响应面法优化爪哇虫草菌的培养条件及其对斜纹夜蛾的毒力和保护酶活性影响

【目的】优化爪哇虫草菌Bd01的固态发酵培养条件,测定分生孢子对斜纹夜蛾3龄幼虫的毒力,研究被爪哇虫草菌侵染后寄主体内的保护酶活性变化。【方法】采用单因素试验确定爪哇虫草菌Bd01最佳的固态培养基及培养条件,利用Box-Behnken响应面法优化发酵参数,采用浸渍法测定分生孢子对斜纹夜蛾3龄幼虫的毒力,同时利用分光光度计法测定斜纹夜蛾3龄幼虫体内酶活性变化。【结果】以产孢量为指标,通过响应曲面法优化的爪哇虫草菌Bd01最佳产孢条件为：培养基营养成分含量为30.24g/L,pH值为7.55,光照时长为12.06h,在该条件下,培养基的产孢量为2.78×10⁸孢子/mL。浓度为1×10⁸孢子/mL的爪哇虫草菌孢子液对斜纹夜蛾3龄幼虫具有一定毒力,处理7 d时致死中浓度(LT₅₀)为3.11 d,致死中时(LC₅₀)为4.68×10⁵孢子/mL,校正死亡率为88.68%。处理后未死亡的斜纹夜蛾幼虫体内保护酶活性与对照组相比发生显著变化。【结论】优化后的培养基能够显著增加爪哇虫草菌的产...     

莱氏绿僵菌FJMR2对草地贪夜蛾不同虫态的致病性研究

【目的】为明确莱氏绿僵菌Metarhizium rileyi FJMR2对草地贪夜蛾Spodoptera frugiperda的生物防治潜力。【方法】在室内条件下,采用浸渍法测定了莱氏绿僵菌FJMR2对草地贪夜蛾卵、幼虫和蛹的致病性。【结果】当孢子浓度为2×10⁸孢子/m L时,草地贪夜蛾1-5龄幼虫和蛹的校正死亡率分别为100%、95.78%、87.15%、64.67%、38.00%和93.93%;草地贪夜蛾1-5龄幼虫和蛹的LC_(50)分别为3.12×108孢子/m L时,草地贪夜蛾1-5龄幼虫和蛹的校正死亡率分别为100%、95.78%、87.15%、64.67%、38.00%和93.93%;草地贪夜蛾1-5龄幼虫和蛹的LC_(50)分别为3.12×10⁴、7.94×104、7.94×10⁴、2.24×104、2.24×10⁶、2.13×106、2.13×10⁷、7.46×107、7.46×10⁸和1.25×108和1.25×10⁵孢子/m L。LT_(50)随孢子浓度的增大而缩短、随幼虫虫龄的增长而延长,当孢子浓度为2×105孢子/m L。LT_(50)随孢子浓度的增大而缩短、随幼虫虫龄的增长而延长,当孢子浓度为2×10⁸孢子/m L时,草地贪夜蛾1-5龄幼虫和蛹的LT_(50)分别为3.93、4.32、5.62、7.18、9.40和4.45 d。卵期为0 h和24 h的草地贪夜蛾卵经莱氏绿僵菌FJMR2浸渍处理后,孵化率分别为84.53%和89.77%,初孵化3 d的幼虫存活率分别为1.81%和3.02%,均显著低于对照组。【结论】莱氏绿僵菌FJMR2对草地贪夜蛾1-4龄幼虫和蛹具有较强侵染致病能力,同时显著降低卵的孵化率和初孵幼虫存活率。     

