The hierarchical cluster tree based on Bray-Curtis distance for bacterial OTUs from CDTs.

<p>PR, QZ, FZ and LB tea samples were indicated by blue, purple, red and green colors, respectively. FZ, Fuzhuan brick tea; QZ, Qingzhuan brick tea; PR, Pu’er tea; LB, Liubao tea.</p

The plots of principal component analysis (PCA) (a) and principal coordinate analysis (PCoA) based on unweighted UniFrac distance metric (b).

<p>Samples of CDTs were presented by different color-filled symbols. FZ1-4, four samples of Fuzhuan brick tea; QZ1-2, two samples of Qingzhuan brick tea; PR1-3, three samples of Pu’er tea; LB1-2, two samples of Liubao tea.</p

Rarefaction analyses for the observed number of OTUs from 11 dark tea samples at a genetic distance of 3%.

<p>The rarefaction curves for each sample of CDTs were displayed by different colors. FZ1-4, four samples of Fuzhuan brick tea; QZ1-2, two samples of Qingzhuan brick tea; PR1-3, three samples of Pu’er tea; LB1-2, two samples of Liubao tea.</p

Numbers of sequences analyzed, Operational Taxonomic Units (OTUs), estimated OUT richness (Chao), sample coverage, and diversity indices of Shannon and Simpson were calculated for 16S rRNA of 11 CDTs samples.

<p>Numbers of sequences analyzed, Operational Taxonomic Units (OTUs), estimated OUT richness (Chao), sample coverage, and diversity indices of Shannon and Simpson were calculated for 16S rRNA of 11 CDTs samples.</p

Diversity and Variation of Bacterial Community Revealed by MiSeq Sequencing in Chinese Dark Teas

<div><p>Chinese dark teas (CDTs) are now among the popular tea beverages worldwide due to their unique health benefits. Because the production of CDTs involves fermentation that is characterized by the effect of microbes, microorganisms are believed to play critical roles in the determination of the chemical characteristics of CDTs. Some dominant fungi have been identified from CDTs. In contrast, little, if anything, is known about the composition of bacterial community in CDTs. This study was set to investigate the diversity and variation of bacterial community in four major types of CDTs from China. First, the composition of the bacterial community of CDTs was determined using MiSeq sequencing. From the four typical CDTs, a total of 238 genera that belong to 128 families of bacteria were detected, including most of the families of beneficial bacteria known to be associated with fermented food. While different types of CDTs had generally distinct bacterial structures, the two types of brick teas produced from adjacent regions displayed strong similarity in bacterial composition, suggesting that the producing environment and processing condition perhaps together influence bacterial succession in CDTs. The global characterization of bacterial communities in CDTs is an essential first step for us to understand their function in fermentation and their potential impact on human health. Such knowledge will be important guidance for improving the production of CDTs with higher quality and elevated health benefits.</p></div

The bacterial communities of CDTs at family level (a) and genus level (b).

<p>Bacterial families were indicated by different colors, and “others” presented the rest families with a relative abundance less than 1%. FZ1-4, four samples of Fuzhuan brick tea; QZ1-2, two samples of Qingzhuan brick tea; PR1-3, three samples of Pu’er tea; LB1-2, two samples of Liubao tea.</p

Silver-Mediated C–H Activation: Oxidative Coupling/Cyclization of <i>N</i>-Arylimines and Alkynes for the Synthesis of Quinolines

A silver-mediated tandem protocol for the synthesis of quinolines involving the oxidative coupling/cyclization of <i>N</i>-arylimines and alkynes has been developed. We demonstrated that scenario-dependent metalation could occur either at the <i>ortho</i> C–H bond of an <i>N</i>-arylimine through protonation-driven enhancement of acidity or at the terminal C–H bond of an alkyne by virtue of the carbophilic π-acidity of silver. The diverse set of mechanistic manifolds implemented with a single type of experimental protocol points toward the importance of stringent reactivity analysis of each individual potentially reactive molecular site. Importantly, the direct arene C–H bond activation provides a unique and distinct mechanistic handle for the expansion of reactivity paradigms for silver. As expected, the protocol allows for the incorporation of both internal and terminal alkynes into the products, and in addition, both electron-withdrawing and -donating groups are tolerated on <i>N</i>-arylimines, thus enabling the vast expansion of substituent architectures on quinoline framework. Further, an intriguing phenomenon of structural isomerization and chemical bond cleavage has been observed for aliphatic internal alkynes

Carbon Quantum Dot-Induced MnO₂ Nanowire Formation and Construction of a Binder-Free Flexible Membrane with Excellent Superhydrophilicity and Enhanced Supercapacitor Performance

