Degradation of 3-chlorobenzoate by benzoate or 3-methylbenzoate-utilising cultures

Abstract 3-Chlorobenzoate (3CB) was incompletely degraded by bacterial cultures growing continuously with benzoate (Ben) or 3-methylbenzoate (3MB). Accumulation of chlorocatechols as dead-end metabolites was avoided if, prior to the exposure to 3CB, the population had been supplemented with Pseudomonas sp. strain B13 as a chlorocatechol-assimilating member. After acclimatisation, the substrate mixture Ben/3CB was completely degraded via 2 compatible ortho -cleavage pathways.
In contrast, 3MB and 3CB were found to be incompatible substrates: as a result of suicide and genetic inactivation of catechol 2,3-dioxygenase, methylcatechols are subject to unproductive ortho -cleavage. In a defined mixed culture ( Pseudomonas putida mt-2 plus strain B13), 4-carboxymethyl-2-methylbut-2-en-4-olide and 4-carboxymethyl-4-methylbut-2-en-4-olide were excreted as dead-end products, whereas in an undefined mixed culture, degraders of these metabolites became stable members of the community.
Characteristically, with increasing 3CB load, the relative number of 3CB-degrading organisms increased which were Ben⁺ or 3MB⁺ and which had acquired from Pseudomonas sp. strain B13 the ability to assimilate chlorocatechols.     

Co‐Culture of Mouse Epidermal Cells for Studies of Pigmentation

Interactions between melanocytes and keratinocytes in the skin suggest bi‐directional interchanges between these two cell types. Thus, melanocytes cultured alone may not accurately reflect the physiology of the skin and the effects of physiological regulators in vivo, because they do not consider possible interactions with keratinocytes. As more and more pigment genes are identified and cloned, the characterization of their functions becomes more of a challenge, particularly with respect to their roles in the processing and transport of melanosomes and their transfer to keratinocytes. Immortalized melanocytes mutant at these loci are now being routinely generated from mice, but interestingly, successful co‐culture of murine melanocytes and keratinocytes is very difficult compared with their human counterparts. Thus, we have now optimized co‐culture conditions for murine melanocytes and keratinocytes so that pigmentation and the effects of specific mutations can be studied in a more physiologically relevant context.     

金属离子对嗜热菌BF80生长及苯酚降解的影响研究

探测了17种金属离子对嗜热菌BF80菌生长和降解苯酚的影响。结果表明：与对照相比, 0.01%的Cu2+、Zn2+、Co2+、Ba2+、Hg2+、Ni2+、Ag+ 和Al3+对嗜热菌BF80有强抑制作用; Cr2+对嗜热菌BF80的苯酚降解特性有强抑制作用, 而其生长量只受到一定的抑制作用; Sn2+、Fe2+、Fe3+和Pn2+ 对嗜热菌BF80的生长和苯酚降解有一定抑制作用, 该作用随金属粒子浓度的增加而增大; 低浓度Mn2+ 和Mo2+可以使其生长量增大且促进苯酚降解, 但超过0.1%的浓度则抑制其生长; Ca2+ 和Mg2+可以加速嗜热菌BF80的生长和降解苯酚的速率, 但对苯酚的最大降解率却几乎没有影响; Mo2+ 和Mn2+的复合作用使嗜热菌BF80的生长量更大, 但是苯酚降解率却比分别单独添加Mo2+ 和Mn2+时低。     

In vitro Degradation of 2,4,6‐Trinitrotoluene Using Plant Tissue Cultures of Solanum aviculare and Rheum palmatum

The degradation of TNT was tested in suspension cultures (Rheum palmatum and Solanum aviculare) and was followed by the identification of degradation products and the determination of the phytotoxicity of TNT to both cultures. The concentration of TNT inhibited the growth of cell cultures by 50 %, i.e., 37.8 mg/ and 38.1 mg/L for Rheum palmatum and Solanum aviculare, respectively. The TNT uptake was studied by determining the concentration of TNT and its degradation products, such as aminodinitrotoluenes and diaminonitrotoluenes, in the cultivation medium as well as in plant cells. The kinetics of the degradation showed that TNT was mostly taken up within 10 hours and 6 hours for S. aviculare and R. palmatum, respectively. Aminodinitrotoluenes were preferentially produced by cultures of S. aviculare, whereas diaminonitrotoluenes and aminodinitrotoluenes were revealed in cultures of R. palmatum. The final concentrations of identified degradation products did not stoichiometrically correspond to the decreased concentration of TNT in the medium. The different concentrations of degradation products in each culture were an indication that the metabolism of TNT is controlled by different enzymatic systems. Therefore, it was concluded that studying different species for TNT degradation is necessary for the search of most suitable candidates for TNT phytoremediation.     

