Host plant root exudates reduce phytonematode cuticle aging to maintain Pasteuria endospore attachment

Endospores of the nematode hyperparasite from the Pasteuria group of Gram-positive bacteria have the potential to suppress phytonematode populations and reduce root infection. Parasitism by the bacteria commences when endospores adhere to the nematode cuticle before they germinate and infect the developing nematode thereby prohibiting the nematode from producing eggs. Here we demonstrate that in a comparison between a Pasteuria endospore population that infects root-knot nematodes (Meloidogyne incognita) and an endospore population that infects pigeon pea cyst nematodes (Heterodera cajani), as the nematodes age there is a similar reduction in endospore encumbrance on both nematode species. To test the hypothesis that multitrophic evolutionary theory would suggest that plants might recruit bacteria that reduce phytonematode root parasitism, we exposed the two phytonematode species to root exudates of hosts, poor hosts and non-hosts plants and undertake standardised endospore encumbrance bioassays over a two-week aging period. The results showed that the normally expected reduction in endospore attachment due to aging was reduced when root-knot nematodes were exposed to root exudates from their host plants, cowpea and tomato, but not potato, whereas in the case of pigeon pea cyst nematode, the root-exudates from the homologous host plant, cowpea, also reduced the expected reduction in the decrease in endospore attachment due to aging. However, unexpectedly similar results were also produced by root exudates of the non-host, potato. These results are discussed in the light of the characterisation of the root-exudates by gas-liquid chromatography. It is concluded that signalling compounds present in root-exudates can affect cuticle aging both positively and negatively that in turn affects endospore attachment. However, the results are not strictly in line with what multitrophic interactions would have predicted.Non peer reviewe

Exploring Bacillus thuringiensis as a model for endospore adhesion and its potential to investigate adhesins in Pasteuria penetrans

© 2022 The Authors. Journal of Applied Microbiology published by John Wiley & Sons Ltd on behalf of Society for Applied Microbiology. https://creativecommons.org/licenses/by/4.0/Aims: Phytonematodes are a constraint on crop production and have been controlled using nematicides; these are highly toxic and legislation in Europe and elsewhere is prohibiting their use and alternatives are being sought. Pasteuria penetrans is a hyperparasitic bacterium that form endospores and have potential to control root‐knot nematodes (Meloidogyne spp.), but their attachment to the nematode cuticle is host‐specific. Understanding host specificity has relied upon endospore inhibition bioassays using immunological and biochemical approaches. Phylogenetic analysis of survey sequences has shown P. penetrans to be closely related to Bacillus and to have a diverse range of collagen‐like fibres which we hypothesise to be involved in the endospore adhesion. However, due to the obligately hyperparasitic nature of Pasteuria species, identifying and characterizing these collagenous‐like proteins through gain of function has proved difficult and new approaches are required.  Methods and Results: Using antibodies raised to synthetic peptides based on Pasteuria collagen‐like genes we show similarities between P. penetrans and the more easily cultured bacterium Bacillus thuringiensis and suggest it be used as a gain of function platform/model. Using immunological approaches similar proteins between P. penetrans and B. thuringiensis are identified and characterized, one >250 kDa and another ~72 kDa are glycosylated with N‐acetylglucosamine and both of which are digested if treated with collagenase. These treatments also affected endospore attachment and suggest these proteins are involved in adhesion of endospores to nematode cuticle.  Conclusion: There are conserved similarities in the collagen‐like proteins present on the surface of endospores of both P. penetrans and B. thuringiensis. Significance and Impact of Study: As B. thuringiensis is relatively easy to culture and can be transformed, it could be developed as a platform for studying the role of the collagen‐like adhesins from Pasteuria in endospore adhesion.Peer reviewedFinal Published versio

Understanding nematode suppressive soils: molecular interactions between Pasteuria endospores and the nematode surface coat

K. G. Davies, A. Srivastava, K. Kumar, and S. Mohan, ‘Understanding nematode suppressive soils: molecular interactions between Pasteuria endospores and the nematode surface coat’, Aspects of Applied Biology 130, 4th Symposium of Potato Cyst Nematode Management (including other nematode parasites of potatoes), pp. 143-147, September 2015.The knowledge that the plant-parasitic nematode hyperparasite Pasteuria penetrans is important in nematode suppressive soils has long been recognised. The ability to mass produce this organism in vitro circumvents one of its major constraints. However, successful biological control can only be established if the strains that are deployed can attach to and infect pest nematodes. Currently, in respect to the Pasteuria that infects root-knot nematodes (Meloidogyne spp), it is thought that collagen-like fibres on the surface of the endospore are interacting with a receptor on the nematode cuticle and that mucin-like molecules play an important role in modulating this process. Here we report that an antibody raised to whole endospores of P. penetrans also recognises extracts from endospores of Bacillus thuringiensis (Bt), suggesting that Bt can be used as a model for Pasteuria endospores. Bioinformatics shows that mucin-like genes identified in C. elegans are present in Globodera pallida.Final Accepted Versio

