The Family Borreliaceae (Spirochaetales), a Diverse Group in Two Genera of Tick-Borne Spirochetes of Mammals, Birds, and Reptiles

Spirochetes of the family Borreliaceae are, with one exception, tick-borne pathogens of a variety of vertebrates. The family at present comprises two genera: Borrelia (Swellengrebel), which includes the agents of relapsing fever, avian spirochetosis, and bovine borreliosis, and Borreliella (Gupta et al.), which includes the agents of Lyme disease and was formerly known as 'Borrelia burgdorferi sensulato complex'. The two genera are distinguished not only by their disease associations but also biological features in the tick vector, including tissue location in unfed ticks and transovarial transmission. Borrelia species transmitted by argasid (soft) ticks tend to have more exclusive relationships with their tick vectors than do other Borrelia species and all Borreliella species that have ixodid (hard) ticks as vectors. The division of genera is supported by phylogenomic evidence from whole genomes and by several specific molecular markers. These distinguishing phylogenetic criteria also applied to three new species or isolates of Borrelia that were discovered in ixodid ticks of reptiles, a monotreme, and birds. Although the deep branching of the family from other spirochetes has been a challenge for inferences about evolution of the family, the discovery of related microorganisms in the gut microbiota of other arachnids suggests an ancestral origin for the family as symbionts of ticks and other arachnids.

Holobionts: Ecological communities, hybrids, or biological individuals? A metaphysical perspective on multispecies systems

Holobionts are symbiotic assemblages composed by a macrobe host (animal or plant) plus its symbiotic microbiota. In recent years, the ontological status of holobionts has created a great amount of controversy among philosophers and biologists: are holobionts biological individuals or are they rather ecological communities of independent individuals that interact together? Chiu and Eberl have recently developed an eco-immunity account of the holobiont wherein holobionts are neither biological individuals nor ecological communities, but hybrids between a host and its microbiota. According to their account, the microbiota is not a proper part of the holobiont. Yet, it should be regarded as a set of scaffolds that support the individuality of the host. In this paper, we approach Chiu and Eberl's account from a metaphysical perspective and argue that, contrary to what the authors claim, the eco-immunity account entails that the microorganisms that compose the host's microbiota are proper parts of the holobiont. Second, we argue that by claiming that holobionts are hybrids, and therefore, not biological individuals, the authors seem to be assuming a controversial position about the ontology of hybrids, which are conventionally characterized as a type of biological individual. In doing so, our paper aligns with the contemporary tendency to incorporate metaphysical resources to shed light on current biological debates and builds on that to provide additional support to the consideration of holobionts as biological individuals from an eco-immunity perspective.

In the beginning: egg-microbe interactions and consequences for animal hosts

Microorganisms are associated with the eggs of many animals. For some hosts, the egg serves as the ideal environment for the vertical transmission of beneficial symbionts between generations, while some bacteria use the egg to parasitize their hosts. In a number of animal groups, egg microbiomes often perform other essential functions. The eggs of aquatic and some terrestrial animals are especially susceptible to fouling and disease since they are exposed to high densities of microorganisms. To overcome this challenge, some hosts form beneficial associations with microorganisms, directly incorporating microbes and/or microbial products on or in their eggs to inhibit pathogens and biofouling. Other functional roles for egg-associated microbiomes are hypothesized to involve oxygen and nutrient acquisition. Although some egg-associated microbiomes are correlated with increased host fitness and are essential for successful development, the mechanisms that lead to such outcomes are often not well understood. This review article will discuss different functions of egg microbiomes and how these associations have influenced the biology and evolution of animal hosts. This article is part of the theme issue 'The role of the microbiome in host evolution'.

Microbiota-host interactions shape ageing dynamics

Occupying the interface between host and environment, host-associated microbes play fundamental roles in nutrient absorption, essential metabolite synthesis, development of the immune system, defence against pathogens and pathogenesis. Microbiota composition and function is rather stable during adulthood, while it dramatically changes during early development, frailty and disease. Ageing is associated with progressive decrease of homeostasis, often resulting in disruption of the physiological balance between host and commensal microbes, ultimately leading to dysbiosis and host demise. Generally, high microbial diversity is associated with health and a youthful state, while low individual microbial diversity and larger inter-individual microbial diversity is associated with ageing and disease states. Different species are equipped with species-specific commensal, symbiotic and pathogenic microbial communities. How and whether the specific host-microbiota consortia co-evolved with host physiology to ensure homeostasis and promote individual fitness remains an open question. In this essay, we propose that the evolution of vertebrate-specific immune adaptations may have enabled the establishment of highly diverse, species-specific commensal microbial communities. We discuss how the maintenance of intact immune surveillance mechanisms, which allow discrimination between commensal and pathogenic bacteria, fail during ageing and lead to the onset of known ageing-related diseases. We discuss how host-microbiota interactions are key to maintaining homeostasis despite external perturbations, but also how they affect a range of host-specific ageing-related phenotypes. This article is part of the theme issue 'The role of the microbiome in host evolution'.

