Streptomyces as symbionts: an emerging and widespread theme?

Streptomyces bacteria are ubiquitous in soil, conferring the characteristic earthy smell, and they have an important ecological role in the turnover of organic material. More recently, a new picture has begun to emerge in which streptomycetes are not in all cases simply free-living soil bacteria but have also evolved to live in symbiosis with plants, fungi and animals. Furthermore, much of the chemical diversity of secondary metabolites produced by Streptomyces species has most likely evolved as a direct result of their interactions with other organisms. Here we review what is currently known about the role of streptomycetes as symbionts with fungi, plants and animals. These interactions can be parasitic, as is the case for scab-causing streptomycetes, which infect plants, and the Streptomyces species Streptomyces somaliensis and Streptomyces sudanensis that infect humans. However, in most cases they are beneficial and growth promoting, as is the case with many insects, plants and marine animals that use streptomycete-produced antibiotics to protect themselves against infection. This is an exciting and newly emerging field of research that will become increasingly important as the search for new antibiotics switches to unusual and under-explored environments.     

Sticky plant captures prey for symbiotic bug: is this digestive mutualism?

Many plants capture and kill insects but, until relatively recently, only carnivorous plants with digestive enzymes were known to gain directly from the nutrients of those insects. Recent studies show that some carnivorous plants lack digestive enzymes and have evolved digestive mutualisms with symbiotic insects that digest their prey for them. Rhododendron macrosepalum, a plant with sticky leaves that captures insects, has an association with symbiotic Mirid bugs that consume the insects captured. Here, we determine what the nature of the relationship is between Mirid and plant. We find that R. macrosepalum has no digestive enzymes of its own but that it does not seem to have the ability to absorb hemipteran faeces through its leaf cuticle. Naturally occurring levels of ¹⁵N and ¹⁴N were used to determine that R. macrosepalum gains no nitrogen through its association with the Mirid bugs and that it obtains all of its nitrogen from the soil. The Mirids, on the other hand, seem to obtain nitrogen from insects captured by the plant, as well as from plant tissues. The relationship between plant and Mirid is not a digestive mutualism but more likely an antagonistic relationship. This study adds to our understanding of how digestive mutualisms evolve and shows that insect capture alone, or in combination with a symbiotic insect relationship does not necessarily make a plant ‘carnivorous’.     

Protection of host anemones by snapping shrimps: a case for symbiotic mutualism?

The sea anemone Bartholomea annulata is an ecologically important member of Caribbean coral reefs which host a variety of symbiotic crustacean associates. Crustacean exosymbionts typically gain protection from predation by dwelling with anemones. Concurrently, some symbionts may provide protection to their host by defending against anemone predators such as the predatory fireworm, Hermodice carunculata, which can severely damage or completely devour prey anemones. Herein we show through both field and laboratory studies that anemones hosting the symbiotic alpheid shrimp Alpheus armatus are significantly less likely to sustain damage by H. carunculata than anemones without this shrimp. Our results suggest that the association between A. armatus and B. annulata, although complex because of the numerous symbionts involved, may be closer to mutualism on the symbiotic continuum.     

Isoprostanes: an emerging role in vascular physiology and disease?

Among the isoprostanes, the 15-series F2-isoprostanes and 15-E2t-IsoP mediate vasoconstriction in different vascular beds and species. In addition, 15-F2t-IsoP induces smooth muscle cells mitogenesis and monocyte adhesion to endothelial cells. In clinical studies, 15-F2t-IsoP levels are increased in some vascular disorders involving atherosclerosis, ischemia-reperfusion and inflammation. Whether the same effects observed in vitro are observed consistently in vivo at physiological concentrations and whether these effects contribute to pathological states in vivo is still debated.     

Campylobacter ureolyticus: an emerging gastrointestinal pathogen?

