Fungal–bacterial interactions and their relevance in health

Cross‐kingdom interactions between bacteria and fungi are a common occurrence in the environment. Recent studies have identified various types of interactions that either can take the form of a synergistic relationship or can result in an antagonistic interplay with the subsequent destruction or inhibition of growth of bacteria, fungi or both. This cross‐kingdom communication is of particular significance in human health and disease, as bacteria and fungi commonly colonize various human surfaces and their interactions can at times alter the outcome of invasive infections. Moreover, mixed infections from both bacteria and fungi are relatively common among critically ill patients and individuals with weak immune responses. The purpose of this review is to summarize our knowledge on the type of interactions between bacteria and fungi and their relevance in human infections.     

白假丝酵母与细菌相互作用机制及其与感染的关系

人体内定植着数目庞大、结构复杂的细菌及真菌等微生物群,它们之间存在复杂的相互作用。既往研究主要集中于细菌或真菌的某个单一物种,但最近研究表明,细菌与真菌之间的相互作用对更好地理解体内的微生态系统至关重要。白假丝酵母(又称白念珠菌)是人备体中最常见的机会性致病真菌,通常被认为是人类正常菌群的一部分。白念珠菌与细菌的相互作用近年来备受关注,其协同和拮抗作用有助于维持不同物种间复杂的平衡关系。了解白念珠菌与细菌的相互作用,不仅可加深对微生物致病机制的理解,还可为预防和治疗白念珠菌或细菌感染及新型抗菌药物研发提供新途径。本文就白念珠菌与细菌共存时的相互作用机制及其对人类健康、疾病的影响进行综述,从而为控制念珠菌或细菌感染提供新的策略。     

两种枝顶孢霉胞内细菌的分离鉴定及种群演替

分离、鉴定了枝顶孢霉(Acremonium strictum Gams.)2种胞内细菌,探讨了细菌在其宿主真菌菌丝细胞内的种群演替规律。结果表明,2种胞内细菌分别为不动杆菌Epbas6菌株(Acinetobacter sp.Epbas6)和地衣芽孢杆菌(Bacillus licheniformis)。镜检分析和原始分离物菌落统计表明,不动杆菌和地衣芽孢杆菌的比例为77.5∶1;然而,4℃保藏6个月的真菌分离物中不动杆菌的数量大大减少,地衣芽孢杆菌占据优势,二者的比例变为1∶50.45;而保藏12个月的真菌分离物中只有地衣芽孢杆菌。根据2种细菌的16SrDNA保守序列设计引物,分别扩增了保藏6个月和12个月的枝顶孢霉分离物,发现保藏6个月的分离物能够扩增出2种细菌的保守序列,而保藏12个月的分离物只能扩增出地衣芽孢杆菌保守序列。研究结果说明在枝顶孢霉人工培养和菌种保藏过程中,2种细菌在其宿主真菌菌丝细胞内发生着复杂的生态互作,存在着动态种群演替过程。     

Crossing the kingdom border: Human diseases caused by plant pathogens

Interactions between pathogenic microorganisms and their hosts are varied and complex, encompassing open-field scale interactions to interactions at the molecular level. The capacity of plant pathogenic bacteria and fungi to cause diseases in human and animal systems was, until recently, considered of minor importance. However, recent evidence suggests that animal and human infections caused by plant pathogenic fungi, bacteria and viruses may have critical impacts on human and animal health and safety. This review analyses previous research on plant pathogens as causal factors of animal illness. In addition, a case study involving disruption of type III effector-mediated phagocytosis in a human cell line upon infection with an opportunistic phytopathogen, Pseudomonas syringae pv. tomato, is discussed. Further knowledge regarding the molecular interactions between plant pathogens and human and animal hosts is needed to understand the extent of disease incidence and determine mechanisms for disease prevention.     

