Phylogenetic Position of Amblyospora Hazard & Oldacre (Microspora: Amblyosporidae) Based on Small Subunit rRNA Data and Its Implication for the Evolution of the Microsporidia

ABSTRACT. Sequences of the small subunit rRNA genes of Amblyospora californica and an Amblyospora sp. from Culex salinarius were determined. These sequences were compared phylogenetically with 16 other microsporidia. The results suggest Amblyospora forms a sister taxon to the rest of the microsporidia examined. The basal position of Amblyospora is discussed with respect to the evolution of microsporidian life cycles. These sequences represent the longest microsporidian small subunit rRNA genes sequenced to date, 1,359 and 1,358 bp, respectively. Structural features and GC content (49% for both) are comparable to those of other microsporidia which have been sequenced.     

榆绿毛萤叶甲寄生微粒子虫新种记述：微孢子门：微粒子科

本文记述寄生于榆绿毛萤叶甲的一种微粒子虫新种的光匀和电镜形态特征及寄生习性。并讨论了新种鉴别特性。     

Nosema parkeri sp. n., a Microsporidan from the Argasid Tick, Ornithodoros parkeri Cooley

SYNOPSIS. Nosema parkeri sp. n. is described from nymphs and adults of the argasid tick, Ornithodoros parkeri Cooley, from a laboratory colony. Schizogonic and sporogonic stages are described from various tick tissues. Spores are binucleate, measuring 3.2 (3–4) × 1.9 (1.8–2.5) μm. Transmission is transovarial and transstadial. The parasite does not appear to affect adversely the development or reproduction of the tick. Dermacentor andersoni Stiles was experimentally infected. Attempts to infect Swiss mice by tick feeding or by injection of infected tick suspensions were unsuccessful. The microsporidan differs in structure from Encephalitozoon ixodis Weiser) and Nosema slovaca Weiser & Reháček, the only other microsporidans known from ticks.     

Recherches Cytochimiques sur la Microsporidie Nosema bomycis au cours de son Développement chez le Ver à Soie (Bombyx mori)*

RESUME. La Microsporidie Nosema bombycis, Protozoaire parasite agent de la pébrine du ver à soie, a étéétudiée cytochimiquement à la fois en microscopie photonique et électronique. Les examens ont porté sur la détection et la localisation des acides nucléiques (ADN et ARN), des polysaccharides, de la phosphatase acide, au cours des différents stades du développement dans les cellules de I'hôte (du schizonte à la spore). Les principaux résultats concernent les observations relatives aux polysaccharides et à la phosphatase qui ne sont détectés qu'au stade de la spore et ne sont pas observés au stade du schizonte. Les polysaccharides sont présents au niveau du sac polaire, du filament polaire et sur la membrane cytoplasmique; la phosphatase acide est localisée au niveau du sac polaire, du filament polaire et dans la vacuole postérieure. SYNOPSIS. Nosema bombycis, agent of pebrine disease of silkworm, was studied cytochemically, using both light and electron microscopy. Presence of nucleic acids (DNA and RNA), polysaccharides, and acid phosphatases was demonstrated and localization of these substances was determined in various stages of the parasite (from the schizont to the spore). DNA and RNA were detected in all these stages. Polysaccharides and acid phosphatase were found in the spore but not in the schizogonic stages. Polysaccharides were detected in the polar cap, the polar filament, and the limiting membrane of the cytoplasm of the spore. Acid phosphatase was found in the polar cap, the polar filament, and the posterior vacuole.     

