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Reef corals are under threat from bleaching and disease outbreaks that target both the host animal and the algal symbionts within the coral holobiont. A viral origin for coral bleaching has been hypothesized, but direct evidence has remained elusive. Using a multifaceted approach incorporating flow cytometry, transmission electron microscopy, DNA and RNA virome sequencing, we show that type C1 Symbiodinium cultures host a nucleocytoplasmic large double-stranded DNA virus (NCLDV) related to Phycodnaviridae and Mimiviridae, a novel filamentous virus of unknown phylogenetic affiliation, and a single-stranded RNA virus related to retroviruses. We discuss implications of these findings for laboratory-based experiments using Symbiodinium cultures. [ABSTRACT FROM AUTHOR]

Background and Aims Sclerotinia stem rot (SSR, Sclerotinia sclerotiorum) is a damaging disease of oilseed brassicas world-wide. Host resistance is urgently needed to achieve control, yet the factors that contribute to stem resistance are not well understood. This study investigated the mechanisms of resistance to SSR. Methods Stems of 5-week-old Brassica carinata, B. juncea and B. napus of known resistance were infected via filter paper discs impregnated with S. sclerotiorum mycelium under controlled conditions. Transverse sections of the stem and portions of the stem surface were examined using optical and scanning electron microscopy. The association of anatomical features with the severity of disease (measured by mean lesion length) was determined. Key Results Several distinct resistance mechanisms were recorded for the first time in these Brassica-pathogen interactions, including hypersensitive reactions and lignification within the stem cortex, endodermis and in tissues surrounding the lesions. Genotypes showing a strong lignification response 72 h post-infection (hpi) tended to have smaller lesions. Extensive vascular invasion by S. sclerotiorum was observed only in susceptible genotypes, especially in the vascular fibres and xylem. Mean lesion length was negatively correlated with the number of cell layers in the cortex, suggesting progress of S. sclerotiorum is impeded by more cell layers. Hyphae in the centre of lesions became highly vacuolate 72 hpi, reflecting an ageing process in S. sclerotiorum hyphal networks that was independent of host resistance. The infection process of S. sclerotiorum was analogous in B. carinata and B. napus. Infection cushions of the highly virulent isolate of S. sclerotiorum MBRS-1 were grouped together in dense parallel bundles, while hyphae in the infection cushions of a less aggressive isolate WW-3 were more diffuse, and this was unaffected by host genotype. Conclusions A variety of mechanisms contribute to host resistance against S. sclerotiorum across the three Brassica species. These complex interactions between pathogen and host help to explain variable expressions of resistance often observed in the field. [ABSTRACT FROM AUTHOR]

Cryptosporidium is a parasite responsible for widespread disease in livestock and humans. Recent phylogenetic reclassification of Cryptosporidium from a coccidian to a gregarine dictates an urgent need to reconsider the biology and behavior of this parasite. Overwhelming data now confirm that, like its close relatives, Cryptosporidium is a facultatively epicellular apicomplexan that is able to multiply in a host cell-free environment. We complement the latest phylogenetic and taxonomic proposals with advances in our understanding of Cryptosporidium 's biology, with particular focus on in vitro studies that have characterized the development of Cryptosporidium stages in the absence of host cells. Opportunities to revisit in vivo infections are discussed and questions about the Cryptosporidium host cell-free life cycle that remain unanswered highlighted. [ABSTRACT FROM AUTHOR]

This study investigated the surface chemistry–microstructure–rheology relationship of two very well characterised, low impurity CMS source kaolinites; low defect KGa-1b and high defect KGa-2. The knowledge gained will improve the overall understanding by acting as a reference material for comparison with other studies. The trend of the yield stress–pH result was adopted to investigate kaolinite properties or factors that affect this trend. Both the KGa-1b and KGa-2 kaolinite slurries displayed similar zeta potential–pH and yield stress–pH behaviour. Crystallinity and particle size therefore did not affect the trend of the yield stress–pH and zeta potential–pH behaviour. The larger yield stress of the finer KGa-2 slurries is due to a higher particle concentration. Both kaolinite slurries exhibited a maximum yield stress at zero zeta potential. Their yield stress–solid volume fraction data were found to obey a power law model with the same exponent value of 3 accounting for a fractal dimension of 2.3 unaffected by pH. Cryo-SEM images of the vitrified microstructure of 35 wt% KGa-1b and 15 wt% KGa-2 suspensions at the maximum yield stress showed a 3-D microstructure formed by compacted clay aggregates which themselves are formed by a mixture of particle interaction configurations – face–face with stair–step feature and edge–face. Particle interaction modelling was discussed. [ABSTRACT FROM AUTHOR]