肠道微生物与人体健康研究进展

人类肠道中定居着许多对宿主有益的微生物,包括细菌、病毒、真核生物等,它们在肠道内能与其他微生物及免疫系统相互作用,对人体健康具有重要影响,被称为"被遗忘的器官",它们的基因组也被誉为人类的"第二基因组",与人体的能量代谢及物质代谢有关。本文总结了人体肠道中病毒、真核生物、细菌和宿主免疫系统的相互作用,微生物群的失衡可能导致的疾病如肥胖和克罗恩病等,以及微生物环境在人体内的成熟过程,期望有助于诊断和治疗与肠道微生物失衡相关的疾病。     

Metagenomic assessment of the global diversity and distribution of bacteria and fungi

Bacteria and fungi are of uttermost importance in determining environmental and host functioning. Despite close interactions between animals, plants, their associated microbiomes, and the environment they inhabit, the distribution and role of bacteria and especially fungi across host and environments as well as the cross-habitat determinants of their community compositions remain little investigated. Using a uniquely broad global dataset of 13 483 metagenomes, we analysed the microbiome structure and function of 25 host-associated and environmental habitats, focusing on potential interactions between bacteria and fungi. We found that the metagenomic relative abundance ratio of bacteria-to-fungi is a distinctive microbial feature of habitats. Compared with fungi, the cross-habitat distribution pattern of bacteria was more strongly driven by habitat type. Fungal diversity was depleted in host-associated communities compared with those in the environment, particularly terrestrial habitats, whereas this diversity pattern was less pronounced for bacteria. The relative gene functional potential of bacteria or fungi reflected their diversity patterns and appeared to depend on a balance between substrate availability and biotic interactions. Alongside helping to identify hotspots and sources of microbial diversity, our study provides support for differences in assembly patterns and processes between bacterial and fungal communities across different habitats.     

In Vitro Interactions Between Yeasts and Bacteria and the Fungal Symbionts of the Mountain Pine Beetle (Dendroctonus ponderosae)

Multi-trophic interactions between prokaryotes, unicellular eukaryotes, and ecologically intertwined metazoans are presumably common in nature, yet rarely described. The mountain pine beetle, Dendroctonus ponderosae, is associated with two filamentous fungi, Grosmannia clavigera and Ophiostoma montium. Other microbes, including yeasts and bacteria, are also present in the phloem, but it is not known whether they interact with the symbiotic fungi or the host beetle. To test whether such interactions occur, we performed a suite of in vitro assays. Overall, relative yield of O. montium grown with microbes isolated from larval galleries was significantly greater than when the fungus was grown alone. Conversely, the yield of G. clavigera grown with these same microbes was less than or equal to when it was grown alone, suggesting that O. montium, and at least some microbes in larval galleries, have a mutualistic or commensal relationship, while G. clavigera and those same microbes have an antagonistic relationship. A bacterium isolated from phloem not colonized by beetles was found to inhibit growth of both G. clavigera and O. montium and appears to be an antagonist to both fungi. Our results suggest that bacteria and yeasts likely influence the distribution of mycangial fungi in the host tree, which, in turn, may affect the fitness of D. ponderosae.     

Production of cross-kingdom oxylipins by pathogenic fungi: An update on their role in development and pathogenicity

Oxylipins are a class of molecules derived from the incorporation of oxygen into polyunsaturated fatty acid substrates through the action of oxygenases. While extensively investigated in the context of mammalian immune responses, over the last decade it has become apparent that oxylipins are a common means of communication among and between plants, animals, and fungi to control development and alter hostmicrobe interactions. In fungi, some oxylipins are derived nonenzymatically while others are produced by lipoxygenases, cyclooxygenases, and monooxygenases with homology to plant and human enzymes. Recent investigations of numerous plant and human fungal pathogens have revealed oxylipins to be involved in the establishment and progression of disease. This review highlights oxylipin production by pathogenic fungi and their role in fungal development and pathogen/host interactions.     

