Behind every great ant, there is a great gut

Ants are quite possibly the most successful insects on Earth, with an estimated 10,000 species worldwide, making up at least a third of the global insect biomass, and comprising several times the biomass of all land vertebrates combined. Ant species have diverse trophic habits, including herbivory, hunting/gathering, scavenging and predation and are distributed in diverse habitats, performing a variety of important ecosystem functions. Often they exert these functions while engaging in symbiotic associations with other insects, plants or microbes; however, remarkably little work has focused on the potential contribution of the ants' gut symbionts. This issue of Molecular Ecology contains a study by Anderson et al. (2012), who take a comparative approach to explore the link between trophic levels and ant microbiomes, specifically, to address three main questions: (i) Do closely related herbivorous ants share similar bacterial communities? (ii) Do species of predatory ants share similar bacterial communities? (iii) Do distantly related herbivorous ants tend to share similar bacterial communities? By doing so, the authors demonstrate that ants with similar trophic habits appear to have relatively conserved gut microbiomes, suggesting symbiont functions that directly relate to dietary preference of the ant host. These findings suggest an ecological role of gut symbionts in ants, for example, in metabolism and/or protection, and the comparative approach taken supports a model of co-evolution between ant species and specific core symbiont microbiomes. This study, thereby, highlights the omnipresence and importance of gut symbioses-also in the Hymenoptera-and suggests that these hitherto overlooked microbes likely have contributed to the ecological success of the ants.

Emerging understanding of dosimetric factors impacting on dysphagia and nutrition following radiotherapy for oropharyngeal cancer

BACKGROUND

Research has reported relationships between 3-dimensional (3D) radiation dose to head and neck structures and consequential swallowing/nutritional outcomes. However, this evidence is preliminary. The current study aimed to identify which reported dose constraints identified functional impairment at 6 months posttreatment.

METHODS

Dose constraints with reported relationships to swallowing and nutrition were identified through a systematic literature review. Dose-volume histograms for 12 patients with T1-T3 oropharyngeal cancer treated with 3D conformal radiotherapy determined dosages delivered to specific structures. Doses were examined in relation to published dose constraints and the swallowing and nutritional outcomes at 6 months posttreatment.

RESULTS

In all, 66% of the reported mean, maximum, and partial doses to 8 structures correctly identified swallowing and nutrition outcomes at 6 months.

CONCLUSION

The relationships observed between known dosimetric constraints and functional outcomes highlight the potential for dosimetric data to assist in prognosis and treatment. Systematic research is required to refine dosimetric parameters and the impact on functional outcomes.

Microtermolides A and B from termite-associated Streptomyces sp. and structural revision of vinylamycin

Microtermolides A (1) and B (2) were isolated from a Streptomyces sp. strain associated with fungus-growing termites. The structures of 1 and 2 were determined by 1D- and 2D-NMR spectroscopy and high-resolution mass spectrometry. Structural elucidation of 1 led to the re-examination of the structure originally proposed for vinylamycin (3). Based on a comparison of predicted and experimental ¹H and ¹³C NMR chemical shifts, we propose that vinylamycin’s structure be revised from 3 to 4.

Exploring the potential for actinobacteria as defensive symbionts in fungus-growing termites

In fungus-growing termites, fungi of the subgenus Pseudoxylaria threaten colony health through substrate competition with the termite fungus (Termitomyces). The potential mechanisms with which termites suppress Pseudoxylaria have remained unknown. Here we explore if Actinobacteria potentially play a role as defensive symbionts against Pseudoxylaria in fungus-growing termites. We sampled for Actinobacteria from 30 fungus-growing termite colonies, spanning the three main termite genera and two geographically distant sites. Our isolations yielded 360 Actinobacteria, from which we selected subsets for morphological (288 isolates, grouped in 44 morphotypes) and for 16S rRNA (35 isolates, spanning the majority of morphotypes) characterisation. Actinobacteria were found throughout all sampled nests and colony parts and, phylogenetically, they are interspersed with Actinobacteria from origins other than fungus-growing termites, indicating lack of specificity. Antibiotic-activity screening of 288 isolates against the fungal cultivar and competitor revealed that most of the Actinobacteria-produced molecules with antifungal activity. A more detailed bioassay on 53 isolates, to test the specificity of antibiotics, showed that many Actinobacteria inhibit both Pseudoxylaria and Termitomyces, and that the cultivar fungus generally is more susceptible to inhibition than the competitor. This suggests that either defensive symbionts are not present in the system or that they, if present, represent a subset of the community isolated. If so, the antibiotics must be used in a targeted fashion, being applied to specific areas by the termites. We describe the first discovery of an assembly of antibiotic-producing Actinobacteria occurring in fungus-growing termite nests. However, due to the diversity found, and the lack of both phylogenetic and bioactivity specificity, further work is necessary for a better understanding of the putative role of antibiotic-producing bacteria in the fungus-growing termite mutualistic system.