金属离子对嗜热菌BF80生长及苯酚降解的影响研究

探测了17种金属离子对嗜热菌BF80菌生长和降解苯酚的影响.结果表明:与对照相比,0.01%的Cu2 、Zn2 、CO2 、Ba2 、Hg2 、Ni2 、Al 0和Al3 对嗜热菌BF80有强抑制作用;Cr2 对嗜热菌BF80的苯酚降解特性有强抑制作用,而其生长量只受到一定的抑制作用;Sn2 、Fe2 、Fe3 和Pn2 对嗜热菌BF80的生长和苯酚降解有一定抑制作用,该作用随金属粒子浓度的增加而增大;低浓度Mn2 和Mo2 可以使其生长量增大且促进苯酚降解,但超过0.1%的浓度则抑制其生长;Ca2 和Mg2 可以加速嗜热菌BF80的生长和降解苯酚的速率,但对苯酚的最大降解率却几乎没有影响;Mo2 和Mn2 的复合作用使嗜热菌BF80的生长量更大,但是苯酚降解率却比分别单独添加Mo2 和Mn2 时低.     

Co‐culture engineering for microbial biosynthesis of 3‐amino‐benzoic acid in Escherichia coli

3‐amino‐benzoic acid (3AB) is an important building block molecule for production of a wide range of important compounds such as natural products with various biological activities. In the present study, we established a microbial biosynthetic system for de novo 3AB production from the simple substrate glucose. First, the active 3AB biosynthetic pathway was reconstituted in the bacterium Escherichia coli, which resulted in the production of 1.5 mg/L 3AB. In an effort to improve the production, an E. coli‐E. coli co‐culture system was engineered to modularize the biosynthetic pathway between an upstream strain and an downstream strain. Specifically, the upstream biosynthetic module was contained in a fixed E. coli strain, whereas a series of E. coli strains were engineered to accommodate the downstream biosynthetic module and screened for optimal production performance. The best co‐culture system was found to improve 3AB production by 15 fold, compared to the mono‐culture approach. Further engineering of the co‐culture system resulted in biosynthesis of 48 mg/L 3AB. Our results demonstrate co‐culture engineering can be a powerful new approach in the broad field of metabolic engineering.     

Co‐occurrence is not evidence of ecological interactions

There is a rich amount of information in co‐occurrence (presence–absence) data that could be used to understand community assembly. This proposition first envisioned by Forbes (1907) and then Diamond (1975) prompted the development of numerous modelling approaches (e.g. null model analysis, co‐occurrence networks and, more recently, joint species distribution models). Both theory and experimental evidence support the idea that ecological interactions may affect co‐occurrence, but it remains unclear to what extent the signal of interaction can be captured in observational data. It is now time to step back from the statistical developments and critically assess whether co‐occurrence data are really a proxy for ecological interactions. In this paper, we present a series of arguments based on probability, sampling, food web and coexistence theories supporting that significant spatial associations between species (or lack thereof) is a poor proxy for ecological interactions. We discuss appropriate interpretations of co‐occurrence, along with potential avenues to extract as much information as possible from such data.     

Ni‐Rich/Co‐Poor Layered Cathode for Automotive Li‐Ion Batteries: Promises and Challenges

To pursue a higher energy density (>300 Wh kg^?1 at the cell level) and a lower cost (<$125 kWh^?1 expected at 2022) of Li‐ion batteries for making electric vehicles (EVs) long range and cost‐competitive with internal combustion engine vehicles, developing Ni‐rich/Co‐poor layered cathode (LiNi_1?x?yCo_xMn_yO₂, x+y ≤ 0.2) is currently one of the most promising strategies because high Ni content is beneficial to high capacity (>200 mAh g^?1) while low Co content is favorable to minimize battery cost. Unfortunately, Ni‐rich cathodes suffer from limited structure stability and electrode/electrolyte interface stability in the charged state, leading to electrode degradation and poor cycling performance. To address these problems, various strategies have been employed such as doping, structural optimization design (e.g., core–shell structure, concentration‐gradient structure, etc.), and surface coating. In this review, five key aspects of Ni‐rich/Co‐poor layered cathode materials are explored: energy density, fast charge capability, service life including cycling life and calendar life, cost and element resources, and safety. This enables a comprehensive analysis of current research advances and challenges from the perspective of both academy and industry to help facilitate practical applications for EVs in the future.     