Pathogen resistance may be the principal evolutionary advantage provided by the microbiome

To survive, plants and animals must continually defend against pathogenic microbes that would invade and disrupt their tissues. Yet they do not attempt to extirpate all microbes. Instead, they tolerate and even encourage the growth of commensal microbes, which compete with pathogens for resources and via direct inhibition. We argue that hosts have evolved to cooperate with commensals in order to enhance the pathogen resistance this competition provides. We briefly describe competition between commensals and pathogens within the host, consider how natural selection might favour hosts that tilt this competition in favour of commensals, and describe examples of extant host traits that may serve this purpose. Finally, we consider ways that this cooperative immunity may have facilitated the adaptive evolution of non-pathogen-related host traits. On the basis of these observations, we argue that pathogen resistance vies with other commensal-provided benefits for being the principal evolutionary advantage provided by the microbiome to host lineages across the tree of life. This article is part of the theme issue 'The role of the microbiome in host evolution'.

The skin microbiome of vertebrates

The skin constitutes the primary physical barrier between vertebrates and their external environment. Characterization of skin microorganisms is essential for understanding how a host evolves in association with its microbial symbionts, modeling immune system development, diagnosing illnesses, and exploring the origins of potential zoonoses that affect humans. Although many studies have characterized the human microbiome with culture-independent techniques, far less is known about the skin microbiome of other mammals, amphibians, birds, fish, and reptiles. The aim of this review is to summarize studies that have leveraged high-throughput sequencing to better understand the skin microorganisms that associate with members of classes within the subphylum Vertebrata. Specifically, links will be explored between the skin microbiome and vertebrate characteristics, including geographic location, biological sex, animal interactions, diet, captivity, maternal transfer, and disease. Recent literature on parallel patterns between host evolutionary history and their skin microbial communities, or phylosymbiosis, will also be analyzed. These factors must be considered when designing future microbiome studies to ensure that the conclusions drawn from basic research translate into useful applications, such as probiotics and successful conservation strategies for endangered and threatened animals.

Host diet and evolutionary history explain different aspects of gut microbiome diversity among vertebrate clades

Multiple factors modulate microbial community assembly in the vertebrate gut, though studies disagree as to their relative contribution. One cause may be a reliance on captive animals, which can have very different gut microbiomes compared to their wild counterparts. To resolve this disagreement, we analyze a new, large, and highly diverse animal distal gut 16 S rRNA microbiome dataset, which comprises 80% wild animals and includes members of Mammalia, Aves, Reptilia, Amphibia, and Actinopterygii. We decouple the effects of host evolutionary history and diet on gut microbiome diversity and show that each factor modulates different aspects of diversity. Moreover, we resolve particular microbial taxa associated with host phylogeny or diet and show that Mammalia have a stronger signal of cophylogeny. Finally, we find that environmental filtering and microbe-microbe interactions differ among host clades. These findings provide a robust assessment of the processes driving microbial community assembly in the vertebrate intestine.

Is gastrointestinal microbiota relevant for endogenous mercury methylation in terrestrial animals?

The active role of gastrointestinal microbiota in mercury (Hg) methylation has been investigated in different terrestrial organisms from insects or annelids to rats and mammals, including the human beings. Some findings reveal the animal digestive tracts as new potential niches for Hg methylation especially in terrestrial invertebrates. However, contradictory results have been reported so far and there is still a long way to fully understand how important the MeHg production in this habitat could be, as well as its implications on the toxicity and biomagnification of MeHg within terrestrial food chains. It is important to know what has been studied in the past and discuss the previous results according to the new perspectives opened in this field. Therefore, the aim of this work is to review the present state of knowledge about the potential capability of gastrointestinal microbiota in Hg methylation with special emphasis in terrestrial animals and to propose new approaches profiting the new and powerful molecular and analytical tools.

