Smoking increases oral mucosa susceptibility to Candida albicans infection via the Nrf2 pathway: In vitro and animal studies

Smoking and Candida albicans (C. albicans) infection are risk factors for many oral diseases. Several studies have reported a close relationship between smoking and the occurrence of C. albicans infection. However, the exact underlying mechanism of this relationship remains unclear. We established a rat infection model and a C. albicans-Leuk1 epithelial cell co-culture model with and without smoke exposure to investigate the mechanism by which smoking contributes to C. albicans infection. Oral mucosa samples from healthy individuals and patients with oral leucoplakia were also analysed according to their smoking status. Our results indicated that smoking induced oxidative stress and redox dysfunction in the oral mucosa. Smoking-induced Nrf2 negatively regulated the NLRP3 inflammasome, impaired the oral mucosal defence response and increased the oral mucosa susceptibility to C. albicans. The results suggest that the Nrf2 pathway could be involved in the pathogenesis of oral diseases by mediating an antioxidative response to cigarette smoke exposure and suppressing host immunity against C. albicans.     

Towards a more versatile alpha-glucan biosynthesis in plants

Starch is an important storage polysaccharide in many plants. It is composed of densely packed alpha-glucans, consisting of 1,4- and 1,4,6-linked glucose residues. The starch polymers are used in many industrial applications. The biosynthetic machinery for assembling the granule has been manipulated in many different ways to gain insight into the process of starch biosynthesis and to engineer starches with improved functionalities. With respect to the latter, two generic technologies with great potential have been developed: (i) introduction of new linkage types in starch polymers (1,3- and 1,6-linkages), and (ii) engineering granule-boundness. The toolbox to engineer this new generation of starch polymers is discussed.     

石油降解菌株的分离鉴定及降油特性

从甘肃华庆油田污染严重的土壤中采样,通过富集培养、多次筛选分离得到1株优势菌F1。依据生理生化特征和16S rDNA序列将菌株F1鉴定为白色类诺卡氏菌(Nocardioides albus)。GS-MC结果表明,等量原油经F1菌株降解前、后,表现出先降解高碳数正构烷烃为低碳数正构烷烃;高碳数正构烷烃中奇数碳向偶数碳正构烷烃演化规律;平均降油率为64%,F1菌株能较好地促使五环三萜类化合物立体构型中不稳定构型向稳定性构型转化。F1菌株在含油浓度0.3%、0.5%、1.0%土样中降解石油烃的半衰期分别为17.2、18.2、23.7 d,42 d后均达到78%以上。     

Is drift ‘directional’? Unequal breeding sex ratio revisited

Unequal breeding sex ratio can significantly reduce effective population size, allowing a rare neutral allele to jump to a high frequency through genetic drift. However, this one-way alteration to allele frequency appears inconsistent with the concept that drift is non-directional. Based on binomial sampling distribution, this study developed a method to directly and exhaustively measure drift by calculating the mean deviation of change in allele frequency, then applied it to cases of unequal breeding sex ratio. The result shows that, under those cases, (1) the mean deviation can always be divided into two halves that are equal in size but opposite in direction; (2) each half consists of one or several categories represented by various allele proportions in the rare sex; (3) this proportion is another factor that determines the outcome of drift, in addition to effective population size and allele frequency; (4) drift is non-directional on a global scale, but whether an allele will drift up or down can be predicted based on the above factors. This method enables us to dissect every component of the expected change in allele frequency caused by drift and to find out the combined effect of population size, allele frequency and allele proportion in the rarer sex under neutrality but unequal breeding sex ratio.     

The critical soil P levels for crop yield, soil fertility and environmental safety in different soil types

Background and aims

Sufficient soil phosphorus (P) is important for achieving optimal crop production, but excessive soil P levels may create a risk of P losses and associated eutrophication of surface waters. The aim of this study was to determine critical soil P levels for achieving optimal crop yields and minimal P losses in common soil types and dominant cropping systems in China.

Methods

Four long-term experiment sites were selected in China. The critical level of soil Olsen-P for crop yield was determined using the linear-plateau model. The relationships between the soil total P, Olsen-P and CaCl₂-P were evaluated using two-segment linear model to determine the soil P fertility rate and leaching change-point.

