Influence of different types of superplasticizers on one-part alkali- activated slag mortars

This paper presents an experimental study carried out to investigate the influence of different types of superplasticizers on the fresh and hardened properties of one-part alkali-activated slag mortars. Three different admixtures were added to the mixes at the level of 1.3% by binder mass. In particular, sulphonated polymer-based, polycarboxylates-based and lignosulfonates-based high-range water reducers were used. In addition, a hardening accelerator was added to the mixes up to 1.0% respect to binder mass. Ground granulated blast furnace slag (according to EN 15167-1) as precursor and sodium metasilicate pentahydrate: potassium hydroxide : sodium carbonate = 7:3:1 in powder form as activator were used to produce different mortars with the dosage of activator between 2% and 16 % vs binder mass. The water was adjusted in order to attain the same workability at the end of the mixing procedure, equal to 160 mm ± 10 mm by means of a flow table. The specimens were cured in climatic chamber at 20°C and R.H. 60%. The effectiveness of the admixtures has been investigated in terms of percentage of water reduction, workability loss over time and compressive strength. The experimental data show that all superplasticizers provides a reduction in mixing water. The admixtures are influenced by the presence of the activator. In fact, the water reduction, at the same initial workability, is maximum in mortars manufactured without activators. However, the ability of water reducers is not influenced by the activator/precursor. Moreover, results indicated that as consequence of superplasticizer addition, the pot-life of reference mortars manufactured without superplasticizer (60 minutes) is extended up to 160 minutes. The addition of high-range water reducers does not delay the development of 1-day compressive strength. On the other hand, it causes a little reduction of mechanical properties at 7 and 28 days respect to the reference mortars, regardless of superplasticizers employed. Finally, the use of hardening accelerator admixture does not determine a reduction in workability loss over time while no improving was detected on the mechanical strength at early and long ages

Microbial symbionts : a resource for the management of insect-related problems

Microorganisms establish with their animal hosts close interactions. They are involved in many aspects of the host life, physiology and evolution, including nutrition, reproduction, immune homeostasis, defence and speciation. Thus, the manipulation and the exploitation the microbiota could result in important practical applications for the development of strategies for the management of insect-related problems. This approach, defined as Microbial Resource Management (MRM), has been applied successfully in various environments and ecosystems, as wastewater treatments, prebiotics in humans, anaerobic digestion and so on. MRM foresees the proper management of the microbial resource present in a given ecosystem in order to solve practical problems through the use of microorganisms. In this review we present an interesting field for application for MRM concept, i.e. the microbial communities associated with arthropods and nematodes. Several examples related to this field of applications are presented. Insect microbiota can be manipulated: (i) to control insect pests for agriculture; (ii) to control pathogens transmitted by insects to humans, animals and plants; (iii) to protect beneficial insects from diseases and stresses. Besides, we prospect further studies aimed to verify, improve and apply MRM by using the insectsymbiont ecosystem as a model

Horizontal transmission of the symbiotic bacterium Asaia sp. in the leafhopper Scaphoideus titanus Ball (Hemiptera: Cicadellidae)

<p>Abstract</p> <p>Background</p> <p>Bacteria of the genus <it>Asaia</it> have been recently recognized as secondary symbionts of different sugar-feeding insects, including the leafhopper <it>Scaphoideus titanus</it>, vector of Flavescence dorée phytoplasmas. <it>Asaia</it> has been shown to be localized in <it>S. titanus</it> gut, salivary glands and gonoducts and to be maternally transmitted to the progeny by an egg smearing mechanism. It is currently not known whether <it>Asaia</it> in <it>S. titanus</it> is transmitted by additional routes. We performed a study to evaluate if <it>Asaia</it> infection is capable of horizontal transmission <it>via</it> co-feeding and venereal routes.</p> <p>Results</p> <p>A Gfp-tagged strain of <it>Asaia</it> was provided to <it>S. titanus</it> individuals to trace the transmission pathways of the symbiotic bacterium. Co-feeding trials showed a regular transfer of bacterial cells from donors to recipients, with a peak of frequency after 72 hours of exposure, and with concentrations of the administrated strain growing over time. Venereal transmission experiments were first carried out using infected males paired with uninfected females. In this case, female individuals acquired Gfp-labelled <it>Asaia</it>, with highest infection rates 72-96 hours after mating and with increasing abundance of the tagged symbiont over time. When crosses between infected females and uninfected males were conducted, the occurrence of “female to male” transmission was observed, even though the transfer occurred unevenly.</p> <p>Conclusions</p> <p>The data presented demonstrate that the acetic acid bacterial symbiont <it>Asaia</it> is horizontally transmitted among <it>S</it>. <it>titanus</it> individuals both by co-feeding and venereal transmission, providing one of the few direct demonstrations of such a symbiotic transfer in Hemiptera. This study contributes to the understanding of the bacterial ecology in the insect host, and indicates that <it>Asaia</it> evolved multiple pathways for the colonization of <it>S</it>. <it>titanus</it> body.</p