草地贪夜蛾高致病力绿僵菌菌株的筛选与鉴定

为获取对草地贪夜蛾Spodoptera frugiperda具有高致病力的生防真菌,从福建省不同地区分离得到8株寄主为鳞翅目和半翅目幼虫僵虫的绿僵菌Metarhizium,采用浸渍法测定了其对草地贪夜蛾2龄幼虫和蛹的致病力,并根据形态学和分子生物学方法对高致病力菌株进行种类鉴定。结果表明,8株绿僵菌菌株对草地贪夜蛾2龄幼虫和蛹均表现出不同程度的致病力,其中菌株FJMR2和FJXY7表现出较强的致病力。在5×107个/mL孢子浓度下,FJMR2和FJXY7对草地贪夜蛾2龄幼虫的致死率分别为88.76%和82.13%,对蛹的致死率分别为86.57%和84.00%;对草地贪夜蛾2龄幼虫的LT50分别为4.81 d和4.93 d,对蛹的LT50分别为4.94 d和4.83 d。经鉴定菌株FJMR2和FJXY7均为莱氏绿僵菌Metarhizium rileyi。本研究获得2株对草地贪夜蛾2龄幼虫和蛹具有高致病力的莱氏绿僵菌菌株,在草地贪夜蛾的生物防治中具有较大应用潜力。     

莱氏绿僵菌对斜纹夜蛾的致病力及生理效应

【目的】测定莱氏绿僵菌Metarhizium rileyi Nr5772菌株对斜纹夜蛾Spodoptera litura幼虫及蛹的致病能力,研究莱氏绿僵菌侵染后在寄主体内的发育及对寄主的生理效应,探讨莱氏绿僵菌的致病机制。【方法】采用浸渍法测定莱氏绿僵菌孢子对斜纹夜蛾3-6龄幼虫及蛹的致死中浓度(LC_(50))和致死中时(LT_(50))。采用微量注射法接种莱氏绿僵菌虫菌体,在不同时间后采集斜纹夜蛾幼虫血淋巴,在显微镜下检查虫菌体的数量、形态及寄主血细胞数量,并用酶标仪测定寄主血淋巴酚氧化酶(Phenoloxidase,PO)的活性。【结果】M.rileyi孢子对3龄斜纹夜蛾幼虫毒力最强,10 d后LC_(50)=3.12×10~6个孢子/mL,龄期越大,致病力越低;孢子浓度为5×10~9个/mL时,对3龄幼虫的致死速度最快,LT_(50)=4.55 d,致死速度随龄期的增大和浓度的降低逐渐减缓;M.rileyi孢子对蛹的致病力远低于对幼虫的致病力。注射接种虫菌体后,64 h内,虫菌体数量在寄主血腔中以幂函数的形式增长,寄主的血细胞数量没有明显的变化;在侵染初期(接种后44 h内),血淋巴PO活性正常;在侵染后期,虫菌体数量不再增加(55-64 h后),逐渐转化为菌丝体,并快速杀死寄主,PO活性受到抑制。【结论】莱氏绿僵菌Nr5772菌株对斜纹夜蛾幼虫有较强的致病力,应在害虫低龄期应用;莱氏绿僵菌在侵染初期对寄主血细胞和血淋巴PO无影响,后期则完全抑制PO活性。     

金龟子绿僵菌对斜纹夜蛾幼虫的生防效果、抗氧化酶活性和肠道细菌群落的影响

【目的】测定金龟子绿僵菌(Metarhizium anisopliae)对斜纹夜蛾(Spodoptera litura) 2龄幼虫的毒力,研究金龟子绿僵菌侵染后寄主体内抗氧化酶活性和肠道内细菌群落的变化,探讨斜纹夜蛾对金龟子绿僵菌侵染的防御机制。【方法】采用浸渍法测定不同浓度金龟子绿僵菌对斜纹夜蛾2龄幼虫的毒力;应用IlluminaMiSeq高通量测序技术测定肠道细菌群落。【结果】不同浓度的孢悬液对斜纹夜蛾2龄幼虫均有一定的毒力,处理7 d时半致死浓度(LC_(50))为3.944 107个孢子/mL;浓度为1.0×10~9个孢子/mL时,半致死时间最短(LT_(50))为4.6 d,校正后的死亡率为81.03%。处理后未致死的斜纹夜蛾幼虫体内抗氧化酶活性显著高于对照组。处理后致死的斜纹夜蛾幼虫肠道细菌群落多样性显著高于对照组;且处理后致死的斜纹夜蛾幼虫肠道细菌群落组成与对照组差异显著。【结论】金龟子绿僵菌对斜纹夜蛾幼虫的致死率和致死效率与金龟子绿僵菌的浓度呈正相关;斜纹夜蛾幼虫体内的抗氧化酶可能在抵抗金龟子绿僵菌侵染的过程中起重要作用。金龟子绿僵菌的侵染会导致斜纹夜蛾幼虫肠道细菌群落多样性升高和组成发生变化,Enterococcus、Escherichia和Pseudomonas等属可能是影响斜纹夜蛾幼虫抵抗金龟子绿僵菌侵染致死的重要因素。     

