Root microbiota shift in rice correlates with resident time in the field and developmental stage

Land plants in natural soil form intimate relationships with the diverse root bacterial microbiota. A growing body of evidence shows that these microbes are important for plant growth and health. Root microbiota composition has been widely studied in several model plants and crops; however, little is known about how root microbiota vary throughout the plant's life cycle under field conditions. We performed longitudinal dense sampling in field trials to track the time-series shift of the root microbiota from two representative rice cultivars in two separate locations in China. We found that the rice root microbiota varied dramatically during the vegetative stages and stabilized from the beginning of the reproductive stage, after which the root microbiota underwent relatively minor changes until rice ripening. Notably, both rice genotype and geographical location influenced the patterns of root microbiota shift that occurred during plant growth. The relative abundance of Deltaproteobacteria in roots significantly increased overtime throughout the entire life cycle of rice, while that of Betaproteobacteria, Firmicutes, and Gammaproteobacteria decreased. By a machine learning approach, we identified biomarker taxa and established a model to correlate root microbiota with rice resident time in the field(e.g., Nitrospira accumulated from 5 weeks/tillering in field-grown rice). Our work provides insights into the process of rice root microbiota establishment.     

Effect of larval fish and nutrient enrichment on plankton dynamics in experimental ponds

The hypotheses that larval fish density may potentially affect phytoplankton abundance through regulating zooplankton community structure, and that fish effect may also depend on nutrient levels were tested experimentally in ponds with three densities of larval walleye, Stizostedion vitreum (0, 25, and 50 fish m^–3), and two fertilizer types (inorganic vs organic fertilizer). A significant negative relationship between larval fish density and large zooplankton abundance was observed despite fertilizer types. Larval walleye significantly reduced the abundances of Daphnia, Bosmina, and Diaptomus but enhanced the abundance of various rotifer species (Brachionus, Polyarthra, and Keratella). When fish predation was excluded, Daphnia became dominant, but Daphnia grazing did not significantly suppress blue-green algae. Clearly, larval fish can be an important regulator for zooplankton community. Algal composition and abundance were affected more by fertilizer type than by fish density. Inorganic fertilizer with a high N:P ratio (20:1) enhanced blue-green algal blooms, while organic fertilizer with a lower N:P ratio (10:1) suppressed the abundance of blue-green algae. This result may be attributed to the high density of blue-green algae at the beginning of the experiment and the fertilizer type. Our data suggest that continuous release of nutrients from suspended organic fertilizer at a low rate may discourage the development of blue-green algae. Nutrient inputs at a low N:P ratio do not necessarily result in the dominance of blue-green algae.     

Incidence of toxigenic vibrios in foods available in Taiwan.

A total of 1088 vibrios and related species were isolated from seafood and aquacultured foods available in Taiwan. They were identified as Vibrio alginolyticus, V. cholerae, V. fluvialis I, V. fluvialis II, V. parahaemolyticus, V. mimicus, Aeromonas caviae, A. hydrophila, A. sobria and other species. Incidence of these Vibrio and Aeromonas species in these foods was high. Vibrio parahaemolyticus was frequently found in seawater and in foods of freshwater origin. The Vibrio isolates were examined for enzymatic and toxigenic activities. Most of them showed strong lipase or protease activities. Haemolytic activities of V. cholerae, V. fluvialis I and V. fluvialis II isolates were mostly strong. About 49% showed cytotoxic activity and 5% cytotonic activity in Chinese hamster ovary cell culture assay. Nevertheless, only three non-O1 V. cholerae (2.07%) and two V. parahaemolyticus isolates (1.65%) produced cholera toxin and thermostable direct haemolysin activity, respectively. Various toxigenic vibrios may be important food-borne pathogens in this region because of their high incidence in foods.     