Masters of conquest and pillage: Xenorhabdus nematophila global regulators control transitions from virulence to nutrient acquisition

Invertebrate animal models are experimentally tractable and have immunity and disease symptoms that mirror those of vertebrates. Therefore they are of particular utility in understanding fundamental aspects of pathogenesis. Indeed, artificial models using human pathogens and invertebrate hosts have revealed conserved and novel molecular mechanisms of bacterial infection and host immune responses. Additional insights may be gained from investigating interactions between invertebrates and pathogens they encounter in their natural environments. For example, enteric bacteria in the genera Photorhabdus and Xenorhabdus are pathogens of insects that also mutualistically associate with nematodes in the genera Heterorhabditis and Steinernema respectively. These bacteria serve as models to understand naturally occurring symbiotic associations that result in disease in or benefit for animals. Xenorhabdus nematophila is the best-studied species of its genus with regard to the molecular mechanisms of its symbiotic associations. In this review, we summarize recent advances in understanding X. nematophila –host interactions. We emphasize regulatory cascades involved in coordinating transitions between various stages of the X. nematophila life cycle: infection, reproduction and transmission.     

Predicting and Analyzing Interactions between Mycobacterium tuberculosis and Its Human Host

The outcome of infection by Mycobacterium tuberculosis (Mtb) depends greatly on how the host responds to the bacteria and how the bacteria manipulates the host, which is facilitated by protein–protein interactions. Thus, to understand this process, there is a need for elucidating protein interactions between human and Mtb, which may enable us to characterize specific molecular mechanisms allowing the bacteria to persist and survive under different environmental conditions. In this work, we used the interologs method based on experimentally verified intra-species and inter-species interactions to predict human-Mtb functional interactions. These interactions were further filtered using known human-Mtb interactions and genes that are differentially expressed during infection, producing 190 interactions. Further analysis of the subcellular location of proteins involved in these human-Mtb interactions confirms feasibility of these interactions. We also conducted functional analysis of human and Mtb proteins involved in these interactions, checking whether these proteins play a role in infection and/or disease, and enriching Mtb proteins in a previously predicted list of drug targets. We found that the biological processes of the human interacting proteins suggested their involvement in apoptosis and production of nitric oxide, whereas those of the Mtb interacting proteins were relevant to the intracellular environment of Mtb in the host. Mapping these proteins onto KEGG pathways highlighted proteins belonging to the tuberculosis pathway and also suggested that Mtb proteins might use the host to acquire nutrients, which is in agreement with the intracellular lifestyle of Mtb. This indicates that these interactions can shed light on the interplay between Mtb and its human host and thus, contribute to the process of designing novel drugs with new biological mechanisms of action.     

Iron and siderophores in fungal–host interactions

Most fungi and bacteria express specific mechanisms for the acquisition of iron from the hosts they infect for their own survival. This is primarily because iron plays a key catalytic role in various vital cellular reactions in conjunction with the fact that iron is not freely available in these environments due to host sequestration. High-affinity iron uptake systems, such as siderophore-mediated iron uptake and reductive iron assimilation, enable fungi to acquire limited iron from animal or plant hosts. Regulating iron uptake is crucial to maintain iron homeostasis, a state necessary to avoid iron-induced toxicity from iron abundance, while simultaneously supplying iron required for biochemical demand. Siderophores play diverse roles in fungal–host interactions, many of which have been principally delineated from gene deletions in non-ribosomal peptide synthetases, enzymes required for siderophore biosynthesis. These analyses have demonstrated that siderophores are required for virulence, resistance to oxidative stress, asexual/sexual development, iron storage, and protection against iron-induced toxicity in some fungal organisms. In this review, the strategies fungi employ to obtain iron, siderophore biosynthesis, and the regulatory mechanisms governing iron homeostasis will be discussed with an emphasis on siderophore function and relevance for fungal organisms in their interactions with their hosts.     

Perspectives on interactions between lactoferrin and bacteria.

