The influence of diet on the grass carp intestinal microbiota and bile acids

To elucidate the influence of different diet on the intestinal microbe and bile acids, we characterized the microbiota and bile acids in the hindgut content of grass carp fed on formula feed (FF group) or Sudan grass (SG group). Fusobacteria and Proteobacteria were significantly more represented in FF group than in SG group whereas Bacteroidetes was significantly more abundant in SG group than in FF group. Simpson diversity was significantly higher in FF group than in SG group (t = 2.33, P < 0.05). Chenodeoxycholic acid (CDCA) was the most abundant primary bile acid in the two groups, with average concentrations of 1.03 ± 0.62 and 4.44 ± 1.80 ng mg^?1 in SG and FF group respectively. The most abundant secondary bile acid was deoxycholic acid (DCA) in SG group and ursodeoxycholic acid (UDCA) in FF group, with average concentrations of 0.17 ± 0.06 and 2.67 ± 0.88 ng mg^?1 respectively. UDCA is significantly more abundant in FF group than in SG group, and the total bile acids were higher in FF group than in SG group. Cetobacterium and Fusobacteriaceae U114 were significantly related with the concentrations of CDCA (r = 0.85, P < 0.05 and r = 0.82, P < 0.05 respectively) and UDCA (r = 0.92, P < 0.01 and r = 0.92, P < 0.01 respectively). However, Bacteroides was negatively related with the concentration of UDCA (r = ?0.67, P < 0.05). Overall, there existed certain relationship between the intestinal microbes and the faecal bile acids, and they were both influenced by the diet.     

Impacts of diet on hindgut microbiota and short‐chain fatty acids in grass carp (Ctenopharyngodon idellus)

Diet is known to influence intestinal microbiota in fish, but the specifics of these impacts are still poorly understood. Different protein/fibre ratio diets may result in differing structures and activities of gut microbiota. We examined the hindgut microbiome of grass carp (Ctenopharyngodon idellus) fed three different diets: fish meal (FM, high protein – low fibre), Sudan grass (SG, high fibre – low protein) and compound feed (CF, intermediate). Microbial profiles of fish fed on FM were significantly different from profiles of fish fed CF and SG (F = 18.85, p < .01). Cetobacterium, known to be positively associated with protein digestion, was the dominant microbial group in FM samples (approximately 75.7%), while Lachnospiraceae and Erysipelotrichaceae, thought to be involved in fermentation of plant polysaccharides, were dominant in CF and SG samples (46.8% and 42.9% respectively). Network analyses indicated that the abundance of Lachnospiraceae and Erysipelotrichaceae was in a significantly positive correlation (r = .895, p = .001). Short‐chain fatty acid (SCFA) levels may indicate that the digestibility of diet by microbiota in the grass carp gut decreased from FM to SG (FM>CF>SG). Overall low SCFA levels indicate that hindgut fermentation probably provides a low proportion of energy requirements in grass carp.     

花生栽野种间杂交异源多倍化早期世代基因表达变化分析

为了进一步认识花生种间杂交异源多倍体进化过程中的基因表达变化规律,采用cDNA-HFO-TAG技术,研究花生种间杂交组合(四倍体栽培种‘仲恺花4号’×二倍体野生种Arachis. diogio)杂种F_1和早期多倍体世代S0~S3的基因表达变化情况。14条HFO-TAG引物共扩增出121条cDNA片段,其中差异片段84个,主要包括三种类型:亲本转录物完全沉默(3个),双亲转录物在后代部分材料中沉默(59个)和新转录物激活(22个),上述变化在F1代即开始发生。筛选其中大小为500~2 000 bp的35个TDFs进行克隆测序,有27个和NCBI数据库中已录入的基因具有较高的相似性,包括抗逆相关基因(10条)、未知功能蛋白基因(8条)、能量与代谢相关基因(7条)和转录因子相关的基因(2条)。这些研究结果进一步表明在花生种间杂交异源多倍化早期发生着快速、剧烈的基因表达变化,从中获得的差异基因片段,有助于了解花生属种间杂交异源多倍化早期分子机制变化,这对有效利用野生花生种质优异基因具有重要意义。cDNA-HFO-TAG技术简单、有效且实用,完全适用于花生属基因表达变化研究,可以作为花生属及其它物种基因表达变化分析技术的有效补充。     