Borrelia burgdorferi – morphological structure and motility as adaptation for transmission and survival in the habitat of a tick-vertebrate setup

Lyme borreliosis is a multisystem chronic disease caused by Borrelia burgdorferi sensu lato (s.l.) spirochete transmitted by Ixodes. This bacterium has a remarkable ability to survive in tick-vertebrate setup. Its infection causes diagnostic and clinical difficulties. It was distinguished as a separate disease entity over 30 years ago. Observations made by Steere et al. proved to be a milestone since they found correlation between the occurrence of skin and joint lesions with tick bites. Further studies showed that the disease affects not only joints and skin, but also nervous and circulatory systems. Shortly afterwards, an etiological factor was identified – spirochete isolated by W. Burgdorfer (from ticks) as well as Steer and Benach (from blood). Research conducted by other authors confirmed that the spirochete named after its discoverer (Borrelia burgdorferi) is a common etiological factor for disease entities classified as Lyme borreliosis. The high incidence of Lyme borreliosis among the residents of endemic areas, along with diagnostic and therapeutic difficulties, make it a serious academic, clinical and social problem. The present article elaborates on bacterium structure and selected mechanisms facilitating the colonisation of particular hosts. Knowledge of those processes might be useful in understanding complex pathogenesis of lesions occurring in Lyme disease.

Anaplasma phagocytophilum Uses Common Strategies for Infection of Ticks and Vertebrate Hosts

The tick-borne rickettsial pathogen Anaplasma phagocytophilum develops within membrane-bound inclusions in the host cell cytoplasm. This pathogen has evolved with its tick and vertebrate hosts through dynamic processes involving genetic traits of the pathogen and hosts that collectively mediate pathogen infection, development, persistence, and survival. Herein, we challenge the evidence of tick-host-pathogen coevolution by hypothesizing that A. phagocytophilum utilizes common molecular mechanisms for infection in both vertebrate and tick cells, including remodeling of the cytoskeleton, inhibition of cell apoptosis, and manipulation of the immune response. The discovery of these common mechanisms provides evidence that a control strategy could be developed targeted at both vertebrate and tick hosts for more complete control of A. phagocytophilum and its associated diseases.

Indirect short- and long-term effects of aboveground invertebrate and vertebrate herbivores on soil microarthropod communities

Recognition is growing that besides ungulates, small vertebrate and invertebrate herbivores are important drivers of grassland functioning. Even though soil microarthropods play key roles in several soil processes, effects of herbivores-especially those of smaller body size-on their communities are not well understood. Therefore, we progressively excluded large, medium and small vertebrate and invertebrate herbivores for three growing seasons using size-selective fences in two vegetation types in subalpine grasslands; short-grass and tall-grass vegetation generated by high and low historical levels of ungulate grazing. Herbivore exclusions generally had few effects on microarthropod communities, but exclusion of all herbivore groups resulted in decreased total springtail and Poduromorpha richness compared with exclusion of only ungulates and medium-sized mammals, regardless of vegetation type. The tall-grass vegetation had a higher total springtail richness and mesostigmatid mite abundance than the short-grass vegetation and a different oribatid mite community composition. Although several biotic and abiotic variables differed between the exclusion treatments and vegetation types, effects on soil microarthropods were best explained by differences in nutrient and fibre content of the previous year's vegetation, a proxy for litter quality, and to a lesser extent soil temperature. After three growing seasons, smaller herbivores had a stronger impact on these functionally important soil microarthropod communities than large herbivores. Over longer time-scales, however, large grazers created two different vegetation types and thereby influenced microarthropod communities bottom-up, e.g. by altering resource quality. Hence, both short- and long-term consequences of herbivory affected the structure of the soil microarthropod community.

Feedback-based, system-level properties of vertebrate-microbial interactions

Background

Improved characterization of infectious disease dynamics is required. To that end, three-dimensional (3D) data analysis of feedback-like processes may be considered.

Methods

To detect infectious disease data patterns, a systems biology (SB) and evolutionary biology (EB) approach was evaluated, which utilizes leukocyte data structures designed to diminish data variability and enhance discrimination. Using data collected from one avian and two mammalian (human and bovine) species infected with viral, parasite, or bacterial agents (both sensitive and resistant to antimicrobials), four data structures were explored: (i) counts or percentages of a single leukocyte type, such as lymphocytes, neutrophils, or macrophages (the classic approach), and three levels of the SB/EB approach, which assessed (ii) 2D, (iii) 3D, and (iv) multi-dimensional (rotating 3D) host-microbial interactions.