Prediction of turbine rotor-stator interaction using Navier-Stokes methods

Flows in turbomachinery are generally complex and do not easily lend themselves to numerical computation. The flows are three-dimensional and inherently unsteady. Complicated blade geometries and flow phenomena such as separation and periodic transition from laminar to turbulent flow add to the numerical complexity. Nevertheless, the accurate numerical analysis of such flows is a problem of considerable interest and practical importance to the turbomachinery community. Much of the early work in turbomachinery flow prediction focussed on airfoil cascades. While such analyses of flows in isolated airfoil rows have helped improve understanding of the flow phenomena and have gained widespread acceptance in the industrial community as a design tool, they do not yield any information regarding the unsteady effects arising out of rotor-stator aerodynamic interaction. These interaction effects become increasingly important as the distance between successive stator and rotor rows is decreased. Thus, the need exists for analytical tools that treat the rotor and stator airfoils as a system and provide information regarding the magnitude and the impact of the unsteady effects. The focus a three-dimensional, time-accurate, thin-layer Navier-Stokes code that was recently developed to study rotor-stator interaction problems. A system of patched and overlaid grids that move relative to each other is used to discretize the flow field and the governing equations are integrated using a third-order upwind scheme set in an iterative, implicit framework. The code was used to simulate subsonic flow through an axial turbine configuration for which considerable experimental data exists. Grid refinement studies were also conducted as part of the code validation process. The current status of the research, along with planned future directions, are also discussed

Simulation of wind power with front-end converter into interconnected grid system

In the growing electricity supply industry and open access market for electricity worldwide, renewable sources are getting added into the grid system. This affects the grid power quality. To assess the impact on grid due to wind energy integration, the knowledge of electrical characteristic of wind turbine and associated control equipments are required. The paper presents a simulation set-up for wind turbine in MATLAB / SIMULINK, with front end converter and interconnected system. The presented control scheme provides the wind power flow to the grid through a converter. The injected power in the system at the point of common coupling is ensured within the power quality normsPeer Reviewe

Assessment of Implementation of Integrated Management of Neonatal and Childhood Illness in India

At the current rate of decline in infant mortality, India is unlikely to achieve the Millennium Development Goal on child survival. Integrated Management of Neonatal and Childhood Illness (IMNCI), adapted from the global Integrated Management of Childhood Illness to enhance the focus on newborns and on community health workers, is the central strategy within the National Reproductive and Child Health Programme to address high infant mortality. This paper assessed the progress of IMNCI in India, identified the programme bottlenecks, and also assessed the effect on coverage of key newborn and childcare practices. Programme data were analyzed to ascertain the implementation status; rapid programme assessment was conducted for identifying the programme bottlenecks; and results of analysis of two rounds of district-level household surveys were used for comparing the change in the coverage of child-health interventions in IMNCI and control districts. More than 200,000 community health workers and first-level healthcare providers were trained during 2005-2009 at a variable pace across 223 districts. Of the reported births (n=1,102,573), 65.5% were visited by a trained worker within 24 hours, and 63.1% were visited three times within 10 days. Poor supervision and inadequate essential supplies affected the performance of trained workers. During 2004-2008, 12 early-implementing districts had covered most key newborn and child practice indicators compared to the control districts; however, the difference was significant only for care-seeking for acute respiratory infection (net difference: 17.8%; 95% confidence interval 2.3-33.2, p<0.026). Based on the early experience of IMNCI implementation in different states of India, measures need to be taken to improve supportive supervision, availability of essential supplies, and monitoring of the programme if the strategy has to translate into improved child survival in India

Exploring the mechanisms of host-specificity of a hyperparasitic bacterium (Pasteuria spp.) with potential to control tropical root-knot nematodes (Meloidogyne spp.): insights from Caenorhabditis elegans

Plant-parasitic nematodes are important economic pests of a range of tropical crops. Strategies for managing these pests have relied on a range of approaches, including crop rotation, the utilization of genetic resistance, cultural techniques, and since the 1950’s the use of nematicides. Although nematicides have been hugely successful in controlling nematodes, their toxicity to humans, domestic animals, beneficial organisms, and the environment has raised concerns regarding their use. Alternatives are therefore being sought. The Pasteuria group of bacteria that form endospores has generated much interest among companies wanting to develop microbial biocontrol products. A major challenge in developing these bacteria as biocontrol agents is their host-specificity; one population of the bacterium can attach to and infect one population of plant-parasitic nematode but not another of the same species. Here we will review the mechanism by which infection is initiated with the adhesion of endospores to the nematode cuticle. To understand the genetics of the molecular processes between Pasteuria endospores and the nematode cuticle, the review focuses on the nature of the bacterial adhesins and how they interact with the nematode cuticle receptors by exploiting new insights gained from studies of bacterial infections of Carnorhabditis elegans. A new Velcro-like multiple adhesin model is proposed in which the cuticle surface coat, which has an important role in endospore adhesion, is a complex extracellular matrix containing glycans originating in seam cells. The genes associated with these seam cells appear to have a dual role by retaining some characteristics of stem cells

