昆虫体外共生菌研究进展

昆虫体外共生菌是指能在体外与宿主发生互利共生关系的微生物。体外共生菌虽然不如肠道微生物那样普遍存在于昆虫中,但也在宿主生长发育过程中扮演着重要的角色。昆虫体外共生菌一般寄生于昆虫体表或体内特异器官(如储菌器),在特定时期转移到植物组织中。体外共生菌产生的挥发物能作为宿主定位寄主植物的信号物质,能为宿主提供生长发育所需的营养物质,还参与了宿主体外免疫。对昆虫体外共生菌的研究,不仅能进一步揭示昆虫与微生物之间的互作关系,丰富昆虫共生菌的研究,还能从共生菌的角度探索害虫引诱剂和昆虫免疫豁免机制。本文对昆虫体外共生菌寄生方式、传播途径、对宿主的影响等研究成果进行了综述,旨在为害虫综合防控提供新思路。     

昆虫共生微生物：研究进展与展望

昆虫共生微生物是指与昆虫宿主建立持久互作关系的微生物，这些微生物分布于昆虫的体表、肠道、血腔或者细胞内，参与调节宿主昆虫的多种生理功能。昆虫-共生微生物互作研究涉及多个学科领域的交叉。深入研究昆虫共生微生物的功能及其与宿主的互作关系不仅有助于阐明重要的生命科学机理，还将为害虫治理和虫传病害的防控以及益虫的有效利用提供新的思路和方法。近年来，我国学者在昆虫微生物组研究领域取得显著进展，在多个研究方向取得重要成果。本文概述了国内外昆虫共生微生物研究的最新进展，介绍了本专辑论文的主要研究内容，并提出了值得关注的3个研究方向：(1)昆虫细胞内共生微生物的功能；(2)昆虫调控共生微生物丰度和传播的机制；(3)昆虫共生微生物的遗传改造和应用。     

昆虫完全变态发育与其共生微生物之间的相互影响

完全变态昆虫在发育过程中要经过卵、幼虫、蛹和成虫四个阶段,它们在幼虫和成虫阶段形态构造和生活习性明显不同,这一现象被称为适应性解耦,使幼虫和成虫能够更独立地完成不同的任务,各自获得更高的效率,这对完全变态昆虫有巨大的生态和进化意义。然而这种发育方式为完全变态昆虫与微生物建立稳定的共生关系带来了巨大的挑战。它们在变态过程中身体结构的重塑、饮食习惯的改变等使微生物居住的栖息地发生彻底转变,微生物在昆虫宿主个体不同发育阶段和不同个体代际之间的垂直传递也受到了限制。为了高保真地维持稳定的共生关系,部分完全变态昆虫和共生微生物进化出多样的严格垂直传递或者规避完全变态发育的传递方式。也有部分完全变态昆虫趁此机会实现与共生微生物的关系解绑,与新的微生物建立联系,呈现出在不同生命阶段共生微生物的动态变化。此外,昆虫变态发育还直接受到共生微生物的影响,微生物能保护宿主在变态发育中最脆弱的阶段免受病原体感染,为变态发育提供必需的营养物质和促进变态发育的因子。因此,本综述将总结和深入探究昆虫完全变态发育与其共生微生物之间的相互影响。     

病毒与宿主互利共生的研究

在病毒与其宿主的相互作用中,病毒所扮演的角色不仅仅是病原体,它们也是宿主保持健康的重要共生体。病毒与微生物、植物、昆虫和哺乳动物之间存在互利共生作用,有的甚至涉及共生功能体的多个生物体。随着新病毒的不断发现,越来越多的互利共生关系被发掘,也还有许多有待发掘。本文旨在突出一些近年来关于有益病毒的典型例子,阐明为何需要重新认识病毒——病毒不仅是病原体,同时也是共生功能体中的一个完整个体。     

共生微生物对昆虫化学感受的影响北大核心

共生微生物通过影响昆虫信息化合物的合成或感受来调控宿主的化学通讯,进而影响昆虫的交流、防御、捕食和扩散行为。这种调控作用有助于共生微生物的扩散,但对宿主可能是有利的,也可能是有害的,并为共生体系的协同进化提供动力。本文围绕近年来共生微生物对昆虫化学感受的影响及其机制展开综述,并分析其进化意义,旨在为昆虫化学生态学理论提供补充,并为开发新的害虫防治策略提供思路。     

