogen-rich polymers was introduced. A series of poly(vinyl sulfones) (PVSs) were synthesized at room temperature using readily prepared monomers. PVSs were generated with high regio- and stereo-selectivity in high yields (up to 92.3%). Rich chalcogen elements endowed PVSs with distingctive multifunctionalities. The PVSs possessed good solubility and film-forming ability. Their thin films exhibited outstanding refractive indices up to 1.8062 at 550.0 nm together with good optical transparency in the visible region. Thin films of some polymers can also be fabricated into well-resolved fluorescent photopatterns by photolithography. Thanks to the unique redox properties of selenium, postmodification by oxidation reaction of P1a/2/3a successfully eliminates the caused heavy atom effect and endow resulting polymers with novel functionality as fluorescent bioprobes for cellular imaging.

It has become increasingly clear that deviations from local thermodynamic equilibrium occur in thermal plasmas. This paper is devoted to investigating the non-equilibrium characteristics of CO2 thermal plasmas, which have wide application in industry. A two-temperature chemical kinetic model with a comprehensive chemical system is developed to calculate the non-equilibrium characteristics of CO2 thermal plasmas for a wide temperature range, from 12,000 to 500 K, at atmospheric pressure. The non-equilibrium results are compared to the equilibrium composition obtained by Gibbs free energy minimization, and significant deviations are found at lower temperatures. Based on the dependence of molar fractions on temperature, the dominant species are determined in three temperature ranges. The dominant reactions are then obtained by considering their contribution to the generation and loss of the dominant species. Using the dominant species and reactions, the full model is simplified into three simpler models and the accuracy of the simplified models is evaluated. It is shown that this approach greatly reduces the number of species and reactions considered, while showing good agreement with the full model, with a root-mean-square error of no more than 4 %. Thus, the complicated physicochemical processes in non-equilibrium CO2 thermal plasmas can be characterized by relatively few species and reactions. It is suggested that the two-temperature chemical kinetic model developed in this paper can be applied to the full range of pressures that occur in arc welding, arc quenching and other industrial applications. In addition, the simplified methods can be applied in multi-dimensional models to reduce the chemical complexity and computing time while capturing the main physicochemical processes in non-equilibrium CO2 thermal plasmas.

Wall slip of styrene-isoprene-styrene (SIS) triblock copolymer was investigated during the capillary extrusion flow. The origin of the unique flow behavior of SIS was explored. Wall slip velocity of the SIS at 150 °C was calculated by the Mooney method. The non-monotonic wall slip behavior exhibited by the SIS system in the weak wall slip region was due to the change of PS micro elastic phase. SAXS and DMA data confirmed that SIS had a viscous flow transition near 170 °C. The occurrence of this transition caused a significant change in the flow curve and wall slip state of the SIS.

As a new class of functional luminescent materials, polymers with aggregation-induced emission (AIE) feature attract much attention because of their advantages of efficient solid-state fluorescence, excellent processability, structural diversity, and multifunctionalities. Among all polymerization methods toward AIE polymers, multicomponent polymerizations (MCPs) exhibit the merits of simple operation, good atom economy, high polymerization efficiency, broad functional-group tolerance, etc. In this feature article, the recent progress on the development of one-step MCPs for the synthesis of AIE polymers is highlighted. The representative functionalities of the resulting AIE polymers are illustrated. Perspectives on the challenges and future development directions of this field are also discussed.

The expression of aerobactin accounts for much of the pathogenesis of avian pathogenic Escherichia coli (APEC). iucA, iucB, iucC and iucD are involved in aerobactin synthesis and iutA is responsible for the expression of a specific outer membrane receptor protein for ferric aerobactin. Knockout mutants of iucD and iucDiutA in the APEC O2 strain E058 were constructed and named E058ΔiucD and E058ΔiucDΔiutA, respectively. To evaluate the pathogenicity of these mutants, we used multiple approaches to assess the effects of mutations on the virulence of APEC E058. Aerobactin-defective mutants E058ΔiucD and E058ΔiucDΔiutA showed significantly decreased pathogenicity compared with the wild-type strain E058, evidenced by the low extent of colonization in selected organs or being outcompeted by E058 in vivo. Chickens challenged with APEC E058 exhibited typical signs and lesions of avian colibacillosis, while those inoculated with the mutants E058ΔiucD or E058ΔiucDΔiutA showed moderate airsacculitis, mild pericarditis and perihepatitis. However, no significant differences in resistance to specific-pathogen-free chicken serum, ingestion by HD-11 cells, and growth rates in LB were observed between the mutants and the wild-type strain. These results indicated that the IucD- and IutA-related virulence factors play a significant role in the pathogenesis of the APEC strain E058.