Recent advances have rapidly facilitated development of new and improved high-resolution, high-throughput volume electron microscopy techniques. Investigating cell structures and interactions at higher resolution and in three dimensions is becoming increasingly important in parasitology. Understanding the different capabilities of light, X-ray, electron, and ion microscopy technologies is essential for choosing the right technique to solve current and challenging parasitology research questions. Volume electron microscopy techniques are underutilised in most fields of parasitology despite recent improvements in accessibility, user-friendliness, and cost. To best understand parasite, host, and vector morphologies, host–parasite interactions, and to develop new drug and vaccine targets, structural data should, ideally, be obtained and visualised in three dimensions (3D). Recently, there has been a significant uptake of available 3D volume microscopy techniques that allow collection of data across centimetre (cm) to Angstrom (Å) scales by utilising light, X-ray, electron, and ion sources. Here, we present and discuss microscopy tools available for the collection of 3D structural data, focussing on electron microscopy-based techniques. We highlight their strengths and limitations, such that parasitologists can identify techniques best suited to answer their research questions. Additionally, we review the importance of volume microscopy to the advancement of the field of parasitology. [ABSTRACT FROM AUTHOR]

The reproductive phase in chickpea ( C icer arietinum L.) is affected by salinity, but little is known about the underlying cause. We investigated whether high concentrations of Na + and Cl- in the reproductive structures influence reproductive processes. Chickpea genotypes contrasting in tolerance were subjected to 0, 35 or 50 m m NaCl applied to soil in pots. Flower production and abortion, pod number, percentage of empty pods, seed number and size were evaluated. The concentrations of Na+, K+ and Cl- were measured in various plant tissues and, using X-ray microanalysis, in specific cells of developing reproductive structures. Genotypic variation in reproductive success measured as seed yield in saline conditions was associated with better maintenance of flower production and higher numbers of filled pods (and thus seed number), whereas seed size decreased in all genotypes. Despite the variation in reproductive success, the accumulation of Na+ and Cl- in the early reproductive tissues of developing pods did not differ between a tolerant ( Genesis836) and a sensitive ( Rupali) genotype. Similarly, salinity tolerance was not associated with the accumulation of salt ions in leaves at the time of reproduction or in seeds at maturity. [ABSTRACT FROM AUTHOR]

Plants rapidly release photoassimilated carbon (C) to the soil via direct root exudation and associated mycorrhizal fungi, with both pathways promoting plant nutrient availability. This study aimed to explore these pathways from the root's vascular bundle to soil microbial communities., Using nanoscale secondary ion mass spectrometry (Nano SIMS) imaging and 13C-phospho- and neutral lipid fatty acids, we traced in-situ flows of recently photoassimilated C of 13 CO2-exposed wheat ( Triticum aestivum) through arbuscular mycorrhiza ( AM) into root- and hyphae-associated soil microbial communities., Intraradical hyphae of AM fungi were significantly 13C-enriched compared to other root-cortex areas after 8 h of labelling. Immature fine root areas close to the root tip, where AM features were absent, showed signs of passive C loss and co-location of photoassimilates with nitrogen taken up from the soil solution. A significant and exclusively fresh proportion of 13C-photosynthates was delivered through the AM pathway and was utilised by different microbial groups compared to C directly released by roots., Our results indicate that a major release of recent photosynthates into soil leave plant roots via AM intraradical hyphae already upstream of passive root exudations. AM fungi may act as a rapid hub for translocating fresh plant C to soil microbes. [ABSTRACT FROM AUTHOR]

Background: Aquatic biofilms often serve as environmental reservoirs for microorganisms and provide them with a nutrient-rich growth environment under harsh conditions. With regard to Cryptosporidium, biofilms can serve as environmental reservoirs for oocysts, but may also support the growth of additional Cryptosporidium stages. Results: Here we used confocal laser scanning microscopy, scanning electron microscopy (SEM), and flow cytometry to identify and describe various Cryptosporidium developmental stages present within aquatic biofilm systems, and to directly compare these to stages produced in cell culture. We also show that Cryptosporidium has the ability to form a parasitophorous vacuole independently, in a host-free biofilm environment, potentially allowing them to complete an extracellular life cycle. Correlative data from confocal and SEM imaging of the same cells confirmed that the observed developmental stages (including trophozoites, meronts, and merozoites) were Cryptosporidium. These microscopy observations were further supported by flow cytometric analyses, where excysted oocyst populations were detected in 1, 3 and 6 day-old Cryptosporidium-exposed biofilms, but not in biofilm-free controls. Conclusions: These observations not only highlight the risk that aquatic biofilms pose in regards to Cryptosporidium outbreaks from water distribution systems, but further indicate that even simple biofilms are able to stimulate oocyst excystation and support the extracellular multiplication and development of Cryptosporidium within aquatic environments. [ABSTRACT FROM AUTHOR]