A total of 7194 faecal samples collected over a 1-year period from patients presenting with diarrhoea were screened for Campylobacter spp. using EntericBio(?) , a multiplex-PCR system. Of 349 Campylobacter-positive samples, 23.8% were shown to be Campylobacter ureolyticus, using a combination of 16S rRNA gene analysis and highly specific primers targeting the HSP60 gene of this organism. This is, to the best of our knowledge, the first report of C. ureolyticus in the faeces of patients presenting with gastroenteritis and may suggest a role for this organism as an emerging enteric pathogen.     

Echinococcosis: an emerging or re-emerging zoonosis?

The aim of this review is a critical discussion of factors actually or potentially contributing to persistence or emergence of echinococcosis in humans. Alveolar echinococcosis (AE), a life-threatening infection of humans, is caused by a larval stage of Echinococcus multilocularis. The adult parasite inhabits the intestine of foxes and other carnivores and has a wide distribution in the northern hemisphere (North America and northern and central Eurasia). Recent surveys in central Europe have extended the known geographical occurrence of E. multilocularis in foxes from four countries at the end of the 1980s to at least 11 countries in 1999. Cases of human AE previously regularly reported from only four countries are now recorded from seven countries, but the annual incidences are low. Since adequate information from earlier surveys is not available, it is not possible to conclude if the new findings reflect a recent extension of the parasite's range or just the first identification of hitherto unnoticed endemic areas. Evidence of parasite spreading has been reported from North America and Japan. Factors with the potential of enhancing the infection risk for humans in the future include increasing fox populations and parasite prevalences, progressing invasion of cities by foxes, the establishment of urban cycles of the parasite, and the spill-over of the E. multilocularis infection from wild carnivores to domestic dogs and cats. In view of the potential severity and fatality of AE in humans health authorities should initiate internationally coordinated countermeasures. Although control programmes against human cystic echinococcosis (CE), caused by E. granulosus, have been established in some countries and effective control strategies are available, the parasite has still a wide geographical distribution affecting many countries of all continents. Thus, human CE is persisting in many parts of the world with high incidences, and in some areas it is a re-emerging problem. For example, alarming increases of the number of human cases have been reported from Bulgaria and Kazakhstan, and the People's Republic of China. Progress in control can only be expected if health authorities attribute a higher priority to this disease and if all modern diagnostic and control options (for example vaccination of intermediate host animals) can be used.     

Uncommon specialization in a mutualism between a temperate herbaceous plant guild and an ant: are Aphaenogaster ants keystone mutualists?

Ant‐dispersed herbs (myrmecochores) can account for more than one‐third of the stems in the temperate deciduous forests of eastern North America. Because many ant species have been observed collecting the seeds, this interaction is often described as a generalized mutualism. Here, we combine fieldwork and meta‐analyses to test this assumption. Our meta‐analysis demonstrated that Aphaenogaster ants (predominantly A. rudis) collect approximately 74±26% (mean±SD) of the myrmecochorous seeds in eastern North American forests where any encounters with Aphaenogaster were reported, and approximately 61±37% of the seeds in all the eastern forests where any seed collection has been monitored. This remarkable monopolization of seeds is due to at least two factors: 1) Aphaenogaster are significantly more likely to collect the ant‐adapted seeds they discover than are ten other ant genera found in these forests and 2) the densities of Aphaenogaster and myrmecochorous plants are positively correlated at three nested spatial scales (within 20×20 m patches, among patches within a forest, and among 41 forests in the eastern United States). Although other ants can collect seeds, our analyses demonstrate that A. rudis is the primary seed dispersal vector for most of this rich temperate ant‐dispersed flora. The low levels of plant partner diversity for myrmecochores demonstrated here rivals that of tropical ant‐plants (myrmecophytes) and well exceeds that typically observed in temperate plant–frugivore and plant–pollinator mutualisms and myrmecochory in other biomes.     

Cytokinesis: an emerging unified theory for eukaryotes?