Results

In all studies, no classic data structure discriminated disease-positive (D+, or observations in which a microbe was isolated) from disease-negative (D–, or microbial-negative) groups: D+ and D– data distributions overlapped. In contrast, multi-dimensional analysis of indicators designed to possess desirable features, such as a single line of observations, displayed a continuous, circular data structure, whose abrupt inflections facilitated partitioning into subsets statistically significantly different from one another. In all studies, the 3D, SB/EB approach distinguished three (steady, positive, and negative) feedback phases, in which D– data characterized the steady state phase, and D+ data were found in the positive and negative phases. In humans, spatial patterns revealed false-negative observations and three malaria-positive data classes. In both humans and bovines, methicillin-resistant Staphylococcus aureus (MRSA) infections were discriminated from non-MRSA infections.

Conclusions

More information can be extracted, from the same data, provided that data are structured, their 3D relationships are considered, and well-conserved (feedback-like) functions are estimated. Patterns emerging from such structures may distinguish well-conserved from recently developed host-microbial interactions. Applications include diagnosis, error detection, and modeling.

Exploring symbioses by single-cell genomics

Single-cell genomics has advanced the field of microbiology from the analysis of microbial metagenomes where information is "drowning in a sea of sequences," to recognizing each microbial cell as a separate and unique entity. Single-cell genomics employs Phi29 polymerase-mediated whole-genome amplification to yield microgram-range genomic DNA from single microbial cells. This method has now been applied to a handful of symbiotic systems, including bacterial symbionts of marine sponges, insects (grasshoppers, termites), and vertebrates (mouse, human). In each case, novel insights were obtained into the functional genomic repertoire of the bacterial partner, which, in turn, led to an improved understanding of the corresponding host. Single-cell genomics is particularly valuable when dealing with uncultivated microorganisms, as is still the case for many bacterial symbionts. In this review, we explore the power of single-cell genomics for symbiosis research and highlight recent insights into the symbiotic systems that were obtained by this approach.

Post-mortem volatiles of vertebrate tissue

Volatile emission during vertebrate decay is a complex process that is understood incompletely. It depends on many factors. The main factor is the metabolism of the microbial species present inside and on the vertebrate. In this review, we combine the results from studies on volatile organic compounds (VOCs) detected during this decay process and those on the biochemical formation of VOCs in order to improve our understanding of the decay process. Micro-organisms are the main producers of VOCs, which are by- or end-products of microbial metabolism. Many microbes are already present inside and on a vertebrate, and these can initiate microbial decay. In addition, micro-organisms from the environment colonize the cadaver. The composition of microbial communities is complex, and communities of different species interact with each other in succession. In comparison to the complexity of the decay process, the resulting volatile pattern does show some consistency. Therefore, the possibility of an existence of a time-dependent core volatile pattern, which could be used for applications in areas such as forensics or food science, is discussed. Possible microbial interactions that might alter the process of decay are highlighted.

[Unique characteristics of the energy metabolism in Microsporidia as a result of durational adaptation to the intracellular development]

Microsporidia is a large group of fungi-related unicellular eukaryotes with obligate intracellular lifestyle infecting a wide range of invertebrate and vertebrate hosts. Long adaptation of the parasites to intracellular development resulted in extraordinary minimization of their metabolic system. The paper summarizes the original results and literature data on the study of microsporidian carbohydrate and energy metabolism. On the basis of the material, it is concluded that minimization of microsporidian cell machinery was accompanied by the acquisition of a number of unique characteristics, which were not found in other eukaryotes.

The evolution of host specialization in the vertebrate gut symbiont Lactobacillus reuteri

