Cooperative secretions facilitate host range expansion in bacteria

The majority of emergent human pathogens are zoonotic in origin, that is, they can transmit to humans from other animals. Understanding the factors underlying the evolution of pathogen host range is therefore of critical importance in protecting human health. There are two main evolutionary routes to generalism: organisms can tolerate multiple environments or they can modify their environments to forms to which they are adapted. Here we use a combination of theory and a phylogenetic comparative analysis of 191 pathogenic bacterial species to show that bacteria use cooperative secretions that modify their environment to extend their host range and infect multiple host species. Our results suggest that cooperative secretions are key determinants of host range in bacteria, and that monitoring for the acquisition of secreted proteins by horizontal gene transfer can help predict emerging zoonoses

The molecular basis of host specialization in bean pathovars of Pseudomonas syringae

Biotrophic phytopathogens are typically limited to their adapted host range. In recent decades, investigations have teased apart the general molecular basis of intraspecific variation for innate immunity of plants, typically involving receptor proteins that enable perception of pathogen-associated molecular patterns or avirulence elicitors from the pathogen as triggers for defense induction. However, general consensus concerning evolutionary and molecular factors that alter host range across closely related phytopathogen isolates has been more elusive. Here, through genome comparisons and genetic manipulations, we investigate the underlying mechanisms that structure host range across closely related strains of Pseudomonas syringae isolated from different legume hosts. Although type III secretionindependent virulence factors are conserved across these three strains, we find that the presence of two genes encoding type III effectors (hopC1 and hopM1) and the absence of another (avrB2) potentially contribute to host range differences between pathovars glycinea and phaseolicola. These findings reinforce the idea that a complex genetic basis underlies host range evolution in plant pathogens. This complexity is present even in host–microbe interactions featuring relatively little divergence among both hosts and their adapted pathogens

Estimating parasite host range

© 2017 The Author(s) Published by the Royal Society. All rights reserved. Estimating the number of host species that a parasite can infect (i.e. host range) provides key insights into the evolution of host specialism and is a central concept in disease ecology. Host range is rarely estimated in real systems, however, because variation in species relative abundance and the detection of rare species makes it challenging to confidently estimate host range. We applied a non-parametric richness indicator to estimate host range in simulated and empirical data, allowing us to assess the influence of sampling heterogeneity and data completeness. After validating our method on simulated data, we estimated parasite host range for a sparsely sampled global parasite occurrence database (Global Mammal Parasite Database) and a repeatedly sampled set of parasites of small mammals from New Mexico (Sevilleta Long Term Ecological Research Program). Estimation accuracy varied strongly with parasite taxonomy, number of parasite occurrence records, and the shape of host species-abundance distribution (i.e. the dominance and rareness of species in the host community). Our findings suggest that between 20% and 40% of parasite host ranges are currently unknown, highlighting a major gap in our understanding of parasite specificity, host–parasite network structure, and parasite burdens

Host Range of Myrmecophiles

Diabetic Retinopathy (DR) is a major complication of diabetes and is a leading cause of blindness in western countries. DR has been considered a microvascular disease, and the blood-retinal barrier breakdown is a hallmark of this disease. The available treatments are scarce and not very effective. Despite the attempts to control blood glucose levels and blood pressure, many diabetic patients are affected by DR, which progresses to more severe forms of disease, where laser photocoagulation therapy is needed. DR has a huge psychological impact in patients and tremendous economic and social costs. Taking this into account, the scientific community is committed to find a treatment to DR. Understanding the cellular and molecular mechanisms underlying the pathogenesis of DR will facilitate the development of strategies to prevent, or at least to delay the progression of the disease. The involvement of the polyol pathway, advanced glycation end products, protein kinase C and oxidative stress in the pathogenesis of DR is well-documented, and several clinical trials have been conducted to test the efficacy of various drugs. More recent findings also demonstrate that DR has characteristics of chronic inflammatory disease and neurodegenerative disease, which increases the opportunity of intervention at the pharmacological level. This review presents past and recent evidences demonstrating the involvement of different molecules and processes in DR, and how different approaches and pharmacological tools have been used to prevent retinal cell dysfunction.Fundação para a Ciência e Tecnologia (FCT) e FEDE