In animal and fungal cells, cytokinesis involves an actomyosin ring that forms and contracts at the division plane. Important new details have emerged concerning the composition, assembly, and dynamics of these contractile rings. In addition, recent advances suggest that targeted membrane addition is a central feature of cytokinesis in animal cells - as it is in fungi and plants - and the coordination of actomyosin ring function with targeted exocytosis at the cleavage plane is being explored. Important new information has also emerged about the spatial and temporal regulation of cytokinesis, especially in relation to the function of the spindle midzone in animal cells and the control of cytokinesis by GTPase systems.     

Interactions between malaria and HIV infection-an emerging public health problem?

Recent evidence demonstrates interactions between malaria and HIV infection. HIV-infected people are more likely to experience clinical malaria, and acute malaria can up-regulate HIV replication, leading to higher plasma viral loads. This is most serious in pregnant women, where HIV infection increases the risk of placental malaria, leading to increased infant morbidity and mortality.     

Is There an Association between Dryland Salinity and Ross River Virus Disease in Southwestern Australia?

Land use change has the potential to cause severe ecosystem degradation and drive changes in disease transmission and emergence. Broadscale clearing of native vegetation for agriculture in southwestern Australia has resulted in severe ecosystem degradation, which has been compounded by the subsequent development of large areas of dryland salinity. The mosquito-borne disease, Ross River virus (RRV), has been noted as a potential adverse human health outcome in these salinity affected regions. The association between dryland salinity and RRV disease was therefore tested by undertaking a spatial analysis of disease notification records using standard and Bayesian techniques. To overcome inherent limitations with notification data, serological RRV antibody prevalence was also investigated. Neither method revealed a significant association with dryland salinity, however, the spatial scale imposed limited the sensitivity of both studies. Thus, further multidisciplinary studies are required to overcome these limitations and advance understanding of this ecosystem health issue, particularly using variables that can be investigated on a finer scale.     

Is There an Association between Sleeping Patterns and Other Environmental Factors with Obesity and Blood Pressure in an Urban African Population?

Beyond changing dietary patterns, there is a paucity of data to fully explain the high prevalence of obesity and hypertension in urban African populations. The aim of this study was to determine whether other environmental factors (including sleep duration, smoking and physical activity) are related to body anthropometry and blood pressure (BP). Data were collected on 1311 subjects, attending two primary health care clinics in Soweto, South Africa. Questionnaires were used to obtain data on education, employment, exercise, smoking and sleep duration. Anthropometric and BP measurements were taken. Subjects comprised 862 women (mean age 41 ± 16 years and mean BMI 29.9 ± 9.2 kg/m²) and 449 men (38 ± 14 years and 24.8 ± 8.3 kg/m²). In females, ANOVA showed that former smokers had a higher BMI (p<0.001) than current smokers, while exposure to second hand smoking was associated with a lower BMI (p<0.001) in both genders. Regression analyses demonstrated that longer sleep duration was associated with a lower BMI (p<0.05) in older females only, and not in males, whilst in males napping during the day for > 30 minutes was related to a lower BMI (β = -0.04, p<0.01) and waist circumference (β = -0.03, p<0.001). Within males, napping for >30 minutes/day was related to lower systolic (β = -0.02, p<0.05) and lower diastolic BP (β = -0.02, p = 0.05). Longer night time sleep duration was associated with higher diastolic (β = 0.005, p<0.01) and systolic BP (β = 0.003, p<0.05) in females. No health benefits were noted for physical activity. These data suggest that environmental factors rarely collected in African populations are related, in gender-specific ways, to body anthropometry and blood pressure. Further research is required to fully elucidate these associations and how they might be translated into public health programs to combat high levels of obesity and hypertension.     