Recent research has provided mechanistic insight into the important contributions of the gut microbiota to vertebrate biology, but questions remain about the evolutionary processes that have shaped this symbiosis. In the present study, we showed in experiments with gnotobiotic mice that the evolution of Lactobacillus reuteri with rodents resulted in the emergence of host specialization. To identify genomic events marking adaptations to the murine host, we compared the genome of the rodent isolate L. reuteri 100-23 with that of the human isolate L. reuteri F275, and we identified hundreds of genes that were specific to each strain. In order to differentiate true host-specific genome content from strain-level differences, comparative genome hybridizations were performed to query 57 L. reuteri strains originating from six different vertebrate hosts in combination with genome sequence comparisons of nine strains encompassing five phylogenetic lineages of the species. This approach revealed that rodent strains, although showing a high degree of genomic plasticity, possessed a specific genome inventory that was rare or absent in strains from other vertebrate hosts. The distinct genome content of L. reuteri lineages reflected the niche characteristics in the gastrointestinal tracts of their respective hosts, and inactivation of seven out of eight representative rodent-specific genes in L. reuteri 100-23 resulted in impaired ecological performance in the gut of mice. The comparative genomic analyses suggested fundamentally different trends of genome evolution in rodent and human L. reuteri populations, with the former possessing a large and adaptable pan-genome while the latter being subjected to a process of reductive evolution. In conclusion, this study provided experimental evidence and a molecular basis for the evolution of host specificity in a vertebrate gut symbiont, and it identified genomic events that have shaped this process.

The gastrointestinal microbiota of vertebrates is important for nutrient utilization, resistance against pathogens, and immune maturation of its host, but little is known about the evolutionary relationships between vertebrates and individual bacterial members of these communities. Here we provide robust evidence that the evolution of the gut symbiont Lactobacillus reuteri with vertebrates resulted in the emergence of host specialization. Genomic approaches using a combination of genome sequence comparisons and microarray analysis were used to identify the host-specific genome content in rodent and human strains and the evolutionary events that resulted in host adaptation. The study revealed divergent patterns of genome evolution in rodent and human lineages and a distinct genome inventory in host-restricted sub-populations of L. reuteri that reflected the niche characteristics in the gut of their particular vertebrate hosts. The ecological significance of representative rodent-specific genes was demonstrated in gnotobiotic mice. In conclusion, this work provided evidence that the vertebrate gut symbiont Lactobacillus reuteri, despite the likelihood of horizontal transmission, has remained stably associated with related groups of vertebrate hosts over evolutionary time and has evolved a lifestyle specialized to these host animals.

[Mycoses and zoonoses: Cryptococcus spp]

The term "zoonosis" is difficult to delimit because different authors have various definitions for this term. Few mycoses are usually considered zoonoses. However, the role that animals play in the epidemiology of the main human mycoses is still not well known. Moreover, the environmental niches for these fungal agents have not yet been completely determined. This special issue of the "Revista Iberoamericana de Micología" deals with the talks and round table presented at the VIII Spanish Mycological Congress held in October 2006 in Barcelona, Spain on "Cryptococcus spp. and zoonoses".

We know you are in there: conversing with the indigenous gut microbiota

The vertebrate gut harbors a coevolved consortium of microbes that plays critical roles in the development and health of this organ. Here we discuss recent insights into the microbial-host molecular dialogs that shape the digestive tracts of the model vertebrates, mice and zebrafish, and consider the parallels between vertebrate-microbial mutualisms and the well-studied squid-Vibrio symbiosis.

Spiroplasmas: evolutionary relationships and biodiversity

Spiroplasmas are wall-less descendants of Gram-positive bacteria that maintain some of the smallest genomes known for self-replicating organisms. These helical, motile prokaryotes exploit numerous habitats, but are most often found in association with insects. Co-evolution with their insect hosts may account for the highly speciose nature of the genus Spiroplasma, with many spiroplasmas existing in obligate insect/plant transmission cycles. In addition to insect and plant hosts, spiroplasmas are found in association with ticks and crustaceans. Although most spiroplasma associations appear to be commensal, some cases of pathogenicity or mutualism have been described. Most notably, spiroplasmas have been identified as the causative agents of agricultural and aquacultural diseases and the sex ratio disorder in insects. Some spiroplasmas exhibit strict host and/or geographical ranges, but others are relative generalists. Species of the genus Spiroplasma have been traditionally classified into 34 groups based on cross-reactivity of surface antigens. Three of the serogroups contain closely related strain complexes that are further divided into subgroups. Phylogenetic reconstructions based on 16S rDNA sequence strongly support the closely related serogroups. To date, less than 40 Spiroplasma species have been fully characterized and given binomial names. Complete characterization of a new species involves numerous phenotypic and genotypic tests as outlined in the minimal standards document; this document is currently under revision to include phylogenetic data and a reevaluated set of required phenotypic and genotypic tests. The area of spiroplasma research is poised for major advances with new criteria for naming species in preparation, a dramatic increase in available molecular characters, the promise of full genome sequences, and advances in genetic tools for manipulation of these organisms.