响应面设计优化绿僵菌固体发酵条件

【目的】为了提高绿僵菌分生孢子产量及孢子质量,应用响应面设计对金龟子绿僵菌菌株CY-1(Metarhizium anisopliae)进行固体发酵培养基的优化。【方法】单因素试验基础上,采用响应面试验设计方法优化培养基组分。【结果】添加了碳、氮营养的最佳固体发酵培养基为玉米粉:稻壳=8:2,料水比1:0.8,葡萄糖0.8%,硫酸铵2.5%,磷酸二氢钾0.8%;在固体培养基上的理论产孢量为7.45×10~9个/g;验证后实际为6.94×10~9个/g。【结论】运用响应面法对绿僵菌固体发酵的培养基成分进行优化,得到了绿僵菌孢子粉,为孢子粉进行地下害虫防治和制剂加工的研究奠定了基础。     

草地贪夜蛾幼虫僵虫发生率调查及致病菌分离鉴定

草地贪夜蛾Spodoptera furgiperda (J.E.Smith)是一种新的入侵害虫,目前已侵入我国多个省区,严重危害玉米。本研究调查了广州地区草地贪夜蛾僵虫的自然发生率,并分离出具有较高致病性的白僵菌,测定了对草地贪夜蛾3龄幼虫的致病性。结果表明：广州地区草地贪夜蛾幼虫僵虫发生普遍,田间僵虫率最高为20.99%,累积僵虫率达43.21%;结合僵虫、致病菌菌落、显微超微等形态和分子生物学分析,以及致病性测定,确定从草地贪夜蛾幼虫上分离的真菌为球孢白僵菌Beauveria bassiana;分离培养的分生孢子和僵虫体表洗脱的分子孢子对幼虫致病力相近,有效致死浓度为1107 cfu/mL,幼虫的累积校正死亡率达78.57%。研究表明,该白僵菌菌株对草地贪夜蛾幼虫具有较高的致病性,可作为生防真菌进一步的研究。     

球孢白僵菌Bb378菌株的分离、鉴定及对草地贪夜蛾的致病性研究

【目的】筛选出对草地贪夜蛾Spodoptera frugiperda高致病性的球孢白僵菌Bb378,并进一步研究菌株对玉米生长的影响及对草地贪夜蛾的驱避效果,为应用球孢白僵菌防治草地贪夜蛾奠定基础。【方法】分别用0.05%Tween-80水溶液和1×10⁴、1×10⁵、1×10⁶、1×10⁷和1×10⁸孢子/m L的球孢白僵菌孢子悬浮液接种草地贪夜蛾3龄幼虫,第3、7及14天后观察记录感染情况及死亡虫数;分别用浸种法、灌根法、叶面喷施法研究球孢白僵菌Bb378菌株对玉米的促生性及对草地贪夜蛾取食行为的影响。【结果】筛选出的高致病性菌株Bb378处理草地贪夜蛾3龄幼虫14 d后累计校正死亡率为48.61%,LC₅₀为1.11×10⁸孢子/m L。使用叶面喷施法接种,球孢白僵菌Bb378对玉米叶面积和鲜重的影响最大;使用灌根法和浸种法接种,Bb378菌株对株高的影响较为明显;当Bb378浓度为1×10⁷和1×10     