Partial discharge (corona discharge) is generated in the gas-insulated switchgear (GIS) before faults occur due to insulation defects. The GIS is usually filled with compressed SF 6 for electric insulation. When partial discharge occurs, a portion of SF6 will decompose and oxidize in the presence of oxygen and water vapor to form various stable gaseous by-products, including SO2F2, SOF2, SOF4, SO2, S2F10, S2OF10, S2O2F10, SF4, HF and so on. In order to analyze the discharge mechanism, two zone chemical kinetic models are coupled to interpret the chemical process of point-to-plane 50 Hz ac corona discharge. In the plasma region, the electron impact dissociation reactions, electron-impact ionization reactions, electron-impact attachment reactions, radical-radical reactions, and ion-radical reactions are considered. SF 6 decomposes into various low fluorine sulfides, which continue to react with the radicals O or OH, produced from the dissociation of H 2 O and O 2 . The electron energy is the function of electric field at 300K. In addition, the stable fragments from SF6 decomposition in the plasma region, like SF2 and SF4, diffuse into the main gas volume and react with water or oxygen to produce the feature by-products SO2F2, SOF2 and SOF4. With comparing the variation rules of these decomposition byproducts with time from simulation and the experimental results, the model is verified to be reliable and reasonable. And also, the physicochemical process of SF 6 decomposition mechanism under corona discharge can be captured.

It's increasing clear that departures from both thermal and chemical equilibrium exist in conditions relevant to high-voltage circuit breakers after current zero. The electron temperature (T e ) is often higher than the heavy species temperature (T h ). We are intended to investigate the effects of N 2 contents on the electron temperature and non-equilibrium composition during the arc decaying process, when the heavy species temperature decreases from 12000 K to 1000 K at 4 atm. A two-temperature chemical kinetic model of SF 6 /N 2 thermal plasma containing all the reactions available is developed. The ratio of T e to T h is defined as the function of electron number density. And also, T∗ is introduced to allow a smooth transition between T e and T h . The ratio of T e to T h and the kinetic compositions at different N 2 contents are compared and analyzed. Then, the physicochemical process can be better interpreted based on the non-equilibrium phenomenon.

SF 6 has been widely used as insulating and arc-extinguishing medium in power equipment. Under discharges, lower fluorides of sulfur generated by the dissociations of SF6 will react with unavoidable moisture and oxygen to form corrosive byproducts (etc., SOF 2 , SO 2 F 2 , SOF 4 ). These byproducts will reduce the insulating and arc-quenching capacity of SF 6 power equipment, so it is necessary to study their varying characteristics. In present paper, non-chemical and non-thermodynamic equilibriums were taken into consideration applying chemical kinetic model. The basic reactions of SF 6 with H2O and O2 were obtained from literatures. Finally we got the temperature-varying concentrations of the main byproducts SOF2, SO2F2 and SOF4 as well as other important particles. We also analyzed the dominant reactions in different selected temperature ranges. This work can help to understand the varying mechanism of the key species and lay a theoretical basis for life-assessment of SF 6 power equipment in further studies.

It is common to identify the internal insulation conditions of Sulfur Hexafluoride (SF6) insulated equipment by monitoring the concentrations of SF6 decomposition products. Corona discharge can lead to the decomposition of SF6, and thus, a lot of reactions occur in the mixture of SF6 with the impurities H2O and O2. Even under the same strength of corona discharge, the reactions can cause the decomposition products to differ due to the different concentrations of H2O and O2. This paper systematically studies the effects of H2O and O2 on the formation mechanism of SF6 decomposition products from a theoretical perspective. Two coupled zero-dimensional chemical kinetic models were built to investigate the discharge mechanism of 50 Hz ac point-plane corona discharge. By calculating the related contributions of the pathways at different moisture and oxygen contents (from 200 ppm to 5000 ppm), the main chemical process and the influence of the moisture and oxygen contents on the main discharge mechanism are analyzed.