Cycling tourism in Italy: Multimodal transport behaviours in a latent class analysis

In the last years, sustainability has become an important issue in tourism debate, and more, cycling tourism as an alternative and green way of travel during holidays has gained popularity. However, the choice of other transport means, complementary to bikes, is of key importance to address the sustainability of cycling experiences. In this paper, we used primary data collected from an on-line survey on bike tourism in Italy in 2020. Besides sociodemographic and bike-related questions, 858 individuals were asked about their own transport modes to move across destinations during cycling holidays. A latent class analysis has been used to identify three groups of people with segmented preferences for bike tourism experiences, including destinations, accommodation, and multimodal behaviours. We found that the largest latent class in Italy is composed by bike tourists with the highest share of females compared to the other two classes, under 60 years old, and with a strong preference for collective transport means. Both from a management and policy perspective, our results support the claim for investments to improve the transport connection among tourism destinations, and to stimulate the creation of bike-friendly environments and tourism facilities

What lies on macroalgal surface: diversity of polysaccharide degraders in culturable epiphytic bacteria

Macroalgal surface constitutes a peculiar ecological niche and an advantageous substratum for microorganisms able to degrade the wide diversity of algal glycans. The degrading enzymatic activities of macroalgal epiphytes are of paramount interest for the industrial by-product sector and biomass resource applications. We characterized the polysaccharide hydrolytic profle of bacterial isolates obtained from three macroalgal species: the red macroalgae Asparagopsis taxiformis and Sphaerococcus coronopifolius (Rhodophyceae) and the brown Halopteris scoparia (Phaeophyceae), sampled in South Portugal. Bacterial enrichment cultures supplemented with chlorinated aliphatic compounds, typically released by marine algae, were established using as inoculum the decaying biomass of the three macroalgae, obtaining a collection of 634 bacterial strains. Although collected from the same site and exposed to the same seawater seeding microbiota, macroalgal cultivable bacterial communities in terms of functional and phylogenetic diversity showed host specifcity. Isolates were tested for the hydrolysis of starch, pectin, alginate and agar, exhibiting a diferent hydrolytic potential according to their host: A. taxiformis showed the highest percentage of active isolates (91%), followed by S. coronopifolius (54%) and H. scoparia (46%). Only 30% of the isolates were able to degrade starch, while the other polymers were degraded by 55–58% of the isolates. Interestingly, several isolates showed promiscuous capacities to hydrolyze more than one polysaccharide. The isolate functional fngerprint was statistically correlated to bacterial phylogeny, host species and enrichment medium. In conclusion, this work depicts macroalgae as holobionts with an associated microbiota of interest for blue biotechnologies, suggesting isolation strategies and bacterial targets for polysaccharidases’ discoveryinfo:eu-repo/semantics/publishedVersio

Structure/activity virtual screening and in vitro testing of small molecule inhibitors of 8-hydroxy-5-deazaflavin:NADPH oxidoreductase from gut methanogenic bacteria

Abstract Virtual screening techniques and in vitro binding/inhibitory assays were used to search within a set of more than 8,000 naturally occurring small ligands for candidate inhibitors of 8-hydroxy-5-deazaflavin:NADPH oxidoreductase (FNO) from Methanobrevibacter smithii, the enzyme that catalyses the bidirectional electron transfer between NADP+ and F420H2 during the intestinal production of CH4 from CO2. In silico screening using molecular docking classified the ligand-enzyme complexes in the range between − 4.9 and − 10.5 kcal/mol. Molecular flexibility, the number of H-bond acceptors and donors, the extent of hydrophobic interactions, and the exposure to the solvent were the major discriminants in determining the affinity of the ligands for FNO. In vitro studies on a group of these ligands selected from the most populated/representative clusters provided quantitative kinetic, equilibrium, and structural information on ligands' behaviour, in optimal agreement with the predictive computational results

Delayed larval development in Anopheles mosquitoes deprived of Asaia bacterial symbionts