一株球孢白僵菌的分离鉴定及其对草地贪夜蛾的致病性

草地贪夜蛾Spodoptera frugiperda(J. E.Smith)是我国于2019年新发现的一种迁飞性重大害虫。为了寻找对草地贪夜蛾有高致病性的昆虫病原真菌,本实验对采自广东省广州市华南农业大学湿地的感菌稻黑蝽Scotinophara lurida若虫僵虫进行了室内分离培养,结合形态学和rDNA-ITS序列分析,采用浸虫法研究了该菌对草地贪夜蛾各龄幼虫的致病力。鉴定结果表明该病原真菌为球孢白僵菌Beauveria bassiana,编号为GZSL-1菌株。菌株GZSL-1可侵染草地贪夜蛾6个龄期的幼虫,随孢子浓度的升高,草地贪夜蛾幼虫感病死亡率增加,当浓度达到1×10~8孢子/mL时,1～3龄幼虫的累计校正死亡率皆为100%,4龄和5龄幼虫也达到57.47%和55.06%,6龄仅25.28%。接菌6 d后1～5龄幼虫的LC_(50)值分别为1.32×10~3、3.42×10~3、1.01×10~4、1.61×10~5和1.23×10~7孢子/mL。幼虫LT_(50)值随孢子悬浮液浓度增加而递减,在孢子浓度为1.0×10~4～1.0×10~8孢子/mL范围内,1龄、2龄和3龄幼虫的LT_(50)值分别为3.58～1.69 d、4.30～1.78 d和5.70～3.12 d;浓度为1.0×10~5～1.0×10~8孢子/mL时,对4龄幼虫的LT_(50)为5.45～4.85 d;浓度为1.0×10~7～1.0×10~8孢子/mL时,对5龄幼虫的LT_(50)为5.04～5.02 d。上述研究结果表明,鉴定的球孢白僵菌菌株GZSL-1对草地贪夜蛾幼虫具有较强致病性,可为草地贪夜蛾微生物防治提供候选菌种资源。     

感染松墨天牛的金龟子绿僵菌菌株的初步筛选

松墨天牛是松材线虫病的主要媒介昆虫,本文对分离自松墨天牛的6株金龟子绿僵菌,以及从光肩星天牛、大蜡螟、伊藤厚丝角叶蜂和土蝽上分离的各1个菌株,共10个菌株的产孢情况、孢子萌发率进行研究;在此基础上选出金龟子绿僵菌1291、1349和2049三个菌株及球孢白僵菌F-263菌株,采用成虫跗节接种法和幼虫浸渍法进行室内松墨天牛及大蜡螟的毒力测定比较。结果表明,供试绿僵菌菌株对松墨天牛幼虫在接种15天后的感染僵虫率为76.9％～93.1％(1×10⁷孢子/mL);成虫在接种20天后的僵虫率亦达57.9％～75.0％(6.5×10⁵～3.4×10⁶孢子/成虫);2049菌株表现尤其突出;对应的球孢白僵菌F-263对幼虫和成虫的僵虫率分别是96.3％(1×10⁷孢子/mL)和55％(9.7×10⁵孢子/成虫)。但这3个金龟子绿僵菌菌株对大蜡螟的毒力较低,存在较明显的寄主专化性。这3个菌株今后在防治松墨天牛方面具有较大开发应用价值。     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Hectorella: A member of the betalain-suborderChenopodiineae of the orderCentrospermae

Roots ofHectorella caespitosa Hook. f. were induced to produce a red pigment which was shown to be a betalain and not an anthocyanin. These data indicate thatHectorella belongs to theChenopodiineae, the betalain suborder of theCentrospermae, and excludes alignment with the anthocyanin family theCaryophyllaceae.     