Effect of Electron‐Transport Material on Light‐Induced Degradation of Inverted Planar Junction Perovskite Solar Cells

This paper presents a systematic study of the influence of electron‐transport materials on the operation stability of the inverted perovskite solar cells under both laboratory indoor and the natural outdoor conditions in the Negev desert. It is shown that all devices incorporating a Phenyl C₆₁ Butyric Acid Methyl ester ([60]PCBM) layer undergo rapid degradation under illumination without exposure to oxygen and moisture. Time‐of‐flight secondary ion mass spectrometry depth profiling reveals that volatile products from the decomposition of methylammonium lead iodide (MAPbI₃) films diffuse through the [60]PCBM layer, go all the way toward the top metal electrode, and induce its severe corrosion with the formation of an interfacial AgI layer. On the contrary, alternative electron‐transport material based on the perylendiimide derivative provides good isolation for the MAPbI₃ films preventing their decomposition and resulting in significantly improved device operation stability. The obtained results strongly suggest that the current approach to design inverted perovskite solar cells should evolve with respect to the replacement of the commonly used fullerene‐based electron‐transport layers with other types of materials (e.g., functionalized perylene diimides). It is believed that these findings pave a way toward substantial improvements in the stability of the perovskite solar cells, which are essential for successful commercialization of this photovoltaic technology.     

Free‐Radical Degradation of High‐Molar‐Mass Hyaluronan Induced by Ascorbate plus Cupric Ions: Evaluation of Antioxidative Effect of Cysteine‐Derived Compounds

Based on our previous findings, the present study has focused on free‐radical‐mediated degradation of the synovial biopolymer hyaluronan. The degradation was induced in vitro by the Weissberger's system comprising ascorbate plus cupric ions in the presence of oxygen, representing a model of the early phase of acute synovial joint inflammation. The study presents a novel strategy for hyaluronan protection against oxidative degradation with the use of cysteine‐derived compounds. In particular, the work objectives were to evaluate potential protective effects of reduced form of L ‐glutathione, L ‐cysteine, N‐acetyl‐L ‐cysteine, and cysteamine, against free‐oxygen‐radical‐mediated degradation of high‐molar‐mass hyaluronan in vitro. The hyaluronan degradation was influenced by variable activity of the tested thiol compounds, also in dependence of their concentration applied. It was found that L ‐glutathione exhibited the most significant protective and chain‐breaking antioxidative effect against the hyaluronan degradation. Thiol antioxidative activity, in general, can be influenced by many factors such as various molecule geometry, type of functional groups, radical attack accessibility, redox potential, thiol concentration and pK_a, pH, ionic strength of solution, as well as different ability to interact with transition metals. Antioxidative activity was found to decrease in the following order: L ‐glutathione, cysteamine, N‐acetyl‐L ‐cysteine, and L ‐cysteine. These findings might be beneficial in future development of potential drugs in the treatment of synovial hyaluronan depletion‐derived diseases.     

Co‐regulation proteomics reveals substrates and mechanisms of APC/C‐dependent degradation

Using multiplexed quantitative proteomics, we analyzed cell cycle‐dependent changes of the human proteome. We identified >4,400 proteins, each with a six‐point abundance profile across the cell cycle. Hypothesizing that proteins with similar abundance profiles are co‐regulated, we clustered the proteins with abundance profiles most similar to known Anaphase‐Promoting Complex/Cyclosome (APC/C) substrates to identify additional putative APC/C substrates. This protein profile similarity screening (PPSS) analysis resulted in a shortlist enriched in kinases and kinesins. Biochemical studies on the kinesins confirmed KIFC1, KIF18A, KIF2C, and KIF4A as APC/C substrates. Furthermore, we showed that the APC/C^CDH1‐dependent degradation of KIFC1 regulates the bipolar spindle formation and proper cell division. A targeted quantitative proteomics experiment showed that KIFC1 degradation is modulated by a stabilizing CDK1‐dependent phosphorylation site within the degradation motif of KIFC1. The regulation of KIFC1 (de‐)phosphorylation and degradation provides insights into the fidelity and proper ordering of substrate degradation by the APC/C during mitosis.     