Factors affecting parasite prevalence among wild bumblebees

1. Bumblebees are important pollinators in North America and are attacked by a range of parasites that impact their fitness; however, few studies have investigated the extent or causes of parasitism in North America. 2. This study used a 2‐year multi‐site survey of bumblebee parasitism to ask: (i) how common are parasitoid conopid flies and the internal parasites Crithidia bombi and Nosema bombi in Massachusetts; and (ii) what factors are correlated with parasitism? 3. Infection rates by all three parasites were higher in this study than previously documented in North America. Overall, conopids infected 0–73% of bees in each sample, C. bombi infected 0–82% of bees, and N. bombi infected 0–32%. 4. Conopid flies infected female bees more than males and intermediate‐sized bees more than large or small bees. Crithidia bombi infection rates were higher in certain bee species and sites, and exhibited a unimodal pattern of prevalence over time. Nosema bombi parasitism was higher in male than female bees. 5. Infection by N. bombi in two rare bumblebee species was higher than expected based on parasitism rates of common bee species but C. bombi infection was lower. If high prevalence of N. bombi in these bumblebee species is common, parasitism may be a potential cause of their decline. 6. Given the documented effects of these parasites, the high levels of infection may affect bee populations in Massachusetts and threaten the stability of their valuable ecosystem services.     

Influence of the forest caterpillar hunter Calosoma sycophanta on the transmission of microsporidia in larvae of the gypsy moth Lymantria dispar

• 1 The behaviour of predators can be an important factor in the transmission success of an insect pathogen. We studied how Calosoma sycophanta influences the interaction between its prey [Lymantria dispar (L.) (Lepidoptera, Lymantriidae)] and two microsporidian pathogens [Nosema lymantriae (Microsporidia, Nosematidae) and Vairimorpha disparis (Microsporidia, Burellenidae)] infecting the prey.
• 2 Using laboratory experiments, C. sycophanta was allowed to forage on infected and uninfected L. dispar larvae and to disseminate microsporidian spores when preying or afterwards with faeces.
• 3 The beetle disseminated spores of N. lymantriae and V. disparis when preying upon infected larvae, as well as after feeding on such prey. Between 45% and 69% of test larvae became infected when C. sycophanta was allowed to disseminate spores of either microsporidium.
• 4 Laboratory choice experiments showed that C. sycophanta did not discriminate between Nosema‐infected and uninfected gypsy moth larvae. Calosoma sycophanta preferred Vairimorpha‐infected over uninfected gypsy moth larvae and significantly influenced transmission.
• 5 When C. sycophanta was allowed to forage during the latent period on infected and uninfected larvae reared together on caged, potted oak saplings, the percentage of V. disparis infection among test larvae increased by more than 70%. The transmission of N. lymantriae was not affected significantly in these experiments.
• 6 Beetles never became infected with either microsporidian species after feeding on infected prey.
• 7 We conclude that the transmission of N. lymantriae is not affected. Because no V. disparis spores are released from living larvae, feeding on infected larvae might enhance transmission by reducing the time to death and therefore the latent period.

     

Increased survival of the honey bee Apis mellifera infected with the microsporidian Nosema ceranae by effective gene silencing

This study examined the control of nosemosis caused by Nosema ceranae, one of the hard-to-control diseases of honey bees, using RNA interference (RNAi) technology. Double-stranded RNA (dsRNA) for RNAi application targeted the mitosome-related genes of N. ceranae. Among the various mitosome-related genes, NCER_100882, NCER_101456, NCER_100157, and NCER_100686 exhibited relatively low homologies with the orthologs of Apis mellifera. Four gene-specific dsRNAs were prepared against the target genes and applied to the infected A. mellifera to analyze Nosema proliferation and honey bee survival. Two dsRNAs specifics to NCER_101456 and NCER_100157 showed high inhibitory effects on spore production by exhibiting only 62% and 67%, respectively, compared with the control. In addition, these dsRNA treatments significantly rescued the honey bees from the fatal nosemosis. It was confirmed that the inhibition of Nosema spore proliferation and the increase in the survival rate of honey bees were resulted from a decrease in the expression level of each target gene by dsRNA treatment. However, dsRNA mixture treatment was no more effective than single treatments in the rescue from the nosemosis. It is expected that the four newly identified mitosome-related target genes in this study can be effectively used for nosemosis control using RNAi technology.     

