The ribosomal maturation factor P (RimP) is a highly conserved protein in bacteria and has been shown to be important in ribosomal assembly in Escherichia coli. Because of its central importance in ...bacterial metabolism, RimP represents a good potential target for drug design to combat human pathogens such as Mycobacterium tuberculosis. However, to date, the only RimP structure available is the NMR structure of the ortholog in another bacterial pathogen, Streptococcus pneumoniae. Here, we report a 2.2 Å resolution crystal structure of MSMEG_2624, the RimP ortholog in the close M. tuberculosis relative Mycobacterium smegmatis, and using in vitro binding assays, we show that MSMEG_2624 interacts with the small ribosomal protein S12, also known as RpsL. Further analyses revealed that the conserved residues in the linker region between the N- and C-terminal domains of MSMEG_2624 are essential for binding to RpsL. However, neither of the two domains alone was sufficient to form strong interactions with RpsL. More importantly, the linker region was essential for in vivo ribosomal biogenesis. Our study provides critical mechanistic insights into the role of RimP in ribosome biogenesis. We anticipate that the MSMEG_2624 crystal structure has the potential to be used for drug design to manage M. tuberculosis infections.
Obesity is a risk factor for colorectal cancer (CRC). The role of gut microbiota in mediating the cancer-promoting effect of obesity is unknown.
Azoxymethane (AOM)-treated, ApcMin/+ and germ-free ...mice were gavaged with feces from obese individuals and control subjects respectively. The colonic tumor load and number were recorded at the endpoint in two carcinogenic models. The gut microbiota composition and colonic transcriptome were assessed by metagenomic sequencing and RNA sequencing, respectively. The anticancer effects of bacteria depleted in fecal samples of obese individuals were validated.
Conventional AOM-treated and ApcMin/+ mice receiving feces from obese individuals showed significantly increased colon tumor formation compared with those receiving feces from control subjects. AOM-treated mice receiving feces from obese individuals showed impaired intestinal barrier function and significant upregulation of pro-inflammatory cytokines and activation of oncogenic Wnt signaling pathway. Consistently, transferring feces from obese individuals to germ-free mice led to increased colonic cell proliferation, intestinal barrier function impairment, and induction of oncogenic and proinflammatory gene expression. Moreover, germ-free mice transplanted with feces from obese human donors had increased abundance of potential pathobiont Alistipes finegoldii, and reduced abundance of commensals Bacteroides vulgatus and Akkermansia muciniphila compared with those receiving feces from human donors with normal body mass index (BMI). Validation experiments showed that B. vulgatus and A. muciniphila demonstrated anti-proliferative effects in CRC, while A. finegoldii promoted CRC tumor growth.
Our results supported the role of obesity-associated microbiota in colorectal carcinogenesis and identified putative bacterial candidates that may mediate its mechanisms. Microbiota modulation in obese individuals may provide new approaches to prevent or treat obesity-related cancers including CRC.
This work was funded by National Key Research and Development Program of China (2020YFA0509200/2020YFA0509203), National Natural Science Foundation of China (81922082), RGC Theme-based Research Scheme Hong Kong (T21-705/20-N), RGC Research Impact Fund Hong Kong (R4632-21F), RGC-CRF Hong Kong (C4039-19GF and C7065-18GF), RGC-GRF Hong Kong (14110819, 14111621), and NTU Start-Up Grant (021337-00001).
Efficient conversion of beer lees wastes into biohydrogen gas by microorganisms was reported for the first time. Batch tests were carried out to analyze influences of several environmental factors on ...yield of H
2 from beer lees wastes. The maximum yield of H
2 68.6
ml
H
2/g TVS was observed, the value is about 10-fold as compared with that of raw beer lees wastes. The hydrogen content in the biogas was more than 45% and there was no significant methane observed in this study. In addition, biodegradation characteristics of the substrate were also discussed. The results indicated that the HCl pretreatment of the substrate plays a key role in the conversion of the beer lees wastes into biohydrogen by the cow dung composts.
Influence of Co doping for In in In2O3 matrix has been investigated to study the effect on magnetic vs. electronic properties. Rietveld refinement of X-ray diffraction patterns confirmed formation of ...single phase cubic bixbyite structure without any parasitic phase. Photoelectron spectroscopy and refinement results further revealed that dopant Co2+ ions are well incorporated at the In3+ sites in In2O3 lattice and also ruled out formation of cluster in the doped samples. Magnetization measurements infer that pure In2O3 is diamagnetic and turns to weak ferromagnetic upon Co doping. Hydrogenation further induces a huge ferromagnetism at 300K that vanishes upon re-heating. Experimental findings confirm the induced ferromagnetism to be intrinsic, and the magnetic moments to be associated with the point defects (oxygen vacancies V o) or bound magnetic polarons around the dopant ions.