Lactoferrin has long been recognized for its antimicrobial properties, initially attributed primarily to iron sequestration. It has since become apparent that interaction between the host and bacteria is modulated by a complex series of interactions between lactoferrin and bacteria, lactoferrin and bacterial products, and lactoferrin and host cells. The primary focus of this review is the interaction between lactoferrin and bacteria, but interactions with the lactoferrin-derived cationic peptide lactoferricin will also be discussed. We will summarize what is currently known about the interaction between lactoferrin (or lactoferricin) and surface or secreted bacterial components, comment on the potential physiological relevance of the findings, and identify key questions that remain unanswered.     

A centralized resource for bacterial–fungal interactions research

Research on bacterial-fungal interactions (BFIs) has revealed that fungi and bacteria frequently interact with one another within diverse ecosystems and microbiomes. Assessing the current state of knowledge within the field of BFI research, particularly with respect to what interactions between bacteria and fungi have been previously described, is very challenging and time consuming. This is largely due to a lack of any centralized resource, with reports of BFIs being spread across publications in numerous journals using non-standardized text to describe the relationships. To address this issue, we have developed the BFI Research Portal, a publicly accessible database of previously reported interactions between bacterial and fungal taxa to serve as a centralized resource for the field. Users can query bacterial or fungal taxa to see what members from the other kingdom have been observed as interaction partners. Search results are accompanied by interactive and intuitive visual outputs, and the database is a dynamic resource that will be updated as new BFIs are reported.     

真菌内共生细菌研究进展

自真菌内共生细菌在1970年被首次发现以来,各个时期的学者都采用当时流行的研究方法关注宿主真菌及其内共生细菌之间的关联现象。近年来科技手段日益多样,对二者相互作用的探索逐渐成为新的研究热点,随着研究的不断拓展和深入,越来越多的生物学现象和原理被揭示。本文在真菌内共生细菌的研究方法、定殖位置、形态、分类、宿主类群、共生关联的建立、生物学功能、宿主治愈、分离和重新植入等方面进行综述,并在此基础上进行展望,以期为真菌内共生细菌的广泛深入研究提供借鉴。     

RNA profiling in host-pathogen interactions

The development of novel anti-bacterial treatment strategies will be aided by an increased understanding of the interactions that take place between bacteria and host cells during infection. Global expression profiling using microarray technologies can help to describe and define the mechanisms required by bacterial pathogens to cause disease and the host responses required to defeat bacterial infection.     

Interference with the Host Haemostatic System by Schistosomes

Schistosomes, parasitic flatworms that cause the tropical disease schistosomiasis, are still a threat. They are responsible for 200 million infections worldwide and an estimated 280,000 deaths annually in sub-Saharan Africa alone. The adult parasites reside as pairs in the mesenteric or perivesicular veins of their human host, where they can survive for up to 30 years. The parasite is a potential activator of blood coagulation according to Virchow''s triad, because it is expected to alter blood flow and endothelial function, leading to hypercoagulability. In contrast, hepatosplenic schistosomiasis patients are in a hypocoagulable and hyperfibrinolytic state, indicating that schistosomes interfere with the haemostatic system of their host. In this review, the interactions of schistosomes with primary haemostasis, secondary haemostasis, fibrinolysis, and the vascular tone will be discussed to provide insight into the reduction in coagulation observed in schistosomiasis patients.Interference with the haemostatic system by pathogens is a common mechanism and has been described for other parasitic worms, bacteria, and fungi as a mechanism to support survival and spread or enhance virulence. Insight into the mechanisms used by schistosomes to interfere with the haemostatic system will provide important insight into the maintenance of the parasitic life cycle within the host. This knowledge may reveal new potential anti-schistosome drug and vaccine targets. In addition, some of the survival mechanisms employed by schistosomes might be used by other pathogens, and therefore, these mechanisms that interfere with host haemostasis might be a broad target for drug development against blood-dwelling pathogens. Also, schistosome antithrombotic or thrombolytic molecules could form potential new drugs in the treatment of haemostatic disorders.     