Small area estimates of smoking prevalence in London. Testing the effect of input data

Small area estimates (SAEs) can provide information about health behaviour at small area levels that is otherwise not available. Because of its increasing use by policy makers, more attention needs to be paid to the reliability of these estimates. This paper reports on smoking prevalence data generated for London at the neighbourhood level using spatial microsimulation modelling. We test the reliability of smoking prevalence estimates at the neighbourhood level using different input datasets. The paper further underlines the importance of estimating health behaviours at the small area level, particularly in diverse cities such as London, where estimation at the city level can mask significant spatial differences.

Merkel cell carcinoma: the prognostic implications of an occult primary in stage IIIB (nodal) disease

BACKGROUND

Merkel cell carcinoma is a highly aggressive cutaneous malignancy with a high rate of lymph node and distant metastatic disease. Approximately one third of patients present with stage IIIB (nodal) disease.

OBJECTIVE

This cohort study was performed to analyze the outcome of patients with stage IIIB disease with or without an occult primary.

METHODS

The details of 91 patients with stage IIIB (nodal) Merkel cell carcinoma treated curatively between 1985 and 2010 at 3 tertiary referral hospitals in Australia were reviewed. Kaplan-Meier plots were used with the primary end point being overall survival. Secondary end points were disease-free survival and relapse-free survival. A multivariate Cox regression analysis was performed for known prognostic factors.

RESULTS

Of 91 patients with stage IIIB (nodal) disease, 36 (40%) had an occult primary. A total of 78 patients (86%) had surgery and 79 patients (87%) had definitive or adjuvant radiotherapy. With a median follow-up of 4.3 years, those with an occult primary did significantly better in terms of overall survival, disease-free survival, and relapse-free survival. On multivariate analysis, occult primary and patient age were the only factors predicting survival with hazard ratios of 0.30 (95% confidence interval 0.13-0.67) and 1.64 (95% confidence interval 1.13-2.38), respectively.

LIMITATIONS

This is a retrospective study over several decades with patients treated using various modalities.

CONCLUSION

This study indicates that for patients with stage IIIB (nodal) Merkel cell carcinoma, the presence of an occult primary confers a significantly better prognosis that may have implications in the future staging and treatment of patients with stage III disease.

Specificity in the symbiotic association between fungus-growing ants and protective Pseudonocardia bacteria

Fungus-growing ants (tribe Attini) engage in a mutualism with a fungus that serves as the ants' primary food source, but successful fungus cultivation is threatened by microfungal parasites (genus Escovopsis). Actinobacteria (genus Pseudonocardia) associate with most of the phylogenetic diversity of fungus-growing ants; are typically maintained on the cuticle of workers; and infection experiments, bioassay challenges and chemical analyses support a role of Pseudonocardia in defence against Escovopsis through antibiotic production. Here we generate a two-gene phylogeny for Pseudonocardia associated with 124 fungus-growing ant colonies, evaluate patterns of ant-Pseudonocardia specificity and test Pseudonocardia antibiotic activity towards Escovopsis. We show that Pseudonocardia associated with fungus-growing ants are not monophyletic: the ants have acquired free-living strains over the evolutionary history of the association. Nevertheless, our analysis reveals a significant pattern of specificity between clades of Pseudonocardia and groups of related fungus-growing ants. Furthermore, antibiotic assays suggest that despite Escovopsis being generally susceptible to inhibition by diverse Actinobacteria, the ant-derived Pseudonocardia inhibit Escovopsis more strongly than they inhibit other fungi, and are better at inhibiting this pathogen than most environmental Pseudonocardia strains tested. Our findings support a model that many fungus-growing ants maintain specialized Pseudonocardia symbionts that help with garden defence.

