肠道菌群在蜜蜂健康与疾病中的作用研究进展

蜜蜂是重要的经济昆虫,在农作物授粉和维持生态平衡等方面扮演了重要角色。随着生态环境的逐步恶化,蜜蜂极易受到寄生虫、农药、抗生素和病原微生物等的危害。肠道作为蜜蜂的重要免疫器官,在抵抗外源刺激等方面具有不可替代的作用。而肠道菌群作为肠道的重要组成部分,对蜜蜂的健康有着至关重要的影响。其拥有高度保守和专门的核心微生物群,主要由九大类细菌组成。近年来,有关肠道菌群的研究主要集中在新陈代谢、免疫防御、生长发育等方面。肠道菌群不仅可以帮助宿主消化和制造营养素,还可维持宿主体内能量稳态,其对蛋白质的代谢也使菌群丰度增加。越来越多的证据表明,肠道菌群紊乱会导致蜜蜂健康受损,其多样性对宿主健康和疾病影响甚广。因此,肠道菌群成为近年来微生物学领域研究的焦点。主要综述了蜜蜂属、熊蜂属等主要传粉蜂类肠道菌群的组成及其在健康与疾病中的作用,为深入了解传粉昆虫肠道菌群功能提供参考。     

蜜蜂肠道菌群结构功能研究进展

在长期的共同进化中,肠道菌群与其宿主形成了紧密的联系,为宿主提供了许多有益的作用。作为一种社会性昆虫,蜜蜂的生活习性为其肠道菌群提供了良好而稳定的传播途径,因此,蜜蜂与其肠道菌群形成了一种紧密的互惠互利共生关系。近年来,随着对蜜蜂肠道菌群了解的不断加深,对蜜蜂肠道菌群功能的研究也不断深入,大量研究表明蜜蜂的肠道菌群在宿主食物的消化代谢、宿主免疫的激活和抵抗致病菌、调节宿主生理等方面都有着重要的作用,同时破坏肠道菌群的稳定对蜜蜂的健康有着明显的负面影响。本文对近年来西方蜜蜂肠道菌群功能研究进行了总结,旨在为进一步深入探索蜜蜂肠道菌群与其宿主的相互作用及在养蜂生产上应用肠道菌群防控疾病提供参考。     

蜜蜂肠道菌群定殖研究进展

肠道菌群在其宿主健康中发挥着各种各样的重要功能。蜜蜂是高度社会化的昆虫,其肠道菌群与大多数昆虫明显不同,由兼性厌氧和微好氧的细菌组成,具有高度保守性和专门的核心肠道微生物群。近年来的研究表明,蜜蜂肠道微生物群在代谢、免疫功能、生长发育以及保护机体免受病原体侵袭等方面起着重要作用,并已证实肠道微生物在蜜蜂健康和疾病中起着重要作用,肠道微生物群的破坏对蜜蜂健康会产生不利影响。本文综述了蜜蜂肠道菌群的特征及菌群定殖研究进展,介绍了蜜蜂的日龄、群体、季节等对蜜蜂肠道菌群定殖的影响,探讨了宿主的功能和新陈代谢对肠道菌群的影响。     

果蝇肠道共生菌对宿主作用的研究进展

肠道共生菌是动物体内的重要组成部分,在宿主的生长发育和健康等方面发挥着重要作用,近年来已成为国内外的研究热点。果蝇作为研究肠道微生物菌群功能的优秀模型,在肠道共生菌与宿主关系研究方面已取得许多重要进展。在本文中,我们首先对果蝇肠道微生物的组成和特征作了总结,然后对果蝇肠道共生菌在其生长发育、营养与代谢、行为反应、寿命以及免疫与疾病方面的作用进行了综述,以期为研究人类肠道共生菌功能和肠道健康提供一定理论依据和新的思路。     