Melanosome Capping of Keratinocytes in Pigmented Reconstructed Epidermis – Effect of Ultraviolet Radiation and 3‐Isobutyl‐1‐Methyl‐Xanthine on Melanogenesis

Reconstructed pigmented epidermis was established by co‐seeding autologous melanocytes and keratinocytes onto a dermal substrate and culturing for up to 6 weeks at the air–liquid interface. Inspection of the tissue architecture revealed that melanocytes are regularly interspersed only in the basal layer and transfer melanosomes to the keratinocytes. We report for the first time, the in vitro formation of supranuclear melanin caps above the keratinocyte nuclei. The formation and abundance of these melanin caps could be enhanced by pigment modifiers such as ultraviolet light and 3‐isobutyl‐1‐methyl‐xanthine (IBMX). In untreated cultures, the capping was observed in the spinous layers after 6 weeks of culture, whereas after irradiation or supplementation of the culture medium with IBMX, the capping occurred already in the basal layer 2 weeks after initiation of the stimulus. In this study, we show that IBMX and ultraviolet irradiation stimulate pigmentation via different mechanisms. After supplementation of the culture medium with IBMX the increase in pigmentation was entirely due to the increase in melanocyte activity as observed by increased dendrite formation, melanin production and transport to the keratinocytes and was not due to an increase in melanocyte proliferation. In contrast, after UV irradiation, the increase in pigmentation was also accompanied with an increase in melanocyte proliferation as well as an increase in melanocyte activity. In conclusion, we describe the establishment of pigmented reconstructed epidermis with autologous keratinocytes and melanocytes that can be kept in culture for a period of at least 6 weeks. The complete program of melanogenesis occurs: melanosome synthesis, melanosome transport to keratinocytes, supranuclear capping of keratinocyte nuclei and tanning of the epidermis. This enables sustained application of pigment stimulators over a prolonged period of time and also repeated application of pigment stimulators to be studied.     

Constructing E. coli Co‐Cultures for De Novo Biosynthesis of Natural Product Acacetin

Modular co‐culture engineering is an emerging approach for biosynthesis of complex natural products. In this study, microbial co‐cultures composed of two and three Escherichia coli strains, respectively, are constructed for de novo biosynthesis of flavonoid acacetin, a value‐added natural compound possessing numerous demonstrated biological activities, from simple carbon substrate glucose. To this end, the heterologous biosynthetic pathway is divided into different modules, each of which is accommodated in a dedicated E. coli strain for functional expression. After the optimization of the inoculation ratio between the constituent strains, the engineered co‐cultures show a 4.83‐fold improvement in production comparing to the mono‐culture controls. Importantly, cultivation of the three‐strain co‐culture in shake flasks result in the production of 20.3 mg L^?1 acacetin after 48 h. To the authors' knowledge, this is the first report on acacetin de novo biosynthesis in a heterologous microbial host. The results of this work confirm the effectiveness of modular co‐culture engineering for complex flavonoid biosynthesis.     

H2‐Directing Strategy on In Situ Synthesis of Co‐MoS2 with Highly Expanded Interlayer for Elegant HER Activity and its Mechanism

MoS₂ has drawn great attention as a promising Pt‐substituting catalyst for the hydrogen evolution reaction (HER). This work utilizes H₂ as the structure directing agent (SDA) to in situ synthesize a range of Co‐MoS₂‐n (n = 0, 0.5, 1.0, 1.4, 2.0) with expanded interlayer spacings (d = 9.2 – 11.1 Å), which significantly boost their HER activities. The Co‐MoS₂‐1.4 with an interlayer spacing of 10.3 Å presents an extremely low overpotential of 56 mV (at 10 mA cm^?2) and a Tafel slope of 32 mV dec^?1, which is superior than most reported MoS₂‐based catalysts. Density function theory calculations are used to gain insights that i) the H₂ can be dissociatively adsorbed on MoS₂ and greatly affect the related surface free energy by regulating the interlayer spacing; ii) the expanded interlayer spacing can significantly decrease the absolute value of ΔG_H, thereby leading to greatly promoted HER activity. Additionally, the large amounts of 1T phase (73.9–79.2%) and Co‐Mo‐S active sites (40.9–91.3%) also contribute to the enhanced HER activity of the synthesized samples. Overall, a simple new strategy for in situ synthesis of Co‐MoS₂ with an expanded interlayer spacing is proposed, which sheds light on other 2D energy material designs.