昆虫病原线虫共生细菌胞内晶体蛋白的研究进展

初生型发光杆菌属（Photorhabdus）及嗜线虫致病杆菌属（Xenorhabdus）细菌分别与异小杆线虫属（Heterorhabdltis）和斯氏线虫属（Steinernema）昆虫病原线虫互惠共生。这类昆虫病原细菌在稳定生长期分别产生两种形态各异的胞内晶体蛋白。本文回顾了这类蛋白的研究历史和最新的研究进展，特别是胞内晶体蛋白的理化性质和生物学功能，同时讨论这种晶体蛋白的研究方法与技术。     

长期免耕稻田的土壤微生物与肥力关系研究

对经过10年自然免耕后稻田的基本肥力特征、主要微生物类群的数量以及水稻农艺性状进行了探讨。结果表明：土壤肥力方面,该免耕方式能提高土壤肥力,垄作和厢作的全氮、全磷、速效氮、速效磷以及有机质显著比常规平作高,且上层（0-7.5cm)和下层（7.5-30cm）的肥力水平差异不显著,但仍有上层高于下层的规律;微生物持征方面,各处理细菌数量呈明显的季节性变化,但免耕处理的微生物生长条件较稳定,季节性不明显;自生固氮菌与纤维素分解菌之间相互促进,有利于有机质的积累;自然免耕能提高作物产量,减少杂草生长。     

Effect of cyclodextrin diallyl maleate on methane production, ruminal fermentation and microbes in vitro and in vivo

Effects of β‐cyclodextrin diallyl maleate (CD‐M) on methane production, ruminal fermentation and digestibility were studied both in vitro and in vivo. In in vitro study, diluted ruminal fluid (30 mL) was incubated anaerobically at 38°C for 6 and 24 h with or without CD‐M using hay plus concentrate (1.5:1) as a substrate. The CD‐M was added at different concentrations (0, 1.25, 2.5, 5.0 and 7.5 g/L). The pH of the medium and numbers of protozoa were not affected by the addition of CD‐M. Total volatile fatty acids were increased and ammonia‐N was decreased, molar proportion of acetate was decreased and propionate was increased (P < 0.05) by CD‐M. Methane was inhibited (P < 0.05) by 14–76%. The effect of CD‐M on methane production and ruminal fermentation was further investigated in vivo using four Holstein steers in a cross‐over design. The steers were fed Sudangrass hay and concentrate mixture (1.5:1) with or without CD‐M (2% of feed dry matter) as a supplement. Ruminal proportion of acetate tended to decrease and that of propionate was increased (P < 0.05) 2 h after CD‐M dosing. Total viable counts, cellulolytic, sulfate reducing, acetogenic bacteria and protozoa were unaffected while methanogenic bacteria were decreased (P < 0.05) by CD‐M. The plasma concentration of glucose was increased, whereas that of urea‐N was decreased (P < 0.05). Methane was inhibited (P < 0.05) from 36.4 to 30.1 L/kg dry matter intake by the addition of CD‐M. Apparent digestibilities of dry matter and neutral detergent fiber were not affected while that of crude protein was increased (P < 0.05) in the medicated steers. These data suggested that dietary supplementation of CD‐M decreased methane production and improved nutrient use.     

Biological control of the Western flower thripsFrankliniella occidentalis in cucumber using the entomopathogenic fungusMetarhizium anisopliae

Biological control of the western flower thrips (WFT)Frankliniella occidentalis, using the entomopathogenicMetarhizium anisopliae-7 (M. a-7) strain was studied in three consecutive seasons under greenhouse conditions. Cucumber plants infested with WFT were sprayed with spore suspension of the fungusM. a-7 (0.5 g m^-2), or the soil was treated with dry powder of the fungus (0.5 g m^-2); the control was without fungus application. In the 1997 spring experiment, when the cucumber plants were initially infested with only three or four insects per leaf, the spore suspension spray caused a significant reduction in growth of the thrips population compared with the other treatments and the control. However, in the 1997 summer experiment, when the plants were initially heavily infested with WFT (10–15 insects per leaf), the spray treatment caused only a modest reduction in WFT population growth, and only after 4 weeks of treatment was the reduction significant. In the 1999 experiment, with a low initial WFT population of three or four insects per leaf, the spray treatment was effective in reducing the population growth to a lower level than in the other treatments or control. TheM. a-7 strain was found to be effective in reducing the population growth of WFT under greenhouse conditions, particularly when the initial thrips population was low to moderate. http://www.phytoparasitica.org posting Nov. 4, 2001.     