Corona (partial) discharges are generated in electrical equipment before faults occur due to insulation defects. The SF6-decomposition byproducts induced by the partial discharge are closely related to the insulation state of electrical equipment, so understanding the decomposition mechanisms of the byproducts is very important. In order to analyze the chemical processes and the generation mechanisms of the products of decomposition, two coupled 0D chemical kinetic models were developed and an experiment platform was established to verify the simulation results. The measured and predicted concentrations of SOF2, SO2F2 and SO2 were compared and found to have a reasonable agreement. The time-dependent generation mechanisms of SOF4 and HF were also predicted by the simulation model. The influence of moisture and oxygen impurities was examined; their presence increased the concentration of most of the decomposition products, with moisture generally having a stronger effect; the main exception is SOF4, whose production is predicted to be inhibited by the presence of moisture. Finally, the dominant pathways involving these five species in the plasma region and the gas region were analyzed to determine the dominant chemical processes for the generation and loss of these decomposition products.

Cu2 MoS4 nanosheets are synthesized by a solvothermal method in which the Cu2 O starting material acts as a sacrificial template. The microstructure of the Cu2 MoS4 nanosheets is characterized at the atomic level, and the growth mechanism is monitored at the nanoscale through systematic time-dependent experiments. As a result, the unprecedented observation of the allotropic phase change in Cu2 MoS4 that occurs during the solvothermal process is possible.

A series of experiments pointed out that compact states of DNA condensed by multivalent cation prefer higher temperature. The condensed DNA takes elongated coil or compact globule states and the population of the compact globule states increases with an increase in temperature. At the same time, a recent experimental work carried out in buffer solution without multivalent cation points out that DNA persistence length strongly depends on the temperature. DNA persistence length is a key parameter for quantitative interpretation of the conformational properties of DNA and related to the bending rigidity of DNA. It is necessary to revolve the effects of temperature dependence of persistence length on DNA condensation, and a model including the temperature dependence of persistence length and strong correlation of multivalent cation on DNA is provided. The autocorrelation function of the tangent vectors is found as an effective way to detect the temperature dependence of toroid conformations. With an increase in temperature, the first periodic oscillation in the autocorrelation function shifts left and the number of segments containing the first periodic oscillation decreases gradually. According to the experiments mentioned above, the long-axis length is defined to estimate the temperature dependence of condensation process further. At the temperatures defined in experiments mentioned above, the relation between long-axis length and temperature matches the experimental results.

This paper is devoted to the computation of the non-equilibrium composition of an SF6 plasma, and determination of the dominant particles and reactions, at conditions relevant to high-voltage circuit breakers after current zero (temperatures from 12 000 K to 1000 K and a pressure of 4 atm). The non-equilibrium composition is characterized by departures from both thermal and chemical equilibrium. In thermal non-equilibrium process, the electron temperature (T e) is not equal to the heavy-particle temperature (T h), while for chemical non-equilibrium, a chemical kinetic model is adopted. In order to evaluate the reasonableness and reliability of the non-equilibrium composition, calculation methods for equilibrium composition based on Gibbs free energy minimization and kinetic composition in a one-temperature kinetic model are first considered. Based on the one-temperature kinetic model, a two-temperature kinetic model with the ratio T e/T h varying as a function of the logarithm of electron density ratio (n e/ nemax ?> ) was established. In this model, T* is introduced to allow a smooth transition between T h and T e and to determine the temperatures for the rate constants. The initial composition in the kinetic models is obtained from the asymptotic composition as infinite time is approached at 12 000 K. The molar fractions of neutral particles and ions in the two-temperature kinetic model are consistent with the equilibrium composition and the composition obtained from the one-temperature kinetic model above 10 000 K, while significant differences appear below 10 000 K. Based on the dependence of the particle distributions on temperature in the two-temperature kinetic model, three temperature ranges, and the dominant particles and reactions in the respective ranges, are determined. The full model is then simplified into three models and the accuracy of the simplified models is assessed. The simplified models reduce the number of species and reactions by a factor of about 2, while providing results that agree closely with the full model. Thus, the physicochemical processes of SF6 arc can be characterized by relatively few species and reactions in each temperature range. It is noted that the simplified models can also be applied to a wide range of pressures, 1–16 atm, conditions which cover most circuit breaker applications. The simplified species and reactions will allow the computing time of multi-dimensional models, taking into account departures from both thermal and chemical equilibrium, to be decreased dramatically while capturing the main physicochemical processes in SF6 arcs.