单胃动物肠道微生物菌群与肠道免疫功能的相互作用

动物胃肠道栖息着大量的微生物,这些微生物及其代谢产物在营养、免疫等方面对宿主的健康有重要的意义。近年来研究发现肠道微生物与免疫系统间存在密切的交流和互作机制,尽管肠道共生菌具有定植抑制效应,但肠道微生物也可通过其特定组分刺激免疫细胞如Tregs细胞、Th17细胞的分化,肠道菌群的紊乱可能导致细菌移位、肠道屏障功能损伤,影响机体健康。宿主免疫系统可通过分泌多种免疫效应因子如MUC、sIgA、ITF、RegIIIγ、α-防御素等调节肠道微生物的分布和组成,调节肠道菌群的稳态。本文综述了单胃动物肠道微生物菌群的组成,深入探讨了肠道微生物菌群与动物肠道免疫功能之间的相互作用。     

蜜蜂肠道菌群的培养方法及特性研究进展

肠道菌群在蜜蜂的消化、营养和抗病性等方面发挥了很多潜在的益生作用。为了加深对以蜜蜂为主的传粉昆虫肠道菌群的了解,本文综述了蜜蜂肠道菌群的人工厌氧培养方法及特性,重点综述了Snodgrassella属、Gilliamella属、Frischella属、Lactobacillus属、Bifidobacterium属和Alpha-1,Alpha-2厌氧细菌类群。旨在通过特定的培养方法获取纯培养的细菌,以供进一步研究特定肠道菌群与特定功能的直接联系。希望这些培养技术能帮助大家提升对蜜蜂肠道共生菌在蜜蜂营养和健康方面所起的作用有所了解。     

肠道菌群功能与影响因素研究进展

人体肠道作为一种营养丰富的天然环境有多达100兆个微生物,其中绝大多数存于结肠内,密度接近1011~1012/m L。人类肠道内的微生物多样性是微生物菌落和宿主共同进化的结果,自然选择和进化使肠道菌群与宿主处于一种动态平衡且稳定的关系。文章综述了肠道菌群对宿主可能产生的影响以及引起肠道菌群发生改变的某些因素,肠道微生物影响宿主的代谢、营养吸收、免疫功能以及神经功能调节,而饮食及其他条件又能引起肠道菌群的改变。深入分析肠道菌群的具体结构、探索不同微生物在宿主体内究竟发挥着怎样的作用以及如何充分利用微生物的不同特性改善人类健康应成为今后研究的重点方向。     

油茶地蜂不同龄期幼虫肠道细菌多样性及其差异分析

蜜蜂肠道微生物在其宿主健康与调控宿主生长发育中起着重要作用。油茶地蜂Andrena camellia Wu是油茶的优势传粉昆虫。本研究从野外挖掘该蜂典型样地的巢穴得到油茶地蜂1~5龄及滞育阶段的幼虫,通过PCR扩增得到幼虫肠道微生物16S rRNA基因文库,利用Illumina Miseq二代高通量测序技术首次研究了油茶地蜂不同龄期幼虫肠道细菌的群落结构和多样性。结果显示,油茶地蜂幼虫肠道细菌菌群共检测到27个门,72个纲,155个目,278个科,570个属。其中,最主要的门为变形菌门Proteobacteria（占40.05%）,最主要的目为乳杆菌目Lactobacillales（占12.16%）,最主要的科为乳杆菌科Lactobacillaceae(占11.27%）,最主要的属是乳杆菌属Lactobacillus（占11.27%）。核心细菌群落组间差异、Alpha多样性以及Beta多样性分析显示：不同龄期油茶地蜂幼虫肠道细菌群落在组成、多样性以及结构上均存在显著差异。线性判别分析结果显示,不动杆菌属Acinetobacter和红球菌属Rhodococcus主要存在于5龄幼虫阶段,巴尔通氏体属Bartonella和肠杆菌属Enterobacter主要存在于1龄幼虫阶段。本研究明确了油茶地蜂不同龄期幼虫肠道微生物组成、优势菌群及其群落变化规律,为油茶地蜂等土壤筑巢独栖野生蜜蜂肠道微生物学及其保护生物学的相关研究提供理论依据及研究角度。     

microRNA 对宿主和肠道微生物互作的调控

摘要:肠道内环境是宿主和肠道微生物菌群互作的结果,肠道菌群一方面通过抗原物质调节肠道组织的免疫稳定,另一方面,肠道菌群参与糖、脂、蛋白质代谢,产生的代谢产物能够调控细菌营养代谢、群体结构和肠道组织的营养吸收等。microRNA是宿主细胞内调控基因表达的重要因子,肠道微生物菌群不仅调控宿主mRNA的转录,同时也影响某些基因的转录后修饰。研究表明,肠道菌群通过与宿主肠道组织互作,调节肠上皮组织内某些参与炎症应答和屏障功能的microRNA 的表达。本文介绍了肠道微生物与宿主互作的基本内容,对microRNA在肠道微生物与宿主互作和肠道健康中的调节进行综述。     