Pathogenic potential of novel Chlamydiae and diagnostic approaches to infections due to these obligate intracellular bacteria

Novel chlamydiae are newly recognized members of the phylum Chlamydiales that are only distantly related to the classic Chlamydiaceae, i.e., Chlamydia and Chlamydophila species. They also exhibit an obligate biphasic intracellular life cycle within eukaryote host cells. Some of these new chlamydiae are currently considered potential emerging human and/or animal pathogens. Parachlamydia acanthamoebae and Simkania negevensis are both emerging respiratory human pathogens, Waddlia chondrophila could be a novel abortigenic bovine agent, and Piscichlamydia salmonis has recently been identified as an agent of the gill epitheliocystis in the Atlantic salmon. Fritschea spp. and Rhabdochlamydia spp. seem to be confined to arthropods, but some evidence for human exposure exists. In this review, we first summarize the data supporting a pathogenic potential of the novel chlamydiae for humans and other vertebrates and the interactions that most of these chlamydiae have with free-living amoebae. We then review the diagnostic approaches to infections potentially due to the novel chlamydiae, especially focusing on the currently available PCR-based protocols, mammalian cell culture, the amoebal coculture system, and serology.

Battle for survival: interplay between pathogenic mycobacteria and the host immune system

Mycobacteria tuberculosis infects about one third of the world population in their life times and causes millions of deaths each year. M. tuberculosis has a unique capability to circumvent the bactericidal activities of macrophages - the frontline defenders of the host immunity. New understanding of this mechanism has positioned scientists to develop therapies that allow host immune system to gain an upper hand.

Clostridium perfringens: insight into virulence evolution and population structure

Clostridium perfringens is an important pathogen in veterinary and medical fields. Diseases caused by this organism are in many cases life threatening or fatal. At the same time, it is part of the ecological community of the intestinal tract of man and animals. Virulence in this species is not fully understood and it does seem that there is erratic distribution of the toxin/enzyme genes within C. perfringens population. We used the recently developed multiple-locus variable-number tandem repeat analysis (MLVA) scheme to investigate the evolution of virulence and population structure of this species. Analysis of the phylogenetic signal indicates that acquisition of the major toxin genes as well as other plasmid-borne toxin genes is a recent evolutionary event and their maintenance is essentially a function of the selective advantage they confer in certain niches under different conditions. In addition, it indicates the ability of virulent strains to cause disease in different host species. More interestingly, there is evidence that certain normal flora strains are virulent when they gain access to a different host species. Analysis of the population structure indicates that recombination events are the major tool that shapes the population and this panmixia is interrupted by frequent clonal expansion that mostly corresponds to disease processes. The signature of positive selection was detected in alpha toxin gene, suggesting the possibility of adaptive alleles on the other chromosomally encoded determinants. Finally, C. perfringens proved to have a dynamic population and availability of more genome sequences and use of comparative proteomics and animal modeling would provide more insight into the virulence of this organism.

Use of amplified fragment length polymorphism (AFLP) markers in surveys of vertebrate diversity

The amplified fragment length polymorphism (AFLP) technique is one of the most informative and cost-effective fingerprinting methods. It produces polymerase chain reaction (PCR)-based multi-locus genotypes helpful in many areas of population genetics. This chapter focuses on technical laboratory information to successfully develop the AFLP technique for vertebrates. Several AFLP protocols are described, as well as recommendations about important factors of the procedure such as the choice of enzyme and primer combinations, the choice and scoring of markers, the influence of the genome size on the AFLP procedure, and the control and estimation of genotyping errors. Finally, this chapter proposes a troubleshooting guide to help resolve the main technical difficulties encountered during the AFLP procedure.

The First United Workshop on Microsporidia from Invertebrate and Vertebrate Hosts