Results

The critical levels of soil Olsen-P for optimal crop yield ranged from 10.9 mg kg^?1 to 21.4 mg kg^?1, above which crop yield response less to the increasing of soil Olsen-P. The P leaching change-points of Olsen-P ranged from 39.9 mg kg^?1 to 90.2 mg kg^?1, above which soil CaCl₂-P greatly increasing with increasing soil Olsen-P. Similar change-point was found between soil total P and Olsen-P. Overall, the change-point ranged from 4.6 mg kg^?1 to 71.8 mg kg^?1 among all the four sites. These change-points were highly affected by crop specie, soil type, pH and soil organic matter content.

Conclusions

The three response curves could be used to access the soil Olsen-P status for crop yield, soil P fertility rate and soil P leaching risk for a sustainable soil P management in field.     

Hierarchically Clustering to 1,033 Genes Differentially Expressed in Mouse Superior Colliculus in the Courses of Optic Nerve Development and Injury

Tempo spatially specific expression of many development-related genes is the molecular basis for the formation of the central nervous system (CNS), especially those genes regulating the proliferation, differentiation, migration, axon growth, and orientation of nerve cells. The development-related genes are usually prominent during the embryonic and newborn stages, but rarely express during the adulthood. These genes are believed to be suitable target genes for promoting CNS regeneration, despite majority of which remains unknown. Hence, the aim of this study was to screen development-related genes which might contribute to CNS regeneration. In this study, 1,033 differentially-expressed genes of superior colliculus in the courses of mouse optic nerve development and injury, as previously identified by cDNA microarrays, were hierarchically clustered to display expression pattern of each gene and reveal the relationships among these genes, and infer the functions of some unknown genes based on function-identified genes with the similar expression patterns. Consequently, the expression patterns of 1,033 candidate genes were revealed at eight time points during optic nerve development or injury. According to the similarity among gene expression patterns, 1,033 genes were divided into seven groups. The potential function of genes in each group was inferred on the basis of the dynamic trend for mean gene expression values. Moreover, the expression patterns of six function-unidentified genes were extremely similar to that of the ptn gene which could promote and guide axonal extension. Therefore, these six genes are temporally regarded as candidate genes related to axon growth and guidance. The results may help to better understand the roles of function-identified genes in the stages of CNS development and injury, and offer useful clues to evaluate the functions of hundreds of unidentified genes.     

中印度洋与南海西部表层海水细菌多样性

细菌在海洋生物地球化学循环中发挥着重要作用。为更好地了解海洋细菌的特征及其在海洋环境中的潜在作用, 本文利用纯培养与16S rRNA基因高通量测序技术对中印度洋与南海西部海域表层海水细菌多样性进行研究。纯培养结果表明, 自中印度洋与南海西部表层海水中共分离275株可培养海洋细菌, 隶属于4门49属75种。变形菌门是绝对优势类群(占总株数的68.7%), 其次是放线菌门(21.5%)、拟杆菌门(9.1%)和厚壁菌门(0.7%)。在属水平, 微杆菌属(Microbacterium)与弧菌属(Vibrio)是主要的优势属, 共占总株数的30.0%。在3种分离培养基中, 自1/10 × 2216E培养基中分离细菌的数目与种类最多(89株, 30属); 分离菌株中的细菌菌株有7、9与3个属分别仅在2216E、1/10 × 2216E及葡萄糖甘露糖(glucose-mannose, GM)培养基中生长。此外, 共分离培养出50株细菌(26种)可能代表潜在新分类单元。高通量测序结果显示, 中印度洋和南海西部表层海水中共有23个门531个属。优势门类为变形菌门(72.2%)和拟杆菌门(15.3%), 优势属为嗜冷杆菌属(Psychrobacter, 24.4%)、盐单胞菌属(Halomonas, 16.3%)和亚硫酸杆菌属(Sulfitobacter, 13.9%)。此外, 中印度洋表层海水细菌Shannon-Wiener指数与Pielou均匀度指数显著高于南海西部(P < 0.05), 且细菌群落结构显著不同(P < 0.05)。综合纯培养与原位细菌数据得出, 中印度洋与南海西部海洋细菌具有丰富的多样性, 具有进一步开发研究的价值。