Manganese oxides (MnO₂) are regarded as typical and promising electrode materials for supercapacitors. However, the practical electrochemical performance of MnO₂ is far from its theoretical value. Nowadays, numerous efforts are being devoted to the design and preparation of nanostructured MnO₂ with the aim of improving its electrochemical properties. In this work, ultralong MnO₂ nanowires were fabricated in a process induced by carbon quantum dots (CQDs); subsequently, a binder-free flexible electrode membrane was easily obtained by vacuum filtration of the MnO₂ nanowires. The effects of the CQDs not only induced the formation of one-dimensional nanostructured MnO₂, but also significantly improved the wettability between electrode and electrolyte. In other words, the MnO₂ membrane demonstrated a superhydrophilic character in aqueous solution, indicating the sufficient and abundant contact probability between electrode and electrolyte. The binder-free flexible MnO₂ electrode exhibited a preeminent specific capacitance of 340 F g^–1 at 1 A g^–1; even when the current density reached 20 A g^–1, it still maintained 260 F g^–1 (76% retention rate compared to that at 1 A g^–1). Moreover, it also showed good cycling stability with 80.1% capacity retention over 10 000 cycles at 1 A g^–1. Furthermore, an asymmetric supercapacitor was constructed using the MnO₂ membrane and active carbon as the positive and negative electrodes, respectively, which exhibited a high energy density of 33.6 Wh kg^–1 at 1.0 kW kg^–1, and a high power density of 10 kW kg^–1 at 12.5 Wh kg^–1

Table_2_Comparative Proteomic and Morphological Change Analyses of Staphylococcus aureus During Resuscitation From Prolonged Freezing.XLSX

<p>When frozen, Staphylococcus aureus survives in a sublethally injured state. However, S. aureus can recover at a suitable temperature, which poses a threat to food safety. To elucidate the resuscitation mechanism of freezing survived S. aureus, we used cells stored at -18°C for 90 days as controls. After resuscitating the survived cells at 37°C, the viable cell numbers were determined on tryptic soy agar with 0.6% yeast extract (TSAYE), and the non-injured-cell numbers were determined on TSAYE supplemented with 10% NaCl. The results showed that the total viable cell number did not increase within the first 3 h of resuscitation, but the osmotic regulation ability of freezing survived cells gradually recovered to the level of healthy cells, which was evidenced by the lack of difference between the two samples seen by differential cell enumeration. Scanning electron microscopy (SEM) showed that, compared to late exponential stage cells, some frozen survived cells underwent splitting and cell lysis due to deep distortion and membrane rupture. Transmission electron microscopy (TEM) showed that, in most of the frozen survived cells, the nucleoids (low electronic density area) were loose, and the cytoplasmic matrices (high electronic density area) were sparse. Additionally, a gap was seen to form between the cytoplasmic membranes and the cell walls in the frozen survived cells. The morphological changes were restored when the survived cells were resuscitated at 37°C. We also analyzed the differential proteome after resuscitation using non-labeled high-performance liquid chromatography–mass spectrometry (HPLC-MS). The results showed that, compared with freezing survived S. aureus cells, the cells resuscitated for 1 h had 45 upregulated and 73 downregulated proteins. The differentially expressed proteins were functionally categorized by gene ontology enrichment, KEGG pathway, and STRING analyses. Cell membrane synthesis-related proteins, oxidative stress resistance-related proteins, metabolism-related proteins, and virulence factors exhibited distinct expression patterns during resuscitation. These findings have implications in the understanding of the resuscitation mechanism of freezing survived S. aureus, which may facilitate the development of novel technologies for improved detection and control of foodborne pathogens in frozen food.</p

Table_1_Comparative Proteomic and Morphological Change Analyses of Staphylococcus aureus During Resuscitation From Prolonged Freezing.XLSX

<p>When frozen, Staphylococcus aureus survives in a sublethally injured state. However, S. aureus can recover at a suitable temperature, which poses a threat to food safety. To elucidate the resuscitation mechanism of freezing survived S. aureus, we used cells stored at -18°C for 90 days as controls. After resuscitating the survived cells at 37°C, the viable cell numbers were determined on tryptic soy agar with 0.6% yeast extract (TSAYE), and the non-injured-cell numbers were determined on TSAYE supplemented with 10% NaCl. The results showed that the total viable cell number did not increase within the first 3 h of resuscitation, but the osmotic regulation ability of freezing survived cells gradually recovered to the level of healthy cells, which was evidenced by the lack of difference between the two samples seen by differential cell enumeration. Scanning electron microscopy (SEM) showed that, compared to late exponential stage cells, some frozen survived cells underwent splitting and cell lysis due to deep distortion and membrane rupture. Transmission electron microscopy (TEM) showed that, in most of the frozen survived cells, the nucleoids (low electronic density area) were loose, and the cytoplasmic matrices (high electronic density area) were sparse. Additionally, a gap was seen to form between the cytoplasmic membranes and the cell walls in the frozen survived cells. The morphological changes were restored when the survived cells were resuscitated at 37°C. We also analyzed the differential proteome after resuscitation using non-labeled high-performance liquid chromatography–mass spectrometry (HPLC-MS). The results showed that, compared with freezing survived S. aureus cells, the cells resuscitated for 1 h had 45 upregulated and 73 downregulated proteins. The differentially expressed proteins were functionally categorized by gene ontology enrichment, KEGG pathway, and STRING analyses. Cell membrane synthesis-related proteins, oxidative stress resistance-related proteins, metabolism-related proteins, and virulence factors exhibited distinct expression patterns during resuscitation. These findings have implications in the understanding of the resuscitation mechanism of freezing survived S. aureus, which may facilitate the development of novel technologies for improved detection and control of foodborne pathogens in frozen food.</p