MicroMeeting: Who's talking to whom? Epithelial–bacterial pathogen interactions

Our perception that host-bacterial interactions lead to disease comes from rare, unsuccessful interactions resulting in the development of detectable symptoms. In contrast, the majority of host-bacterial interactions go unnoticed as the host and bacteria perceive each other to be no threat. In July 2004, a focused international symposium on epithelial-bacterial pathogen interactions was held in Newcastle upon Tyne (UK). The symposium concentrated on recent advances in our understanding of bacterial interactions at respiratory and gastrointestinal mucosal epithelial layers. For the host these epithelial tissues represent a first line of defence against invading bacterial pathogens. Through the discovery that the innate immune system plays a pivotal role during host-bacterial interactions, it has become clear that epithelia are being utilized by the host to monitor or communicate with both pathogenic and commensal bacteria. Interest in understanding the bacterial perspective of these interactions has lead researchers to realize that the bacteria utilize the same factors associated with disease to establish successful long-term interactions. Here we discuss several common themes and concepts that emerged from recent studies that have allowed physiologists and microbiologists to interact at a common interface similar to their counterparts -- epithelia and bacterial pathogens. These studies highlight the need for further multidisciplinary studies into how the host differentiates between pathogenic and commensal bacteria.     

The transmission of digenetic trematodes: style, elegance, complexity

Traditionally, the field of parasitology has dealt with eukaryoticanimals, to the exclusion of viruses, bacteria, fungi, etc.,which is the way it will be approached here. The focus of thepresent paper will be on certain ecological aspects of the lifecycles and life-history strategies employed by the Digenea,a diverse group of platyhelminths that includes some 25,000species. More specifically, the review will consider the natureof host/parasite interactions within molluscan intermediatehosts and the manner in which these interactions, or lack thereof,function in structuring trematode infracommunities within thesemolluscan intermediate hosts. Literature in this area suggeststhat predation/competition may be a significant structuringforce for infracommunities in certain marine prosobranchs, butnot others, and that temporal/spatial factors may be involvedas structuring mechanisms in at least some freshwater pulmonates.     

噬菌体疗法在疾病中的应用进展

随着耐药菌在世界范围内不断传播,应用噬菌体作为有效的抗生素替代疗法重新受到研究者的关注。另一方面,人体微生物群与宿主健康的相互作用研究不断深入,靶向调控微生物群来影响人体健康成为多项研究的关注焦点,利用噬菌体靶向降低与疾病发展正相关的特征性细菌的丰度,成为肿瘤、酒精性肝病及糖尿病等非感染性疾病更精准的预防或辅助治疗策略。本文对噬菌体疗法在感染性和非感染性疾病中的应用进展进行了综述。     

微生物共同作用下的铁皮石斛组培苗生长效应研究

植物体和植物根际均是复杂的微生态系统,其内栖息着关系复杂的共生微生物,共同影响植物的生长发育.为探讨混合接种真菌与细菌对兰科植物生长的影响,筛选出真菌与细菌的优势促生组合,本研究选取经分离、筛选获得的4株促生内生真菌(铁皮石斛内生真菌C22、C35,美花石斛内生真菌L12、L28)和3株促生内生细菌(铁皮石斛菌内生细菌TX-7、TX-16、TX-19),以"真菌+细菌"的方式混合接种于铁皮石斛无菌组培苗中,共培养120 d.结果获得了3组优势组合:C22+TX-19、L28+TX-16和L28+TX-19,它们对铁皮石斛组培苗的生长均表现出正效应,其中C22+TX-19和L28+TX-19对促进组培苗生物量的增长具有协同效应,L28+TX-19对提高组培苗的根分枝率具有协同效应,3个组合对增加组培苗的分蘖数和根尖数均表现为累加效应.研究结果表明,内生真菌与内生细菌的共同作用可显著促进铁皮石斛的生长,混合接种有可能更大地发挥微生物的效能.