夹指链式残膜回收机脱膜装置设计与试验

针对现有残膜回收机脱膜困难的问题,该研究设计了一种夹指链式残膜回收机脱膜装置,主要由刮板总成、曲柄摇杆机构和膜杂分离机构等组成,可一次性完成脱膜、膜杂分离和输膜作业。为增加夹指随夹指链转过上收膜轮的过程中与刮板接触的次数,将刮板总成中的刮板设为双层,并通过作业过程分析对其结构参数进行设计;使用ADAMS软件对刮板末端运动轨迹进行仿真分析,并根据仿真结果对曲柄摇杆机构的杆件长度及安装角进行设计;通过对残膜受力情况的分析,确定了曲柄摇杆机构的安装位置;通过运动学分析获得了夹指不被漏刮时上收膜轮角速度与曲柄角速度比的最大值;为实现输膜与膜杂分离,设计了往复摆动式膜杂分离机构,并通过作业机理分析及性能试验对相关部件的结构参数进行设计。田间试验结果表明,当机具作业速度为4.5 km/h、刮板宽度为100 mm、曲柄回转中心与上收膜轮中心间的水平安装距离为290 mm、竖直安装距离为200 mm、上收膜轮角速度与曲柄角速度比为0.5、输膜筛相邻棒条间的安装距离为50mm时,残膜回收率为93.12%,脱膜率为98.2%,含杂率为16.08%,能够满足残膜回收机田间作业要求。研究成果可为相关装置的设计提供参考。     

浅谈深圳市水土流失现状、危害及防治对策

深圳市水土流失面积逐年减少,并在近4年保持稳定,水土保持工作成效显著。本文在分析深圳市水土流失现状和危害的基础上,详细介绍了深圳市生产建设项目水土保持工作近年来推行的政策及采取的措施,总结了工作中的经验和目前存在的问题,为全国城市水土保持工作提供参考、借鉴。     

采用卷积神经网络构建西北太平洋柔鱼渔场预报模型

对远洋渔场资源和位置进行预报可以为远洋渔业生产及管理提供重要信息。该研究针对西北太平洋柔鱼渔场，利用海洋表面温度遥感信息和中国远洋渔船生产资料，基于深度学习原理，选取卷积神经网络构建西北太平洋柔鱼渔场预报模型。根据不同月份、不同通道构建了多种数据集，用于训练渔场预报模型。训练结果表明，4个通道组合的数据集的训练结果最优，渔汛早期（7-8月）、中期（9月）和后期（10-11月）测试样本的准确率分别为80.5%、81.5%和81.4%。以2015年的真实渔场数据对模型进行验证，模型的平均召回率为82.3%，平均精确率为66.6%，F1得分平均值为73.1%，预测的高产渔区与实际作业的高单位捕捞努力量渔获量区基本匹配。该研究构建的渔场预报模型可以获得较好的准确率，可为其他鱼种的渔场预报模型构建提供新的思路。     

基于适宜性与发展水平评价的村庄用地类型划分

科学划分村庄用地类型并提出差异化的整治策略,是编制村庄发展规划和建设用地减量规划的基础。该文以北京市密云区为例,基于土地利用、兴趣点和社会统计等数据,从自然条件和用地形态2方面构建村庄用地适宜性评价模型,从区位条件、基础设施、生态条件和资源产业4方面构建村庄发展状况评价模型,系统分析村庄用地适宜性与村庄发展状况及其二者的组合状态,进而划分村庄用地类型。结果表明:1)密云区村庄用地适宜性呈现明显的从西南到东北降低的分布趋势;2)村庄发展指数较高的村庄主要分布在西南区域的环密云城区一带,其次是中部围绕密云水库区域,北部区域村庄发展水平较低;3)基于二者的评价结果将全区村庄用地划分为9种组合,进而合并为4种村庄用地类型。该研究可为村庄用地的高效、有序整治利用提供依据。     