184株铜绿假单胞菌的耐药性分析

目的：研究铜绿假单胞菌的耐药性,以指导临床合理用药。方法：对184株铜绿假单胞菌选用16种常用抗生素进行药敏试验。药敏试验采用WHO推荐的Kirby-Bauer纸片扩散法按NCCLS标准进行,同时对184株铜 绿假单胞菌进行诱导型β－内酰胺酶的检测。结果：184株铜绿假单胞菌中检出诱导酶115株,占62．2％,所有菌株无一例对全部抗生素敏感。亚胺培南、氨曲南、庆大霉素、阿米卡星、环丙沙星、诺氟沙星、哌拉西林、头孢哌酮、头孢他啶对铜绿假单胞菌的抗菌活性较强,敏感率为76．1％－92．9％,而三代头孢中的头孢噻肟和头孢曲椴的敏感率仅为8．7％和12．0％。诱导酶株组对三代头孢中的头孢哌酮、头孢他啶的耐药率比非产酶株组低、尤其头孢他淀的耐药率比产酶株组明显降低,仅为3．4％;亚胺培南和派拉西林的耐药率也比非产酶株组低,耐药率分别为6．5％和5．1％。结论：对于产诱导型β－内酰胺酶的铜绿假单胞菌株应选用亚胺培南、氟喹诺酮类及氨基糖甙类抗生素,常规的体外药敏试验不能完全正确的反映细菌的耐药性。通过诱导酶的检测,可以较好地弥补敏试验的不足。     

生态系统健康评价的研究进展

生态系统健康评价是环境管理和生态系统监控的基础,生态系统监控可促进生态系统健康评价。首先介绍了生态系统健康概念的产生,发展及其不同的内涵,并着重回顾和讨论了生态系统健康评价指标及其存在的问题,生态系统健康评价指标包括生态指标,物理化学指标,人类健康与社会经济指标3大类,生态指标是反映生态系统特征和状态的生物指标,它分为生态系统,群落和种群与个体等不同层次的指标或指标体系,物理化学指标是检测生态系统的非生物环境的指标。人类健康与社会经济指标着眼于生态系统对人类生存与社会发展的支持作用,采用经济参数和社会发展的环境压力指标等来衡量生态服务的质量与可持续性,根据其敏感程度和功能性,生态系统健康评价指标分为早期预警指标,适宜程度指标和诊断指标3类,一个完整的生态系统评价应包括上述3大类指标或指标体系,但在具体的评价实践中往往因评价目的和对象的不同而有所选择,生态系统健康评价目前有两个亟待解决的问题,如何有效确立评价标准与参照系以及如何正确区分人为压力和自然干扰。     

Assessment of differences in morphological and physiological leaf lodging characteristics between two cultivars of Hippeastrum rutilum

Kernel weight and morphology are important traits affecting cereal yields and quality. Dissecting the genetic basis of thousand kernel weight (TKW) and its related traits is an effective method to improve wheat yield. In this study, we performed quantitative trait loci (QTL) analysis using recombinant inbred lines derived from the cross ‘PuBing3228 × Gao8901’ (PG-RIL) to dissect the genetic basis of kernel traits. A total of 17 stable QTLs related to kernel traits were identified, notably, two stable QTLs QTkw.cas-1A.2 and QTkw.cas-4A explained the largest portion of the phenotypic variance for TKW and kernel length (KL), and the other two stable QTLs QTkw.cas-6A.1 and QTkw.cas-7D.2 contributed more effects on kernel width (KW). Conditional QTL analysis revealed that the stable QTLs for TKW were mainly affected by KW. The QTLs QTkw.cas-7D.2 and QKw.cas-7D.1 associated with TKW and KW were delimited to the physical interval of approximately 3.82 Mb harboring 47 candidate genes. Among them, the candidate gene TaFT-D1 had a 1 bp insertions/deletion (InDel) within the third exon, which might be the reason for diversity in TKW and KW between the two parents. A Kompetitive Allele-Specific PCR (KASP) marker of TaFT-D1 allele was developed and verified by PG-RIL and a natural population consisted of 141 cultivar/lines. It was found that the favorable TaFT-D1 (G)-allele has been positively selected during Chinese wheat breeding. Thus, these results can be used for further positional cloning and marker-assisted selection in wheat breeding programs. Seventeen stable QTLs related to kernel traits were identified. The stable QTLs for thousand kernel weight were mainly affected by kernel width. TaFT-D1 could be the candidate gene for QTLs QTkw.cas-7D.2 and QKw.cas-7D.1.     