The phylum Microsporidia is a large group of parasitic unicellular eukaryotes that infect a wide range of invertebrate and vertebrate taxa. These organisms are significant human and veterinary pathogens with impacts on medicine, agriculture and aquaculture. Scientists working on these pathogens represent diverse disciplines that have had limited opportunities for detailed interactions. A NATO Advanced Research Workshop 'Emergent Pathogens in the 21st Century: First United Workshop on Microsporidia from Invertebrate and Vertebrate Hosts' was held July 12-15, 2004 at the Institute of Parasitology of the Academy of Sciences of the Czech Republic to bring together experts in insect, fish, veterinary and human microsporidiosis for the exchange of information on these pathogens. At this meeting, discussions were held on issues related to taxonomy and phylogeny. It was recognized that microsporidia are related to fungi, but the strong opinion of the participants was that the International Code of Zoological Nomenclature should continue to be applied for taxonomic descriptions of the Microsporidia and that they be treated as an independent group emerging from a paraphyletic fungi. There continues to be exponential growth in the pace and volume of research on these ubiquitous intracellular protists. The small genomes of these organisms and the reduction in the size of many of their genes are of interest to many disciplines. Many microsporidia are dimorphic and the mechanisms underlying these morphologic changes remain to be elucidated. Epidemiologic studies to clarify the source of human microsporidiosis and ecologic studies to understand the multifaceted relationship of the Microsporidia and their hosts are important avenues of investigation. Studies on the Microsporidia should prove useful to many fields of biologic investigation.

Nucleic Acid Isolation from Ecological Samples—Vertebrate Gut Flora

The utility of DNA molecules in identifying and characterizing intestinal microorganisms depends on methods that facilitate access to DNA of sufficient purity, quantity, and integrity. An efficient and unbiased extraction of DNA is thus critical to the validity of the subsequent analysis of the prevalence and diversity of the DNA sources in the sample. The highly heterogeneous composition of the diet of vertebrates makes DNA isolation challenging for this environment. Here, we consider the key steps involved in DNA isolation from vertebrate gut microflora including sample homogenization, lysis of bacterial cells, and extraction and precipitation of DNA. A detailed protocol for DNA isolation of the microbial contents of intestine and feces is also provided. In addition, we refer to commercially available methods for DNA extraction from the vertebrate gut flora.

Metabolites from symbiotic bacteriaThis review is dedicated to Professor Axel Zeeck on the occasion of his 65th birthday

This review describes natural products that are shown or suspected to be synthesized by symbiotic bacteria. It includes 349 references and covers the literature in this field through 2003.

The distribution and genetic structure of Escherichia coli in Australian vertebrates: host and geographic effects

Escherichia coliwas isolated from more than 2300 non-domesticated vertebrate hosts living in Australia.E. coliwas most prevalent in mammals, less prevalent in birds and uncommon in fish, frogs and reptiles. Mammals were unlikely to harbourE. coliif they lived in regions with a desert climate and less likely to haveE. coliif they lived in the tropics than if they lived in semi-arid or temperate regions. In mammals, the likelihood of isolatingE. colifrom an individual depended on the diet of the host andE. coliwas less prevalent in carnivores than in herbivores or omnivores. In both birds and mammals, the probability of isolatingE. coliincreased with the body mass of the host. Hosts living in close proximity to human habitation were more likely to harbourE. colithan hosts living away from people. The relative abundance ofE. coligroups A, B1, B2 and D strains in mammals depended on climate, host diet and body mass. Group A strains were uncommon, but were isolated from both ectothermic and endothermic vertebrates. Group B1 strains could also be isolated from any vertebrate group, but were predominant in ectothermic vertebrates, birds and carnivorous mammals. Group B2 strains were unlikely to be isolated from ectotherms and were most abundant in omnivorous and herbivorous mammals. Group D strains were rare in ectotherms and uncommon in endotherms, but were equally abundant in birds and mammals. The results of this study suggest that, at the species level, the ecological niche ofE. coliis mammals with hindgut modifications to enable microbial fermentation, or in the absence of a modified hindgut,E. colican only establish a population in ‘large-bodied’ hosts. The non-random distribution ofE. coligenotypes among the different host groups indicates that strains of the fourE. coligroups may differ in their ecological niches and life-history characteristics.

Adaptation of Borrelia burgdorferi in the vector and vertebrate host

Borrelia burgdorferi sensu lato is the causative agent of Lyme disease, which afflicts both humans and some domestic animals. B. burgdorferi, a highly evolved extracellular pathogen, uses several strategies to survive in a complex enzootic cycle involving a diverse range of hosts. This review focuses on the unique adaptive features of B. burgdorferi, which are central to establishing a successful spirochetal infection within arthropod and vertebrate hosts. We also discuss the regulatory mechanisms linked with the development of molecular adaptation of spirochetes within different host environments.