Are men testing? Sex differentials in HIV testing in Mpumalanga Province, South Africa

HIV testing is the centerpiece of the national AIDS program in South Africa and many HIV-endemic countries, yet there is surprisingly little published data on who uses testing services. In 2006, we conducted a census of HIV-testing records in all 282 public and non-governmental voluntary counseling and testing (VCT) sites in Mpumalanga (MP), South Africa, the province with the highest HIV prevalence in the country. We secured data on the age and sex of all those tested in 260 sites since the year testing was initiated, as far back as 1998 in some sites. For the year 2006, we also secured data on whether a client came to VCT through self-referral, antenatal services (prevent mother-to-child transmission (PMTCT)), or medical referral. The results characterize the rapid uptake of testing as facilities increased, with the number of people testing in MP more than doubling each year between 2002 and 2006. However, there is a persistent 3:1 differential of females:males testing, with 72.7% of all testing among females. When pregnancy-related testing (via PMTCT) is excluded, females still account for 65.1% of all testing in MP. The data also suggest men are more likely to test at older ages and as a result of medical referral. In summary, females in MP are far more likely to use HIV testing than males, even after accounting for increased access to testing during pregnancy. Sex differentials in HIV testing warrant closer policy attention.

Microcystic adnexal carcinoma of the skin: the role of adjuvant radiotherapy

INTRODUCTION

Microcystic adnexal carcinoma (MAC) is a rare cutaneous tumour where the role of radiotherapy remains undefined. We contrast our institutional experience with current literature, define the local control rate and suggest a role for adjuvant radiotherapy in the treatment of this cancer.

METHODS

From 1992-2008, a retrospective review was undertaken for MAC treated with curative intent involving surgery and adjuvant radiotherapy at the Royal Brisbane Hospital and Mater Hospital Brisbane. Clinical, pathologic and treatment details as well as patterns of recurrence were analysed.

RESULTS

Fourteen cases of MAC received local excision and adjuvant radiotherapy. The median age was 71 years old, with nine of the cases in men. All cases occurred in the head and neck region with mean tumour size of 20.5 mm and mean depth of invasion of 9.9 mm. Peri-neural invasion occurred in 56% of cases and 69% had positive surgical margins. Various adjuvant radiotherapy schedules were used to treat the primary site resulting in a crude local control rate of 93%. Primary and nodal relapses were subsequently salvaged with further treatment.

CONCLUSION

While Mohs micrographic surgery may be considered the gold standard, wide local excision and adjuvant radiotherapy offers comparable control rates. Doses of 50 Gy or greater should be prescribed with generous margins (3-5 cm) owing to its tendency for peri-neural and deep invasion. There was no evidence that radiotherapy can cause aggressive transformation of the tumour. The role for definitive radiotherapy remains uncertain.

Chemical analyses of wasp-associated streptomyces bacteria reveal a prolific potential for natural products discovery

Identifying new sources for small molecule discovery is necessary to help mitigate the continuous emergence of antibiotic-resistance in pathogenic microbes. Recent studies indicate that one potentially rich source of novel natural products is Actinobacterial symbionts associated with social and solitary Hymenoptera. Here we test this possibility by examining two species of solitary mud dauber wasps, Sceliphron caementarium and Chalybion californicum. We performed enrichment isolations from 33 wasps and obtained more than 200 isolates of Streptomyces Actinobacteria. Chemical analyses of 15 of these isolates identified 11 distinct and structurally diverse secondary metabolites, including a novel polyunsaturated and polyoxygenated macrocyclic lactam, which we name sceliphrolactam. By pairing the 15 Streptomyces strains against a collection of fungi and bacteria, we document their antifungal and antibacterial activity. The prevalence and anti-microbial properties of Actinobacteria associated with these two solitary wasp species suggest the potential role of these Streptomyces as antibiotic-producing symbionts, potentially helping defend their wasp hosts from pathogenic microbes. Finding phylogenetically diverse and chemically prolific Actinobacteria from solitary wasps suggests that insect-associated Actinobacteria can provide a valuable source of novel natural products of pharmaceutical interest.