Soil Characteristics Overwhelm Cultivar Effects on the Structure and Assembly of Root-Associated Microbiomes of Modern Maize

Modern breeding primarily targets crop yield traits and is likely to influence root-associated microbiomes, which play significant roles in plant growth and health. The relative importance of soil and cultivar factors in shaping root-associated microbiomes of modern maize (Zea mays L.) remains uncertain. We conducted a pot experiment in a controlled environment using three soils (Mollisol, Inceptisol, and Ultisol) and four contrasting cultivars, Denghai 605, Nonghua 816, Qiaoyu 8, and Zhengdan 958, which are widely planted in China. We used 16S rRNA gene amplicon sequencing to characterize the bacterial communities in the bulk soil, rhizosphere, and endosphere. Our results showed that the four cultivars had different shoot biomass and root exudate total organic carbon and organic acid contents. The microbiomes in the bulk soil, rhizosphere, and endosphere were different. We observed apparent community divergence between soils rather than cultivars, within which edaphic factors substantially contributed to microbiome variation. Moreover, permutational multivariate analysis of variance corroborated significant contributions of soil type but not cultivar on the root-associated microbiome structure. Differential abundance analysis confirmed that each soil presented a distinct root microbiome, while network analysis indicated different co-occurrence patterns of the root microbiome among the three soils. The core root microbiome members are implicated in plant growth promotion and nutrient acquisition in the roots. In conclusion, root-associated microbiomes of modern maize are much more controlled by soil characteristics than by cultivar root exudation. Our study is anticipated to help improve breeding strategies through integrative interactions of soils, cultivars, and their associated microbiomes.     

Soil bacterial community responses to cadmium and lead stabilization during ecological restoration of an abandoned mine

Ecological restoration refers to the gradual recovery of damaged ecosystems by utilizing their self-recovery capacity and artificial measures. It is considered as an effective technique to alleviate heavy metal pollution in open-pit mining soils. However, little is known about the stability of heavy metals and soil bacterial responses in artificially restored soil-plant systems. In this study, different vegetation restoration strategies were established in the Dabaoshan mining area, China, and the accumulation and transfer of Cd/Pb in the soil-plant system and the responses of the soil bacterial community were investigated. Results showed that ecological restoration with a combination of trees, shrubs and grasses/herbs could increase soil cation-exchange capacity and organic matter content, but not soil pH. The mixture of trees, shrubs and grasses/herbs was most effective for reducing the available Pb content to 33.7% of the content in the control, and the mixture of trees and grasses/herbs was beneficial in reducing Cd to 60.4% of the content in the control. Data showed that ecological restoration could change the quantity, composition and community structure of soil microorganisms. The soils in which a mixture of trees, shrubs and grasses/herbs were grown had the greatest abundance and diversity of bacteria; the abundances of Proteobacteria increased by 12% and Actinobacteria by 5% from those of the control. Plant coverage, soil available Cd content, and organic matter emerged as major determinants of bacterial community composition. This study demonstrates a promising remediation strategy for limiting Cd/Pb mobility in mining areas.     

丁酸钠植物精油复合制剂对南美白对虾生长性能、致病性弧菌和非特异性免疫的影响

研究丁酸钠植物精油复合制剂对南美白对虾(Litopenaeus vannamei)生长性能、肠道微生物及非特异性免疫的影响.试验分为2组,对照组饲喂基础日粮,试验组饲喂基础日粮+2.5 kg/t 丁酸钠植物精油复合制剂.结果显示,相比对照组,试验组南美白对虾增长率提高11.73％(P＜0.01),质量增加率提高13.5...     

昆虫病原线虫与黑色粘板配合使用对韭菜迟眼蕈蚊的防治

为探索昆虫病原线虫与色板配合使用对韭菜迟眼蕈蚊的综合防治技术,采用培养皿滤纸法比较7品系昆虫病原线虫对韭蛆3龄幼虫的致病力,盆栽法研究斯氏线虫属3品系线虫的保苗和防治效果;并通过温室和田间试验比较10种颜色粘板和3个粘板高度对迟眼蕈蚊成虫的诱集效果,研究线虫与黑色粘板配合使用对韭菜迟眼蕈蚊的防治效果。结果表明:SF-SN品系线虫对韭菜迟眼蕈蚊3龄幼虫致病力最高,LD50为60.0条/头,施用线虫剂量为200、400条/头时,其保苗和防治效果高低依次为SF-SN、All、NC116,其中施用SF-SN品系5 d,保苗效果达62.74%,防治效果达60.26%;黑色粘板诱集效果极显著高于其它色板,且下部(色板下缘离地面1 cm处)诱集成虫量最多,与中部(15 cm)、上部(30 cm)之间差异极显著。研究表明,SF-SN品系线虫主要用于防治幼虫,黑色粘板主要诱杀成虫,二者配合使用防治效果可达97.60%,能够极大地降低虫口基数。     

西藏中部农田土壤复退过程中的生物学特征

在西藏中部春播条件下,就不同培肥方式对土壤剖面微生物区系及其主要生理类群变化的影响,以及土壤微生物与土壤有机质、土壤养分的相互关系进行了研究。结果表明,细菌、放线菌、纤维素分解菌的土体差异较大,并主要集中于耕层;真菌、固氮菌的土体差异则极小。2～30,31～60cm土层土壤细菌在微生物区系构成中均占绝对优势,化肥对调控土壤细菌数量具有重要作用。不同培肥方式对2～30,31～60cm土层土壤真菌、固氮菌以及2～30cm土层土壤放线菌的繁殖普遍具有不同程度的抑制作用;2～30,31～60cm土层固氮菌与纤维素分解菌均呈负相关。土壤微生物与土壤有机质的相互促进作用较为明显,对提高土壤有效氮、有效磷亦具重要作用。