Design of mutualistic microbial consortia for stable conversion of carbon monoxide to value-added chemicals

Carbon monoxide (CO) is a promising carbon source for producing value-added biochemicals via microbial fermentation. However, its microbial conversion has been challenging because of difficulties in genetic engineering of CO-utilizing microorganisms and, more importantly, maintaining CO consumption which is negatively affected by the toxicity of CO and accumulated byproducts. To overcome these issues, we devised mutualistic microbial consortia, co-culturing Eubacterium limosum and genetically engineered Escherichia coli for the production of 3-hydroxypropionic acid (3-HP) and itaconic acid (ITA). During the co-culture, E. limosum assimilated CO and produced acetate, a toxic by-product, while E. coli utilized acetate as a sole carbon source. We found that this mutualistic interaction dramatically stabilized and improved CO consumption of E. limosum compared to monoculture. Consequently, the improved CO consumption allowed successful production of 3-HP and ITA from CO. This study is the first demonstration of value-added biochemical production from CO using a microbial consortium. Moreover, it suggests that synthetic mutualistic microbial consortium can serve as a powerful platform for the valorization of CO.     

Degree of bacterial contamination in barbershops using hair dryers in Riyadh

Barbershops provide areas for the growth and transfer of bacterial pathogens and thereby have an impact on public health. Barbershops are ideal places for the interactive spread of infections, including community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). Here, the work determines the degree of bacterial contamination of hair dryers used in barbershops. The samples were collected in the city of Riyadh, the Kingdom of Saudi Arabia on March 2019. Significant bacterial contamination was seen, with total bacterial count increasing when the hair dryers were run for 20 instead of 10 s. The study shows a high level of bacterial contamination barbershops using hair dryers, with MRSA being isolated in some. The results suggest that high quality filters should be used inside hair dryers and filters, and theses should be cleaned frequently.     

Floral fungal-bacterial community structure and co-occurrence patterns in four sympatric island plant species

Flowers’ fungal and bacterial communities can exert great impacts on host plant wellness and reproductive success—both directly and indirectly through species interactions. However, information about community structure and co-occurrence patterns in floral microbiome remains scarce. Here, using culture-independent methods, we investigated fungal and bacterial communities associated with stamens and pistils of four plant species (Scaevola taccada, Ipomoea cairica, Ipomoea pes-caprae, and Mussaenda kwangtungensis) growing together under the same environment conditions in an island located in South China. Plant species identity significantly influenced community composition of floral fungi but not bacteria. Stamen and pistil microbiomes did not differ in community composition, but differed in co-occurrence network topological features. Compared with the stamen network, pistil counterpart had fewer links between bacteria and fungi and showed more modular but less concentrated and connected structure. In addition, degree distribution of microbial network in each host species and each microhabitat (stamen or pistil) followed a significant power-law pattern. These results enhance our understanding in the assembly principles and ecological interactions of floral microbial communities.     

A microaliquoting technique for precise histological annotation and optimization of cell content in frozen tissue specimens

Knowledge of the exact cell content of frozen tissue samples is of growing importance in genomic research. We developed a microaliquoting technique to measure and optimize the cell composition of frozen tumor specimens for molecular studies. Frozen samples of 31 mesothelioma cases were cut in alternating thin and thick sections. Thin sections were stained and evaluated visually. Thick sections, i.e., microaliquots, were annotated using bordering stained sections. A range of cellular heterogeneity was observed among and within samples. Precise annotation of samples was obtained by integration and compared to conventional single face and “front and back” section estimates of cell content. Front and back estimates were more highly correlated with block annotation by microaliquoting than were single face estimates. Both methods yielded discrepant estimates, however, and for some studies may not adequately account for the heterogeneity of mesothelioma or other malignancies with variable cellular composition. High yield and quality RNA was extracted from precision annotated, tumor-enriched subsamples prepared by combining individual microaliquots with the highest tumor cellularity estimates. Microaliquoting provides accurate cell content annotation and permits genomic analysis of enriched subpopulations of cells without fixation or amplification.     

Is the edTPA the Right Choice for Evaluating Teacher Readiness?

The purpose of this article is to describe and analyze the edTPA, a performance assessment created by the Stanford Center for Assessment, Learning, and Equity (SCALE) and administered by Pearson, Inc., to assess the professional readiness of student teachers. We challenge claims made in support of using this assessment, specifically within the context of arts teacher preparation programs, and we address areas of immediate critical concern to make alternative recommendations.     

Preparation of optically active 4-chlorophenylalanine from its racemate by deracemization technique using transformant Escherichia coli cells

We have developed a method for the preparation of l-4-chlorophenylalanine from its racemate with Escherichia coli cells expressing a single foreign gene. l-4-Chlorophenylalanine was obtained in a high optical yield by the inversion of configuration of its d-form via the tandem reactions catalyzed by d-amino acid dehydrogenase (DadA) and branched-chain amino acid aminotransferase (BCAAT). While we constructed a plasmid for BCAAT utilizing the gene from Sinorhizobium meliloti ATCC 51124, the first enzyme DadA was the dadA-gene product from E. coli host cell itself, which was activated by the addition of l-alanine in the growth medium.     