用于蜜蜂和熊蜂肠道微生物分类的细菌16S rRNA数据库优化

蜜蜂和熊蜂是重要的传粉昆虫, 对农业生产及生态平衡的维持具有重要作用。近年来, 研究发现蜜蜂及熊蜂肠道内含有大量微生物, 其组成简单、特异。正常的肠道微生物群落对蜜蜂的生长、激素调节、致病菌抵抗等具有重要作用。随着高通量测序的发展, 研究者们也可快速获得传粉蜂肠道微生物组成, 这给生物多样性和物种保护及蜂类健康等的研究带来了便捷。但是由于蜜蜂和熊蜂肠道微生物群落均由特殊菌种组成, 目前的细菌16S rRNA数据库无法对其进行准确的分类, 并且部分东方蜜蜂(Apis cerana)特有的肠道微生物菌种缺乏16S rRNA序列信息。本文从来源于5个不同省份的东方蜜蜂肠道中分离得到在东方蜜蜂中普遍含有的Apibacter菌属纯菌, 获取其全长16S rRNA序列, 并对目前蜜蜂和熊蜂肠道的5个核心菌种的分类进行了综述, 对其分类和命名进行了修正。根据蜜蜂肠道微生物的明确分类, 在目前常用的SILVA细菌分类数据库基础之上对其进行了命名及分类优化, 并加入东方蜜蜂中普遍含有的Apibacter序列, 从而获得了优化数据库Bee Gut Microbiota-Database (BGM-Db)。通过1组东方蜜峰及1组西方蜜蜂(Apis mellifera)的肠道菌群高通量测序结果, 分析不同数据库的表现, 我们发现相比于SILVA和Ribosomal Database Project (RDP), BGM-Db对蜜蜂肠道16S rRNA高通量测序短序列实现了菌种级别的分类, 分辨率更高。     

常见疾病、抗生素及农药对意大利蜜蜂(Apis mellifera ligustica)肠道微生物多样性的影响研究进展

蜜蜂是对农业生产十分重要的授粉昆虫。蜜蜂肠道微生物与蜜蜂健康有密切关系,但肠道微生物也会受多种外界因素的影响。本文就蜜蜂疾病、抗生素等蜂病治疗药物、农药,以及益生菌的应用等对意大利蜜蜂工蜂肠道微生物影响的研究进行了归纳总结,并对蜜蜂与其肠道菌关系研究进行了展望。     

Gut microbiota composition of Japanese macaques associates with extent of human encroachment

In recent decades, human–wildlife interaction and associated anthropogenic food provisioning has been increasing and becoming more severe due to fast population growth and urban development. Noting the role of the gut microbiome in host physiology like nutrition and health, it is thus essential to understand how human–wildlife interactions and availability of anthropogenic food in habitats can affect an animal's gut microbiome. This study, therefore, set out to examine the gut microbiota of Japanese macaques (Macaca fuscata) with varying accessibility to anthropogenic food and the possibility of using gut microbiota as indicator for macaques’ reliance on anthropogenic food. Using 16S ribosomal RNA gene sequencing, we described the microbial composition of Japanese macaques experiencing different types of human disturbance and anthropogenic food availability—captive, provisioned, crop‐raiding, and wild. In terms of alpha diversity, our results showed that observed richness of gut microbiota did not differ significantly between disturbance types but among collection sites, whereas Shannon diversity index differed by both disturbance types and sites. In terms of beta diversity, captive populations harbored the most distinctive gut microbial composition, and had the greatest difference compared with wild populations. Whereas for provisioned and crop‐raiding groups, the macaques exhibited intermediate microbiota between wild and captive. We identified several potential bacterial taxa at different taxonomic ranks whose abundance potentially could help in assessing macaques’ accessibility to anthropogenic food. This study revealed the flexibility of the gut microbiome of Japanese macaques and provided possible indices based on the gut microbiome profile in assessing macaques’ accessibility to/reliance on anthropogenic foods.     