Succession in the southern part of the Canadian boreal forest

Forest succession following fire in a forest mosaic of northwestern Quebec has been studied in order to: (1) describe the successional pathways using communities of different ages and (2) evaluate convergence of successional pathways and possible effect of fire suppression on the establishment of steady-state communities. As a first step, ordination and classification techniques were used in order to remove changes in forest composition which are related to abiotic conditions. Then, ordinations based on tree diameter distributions were used to study shifts in species composition in relation to time since the last fire.Even under similar abiotic conditions, successional pathways are numerous. However, regardless of forest composition after fire, most stands show convergence toward dominance of Thuja occidentalis and Picea mariana on xeric sites and dominance of Abies balsamea and Thuja occidentalis on more mesic sites. Stable communities of >300 yr occur on xeric sites while on mesic sites directional succession still occurs after 224 yr. Nearly all species involved in succession are present in the first 50 yr following fire. Only Abies balsamea and Thuja occidentalis increase significantly in frequency during succession. Following initial establishment, successional processes can generally be explained by species longevity and shade tolerance. Early successional species may be abundant in the canopy for more than 200 yr while the rapid decrease of Picea glauca, a late successional species could be related to spruce budworm outbreaks. Considering the short fire rotation observed (about 150 yr), a steady-state forest is unlikely to occur under natural conditions, though it may be possible if fire is controlled.     

Analysis of the genes of the OEE1 and OEE3 proteins of the photosystem II complex from Chlamydomonas reinhardtii

The sequences of the nuclear genes of the 33 kDa (OEE1) and the 16 kDa (OEE3) polypeptides of the oxygen evolving complex of Chlamydomonas reinhardtii have been established. Comparison between the OEE1 protein sequences of C. reinhardtii and higher plants and cyanobacteria reveals 67 and 47% homology. In contrast, C. reinhardtii and higher plants have only 28% overall homology for OEE3 which is mostly limited to the central portion of the protein. The transit peptides of the C. reinhardtii proteins consist of 52 (OEE1) and, most likely, 51 (OEE1) amino acids. They have a basic amino terminal region and, at least in the case of OEE1, a hydrophobic segment at their carboxy terminal end typical of thylakoid lumen proteins. Comparison of the genomic and cDNA clones indicates that the OEE1 and OEE3 genes contain five and four introns, respectively, some of which are located within the coding sequences of the transit peptides.     

The purification of the three trimannosyl-N-acetylchitobiose pentasaccharides from the urine of swainsonine-intoxicated sheep

A simple method for the preparative resolution of three Man₃GlcNAc₂ isomers called Ia, Ib and II has been designed. It consists mainly of the use of concanavalin A-Sepharose which allowed the total purification of Man₃GlcNAc₂-Ia, and then of anion-exchange resin in borate buffer-gradient to separate the Ib and II isomers. The purity of each oligosaccharide was checked by two HPLC methods. The use of these oligosaccharides for different analytical and biosynthetic purposes is discussed, and the unexpected resistance of one of the Man₃GlcNAc₂ alditols to the action of endo--N-acetylglucosaminidase H is noted.     

Evaluation of the Pro-Lab ID ring system for the identification of medically important yeasts

We evaluated 151 coded isolates of medically important yeast species belonging to the genera Candida, Cryptococcus, Geotrichum, Rhodoturula, Saccharomyces and Torulopsis using the newly developed rapid Pro-Lab Identification Ring, PL 960 system (PLID-Ring). All isolates were concurrently identified by the API 20C and conventional procedures comprising macro- and micromorphology, assimilation and fermentation of various carbon and nitrogen compounds. The PLID-Ring system identified isolates of Candida albicans, C. kefyr, C. krusei, C. lusitaniae, C. parapsilosis, Rhodotorula rubra, and Torulopsis glabrata with 100% accuracy in 24 h. This system identified C guilliermondii and S. cerevisiae isolates with an accuracy of 90% and 86%, respectively, while those belonging to Cr. neoformans, T. candida (= C. famata), C. rugosa and C. tropicalis were identified with 38.4%, 50%, 12.5% and 50% accuracy, respectively. Three isolates of Cr. laurentii were not identified by the PLID-Ring system. The overall accuracy of the PLID-Ring system was 81.45% (123 of 151 isolates). However, the system does not include species such as Cr. laurentii in its data base. When these three Cr. laurentii isolates were excluded from the evaluation, the accuracy of the PLID-Ring system increased from 81.45% to 83.1%.     