John Salter and the Ediacara Fauna of the Longmyndian Supergroup

John W. Salter's papers of 1856 and 1857 reported trace and body fossils from rocks of the Longmyndian Supergroup, Shropshire, that conventional wisdom had deemed literally “Azoic.” The significance of this work is reflected by its mention in On the Origin of Species, where it is cited as evidence for the existence of life prior to the Cambrian radiation. This study of Salter's historic specimens combined with recent field studies confirms that these structures likely represent microbial rather than metazoan markings. Nevertheless, this review confirms Salter as the unheralded founder of Precambrian palaeontology, many years before the existence of a Precambrian fossil record was widely known. This study also gives credit to a highly skilled palaeontologist, who appears to have struggled with psychological problems throughout his life. Salter had once been Adam Sedgwick's “youthful and cheerful companion” in the field, prior to embarking on an initially successful Geological Survey career. He was a widely renowned expert on Palaeozoic palaeontology, especially trilobites, but eventually fell into serious depression, which culminated in his suicide in 1869. Study and reinterpretation of his original materials reaffirms the importance of Salter's discoveries, and the Longmynd for our understanding of late Ediacaran palaeobiology.     

Soil Microbial Community Response to Nitrobenzene Exposure for a Spartina Wetland

To explore the response of the soil microbial community to nitrobenzene (NB) exposure in a Spartina marsh, a short-term (45 d) mesocosm study was conducted at three NB concentrations of (10, 50, and 100) mg kg^?1. Dry soil, sterile and unsterile controls were also compared. The ability of the microbes to biodegrade NB was studied in an effort to predict the outcome of NB in the mesocosm. The results indicated that a microbial community is capable of doing so. Microbial enumeration and enzyme assays showed that the fluctuations in microbial communities and polyphenol oxidase activities are related to the initial NB concentration. Moreover, cluster analyses through denaturing gradient gel electrophoresis (DGGE) revealed very similar patterns (95.5%) throughout the 45 d term, indicating that the microbial community regenerates when NB is exhausted. Although volatilization and photolysis were the major processes responsible for the reduction in NB in contaminated mesocosms and the microbial community regenerated at the end of incubation, the data indicate potential ecological risks in outfall areas even if the discharged wastewater complies with the national wastewater discharge standards.     

Effects of overexpression of NAPRTase,NAMNAT, and NAD synthetase in the NAD(H) biosynthetic pathways on the NAD(H) pool,NADH/NAD+ ratio,and succinic acid production with different carbon sources by metabolically engineered Escherichia coli

Escherichia coli BA002, the ldhA and pflB deletion strain, cannot utilize glucose anaerobically due to the inability to regenerate NAD⁺. To regulate NAD(H) pool size and NADH/NAD⁺ ratio, overexpression of the enzymes in the NAD(H) biosynthetic pathways in BA002 was investigated. The results clearly demonstrate that the increased NAD(H) pool size and the decreased NADH/NAD⁺ ratio improved the glucose consumption and cell growth, which improved succinic acid production. When the pncB and the nadD genes were co-overexpressed in CA102, the ratio of NADH/NAD⁺ was decreased from 0.60 to 0.12, and the concentration of NAD(H) was the highest among that of all the strains. Moreover, the dry cell weight (DCW), glucose consumption, and the concentration of succinic acid in CA102 were also the highest. Based on the sufficient NAD⁺ supply after gene modification in the NAD(H) biosynthetic pathways, reductive carbon sources with different amounts of NADH can further change the distribution of metabolites. When sorbitol was used as a carbon source in CA102, the byproducts were lower than those of glucose fermentation, and the yield of succinic acid was increased.     

牙体预备对高嵌体修复下颌第一磨牙力学影响的初步研究

目的：通过有限元法,探讨高嵌体修复根管治疗后的下颌第一磨牙后,牙体预备形式对牙体组织受力的影响,为临床提供力学理论依据。方法：模拟右侧下颌第一磨牙的三维有限元模型,磨牙存在合面I类洞缺损,根管治疗后采用高嵌体修复,分别设计三种牙体预备形式,即覆盖全部牙尖、覆盖全部功能尖和覆盖部分功能尖的高嵌体修复,对模型进行加载,观察牙体组织的应力大小及分布。结果：覆盖全部牙尖高嵌体修复时牙釉质出现一个应力集中区,其他两种设计出现两个应力集中区。垂直载荷下,釉质的最大主应力在全部牙尖组分别低于其他两组92．29％和89．76％;舌颊向载荷下比其他两组分别降低80．91％和76．53％。三组牙本质的应力集中区趋于一致。垂直载荷下,牙本质的最大主应力在全部牙尖组分别高出其他两组12．92％和14．73％;舌颊向载荷下较其他两组高1．26％和5．08％。结论：从生物力学角度,覆盖全部牙尖的高嵌体更有利于牙体硬组织的受力,可以更好的对牙釉质起到保护作用。