Species, population and age diversity in cell resistance to adhesion of Neisseria meningitidis serogroups A, B and C

The variation of cell adherence of meningococci serogroups A, B and C and influenza viruses was investigated in 11 animal species and in humans of different age groups (1st, 2nd, 3rd and 4th weeks; 2nd-3rd months; 4th-12th months, 2nd-3rd years; and 18th-60th years of life) as well as in women during pregnancy (17th-36th weeks) and childbirth. Red blood cells of all animals tested as well as of human newborns were absolutely resistant to attachment of meningococci. In neonatal and the later periods the human cells become far differently sensitive individually to meningococcal adhesion. In contrast, the viral adhesion was characterized by different individual cell sensitivity in all age groups tested. Pregnancy and childbirth did not influence the women's cell sensitivity to adhesion of Neisseria meningitidis. Different receptors are involved in interactions of human cells with influenza viruses and meningococci. The function of meningococcal receptors on human cells develops during postnatal ontogenesis. The variations express both specific (genetic) and ontogenetic (individual) differences in natural resistance to meningococcal infection.

Characterization of Lyme disease spirochetes isolated from ticks and vertebrates in North Carolina

Borrelia burgdorferi isolates obtained from numerous locations and from different hosts in North Carolina, were compared to previously characterized strains of the Lyme disease spirochete and other Borrelia spp. The spirochete isolates were confirmed to be B. burgdorferi sensu stricto based on immunofluorescence (IFA) using a monoclonal antibody to outer surface protein A (Osp A [H5332]) and polymerase chain reaction (PCR) using a species-specific nested primer for a conserved region of the gene that encodes for flagellin. In addition, the isolates tested positive in Western blots with species-specific monoclonal antibodies for outer surface protein A and OspB (84c), and the genus-specific, monoclonal antibody to flagellin (H9724). Infectivity studies with several of these isolates were conducted using Mus musculus and Oryzomys palustris and the isolates exhibited markedly different levels of infectivity. This study demonstrates that B. burgdorferi sensu stricto is present and naturally transmitted on the Outer Banks and in the Coastal Plain and Piedmont regions of North Carolina.

Cellulose degradation in anaerobic environments

In anaerobic environments rich in decaying plant material, the decomposition of cellulose is brought about by complex communities of interacting microorganisms. Because the substrate, cellulose, is insoluble, bacterial and fungal degradation occurs exocellularly, either in association with the outer cell envelope layer or extracellularly. Products of cellulose hydrolysis are available as carbon and energy sources for other microbes that inhabit environments in which cellulose is biodegraded, and this availability forms the basis of many microbial interactions that occur in these environments. This review discusses interactions among members of cellulose-decomposing microbial communities in various environments. It considers cellulose decomposing communities in soils, sediments, and aquatic environments, as well as those that degrade cellulose in association with animals. These microbial communities contribute significantly to the cycling of carbon on a global scale.

Flavivirus infections in Chiang Mai area, Thailand, in 1982

Infection by JE virus still constitutes major cause of encephalitis in Chiang Mai Area, although some cases of possible dengue encephalopathy were observed. In spite of many apparent encephalitis cases, infection of vector mosquitoes by JE virus was not demonstrated. Virus isolation from hospitalized patients showed that the principal type of dengue virus circulating in Chiang Mai in 1982 was type 1 virus. Seroepidemiological survey on healthy humans indicated that the northern part of Chiang Mai Province in the region of the Maekong Valley has not yet been invaded so much by dengue viruses, compared with the Chiang Mai Valley, where dengue infection apparently became more prevalent than 12 years ago. The survey also indicated that the spread of JE virus in the study area was not uniform. Survey on vertebrates showed that anti-JE antibodies were highly prevalent among swine, horses, mules, sheep, and dogs. On the other hand, antibody prevalence was low in monkeys, ducks, and sparrows, and was negative among chickens and lizards. IgM-ELISA appeared to help differential diagnosis on JE from dengue even when the HI test did not give positive results.

[Erysipeloid on the islands of the Sea of Okhotsk. I. The sources and vectors of the causative agent of erysipeloid]

The foci of the causative agent of erysipeloid at the islands of the Okhotsk sea were of the polyvector and polyhostal character. There were recorded 92 species of the naturally infected by the erysipeloid causative agent invertebrate inhabitants of the sea, fish, amphibia, reptilia, birds, mammals and ectoparasites of the warm-blooded animals. Gamazoid and ixodes ticks, mosquitoes, horse-flies and flees were found to be naturally infected with erysipelotrix. Ixodes persulcatus were found to be capable of infecting albino mice during blood sucking.