Sceliphrolactam, a polyene macrocyclic lactam from a wasp-associated Streptomyces sp

A previously unreported 26-membered polyene macrocyclic lactam, sceliphrolactam, was isolated from an actinomycete, Streptomyces sp., associated with the mud dauber, Sceliphron caementarium. Sceliphrolactam's structure was determined by 1D- and 2D-NMR, MS, UV, and IR spectral analysis. Sceliphrolactam displays antifungal activity against amphotericin B-resistant Candida albicans (MIC = 4 μg/mL, 8.3 μM).

The role of symbiont genetic distance and potential adaptability in host preference towards Pseudonocardia symbionts in Acromyrmex leaf-cutting ants

Fungus-growing ants display symbiont preference in behavioral assays, both towards the fungus they cultivate for food and Actinobacteria they maintain on their cuticle for antibiotic production against parasites. These Actinobacteria, genus Pseudonocardia Henssen (Pseudonocardiacea: Actinomycetales), help defend the ants' fungal mutualist from specialized parasites. In Acromyrmex Mayr (Hymenoptera: Formicidae) leaf-cutting ants, individual colonies maintain either a single or a few strains of Pseudonocardia, and the symbiont is primarily vertically transmitted between generations by colony-founding queens. A recent report found that Acromyrmex workers are able to differentiate between their native Pseudonocardia strain and non-native strains isolated from sympatric or allopatric Acromyrmex species, and show preference for their native strain. Here we explore worker preference when presented with two non-native strains, elucidating the role of genetic distance on preference between strains and Pseudonocardia origin. Our findings suggest that ants tend to prefer bacteria more closely related to their native bacterium and that genetic similarity is probably more important than whether symbionts are ant-associated or free-living. Preliminary findings suggest that when continued exposure to a novel Pseudonocardia strain occurs, ant symbiont preference is potentially adaptable, with colonies apparently being able to alter symbiont preference over time. These findings are discussed in relation to the role of adaptive recognition, potential ecological flexibility in symbiont preference, and more broadly, in relation to self versus non-self recognition.

Comparison of a Commonwealth-initiated regional radiation oncology facility in Toowoomba with a Queensland Health facility

The aim was to compare a private Commonwealth-initiated regional radiation oncology facility in Toowoomba with a Queensland Health facility (QHF) in Brisbane. The comparison concentrated on staffing, case mix and operational budgets, but was not able to look at changes in access to services. Data were collected from the two facilities from January 2008 to June 2008 inclusive. A number of factors were compared, including case mix, staffing levels, delay times for treatment, research, training and treatment costs. The case mix between the two areas was similar with curative treatments making up just over half the work load in both centres and two-thirds the work being made up of cancers of breast and prostate. Staffing levels were leaner in Toowoomba, especially in the areas of nursing, administration and trial coordinators. Research activity was slightly higher in Toowoomba. The average medicare cost per treatment course was similar in both centres ($5000 per course). Total costs of an average treatment including patient, State and Commonwealth costs, showed a 30% difference in costing favouring Toowoomba. This regional radiation oncology centre has provided state-of-the-art cancer care that is close to home for patients living in the Darling Downs region. Both public and private patients have been treated with modest costs to the patient and significant savings to QH. The case mix is similar to the QHF, and there has been significant activity in clinical research. A paperless working environment is one factor that has allowed staffing levels to be reduced. Ongoing support from Governments are required if private facilities are to participate in important ongoing staff training.

Variation in Pseudonocardia antibiotic defence helps govern parasite-induced morbidity in Acromyrmex leaf-cutting ants

Host-parasite associations are potentially shaped by evolutionary reciprocal selection dynamics, in which parasites evolve to overcome host defences and hosts are selected to counteract these through the evolution of new defences. This is expected to result in variation in parasite-defence interactions, and the evolution of resistant parasites causing increased virulence. Fungus-growing ants maintain antibiotic-producing Pseudonocardia (Actinobacteria) that aid in protection against specialized parasites of the ants' fungal gardens, and current evidence indicates that both symbionts have been associated with the ants for millions of years. Here we examine the extent of variation in the defensive capabilities of the ant-actinobacterial association against Escovopsis (parasite-defence interactions), and evaluate how variation impacts colonies of fungus-growing ants. We focus on five species of Acromyrmex leaf-cutting ants, crossing 12 strains of Pseudonocardia with 12 strains of Escovopsis in a Petri plate bioassay experiment, and subsequently conduct subcolony infection experiments using resistant and non-resistant parasite strains. Diversity in parasite-defence interactions, including pairings where the parasites are resistant, suggests that chemical variation in the antibiotics produced by different actinobacterial strains are responsible for the observed variation in parasite susceptibility. By evaluating the role this variation plays during infection, we show that infection of ant subcolonies with resistant parasite strains results in significantly higher parasite-induced morbidity with respect to garden biomass loss. Our findings thus further establish the role of Pseudonocardia-derived antibiotics in helping defend the ants' fungus garden from the parasite Escovopsis, and provide evidence that small molecules can play important roles as antibiotics in a natural system.