Evidence for diversifying selection of genetic regions of encoding putative collagen-like host-adhesive fibers in Pasteuria penetrans

© FEMS 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Pasteuria spp. belong to a group of genetically diverse endospore-forming bacteria (phylum: Firmicutes) that are known to parasitize plant-parasitic nematodes and water fleas (Daphnia spp.). Collagen-like fibres form the nap on the surface of endospores and the genes encoding these sequences have been hypothesised to be involved in the adhesion of the endospores of Pasteuria spp. to their hosts. We report a group of 17 unique collagen-like genes putatively encoded by Pasteuria penetrans (strain: Res148) that formed five different phylogenetic clusters and suggest that collagen-like proteins are an important source of genetic diversity in animal pathogenic Firmicutes including Pasteuria. Additionally, and unexpectedly, we identified a putative collagen-like sequence which had a very different sequence structure to the other collagen-like proteins but was similar to the protein sequences in Megaviruses that are involved in host-parasite interactions. We, therefore, suggest that these diverse endospore surface proteins in Pasteuria are involved in biological functions, such as cellular adhesion; however, they are not of monophyletic origin and were possibly obtained de novo by mutation or possibly through selection acting upon several historic horizontal gene transfer events.Peer reviewedFinal Published versio

Hexapeptides from mammalian inhibitory hormone hunt activate and inactivate nematode reproduction

© 2022 Hart et al. This is an open access article distributed under the terms of the Creative Commons Attribution License. https://creativecommons.org/licenses/by/4.0/Background: Biopurification has been used to disclose an evolutionarily conserved inhibitory reproductive hormone involved in tissue mass determination. A (rat) bioassay-guided physicochemical fractionation using ovine materials yielded via Edman degradation a 14-residue amino acid (aa) sequence. As a 14mer synthetic peptide (EPL001) this displayed antiproliferative and reproduction-modulating activity, while representing only a part of the native polypeptide. Even more unexpectedly, a scrambled-sequence control peptide (EPL030) did likewise. Methods: Reproduction has been investigated in the nematode Steinernema siamkayai, using a fermentation system supplemented with different concentrations of exogenous hexapeptides. Peptide structure-activity relationships have also been studied using prostate cancer and other mammalian cells in vitro, with peptides in solution or immobilized, and via the use of mammalian assays in vivo and through molecular modelling. Results: Reproduction increased (x3) in the entomopathogenic nematode Steinernema siamkayai after exposure to one synthetic peptide (IEPVFT), while fecundity was reduced (x0.5) after exposure to another (KLKMNG), both effects being dose-dependent. These hexamers are opposite ends of the synthetic peptide KLKMNGKNIEPVFT (EPL030). Bioactivity is unexpected as EPL030 is a control compound, based on a scrambled sequence of the test peptide MKPLTGKVKEFNNI (EPL001). EPL030 and EPL001 are both bioinformatically obscure, having no convincing matches to aa sequences in the protein databases. EPL001 has antiproliferative effects on human prostate cancer cells and rat bone marrow cells in vitro. Intracerebroventricular infusion of EPL001 in sheep was associated with elevated growth hormone in peripheral blood and reduced prolactin. The highly dissimilar EPL001 and EPL030 nonetheless have the foregoing biological effects in common in mammalian systems, while being divergently pro- and anti-fecundity respectively in the nematode Caenorhabditis elegans. Peptides up to a 20mer have also been shown to inhibit the proliferation of human cancer and other mammalian cells in vitro, with reproductive upregulation demonstrated previously in fish and frogs, as well as nematodes. EPL001 encodes the sheep neuroendocrine prohormone secretogranin II (sSgII), as deduced on the basis of immunoprecipitation using an anti-EPL001 antibody, with bespoke bioinformatics. Six sSgII residues are key to EPL001’s bioactivity: MKPLTGKVKEFNNI. A stereospecific bimodular tri-residue signature is described involving simultaneous accessibility for binding of the side chains of two specific trios of amino acids, MKP & VFN. An evolutionarily conserved receptor is conceptualised having dimeric binding sites, each with ligand-matching bimodular stereocentres. The bioactivity of the 14mer control peptide EPL030 and its hexapeptide progeny is due to the fortuitous assembly of subsets of the novel hormonal motif, MKPVFN, a default reproductive and tissue-building OFF signal.Peer reviewe