昆虫肠道微生物分离培养策略及研究进展

昆虫肠道作为一种特殊生境,生存着多种多样的共生微生物,并且肠道内的很多微生物与自然界其他生境的微生物种类显著不同。基于对纯培养微生物的研究,科学家们发现,肠道微生物与昆虫营养、生长发育及免疫等功能密切相关。因此,分离培养是发现微生物新种类、新基因和新功能的基础。然而,自然界可培养的微生物大约只占总数的1%。为了能够对更多的微生物进行分离和培养,近二十年来,微生物学家们发展了诸多新的培养技术和策略并利用它们从昆虫肠道分离出了很多新的难培养微生物。这些新的微生物种类极大地丰富了我们对肠道共生微生物生理作用与功能的认识。以此为基础,本文综述了昆虫肠道微生物分离培养的策略及研究进展,并对未来该领域的发展进行了展望。     

昆虫肠道微生物的研究进展和应用前景

昆虫肠道的独特结构和理化性质为多种多样的微生物定殖提供了特殊环境,肠道微生物的群落组成与宿主昆虫的生长发育、代谢繁殖等生命活动密切相关。种类丰富多样、生态位分布广泛的昆虫体内含有大量特化的肠道微生物群落,经过长期协同进化形成的共生关系具有多方面无可替代的优势。这种相对稳定的共生关系对昆虫整个生命周期具有极其重要的作用,肠道微生物不仅为宿主提供重要的营养物质、协助消化食物、提高宿主防御和解毒能力,还影响宿主昆虫的寿命、发育周期以及交配与繁殖能力等。同时,昆虫肠道微生物在农业、生态、医药以及能源环保等多个学科领域也显示出了巨大的应用前景。本文就昆虫肠道微生物群落的多样性、功能和影响肠道微生物生存因素,以及应用前景等方面进行综述,讨论了昆虫肠道微生物的最新研究进展。     

共生菌与昆虫的免疫

共生菌可通过产生抗菌物质、调控宿主免疫相关基因和微生物种间竞争作用等方式保护昆虫宿主免受病原体的侵染。为维持共生关系,昆虫进化出精细的调控机制避免对共生菌的过激免疫应答,共生菌通过免疫识别信号多态性或化学拟态来降低或躲避宿主免疫系统对自身的伤害。本文在分析共生菌对宿主免疫的功能及其机制的基础上,探讨宿主对免疫应答的精准调控以及共生体系的协同进化,以期为共生菌对宿主免疫影响的深入研究提供参考。     

昆虫共生细菌研究进展

昆虫体内定殖着大量微生物,经过漫长协同进化,昆虫与这些微生物构建了共生体系,这些昆虫共生微生物参与整个生态过程,对于生态系统中物质转化与交换、能量流动与利用、信息传递与调控等均发挥着重要作用。昆虫共生细菌具有丰富的物种多样性;昆虫与其共生细菌之间通过化学机制、生理机制、生态学机制和遗传学机制构建复杂的共生体系;昆虫为细菌提供稳定的生境并共享特定的代谢途径,共生细菌则协助宿主营养代谢,提供食物中缺乏的养分,促进昆虫生长和繁殖;通过分泌抗菌肽、毒素等,细菌能增强昆虫对寄生物的防御能力和抗病性,并通过调节昆虫对非生物因子的抗逆性和耐药性,扩大昆虫的生态位。昆虫共生细菌在农林牧渔业可持续安全生产与医药研发等领域具有应用潜力和广阔的发展前景。     

念珠菌适应宿主环境压力的共生机制研究进展

作为人体微生物菌群中真菌菌群的一个重要组成部分,念珠菌通常定植于人体的众多生态位,在免疫系统功能正常的健康人群中与宿主保持共生状态。为适应宿主体内复杂多变的环境,拮抗宿主免疫系统的攻击,以及应对其他微生物菌群的竞争等诸多生存压力,念珠菌进化出一系列极为有效的应对机制以维持其在宿主体内的共生。本文总结了念珠菌通过形态转换、环境适应、免疫调节以及与其他微生物菌群相互作用等策略应对宿主环境生存压力的分子机制,重点阐述了念珠菌、宿主免疫系统以及微生物菌群三者之间的相互作用和相互平衡对于念珠菌实现成功定植和共生的重要意义。     

Tsetse--A haven for microorganisms

Arthropods are involved in the transmission of parasitic and viral agents that cause devastating diseases in animals and plants. Effective control strategies for many of these diseases still rely on the elimination or reduction of vector insect populations. In addition to these pathogenic organisms, arthropods are rich in microbes that are symbiotic in their associations and are often necessary for the fecundity and viability of their hosts. Because the viability of the host often depends on these obligate symbionts, and because these organisms often live in close proximity to disease-causing pathogens, they have been of interest to applied biologists as a potential means to genetically manipulate populations of pest species. As knowledge on these symbiotic associations accumulates from distantly related insect taxa, conserved mechanisms for their transmission and evolutionary histories are beginning to emerge. Here, Serap Aksoy summarizes current knowledge on the functional and evolutionary biology of the multiple symbionts harbored in the medically and agriculturally important insect group, tsetse, and their potential role in the control of trypanosomiasis.     