Diversity and evolutionary patterns of bacterial gut associates of corbiculate bees

The animal gut is a habitat for diverse communities of microorganisms (microbiota). Honeybees and bumblebees have recently been shown to harbour a distinct and species poor microbiota, which may confer protection against parasites. Here, we investigate diversity, host specificity and transmission mode of two of the most common, yet poorly known, gut bacteria of honeybees and bumblebees: Snodgrassella alvi (Betaproteobacteria) and Gilliamella apicola (Gammaproteobacteria). We analysed 16S rRNA gene sequences of these bacteria from diverse bee host species across most of the honeybee and bumblebee phylogenetic diversity from North America, Europe and Asia. These focal bacteria were present in 92% of bumblebee species and all honeybee species but were found to be absent in the two related corbiculate bee tribes, the stingless bees (Meliponini) and orchid bees (Euglossini). Both Snodgrassella alvi and Gilliamella apicola phylogenies show significant topological congruence with the phylogeny of their bee hosts, albeit with a considerable degree of putative host switches. Furthermore, we found that phylogenetic distances between Gilliamella apicola samples correlated with the geographical distance between sampling locations. This tentatively suggests that the environmental transmission rate, as set by geographical distance, affects the distribution of G. apicola infections. We show experimentally that both bacterial taxa can be vertically transmitted from the mother colony to daughter queens, and social contact with nest mates after emergence from the pupa greatly facilitates this transmission. Therefore, sociality may play an important role in vertical transmission and opens up the potential for co‐evolution or at least a close association of gut bacteria with their hosts.     

Beneficial microorganisms for honey bees: problems and progresses

Nowadays, honey bees are stressed by a number of biotic and abiotic factors which may compromise to some extent the pollination service and the hive productivity. The EU ban of antibiotics as therapeutic agents against bee pathogens has stimulated the search for natural alternatives. The increasing knowledge on the composition and functions of the bee gut microbiota and the link between a balanced gut microbiota and health status have encouraged the research on the use of gut microorganisms to improve bee health. Somehow, we are assisting to the transfer of the “probiotic concept” into the bee science. In this review, we examine the role of the honey bee gut microbiota in bee health and critically describe the available applications of beneficial microorganisms as pest control agents and health support. Most of the strains, mainly belonging to the genera Lactobacillus, Bifidobacterium and Bacillus, are isolated from honey bee crop or gut, but some applications involve environmental strains or formulation for animal and human consumption. Overall, the obtained results show the favourable effect of applied microbial strains on bee health and productivity, in particular if strains of bee origin are used. However, it is actually not yet possible to conclude whether this strategy will ever work. In particular, many aspects regarding the overall setup of the experiments, the dose, the timing and the duration of the treatment need to be optimized, also considering the microbiological safety of the hive products (i.e. pollen and honey). In addition, a deep investigation about the effect on host immunity and physiology is envisaged. Lastly, the final users of the formulations, i.e. beekeepers, should be taken into account for the achievement of high-quality, cost-effective and easy-to-use products.     

Human activity can influence the gut microbiota of Darwin's finches in the Galapagos Islands

The gut microbiota of animal hosts can be influenced by environmental factors, such as unnatural food items that are introduced by humans. Over the past 30 years, human presence has grown exponentially in the Galapagos Islands, which are home to endemic Darwin's finches. Consequently, humans have changed the environment and diet of Darwin's finches, which in turn, could affect their gut microbiota. In this study, we compared the gut microbiota of two species of Darwin's finches, small ground finches (Geospiza fuliginosa) and medium ground finches (Geospiza fortis), across sites with and without human presence, where finches prefer human‐processed and natural food, respectively. We predicted that: (a) finch microbiota would differ between sites with and without humans due to differences in diet, and (b) gut microbiota of each finch species would be most similar where finches have the highest niche overlap (areas with humans) compared to the lowest niche overlap (areas without humans). We found that gut bacterial community structure differed across sites and host species. Gut bacterial diversity was most distinct between the two species at the site with human presence compared to the site without human presence, which contradicted our predictions. Within host species, medium ground finches had lower bacterial diversity at the site with human presence compared to the site without human presence and bacterial diversity of small ground finches did not differ between sites. Our results show that the gut microbiota of Darwin's finches is affected differently across sites with varying human presence.     