<p>Abstract</p> <p>Background</p> <p>In recent years, acetic acid bacteria have been shown to be frequently associated with insects, but knowledge on their biological role in the arthropod host is limited. The discovery that acetic acid bacteria of the genus <it>Asaia</it> are a main component of the microbiota of <it>Anopheles stephensi</it> makes this mosquito a useful model for studies on this novel group of symbionts. Here we present experimental results that provide a first evidence for a beneficial role of <it>Asaia</it> in <it>An. stephensi</it>.</p> <p>Results</p> <p>Larvae of <it>An. stephensi</it> at different stages were treated with rifampicin, an antibiotic effective on wild-type <it>Asaia</it> spp., and the effects on the larval development were evaluated. Larvae treated with the antibiotic showed a delay in the development and an asynchrony in the appearance of later instars. In larvae treated with rifampicin, but supplemented with a rifampicin-resistant mutant strain of <it>Asaia</it>, larval development was comparable to that of control larvae not exposed to the antibiotic. Analysis of the bacterial diversity of the three mosquito populations confirmed that the level of <it>Asaia</it> was strongly decreased in the antibiotic-treated larvae, since the symbiont was not detectable by PCR-DGGE (denaturing gradient gel electrophoresis), while <it>Asaia</it> was consistently found in insects supplemented with rifampicin plus the antibiotic-resistant mutant in the diet, and in those not exposed to the antibiotic.</p> <p>Conclusions</p> <p>The results here reported indicate that <it>Asaia</it> symbionts play a beneficial role in the normal development of <it>An. stephensi</it> larvae.</p

Chimeric symbionts expressing a Wolbachia protein stimulate mosquito immunity and inhibit filarial parasite development

Wolbachia can reduce the capability of mosquitoes to transmit infectious diseases to humans and is currently exploited in campaigns for the control of arboviruses, like dengue and Zika. Under the assumption that Wolbachia-mediated activation of insect immunity plays a role in the reduction of mosquito vectorial capacity, we focused our attention on the Wolbachia surface protein (WSP), a potential inductor of innate immunity. We hypothesized that the heterologous expression of this protein in gut- and tissue-associated symbionts may reduce parasite transmission. We thus engineered the mosquito bacterial symbiont Asaia to express WSP (AsaiaWSP). AsaiaWSP induced activation of the host immune response in Aedes aegypti and Anopheles stephensi mosquitoes, and inhibited the development of the heartworm parasite Dirofilaria immitis in Ae. aegypti. These results consolidate previous evidence on the immune-stimulating property of WSP and make AsaiaWSP worth of further investigations as a potential tool for the control of mosquito-borne diseases

Hydrolytic Profile of the Culturable Gut Bacterial Community Associated With Hermetia illucens

Larvae of the black soldier fly (BSF) Hermetia illucens (L.) convert organic waste into high valuable insect biomass that can be used as alternative protein source for animal nutrition or as feedstock for biodiesel production. Since insect biology and physiology are influenced by the gut microbiome, knowledge about the functional role of BSF-associated microorganisms could be exploited to enhance the insect performance and growth. Although an increasing number of culture-independent studies are unveiling the microbiota structure and composition of the BSF gut microbiota, a knowledge gap remains on the experimental validation of the contribution of the microorganisms to the insect growth and development. We aimed at assessing if BSF gut-associated bacteria potentially involved in the breakdown of diet components are able to improve host nutrition. A total of 193 bacterial strains were obtained from guts of BSF larvae reared on a nutritious diet using selective and enrichment media. Most of the bacterial isolates are typically found in the insect gut, with major representatives belonging to the Gammaproteobacteria and Bacilli classes. The hydrolytic profile of the bacterial collection was assessed on compounds typically present in the diet. Finally, we tested the hypothesis that the addition to a nutritionally poor diet of the two isolates Bacillus licheniformis HI169 and Stenotrophomonas maltophilia HI121, selected for their complementary metabolic activities, could enhance BSF growth. B. licheniformis HI169 positively influenced the larval final weight and growth rate when compared to the control. Conversely, the addition of S. maltophilia HI121 to the nutritionally poor diet did not result in a growth enhancement in terms of larval weight and pupal weight and length in comparison to the control, whereas the combination of the two strains positively affected the larval final weight and the pupal weight and length. In conclusion, we isolated BSF-associated bacterial strains with potential positive properties for the host nutrition and we showed that selected isolates may enhance BSF growth, suggesting the importance to evaluate the effect of the bacterial administration on the insect performance