Mutualism in a community context: the positive feedback between an ant–aphid mutualism and a gall-making midge

Although mutualisms are widespread and often described in natural history accounts, their ecological influences on other community members remain largely unexplored. Many of these influences are likely a result of indirect effects. In this field study, we investigated the indirect effects of an ant–aphid mutualism on the abundance, survival rates and parasitism rates of a co-occurring herbivore. Rabdophaga salicisbrassicoides (Diptera: Cecidomyiidae) induces rosette galls on the developing shoots of Salix exigua trees, and populations can reach outbreak densities (up to 1,000 galls/stem) in central Washington State (USA). Ant-tended aphids feed on these same stems and often feed on gall tissue. In this study we used a combination of manipulative experiments and observational surveys to test the hypothesis that the abundances of aphids, ants, and galls have positive and reciprocal effects on one another, in a manner that would create a positive feedback loop in population growth. In addition, we examined whether the combined presence of ants and aphids reduces parasitism rates for the gallers. In support of the positive feedback loop hypothesis, aphids enjoyed higher population growth rates in the presence of ants and galls, the presence of ants and aphids resulted in increased abundance of galls, and the abundances of ants, aphids and galls were all positively correlated with one another. However, the mechanism underlying the positive effect of ants and aphids on galler density remains unknown, as the mutualism did not affect parasitism rates. More broadly, this study demonstrates that mutualisms can have significant and complex indirect effects on community and population ecology.     

Interactions between seed predators/pollinators and their host plants: a first step towards mutualism?

The mutualisms between fig trees and their pollinator fig wasps and between yucca plants and yucca moths are spectacular examples of coevolution. The characteristics of these independently evolved mutualisms have resulted from long‐term processes, the first stages of which are unknown. A fundamental question in the study of mutualism is how these interactions evolve. Seed predator/pollinator and host plant interactions, which may initially be considered as mainly antagonistic, have the potential to provide good model systems for the study of the first stages of evolution towards mutualism. We present here theoretical models assessing the consequences of interactions between specialized seed predator insects and their host plants. These models describe the parameters that affect the fitness of an individual female seed predator and her influence on the fitness of the host plant. In an optimal strategy for the seed predator, the number of eggs laid in each flower depends on the interaction between the adult and larva survival. Along with a growing predation pressure on adults and larvae several eggs must be laid in each flower by the female seed predator to enhance her fitness. However, in a situation where the host plant selectively aborts flowers with a high number of eggs the fitness of the seed predator will seriously decrease. If the cost of selective abortion is less than the cost of seed predation the host plant will maintain fitness. In a mutualistic relationship a balance between the cost and the benefit of the parameters in the fitness models of the seed predator and the host plant has to occur so that the net seed output is larger than zero (0). Any unselfish behaviour or quality of the seed predator that would benefit the host plant in such a way that the net seed output increases might be a first stage in an interaction becoming mutualistic. The models presented here will not only provide a platform for empirical studies on interactions that may swing from parasitism to mutualism, but also for seed predator/pollinator and host plant interactions in general.     

Animal babesiosis: an emerging zoonosis also in Italy?

In Italy, babesiosis is widespread in several Central and Southern Regions, but few data are available on its presence in most Italian areas. In 2004 a project was financed by the MIUR to investigate on the babesiosis epidemiology in vertebrate and invertebrate hosts, and on the transmission risk for humans in Central and Northern Regions of the country. Microscopy and/or molecular tools were applied to blood samples of wild animals, livestock and pets, and to 1,677 ticks collected on animals or in the environment, with the aim of detect babesial parasites. Moreover, serological tests were used to evaluate the circulation of these protozoa among animals and people at risk. Microscopy identified as positive 5.0% of the animals, mostly living in Central Regions, but also in Northern areas considered Babesia-free. Serology evidenced the same general trend. PCR detected "piroplasm" DNA in 13.8% of the animals, and sequencing identified babesial parasites in 101/233 samples. The ticks were identified as belonging to 12 species, mostly represented by Ixodes ricinus, Rhipicephalus sanguineus and Dermacentor marginatus. Molecular analyses evidenced babesial parasites in 3.8% of them; in Rh. sanguineus was also demonstrated the vertical transmission of Babesia canis canis. To date 30 human sera have been analysed: 3 showed antibodies to B. microti. Animal babesiosis is largely present among pets, wild and farm animals, whereas goats seem refractory to the infection. In wild ungulates have been found the B. divergens-like, and the Babesia EU1 strains (reported in Italy in humans). Our findings evidenced the low reliability of microscopy in epidemiological studies, and the need of new/improved immunological tests to face diagnostic problems. The monitoring of infected areas and infection rates, joined to appropriate control programs, seems necessary to avoid the transmission of babesiosis to humans.     