Honey bee (Apis mellifera) gut microbiota promotes host endogenous detoxification capability via regulation of P450 gene expression in the digestive tract

There is growing number of studies demonstrating a close relationship between insect gut microbiota and insecticide resistance. However, the contribution of the honey bee gut microbiota to host detoxification ability has yet to be investigated. In order to address this question, we compared the expression of cytochrome P450s (P450s) genes between gut microbiota deficient (GD) workers and conventional gut community (CV) workers and compared the mortality rates and the pesticide residue levels of GD and CV workers treated with thiacloprid or tau-fluvalinate. Our results showed that gut microbiota promotes the expression of P450 enzymes in the midgut, and the mortality rate and pesticide residue levels of GD workers are significantly higher than those of CV workers. Further comparisons between tetracycline-treated workers and untreated workers demonstrated that antibiotic-induced gut dysbiosis leads to attenuated expression of P450s in the midgut. The co-treatment of antibiotics and pesticides leads to reduced survival rate and a significantly higher amount of pesticide residues in honey bees. Taken together, our results demonstrated that honey bee gut symbiont could contribute to bee health through the modification of the host xenobiotics detoxification pathways and revealed a potential negative impact of antibiotics to honey bee detoxification ability and health.     

The Effectiveness of Potential Probiotics Lactobacillus rhamnosus Vahe and Lactobacillus delbrueckii IAHAHI in Irradiated Rats Depends on the Nutritional Stage of the Host

Several species of eukaryotic organisms living in the high mountain areas of Armenia with naturally occurring levels of radiation have high adaptive responses to radiation. We speculate on the role of the gastrointestinal microbiota in this protection against radiation. Therefore, seventeen microorganisms with high antagonistic activities against several multi-drug-resistant pathogens were isolated from the human and animal gut microbiota, as well as from traditional Armenian fermented products. These strains were tested in vivo on Wistar rats to determine their ability to protect the eukaryotic host against radiation damages. The efficiency of the probiotics’ application and the dependence on pre- and post-radiation nutrition of rats were described. The effects of Lactobacillus rhamnosus Vahe, isolated from a healthy breastfed infant, and Lactobacillus delbrueckii IAHAHI, isolated from the fermented dairy product matsuni, on the survival of irradiated rats, and their blood leucocyte and glucose levels, were considered to be the most promising, based on this study’s results.

     

Dynamics of gut microbiome upon pollination in bumblebee (Bombus terrestris)

Bumblebees are crucial buzz pollinators of poricidal plants and commercial crops. The population of these crucial pollinators is globally declining. The need to focus on factors contributing to bee health such as gut microbiota is imperative. We evaluated the effect of source on gut microbiota composition in adult worker Bombus terrestris from two environments using multiplexed 16S rRNA amplicon sequencing on the Illumina MiSeq platform. Indoor reared adult worker bees were segregated into non-pollination (NP) and pollination (P) groups. The NP group bumblebees were raised and kept in the insectary for the entire experiment. P group bumblebees worked in a tomato-planted greenhouse for 15 days as pollinators. Our results show that members of Proteobacteria and Firmicutes were significantly different between the two groups. Bifidobacterium bombi (Actinobacteriota) and Candidatus_Schmidhempelia (Proteobacteria) were found to be important gut colonizer exclusive to NP and P group bees, respectively. DESeq2 analysis showed differentially abundant OTUs belonging to Lactobacillus spp. in each group. But for the differentially abundant detected OTUs, resolution till genus level was obtained which impairs our knowledge of the species associated with each group. Our data show that the gut microbiota between the groups differed when indoor- reared adult worker bees were exposed to different environments. The distinct gut microbiota between the two groups may also have been influenced by the different diets fed to bees upon segregation. Further studies can give important insights into the role of gut microbiota on bee health when indoor reared bees are employed for pollination.