Symbiont interactions in a tripartite mutualism: exploring the presence and impact of antagonism between two fungus-growing ant mutualists

Mutualistic associations are shaped by the interplay of cooperation and conflict among the partners involved, and it is becoming increasingly clear that within many mutualisms multiple partners simultaneously engage in beneficial interactions. Consequently, a more complete understanding of the dynamics within multipartite mutualism communities is essential for understanding the origin, specificity, and stability of mutualisms. Fungus-growing ants cultivate fungi for food and maintain antibiotic-producing Pseudonocardia actinobacteria on their cuticle that help defend the cultivar fungus from specialized parasites. Within both ant-fungus and ant-bacterium mutualisms, mixing of genetically distinct strains can lead to antagonistic interactions (i.e., competitive conflict), which may prevent the ants from rearing multiple strains of either of the mutualistic symbionts within individual colonies. The success of different ant-cultivar-bacterium combinations could ultimately be governed by antagonistic interactions between the two mutualists, either as inhibition of the cultivar by Pseudonocardia or vice versa. Here we explore cultivar-Pseudonocardia antagonism by evaluating in vitro interactions between strains of the two mutualists, and find frequent antagonistic interactions both from cultivars towards Pseudonocardia and vice versa. To test whether such in vitro antagonistic interactions affect ant colonies in vivo, we performed sub-colony experiments using species of Acromyrmex leaf-cutting ants. We created novel ant-fungus-bacterium pairings in which there was antagonism from one, both, or neither of the ants' microbial mutualists, and evaluated the effect of directional antagonism on cultivar biomass and Pseudonocardia abundance on the cuticle of workers within sub-colonies. Despite the presence of frequent in vitro growth suppression between cultivars and Pseudonocardia, antagonism from Pseudonocardia towards the cultivar did not reduce sub-colony fungus garden biomass, nor did cultivar antagonism towards Pseudonocardia reduce bacteria abundance on the cuticle of sub-colony workers. Our findings suggest that inter-mutualist antagonism does not limit what combinations of cultivar and Pseudonocardia strains Acromyrmex fungus-growing ants can maintain within nests.

Effect of radiotherapy dose and volume on relapse in Merkel cell cancer of the skin

PURPOSE

To assess the effect of radiotherapy (RT) dose and volume on relapse patterns in patients with Stage I-III Merkel cell carcinoma (MCC).

PATIENTS AND METHODS

This was a retrospective analysis of 112 patients diagnosed with MCC between January 2000 and December 2005 and treated with curative-intent RT.

RESULTS

Of the 112 evaluable patients, 88% had RT to the site of primary disease for gross (11%) or subclinical (78%) disease. Eighty-nine percent of patients had RT to the regional lymph nodes; in most cases (71%) this was for subclinical disease in the adjuvant or elective setting, whereas 21 patients (19%) were treated with RT to gross nodal disease. With a median follow-up of 3.7 years, the 2-year and 5-year overall survival rates were 72% and 53%, respectively, and the 2-year locoregional control rate was 75%. The in-field relapse rate was 3% for primary disease, and relapse was significantly lower for patients receiving >or=50 Gy (hazard ratio [HR] = 0.22; 95% confidence interval [CI], 0.06-0.86). Surgical margins did not affect the local relapse rate. The in-field relapse rate was 11% for RT to the nodes, with dose being significant for nodal gross disease (HR = 0.24; 95% CI, 0.07-0.87). Patients who did not receive elective nodal RT had a much higher rate of nodal relapse compared with those who did (HR = 6.03; 95% CI, 1.34-27.10).

CONCLUSION

This study indicates a dose-response for subclinical and gross MCC. Doses of >or=50 Gy for subclinical disease and >or=55 Gy for gross disease should be considered. The draining nodal basin should be treated in all patients.