按蚊肠道微生物及其在阻断疟疾传播上的应用

按蚊体内,尤其是中肠内定殖着大量的微生物群落。肠道菌群通过与按蚊的长期协同进化形成了相互依存的共生关系。肠道共生菌参与调节按蚊的多种生命活动,对于维持按蚊的健康发挥着重要作用,已经成为一个与宿主按蚊密不可分的重要"器官"。研究表明,肠道共生菌在按蚊物质代谢、营养、发育、生殖、免疫调控和免疫防御等生理过程中发挥着重要的调节作用。蚊虫是疟疾、登革、寨卡等多种疾病的传播媒介,而肠道共生菌对寄生虫和病毒在蚊虫肠道内的发育和感染具有重要影响,因此研究蚊虫与共生菌的相互作用有着重要的理论和实践意义。本文将对按蚊肠道共生菌的多样性、生物学功能、与宿主相互作用的机制及其在防治疟疾上的应用进展进行综述,并对未来的研究提出展望。     

昆虫内共生菌及其功能研究进展

昆虫内共生菌与宿主之间的互作关系已逐渐成为昆虫学的研究热点之一。昆虫内共生菌具有协助宿主营养代谢、 逃避天敌攻击和增强抗药性等功能： 通过协助宿主营养代谢, 提供食物中缺乏的营养物质来弥补食物中营养物质的不足; 分泌抗菌肽、 毒素等物质以增强对外源寄生物等的防御能力, 抑制对宿主的不利影响; 同时, 也可以增强宿主抗逆性, 调控植物生理反应, 抑制植物对宿主的不利影响; 利用对抗逆性基因精确的表达调控来增强宿主抗药性等。因此, 内共生菌介导的宿主生物学性状的改变, 扩大了宿主昆虫的生态位, 成为昆虫生长发育过程中的重要调控因子。目前, 昆虫内共生菌的功能往往是通过研究宿主感染共生菌前后性状的变化而证实。近几年, 转录组学、 蛋白质组学、 基因组学等技术的进步, 促进了内共生菌与宿主昆虫共生机制研究的发展。通过研究内共生菌及其功能基因在昆虫种群动态中的作用, 特别是内共生菌感染对宿主生殖、 存活、 适应环境能力的影响, 将有利于揭示内共生菌与宿主的共生机制, 并最终为开发新的防控技术提供理论依据。本文针对昆虫内共生菌的功能进行了综述, 并对日后的研究方向进行了展望, 提供了研究昆虫内共生菌与宿主互作关系的方法及建议。     

Genetics and evolution of triatomines: from phylogeny to vector control

Triatomines are hemipteran bugs acting as vectors of the protozoan parasite Trypanosoma cruzi. This parasite causes Chagas disease, one of the major parasitic diseases in the Americas. Studies of triatomine genetics and evolution have been particularly useful in the design of rational vector control strategies, and are reviewed here. The phylogeography of several triatomine species is now slowly emerging, and the struggle to reconcile the phenotypic, phylogenetic, ecological and epidemiological species concepts makes for a very dynamic field. Population genetic studies using different markers indicate a wide range of population structures, depending on the triatomine species, ranging from highly fragmented to mobile, interbreeding populations. Triatomines transmit T. cruzi in the context of complex interactions between the insect vectors, their bacterial symbionts and the parasites; however, an integrated view of the significance of these interactions in triatomine biology, evolution and in disease transmission is still lacking. The development of novel genetic markers, together with the ongoing sequencing of the Rhodnius prolixus genome and more integrative studies, will provide key tools to expanding our understanding of these important insect vectors and allow the design of improved vector control strategies.     

Examination of the success rate of secondary symbiont manipulation by microinjection methods in the pea aphid system

Insects harbor a wide range of microbial symbionts, but their influence on host phenotypes is described in a limited number of biological models. One experimental approach to gain knowledge on the effects of symbionts to their hosts is to create insect lines with and without symbionts and examine their phenotypes. However, the success rate of symbiont elimination and introduction methods is dependent on several parameters that are scarcely tested or described. The pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), is a model insect of symbiosis studies. It harbors a primary symbiont that supplies the host with essential amino acids, and an array of secondary symbionts whose effects have been assessed by manipulating their presence/absence in the insect. Here, we describe the influence of key parameters on the success rate of symbiont manipulation using the pea aphid–secondary symbiont system. We compared two elimination methods differing in antibiotic treatment using several aphid–symbiont combinations. We also created new aphid host–symbiont combinations by secondary symbiont introduction and examined the effects of larval stage of recipient aphids on introduction success. Our study revealed that the aphid–symbiont combination has strong influence on both symbiont introduction and elimination success rates, and that the type of antibiotics and the larval stage of recipient aphids influence the elimination and introduction success rate, respectively.     