炭肥比和膨润土粘结剂对炭基肥颗粒理化及缓释特性的影响

为探究炭肥比和膨润土粘结剂对生物炭基肥理化及缓释特性的影响,以生物炭为基底,分别制备了炭肥比1:4,膨润土粘结剂质量分数为20%、15%、10%、5%和粘结剂质量分数10%,炭肥比为1:6、1:5、1:4、1:3的柱状尿素和氯化钾生物炭基肥颗粒,分析了生物炭基肥颗粒的理化及缓释特性。结果表明,在炭肥比为1:4条件下,膨润土粘结剂质量分数越高,生物炭基肥微观结构越紧密,力学和缓释特性越好,质量分数为20%时,氯化钾和尿素生物炭基肥平均抗压强度分别为286.78和281.27 N,前3天养分淋出率分别为45.53%和36.87%。在膨润土粘结剂质量分数为10%条件下,炭肥比越高,生物炭基肥缓释性能越好,炭肥比为1:3时,氯化钾和尿素生物炭基肥前3天养分淋出率分别为42.06%和40.32%。同时,氯化钾生物炭基肥表面孔隙先增后减,炭肥比为1:6和1:3的平均抗压强度分别为271.25和282.42 N。尿素生物炭基肥内部结构中孔隙变多,炭肥比为1:6时,平均抗压强度为最大值267.84 N。综合考虑,满足中等肥料浓度要求时,膨润土粘结剂质量分数为20%、炭肥比为1:4或膨润土粘结剂质量分数为10%、炭肥比为1:3的生物炭基肥成型配方较优。     

Dynamics of nitrogen translocation from mature leaves to new shoots and related gene expression during spring shoots development in tea plants (Camellia sinensis L.)

The contribution of N remobilization is crucial for new shoots growth and quality formation during spring tea shoots development. However, the translocation mechanism of N from source leaves to sink young shoots is not well understood. In the present study, ¹⁵N urea was applied to mature tea leaves one week before bud break to track N remobilization in a field experiment. The dynamic changes in plant ¹⁵N abundance, contents of amino acids, and the expression levels of genes related to N metabolism and translocation were followed during the 18‐d development of new spring shoots until three expanding young leaves. The results showed that during the growth of new shoots the amount of ¹⁵N in the shoots increased, whereas the N_dff (N derived from ¹⁵N‐urea) in mature leaves decreased, showing that the foliar‐applied N in mature leaves was readily exported to new shoots. This process was found to be accompanied by decline of chlorophylls. In the mature leaves, expression CsATG18a and CsSAG12 involved in autophagy was dramatically induced (> 4‐fold) at approximately nine days after the bud breaking. The genes involved in the transformation of amino acids, including primarily CsGDH2, CsGDH4, CsGLT3, CsGS1;3, and CsASN2 were upregulated by > 3‐fold after bud breaking. The expression levels of CsATG8A, CsATG9, CsSAG12, CsGS1;1, CsGDH1, and CsAAP6 correlated negatively with the N_dff in mature leaves, but positively with ¹⁵N amount and total N amount in new shoots, suggesting these genes played important roles in N export from mature leaves. In the new shoots, the expression of most genes showed two defined peaks, one on six days and one on 12 days after bud breaking. The expression of CsGS2, CsASN3, CsGLT1, and CsAAP4 positively correlated with the ¹⁵N amount and total N amount in new shoots. These genes might be involved in the transport and re‐assimilation of N from mature leaves. The overall results demonstrated that the translocation of ¹⁵N from mature leaves to new spring shoots was regulated by the genes involved in autophagy, protein degradation, amino acid transformation and transport.