冬虫夏草多糖的分子结构与免疫活性

 冬虫夏草多糖(在本文中名为CS-81002)是由冬虫夏草菌Cordyceps sinensis(Berk)Sacc在人工发酵条件下产生的胞外多糖。用凝胶过滤法测出CS-81002的分子量Mr=43kD。CS-81002的单糖组成为Man:Gal:Glc=10.3:3.6:1。甲基化分析和部份酸水解结果表明,CS-81002是多分支的杂多糖,由→6)-Manp-(1→形成主链,大约每10个主链Man残基中,有6个在C3位上被取代(即形成→3,6)-Manp-(1→分支),有4个在位C2上被取代(即形成→2,6-Manp-(1→分支),从而形成侧链。主链中还有少许未被取代的Man残基。侧链则由→3-)-Galf-(1→,→4)-Glcf-(1→,→4)-Manp-(1→和→2)-Manp-(1→组成。位于非还原末端的,则三种单糖残基都有。CS-81002在5mg/kg体重×12剂量条件下,对正常的昆明小鼠腹腔巨噬细胞吞噬功能有显著促进作用。在同样剂量条件下,对正常LACA小鼠脾脏溶血斑形成细胞(PFC)对绵羊红细胞的溶血作用无显著影响。不同程度的部份酸水解可使CS-81002的分子量下降,分支减少,并且对巨噬细胞吞噬功能的促进作用亦有下降趋势。在所得到的各个部份酸水解级分(分子量分别为41000,40000,32000,16000和12000)中,分子量为12000的级分对巨噬细胞吞噬功能无促进作用。     

凤丹丹皮酚抗菌作用的研究

用钢管法、滤纸法、挖孔法对凤丹丹皮酚的抗菌作用进行了研究,结果表明：凤丹丹皮酚对黄色八叠球菌、福氏知杆菌、枯草芽孢菌、金黄色葡萄球菌、大肠杆菌等五种供试细菌均有较强的抑制作用,尤其是黄色八叠球菌最为敏感;三种方法中挖孔法效果最佳。     

抗虫的转AaIT基因杨树的获得

通过根癌农杆菌叶盘法将构建在双元载体上的昆虫特异性神经蝎毒素AaIT基因转化至中国南方杨树N106(小叶杨×美洲黑杨,P.deltoides×P.simonii)中,共获得了62株再生植株。PCR分析及PCR产物Southernblotting的分析结果表明,AaIT基因整合在再生植株的基因组上。对部分转AaIT基因植株进行了杀虫实验,转基因植株A5对一龄舞毒蛾(Lymantriadispar)幼虫有明显的抗性,饲喂转基因杨树叶片的幼虫死亡率显著高于未转基因对照植株,其取食面积小,存活幼虫体重明显小于对照。ELISA分析证明了AaIT蛋白的表达。     

米根霉发酵生产L-乳酸

报道了Ｌ－乳酸菌株的分离与筛选,探讨了不同碳源、氮源、通气量、温度等发酵条件对产Ｌ－乳酸的影响,从７８株米根霉中筛选出１３株产Ｌ－乳酸较高的菌株,其中米根霉（Ｒｈｉｚｏｐｕｓ ｏｒｙｚａｅ）Ｒｓ９２８产Ｌ－乳酸最高,产酸最稳定。试验结果表明,该菌株最适发酵培养组成（％）：淀粉水解糖１６,ＭｇＳＯ４ ０．０８,ＫＨ２ＰＯ４ ０．０５,ＺｎＳＯ４ ０．０１,ＣａＣＯ３ ７,ｐＨ自然。在６０ｔ发酵罐中,