Culture and manipulation of insect facultative symbionts

Insects from many different taxonomic groups harbor maternally transmitted bacterial symbionts. Some of these associations are ancient in origin and obligate in nature whereas others originated more recently and are facultative. Previous research focused on the biology of ancient obligate symbionts with essential nutritional roles in their insect hosts. However, recent important advances in understanding the biology of facultative associations have been driven by the development of techniques for the culture, genetic modification and manipulation of facultative symbionts. In this review, we examine these available experimental techniques and illustrate how they have provided fascinating new insight into the nature of associations involving facultative symbionts. We also propose a rationale for future research based on the integration of genomics and experimentation.     

昆虫共生细菌Rickettsia的研究进展

Rickettsia是传播和引起人类与其他脊椎动物疾病的胞内共生菌。引起脊椎动物疾病的这些Rickettsia, 其部分生活史是在节肢动物体内完成的;而另外许多Rickettsia, 其整个生活史都是在宿主节肢动物体内完成。为了叙述方便, 把前者称为脊椎动物Rickettsia, 后者称为节肢动物Rickettsia。过去的研究主要集中在医学上具有重大意义的脊椎动物Rickettsia, 而关于节肢动物Rickettsia的生物学特性等研究则相对较少。近年来, 研究者们加大了对昆虫Rickettsia的研究, 发现昆虫Rickettsia广泛分布于昆虫中, 且有两种存在形式。其可以通过垂直卵传的方式在世代间传递, 也可以通过寄生蜂和寄主植物达到在昆虫之间传播的目的。昆虫Rickettsia可通过诱导孤雌生殖、 诱导杀雄等方式影响宿主的生殖行为。其对不同宿主昆虫可产生对宿主有利或有害的作用;可增强宿主昆虫抵御高温和寄生蜂的能力, 与宿主昆虫对药剂的敏感性相关。最后, 昆虫Rickettsia具有一个简化的基因组, 且存在进一步减小的可能性。     

The evolutionary ecology of symbiont‐conferred resistance to parasitoids in aphids

Aphids may harbor a wide variety of facultative bacterial endosymbionts. These symbionts are transmitted maternally with high fidelity and they show horizontal transmission as well, albeit at rates too low to enable infectious spread. Such symbionts need to provide a net fitness benefit to their hosts to persist and spread. Several symbionts have achieved this by evolving the ability to protect their hosts against parasitoids. Reviewing empirical work and some models, I explore the evolutionary ecology of symbiont‐conferred resistance to parasitoids in order to understand how defensive symbiont frequencies are maintained at the intermediate levels observed in aphid populations. I further show that defensive symbionts alter the reciprocal selection between aphids and parasitoids by augmenting the heritable variation for resistance, by increasing the genetic specificity of the host–parasitoid interaction, and by inducing environment‐dependent trade‐offs. These effects are conducive to very dynamic, symbiont‐mediated coevolution that is driven by frequency‐dependent selection. Finally I argue that defensive symbionts represent a problem for biological control of pest aphids, and I propose to mitigate this problem by exploiting the parasitoids’ demonstrated ability to rapidly evolve counteradaptations to symbiont‐conferred resistance.     

Addicted? Reduced host resistance in populations with defensive symbionts

Heritable symbionts that protect their hosts from pathogens have been described in a wide range of insect species. By reducing the incidence or severity of infection, these symbionts have the potential to reduce the strength of selection on genes in the insect genome that increase resistance. Therefore, the presence of such symbionts may slow down the evolution of resistance. Here we investigated this idea by exposing Drosophila melanogaster populations to infection with the pathogenic Drosophila C virus (DCV) in the presence or absence of Wolbachia, a heritable symbiont of arthropods that confers protection against viruses. After nine generations of selection, we found that resistance to DCV had increased in all populations. However, in the presence of Wolbachia the resistant allele of pastrel—a gene that has a major effect on resistance to DCV—was at a lower frequency than in the symbiont-free populations. This finding suggests that defensive symbionts have the potential to hamper the evolution of insect resistance genes, potentially leading to a state of evolutionary addiction where the genetically susceptible insect host mostly relies on its symbiont to fight pathogens.