Effect of injection of hydrogen ions, followed by their evaporation, has been investigated in the Zn
1−
x
Fe
x
O (
x
=
0.02–0.07) pellets to throw some light on electronic structure and magnetic ...correlations. The XRD patterns show that
x
≤
0.05 samples are single phase and the Fe ions incorporate at the Zn
2+ sites, while a secondary phase ZnFe
2O
4 is detected for
x
≥
0.07. The 2% Fe-doped sample retains a paramagnetic ground state down to 50
K. Likewise, the 5% doped sample also shows paramagnetic state at 300
K but a weak ferromagnetic ordering stems from its cooling (
T
c
∼
160
K). Strikingly, the 5% doped sample, when annealed in hydrogen atmosphere, showed inducement of room temperature ferromagnetism. More significantly, the hydrogen-induced magnetism disappears upon evaporating the H ions by re-heating the sample. The magnetic ordering and the electronic properties exhibit a close parallelism/interplay. The X-ray photoemission spectroscopy results testify the Fe to be in mixed valent state (>2+) in paramagnetic state, however, the ferromagnetic transition stems only upon Fe
3+ reducing to Fe
2+, accompanied by emergence of oxygen vacancies as a parallel electronic phenomenon. Origin of H-mediated ferromagnetism is discussed in the framework of cationic
vs. anionic vacancies and it is suggested that oxygen vacancies play major role in mediating the coupling.
Reducing the resistivity of low temperature grown p-Al0.09Ga0.91N layers is crucial to improving the performance of GaN-based laser diodes. In this study, growth conditions of low temperature grown ...p-Al0.09Ga0.91N layers are monitored and the role of C impurity is investigated systematically. On the basis of the dependence of resistivity on C concentration and the photoluminescence analysis, it is found that C impurities act as donors in p-Al0.09Ga0.91N layer, and reducing the C concentration can reduce its compensation effect on Mg acceptor. Finally, a low resistivity of 4.2 Ω·cm is achieved for the low temperature grown p-Al0.09Ga0.91N.
Substorm processes have been studied in detail, and it is well known that interplanetary (IP) shock encountering the terrestrial magnetosphere causes global responses. However, how IP shock ...compression to the magnetosphere affects the development of an ongoing substorm remains uninvestigated. Herein, the simultaneous satellite and ground-based auroral evolutions associated with an IP shock impact on the magnetopause during an ongoing substorm on May 7th, 2005, were examined. The IMAGE satellite over the Southern Hemisphere captured the global development substorm, which was initiated at 17:38:47 UT. The poleward branch of the nightside auroral oval was fortuitously monitored by an all-sky camera at the Zhongshan Station (−74.5° magnetic latitude, ZHO) in Antarctica. The satellite imager observed continuous brightening and broadening of the nightside auroral oval after the IP shock arrival. The simultaneous ground-based optical aurora measurement displayed the intensification and expansion of a preexisting auroral surge poleward of the aurora oval. The geomagnetic field variations and the instantly increased PC indices indicated an elevated merging rate and enhanced the convection-related DP-2 currents. Therefore, this IP shock transient impact did not significantly change the ongoing development of the substorm, although it meets the magnetospheric precondition hypothesis.
A magnetic model has been proposed that describes the effects of plastic deformation on magnetisation based on the theory of magneto-mechanical effect. In the current model correlating the ...magnetisation with the effective field, the influences of plastic strain on the model parameters and the effective field are taken into account respectively due to the difference between elastic and plastic deformation. Meanwhile, the effective fields under loading and unloading conditions are differentiated attributing to the effects of the applied stress and residual stress on domain wall motion. The computed magnetization shows a sharp change at a rather small plastic deformation even at only 0.5% elongation but subsequently a slow decrease with increasing tension, which is in good agreement with previous experimental results. Different magnetic signal characteristics in the plastic deformation region indicate that metal magnetic memory technique could be used to characterize early damage. PUBLICATION ABSTRACT
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The occurrence of discontinuous reactions under isothermal annealing of melt-spun Cu–10 at. % Co alloys, consisting of ribbons (20 µm thick) with columnar grains in the as-solidified state, has been ...investigated. The microstructure of the ribbons for different annealing temperatures (723–923 K) and annealing times (5–60 min) was determined by transmission electron microscopy, including analysis by energy-dispersive X-ray spectroscopy. Magnetic properties at room temperature were measured by means of hysteresis curve measurements in a vibrating sample magnetometer. Different types of microstructure were observed within grains and at grain boundaries. The spinodal decomposition microstructure was observed during the early stages of annealing for all annealing temperatures. Spherical precipitates grew from the modulated structure at a later stage, forming homogenous distributions throughout the grains. Heterogeneous distributions of incoherent precipitates formed at
T
> 873 K. As result of discontinuous precipitation, all grain boundaries exhibited arrays of rod-like Co precipitates with diameters and inter-rod spacing of few nanometers. The coarsening of discontinuous precipitates is attributed to a grain boundary-controlled phenomenon, called discontinuous coarsening (DC). The columnar morphology of the grains in the as-solidified alloy was connected with Co rods that were primarily oriented along the ribbon plane. This structure is connected with magnetic anisotropy, which is later weakened by DC. These results elucidate the unusual magnetic behavior of melt-spun Cu–Co alloys and provide a key to understanding their higher magnetoresistance in comparison with other heterogeneous systems.
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