The history of the genusHomo

The genusHomo was established by Carolus Linnaeus in 1758. During the course of the past 150 years, the addition of fossil species to the genusHomo has resulted in a genus that, according to the taxonomic interpretation, could span as much time as 2.5 Myr, and include as many as ten species. This paper reviews the fossil evidence for each of the species involved, and sets out the case for their inclusion inHomo. It suggests that while the case for the inclusion of some species in the genus (e.g.Homo erectus) is well-supported, in the case of two of the species,Homo habilis andHomo rudolfensis, the case for their inclusion is much weaker. Neither the cladistic evidence, nor evidence about adaptation suggest a particularly close relationship with laterHomo.     

Comparative analysis of the Kekkon molecules,related members of the LIG superfamily

Leucine-rich repeats (LRRs) and immunoglobulin (Ig) domains represent two of the most abundant sequence elements in metazoan proteomes. Despite this prevalence, comparatively few molecules containing both LRR and Ig (LIG) modules exist, and fewer still have been functionally defined. One LIG whose function has been investigated is the Drosophila protein Kekkon1 (Kek1). In vivo studies have demonstrated a role for Kek1 in Epidermal Growth Factor Receptor (EGFR) signaling and have suggested a role in neuronal pathfinding. Kek1 is the founding member of the Kek family, a group of six Drosophila transmembrane proteins that contain seven LRRs and a single Ig in their extracellular domains. While this arrangement of domains predicts a possible role as cell adhesion molecules (CAMs), to date little is known about the function or evolutionary relationship of these additional Kek molecules. Here we report that orthologs of Kek1, Kek2, Kek5, and Kek6 exist in the mosquito, Anopheles gambiae, and the honeybee, Apis mellifera, indicating that this family has been conserved for ~300 million years of evolutionary time. Comparative sequence analyses reveal remarkable identity among these orthologs, primarily in their extracellular regions. In contrast, the intracellular regions are more divergent, exhibiting only small pockets of conservation. In addition, we provide support for the general notion that these molecules may share common functions as CAMs, by demonstrating that Kek family members can form homotypic and heterotypic complexes.Edited by D. TautzChristina M. MacLaren, Timothy A. Evans and Diego Alvarado contributed equally to this work     

Comparison of the Influence of Carbon Substrates on the Fibrolytic Activities of Anaerobic Rumen Fungi

Cellulolytic and xylanolytic activities among genera of anaerobic fungi when grown on glucose, xylan and the cellulosic substrates, filter paper and Avicel were compared. All the fungi had basal extracellular fibrolytic activities that could be enhanced by growth on xylan or the cellulosic substrates. However,Piromyces communisstrain 22 andNeocallimastix patriciarumstrain 27 had substantially greater levels of fibrolytic activity thanOrpinomyces joyoniistrain 19-2 orNeocallimastix frontalisstrain RE1. Zymogram analysis suggested both structural and regulatory differences amongst the enzyme systems of the fungi. Numerous and varied enzyme bands were evidenced for all the fungi, with substantial substrate influences seen in the xylanase activities. Most commonly the smaller molecular weight bands, found exclusively extracellularly, appeared under the greatest regulatory control. Endoglucanase activities ofP. communisandO. joyoniidemonstrated similar regulatory control, while those of the twoNeocallimastixstrains did not appear to exert such control. These results suggest that while the enzymatic activities are functionally similar, there are likely significant variations in the enzyme systems of the anaerobic fungi.