Lipopolysaccharide (LPS) is a major surface component of avian pathogenic Escherichia coli (APEC), and is a possible virulence factor in avian infections caused by this organism. The contribution of the lpxM gene, which encodes a myristoyl transferase that catalyzes the final step in lipid A biosynthesis, to the pathogenicity of APEC has not previously been assessed. In this study, an isogenic lpxM mutant, E058ΔlpxM, was constructed in APEC O2 strain E058 and then characterized. Structural analysis of lipid A from the parental strain and derived mutant showed that E058ΔlpxM lacked one myristoyl (C14:0) on its lipid A molecules. No differences were observed between the mutant and wild-type in a series of tests including growth rate in different broths and ability to survive in specific-pathogen-free chicken serum. However, the mutant showed significantly reduced invasion and intracellular survival in the avian macrophage HD11 cell line (P

Aerobactin genes are known to be present in virulent strains and absent from avirulent strains, but contributions of iucC and iucA, which are involved in aerobactin synthesis, to the pathogenicity of avian pathogenic Escherichia coli (APEC) have not been clarified. In this study, effects of double mutants (iucA/iutA or iucC/iutA) compared to those of single mutants (iucA, iucC or iutA) of aerobactin genes on the virulence of APEC strain E058 were examined both in vitro (aerobactin production, ingestion into HD-11 cells, survival in chicken serum) and in vivo (competitive growth against parental strain, colonization and persistence). In competitive co-infection assays, compared to the E058 parental strain, the E058ΔiucA mutant was significantly reduced in the liver, kidney, spleen (all P

Background Avian pathogenic Escherichia coli (APEC) and uropathogenic E. coli (UPEC) are the two main subsets of extraintestinal pathogenic E. coli (ExPEC). Both types have multiple iron acquisition systems, including heme and siderophores. Although iron transport systems involved in the pathogenesis of APEC or UPEC have been documented individually in corresponding animal models, the contribution of these systems during simultaneous APEC and UPEC infection is not well described. To determine the contribution of each individual iron acquisition system to the virulence of APEC and UPEC, isogenic mutants affecting iron uptake in APEC E058 and UPEC U17 were constructed and compared in a chicken challenge model. Results Salmochelin-defective mutants E058ΔiroD and U17ΔiroD showed significantly decreased pathogenicity compared to the wild-type strains. Aerobactin defective mutants E058ΔiucD and U17ΔiucD demonstrated reduced colonization in several internal organs, whereas the heme defective mutants E058ΔchuT and U17ΔchuT colonized internal organs to the same extent as their wild-type strains. The triple mutant ΔchuTΔiroDΔiucD in both E058 and U17 showed decreased pathogenicity compared to each of the single mutants. The histopathological lesions in visceral organs of birds challenged with the wild-type strains were more severe than those from birds challenged with ΔiroD, ΔiucD or the triple mutants. Conversely, chickens inoculated with the ΔchuT mutants had lesions comparable to those in chickens inoculated with the wild-type strains. However, no significant differences were observed between the mutants and the wild-type strains in resistance to serum, cellular invasion and intracellular survival in HD-11, and growth in iron-rich or iron-restricted medium. Conclusions Results indicated that APEC and UPEC utilize similar iron acquisition mechanisms in chickens. Both salmochelin and aerobactin systems appeared to be important in APEC and UPEC virulence, while salmochelin contributed more to the virulence. Heme bounded by ChuT in the periplasm appeared to be redundant in this model, indicating that other periplasmic binding proteins likely contributed to the observed no phenotype for the heme uptake mutant. No differences were observed between the mutants and their wild-type parents in other phenotypic traits, suggesting that other virulence mechanisms compensate for the effect of the mutations.