家蚕微孢子虫感染对家蚕海龟蛋白(Bmtutl)基因表达水平的影响

【目的】本研究旨在阐明家蚕微孢子虫Nosema bombycis感染不同时间对家蚕Bombyx mori幼虫不同组织中家蚕海龟蛋白(Bombyx Turtle, Bmtutl)基因表达水平的影响,为揭示家蚕微孢子虫的侵染机制奠定基础。【方法】利用生物信息学方法对家蚕海龟蛋白3种亚型Bmtutl-464, Bmtutl-519和Bmtutl-810的序列结构特征进行了分析;利用qPCR检测家蚕微孢子虫感染后12, 24, 48, 72, 96和120 h,家蚕幼虫中肠、血淋巴与脂肪体组织中Bmtutl-464, Bmtutl-519和Bmtutl-810基因表达水平的变化情况。【结果】家蚕海龟蛋白3种亚型的二级结构均主要由无规则卷曲、α螺旋、β转角和延伸链组成,其中无规则卷曲所占比例最高。但是PredictProtein分析发现,Bmtutl-464, Bmtutl-519和Bmtutl-810之间的蛋白/多核苷酸结合位点存在较大差异。qPCR结果表明,感染家蚕微孢子虫后,家蚕幼虫中肠、血淋巴与脂肪体组织中Bmtutl-464, Bmtutl-519和Bmtutl-810基因的整体表达处于被抑制状态,尤其在脂肪体中最为明显：Bmtutl-519和Bmtutl-810基因的表达在家蚕微孢子虫感染家蚕后的72 h开始受到显著抑制,特别是Bmtutl-519基因,其相对表达水平均不到对照的5.0%。【结论】家蚕海龟蛋白这3种亚型的序列结构特征存在较大差异,家蚕微孢子虫感染在一定程度抑制了家蚕幼虫中肠、血淋巴与脂肪体组织中Bmtutl-464, Bmtutl-519和Bmtutl-810基因尤其是Bmtutl-519的表达。结果说明,与其他两种家蚕海龟蛋白亚型相比,Bmtutl-519蛋白可能在家蚕微孢子虫侵染宿主的过程中起主要作用。     

Differences between Brachiola (Nosema) algerae isolates of human and insect origin when tested using an in vitro spore germination assay and a cultured cell infection assay

Brachiola (Nosema) algerae is a microsporidian species generally believed to be an intracellular parasite of insects, especially mosquitoes. However, both mosquito and human isolates have been shown to infect mammalian cells. The present study was undertaken to determine if spores of two insect and two human isolates of B. algerae cultured at 30 degrees C and 37 degrees C differed in their ability to germinate and infect cultured green monkey kidney cells at these two temperatures. Spores from all four isolates exhibited an optimum pH of 9.5 for germination. Mercury (Hg2+) inhibited germination of all isolates equally. Germination of spores from all four isolates was significantly greater when the parasite was cultured at 30 degrees C than when cultured at 37 degrees C. However, spores from the insect isolates cultivated at 30 degrees C or 37 degrees C infected significantly fewer mammalian cells at 37 degrees C than did spores from the human isolates under the same conditions. Thus, there is no correlation between the effects of temperature on the germination and the infectivity of an isolate. In addition, while exposure of B. algerae to 37 degrees C has been reported to cause spore dysmorphism, we failed to observe any consistent ultrastructural changes that explained the greater infectivity of the human isolates at 37 degrees C.     

Effects of Nosema bombi and its treatment fumagillin on bumble bee (Bombus occidentalis) colonies

We examined the effects of Nosema bombi (Microsporidia: Nosematidae) on colonies of bumble bees, Bombus occidentalis Greene (Hymenoptera: Apidae), used to pollinate tomatoes in commercial greenhouses. We assessed methods of detecting N. bombi and tested the effectiveness of fumagillin to control this parasite. N. bombi did not affect adult population size or amount of brood in B. occidentalis colonies. Fumagillin was not effective against N. bombi at the doses we tested, and frass samples did not provide accurate estimates of the intensity of N. bombi infections. The number of N. bombi spores per bee was highly variable among bumble bees within colonies, and accurate estimates could only be obtained by sampling a large proportion of bees in each colony. Therefore, whole bee and frass sampling is useful for determining if N. bombi is present or absent, but not for obtaining accurate estimates of the intensity of N. bombi infections.