The Association between Overweight and Illegal Drug Consumption in Adolescents: Is There an Underlying Influence of the Sociocultural Environment?

Background

The aims of the study were to: a) Examine the distribution of gender-stratified body mass index (BMI), eating attitudes and use of addictive substances, under the hypothesis of a confluent prevalence of weight abnormalities, eating disorders and substance abuse. b) Demonstrate the extent to which family, peer-related and psychosocial factors are common elements in categories of compulsive behaviour.

Methodology/Principal Findings

In the present cross-sectional study, data were collected through self reported questionnaires administered to a large sample of 33,185 15–19 years old adolescents (ESPAD®Italia), divided into weight categories based on the BMI percentile distribution. Multinomial analyses were adopted to address the influence of social, family, leisure time factors, Eating Attitude Test (EAT26) on the association between weight categories and drug use.Recent drugs use was more frequent in overweight and underweight adolescents (p<0.05), especially in females. An EAT26 score ≥20 was more common in overweight adolescents. Multinomial analysis abolished the relationship between overweight and the use of most drugs, implicating self-esteem, parents'' educational level, and friendships as mediators of the association. Within the overweight category, adolescents reporting recent drug use, showed greater frequency of having drug-abusing friends (∼80%), and severe problems with parents and school (∼30%) compared to overweight adolescents without recent drug use.

Conclusion

The frequent association of overweight and substance use and the presence of common underlying social factors, highlights the need for an interdisciplinary approach involving individual-focused treatment models as well as public health, social and environmental changes to reduce food- and substances-related problems.     

Sanctions and mutualism stability: why do rhizobia fix nitrogen?

Why do rhizobia expend resources on fixing N(2) for the benefit of their host plant, when they could use those resources for their own reproduction? We present a series of theoretical models which counter the hypotheses that N(2) fixation is favoured because it (i) increases the exudation of useful resources to related rhizobia in the nearby soil, or (ii) increases plant growth and therefore the resources available for rhizobia growth. Instead, we suggest that appreciable levels of N(2) fixation are only favoured when plants preferentially supply more resources to (or are less likely to senesce) nodules that are fixing more N(2) (termed plant sanctions). The implications for different agricultural practices and mutualism stability in general are discussed.     

Is There an Association between Traumatic Dental Injury and Social Capital,Binge Drinking and Socioeconomic Indicators among Schoolchildren?

ObjectivesTraumatic dental injury is defined as trauma caused by forces on a tooth with variable extent and severity. The aim of the present study was to investigate the prevalence of traumatic dental injury and its association with overjet, lip protection, sex, socioeconomic status, social capital and binge drinking among 12-year-old students.ResultsThe prevalence of traumatic dental injury was 29.9% (176/588). Traumatic dental injury was more prevalent among male adolescents (p = 0.010), those with overjet greater than 5 mm (p < 0.001) and those with inadequate lip protection (p < 0.001). In the multiple logistic regression analysis, overjet [OR = 3.80 (95% CI: 2.235–6.466), p < 0.0001], inadequate lip protection [OR = 5.585 (95% CI: 3.654–8.535), p < 0.0001] and binge drinking [OR = 1.93 (95% CI: 1.21–3.06), p = 0.005] remained significantly associated with traumatic dental injury.ConclusionsThe present findings suggest that a high level of total social capital and trust are not associated with TDI in adolescents, unlike binge drinking. The effects of social and behavioral factors on TDI are not well elucidated. Therefore, further research involving other populations and a longitudinal design is recommended.