Extending the host range of Listeria monocytogenes by rational protein design

SummaryIn causing disease, pathogens outmaneuver host defenses through a dedicated arsenal of virulence determinants that specifically bind or modify individual host molecules. This dedication limits the intruder to a defined range of hosts. Newly emerging diseases mostly involve existing pathogens whose arsenal has been altered to allow them to infect previously inaccessible hosts. We have emulated this chance occurrence by extending the host range accessible to the human pathogen Listeria monocytogenes by the intestinal route to include the mouse. Analyzing the recognition complex of the listerial invasion protein InlA and its human receptor E-cadherin, we postulated and verified amino acid substitutions in InlA to increase its affinity for E-cadherin. Two single substitutions increase binding affinity by four orders of magnitude and extend binding specificity to include formerly incompatible murine E-cadherin. By rationally adapting a single protein, we thus create a versatile murine model of human listeriosis

Variation in physiological host range in three strains of two species of the entomopathogenic fungus Beauveria

Knowledge of the host range of a biocontrol agent (BCA) is fundamental. Host range determines the BCA's economic potential, as well as the possible risk for non-target organisms. Entomopathogenic fungal strains belonging to the genus Beauveria are widely used as BCA, but our knowledge of their physiological host range is only partial. The aim of this study was to improve our understanding of the physiological host range of three Beauveria strains belonging to two species, B. hoplocheli and B. bassiana. We performed laboratory mortality bioassays to assess their pathogenicity and virulence against nine insect pests, belonging to three orders: Lepidoptera, Coleoptera and Diptera. Mortality rate, mean survival time and mycosis rate were used to estimate virulence. Pathogenicity was assessed as the capacity to cause a disease and induce mortality. Virulence was assessed as the severity of the disease based on mortality rate, mean survival time and mycosis rate. The results of this study revealed significant differences in the physiological host range of the three Beauveria strains tested. The three strains were pathogenic to all Diptera and Lepidoptera species tested. In the case of the Coleoptera, only the B. hoplocheli strain was pathogenic to the white grub Hoplochelus marginalis and only the B. bassiana strains were pathogenic to Alphitobius diaperinus. The B. hoplocheli strain was less virulent on Lepidoptera and Diptera than the two B. bassiana strains. The latter both exhibited very similar virulence patterns. The fact that B. hoplocheli and B. bassiana strains have different host ranges means that they can be used as BCA to target different pests. Impacts on non-target insects across multiple orders cannot be ruled out in the absence of ecological host range studies

Phenotypic, Host Range and Symbiotic

AbstractSoybean is an exotic crop to Ethiopia and may not necessarily have a specific endosymbiont in the soil. However, since it is a promiscuous host, nodulated by cross nodulating rhizobia, it is likely that some compatible endosymbionts exist from heterologous hosts that could nodulate it with effective nitrogen fixation. This necessitated the search for effective indigenous rhizobia isolates and/or compatible and effective cross-inoculating rhizobia that are already adapted to local conditions. To this end, a total of 67 bacterial isolates were trapped from different soil samples using two soybean varieties (Clark-63K and Awassa-95) and one cowpea variety (Bole), to evaluate their diversity and screen for their symbiotic effectiveness. Accordingly, the majority of isolates (93%) were tentatively categorized into alkali producing slow growing Bradyrhiobium spp. and the others (7%) were fast growing and acid producing rhizobia. The isolates showed differences in utilizing various carbon and nitrogen sources and tolerance to acidity, salinity and temperature. The isolates were also diverse in their inherent antibiotic and heavy metal resistance. All the isolates were able to nodulate soybean variety Clark-63K with significant difference in their capacity to infect and effectively fix nitrogen evidenced from variations in nodulation parameters and shoot dry weights. Accordingly, the isolates induced nodulation with nodule number ranging from 2 to 49 nodules plant-1; nodule dry weight of 16 mg plant-1 to 94 mg plant-1 and shoot dry weight between 585 and 1012 mg plant-1. Using shoot dry weight as an indicator of the relative effectiveness of the isolates, 12% of the isolates were highly effective (SE > 80%) and 88% were effective (SE from 50 to 80%) on soybean. Furthermore, the isolates showed narrow and broad host ranges on four legume species viz., cowpea, mung bean, pigeon pea, and peanut. Accordingly, many isolates (67%) formed nodules with effective nitrogen fixation with cowpea (Vigna unguiculata), pigeon pea (Cajanus cajan) (47%), and on few cases with mung bean (Vigna radiata) showing different level of effectiveness. However, the data showed very narrow host range on peanut (Arachis hypogaea) where, only one isolate formed effective nodules