Synthesis of lipophilic tyrosyl esters derivatives and assessment of their antimicrobial and antileishmania activities

<p>Abstract</p> <p>Background</p> <p>Preparation of tyrosyl lipophilic derivatives was carried out as a response to the food, cosmetic and pharmaceutical industries' increasing demand for new lipophilic antioxidants.</p> <p>Results</p> <p>A large series of tyrosyl esters (<b>TyC₂</b>to <b>TyC_18:1</b>) with increasing lipophilicity was synthesized in a good yield using lipase from <it>Candida antarctica </it>(Novozyme 435). Spectroscopic analyses of purified esters showed that the tyrosol was esterified on the primary hydroxyl group. Synthetized compounds were evaluated for either their antimicrobial activity, by both diffusion well and minimal inhibition concentration (MIC) methods, or their antileishmanial activity against <it>Leishmania major </it>and <it>Leishmania infantum </it>parasite species.</p> <p>Among all the tested compounds, our results showed that only <b>TyC₈</b>, <b>TyC₁₀</b>and <b>TyC₁₂</b>exhibited antibacterial and antileishmanial activities. When MIC and IC₅₀values were plotted against the acyl chain length of each tyrosyl derivative, <b>TyC₁₀</b>showed a parabolic shape with a minimum value. This nonlinear dependency with the increase of the chain length indicates that biological activities are probably associated to the surfactant effectiveness of lipophilic derivatives.</p> <p>Conclusion</p> <p>These results open up potential applications to use medium tyrosyl derivatives surfactants, antioxidants, antimicrobial and antileishmanial compounds in cosmetic, food and pharmaceutical industries.</p

Climatic Aridity Gradient Modulates the Diversity of the Rhizosphere and Endosphere Bacterial Microbiomes of Opuntia ficus-indica

© Copyright © 2020 Karray, Gargouri, Chebaane, Mhiri, Mliki and Sayadi. Recent microbiome research has shown that soil fertility, plant-associated microbiome, and crop production can be affected by abiotic environmental parameters. The effect of aridity gradient on rhizosphere-soil (rhizosphere) and endosphere-root (endosphere) prokaryotic structure and diversity associated with cacti remain poorly investigated and understood. In the current study, next-generation sequencing approaches were used to characterize the diversity and composition of bacteria and archaea associated with the rhizosphere and endosphere of Opuntia ficus-indica spineless cacti in four bioclimatic zones (humid, semi-arid, upper-arid, and lower-arid) in Tunisia. Our findings showed that bacterial and archaeal cactus microbiomes changed in inside and outside roots and along the aridity gradient. Plant compartment and aridity gradient were the influencing factors on the differentiation of microbial communities in rhizosphere and endosphere samples. The co-occurrence correlations between increased and decreased OTUs in rhizosphere and endosphere samples and soil parameters were determined according to the aridity gradient. Blastococcus, Geodermatophilus, Pseudonocardia, Promicromonospora, and Sphingomonas were identified as prevailing hubs and were considered as specific biomarkers taxa, which could play a crucial role on the aridity stress. Overall, our findings highlighted the prominence of the climatic aridity gradient on the equilibrium and diversity of microbial community composition in the rhizosphere and endosphere of cactus.We thank the Tunisian authorities for the support in prickly pear tree sampling and also Dr. Fabrice Armougoum from the Mediterranean Institute of Oceanography (MIO, IRD, UM 110, 13288, Marseille, France) for his great help on microbiome analysis

Olive agroforestry shapes rhizosphere microbiome networks associated with annual crops and impacts the biomass production under low-rainfed conditions

Agroforestry (AF) is a promising land-use system to mitigate water deficiency, particularly in semi-arid areas. However, the belowground microbes associated with crops below trees remain seldom addressed. This study aimed at elucidating the effects of olive AF system intercropped with durum wheat (Dw), barely (Ba), chickpea (Cp), or faba bean (Fb) on crops biomass and their soil-rhizosphere microbial networks as compared to conventional full sun cropping (SC) under rainfed conditions. To test the hypothesis, we compared the prokaryotic and the fungal communities inhabiting the rhizosphere of two cereals and legumes grown either in AF or SC. We determined the most suitable annual crop species in AF under low-rainfed conditions. Moreover, to deepen our understanding of the rhizosphere network dynamics of annual crops under AF and SC systems, we characterized the microbial hubs that are most likely responsible for modifying the microbial community structure and the variability of crop biomass of each species. Herein, we found that cereals produced significantly more above-ground biomass than legumes following in descending order: Ba > Dw > Cp > Fb, suggesting that crop species play a significant role in improving soil water use and that cereals are well-suited to rainfed conditions within both types of agrosystems. The type of agrosystem shapes crop microbiomes with the only marginal influence of host selection. However, more relevant was to unveil those crops recruits specific bacterial and fungal taxa from the olive-belowground communities. Of the selected soil physicochemical properties, organic matter was the principal driver in shaping the soil microbial structure in the AF system. The co-occurrence network analyses indicated that the AF system generates higher ecological stability than the SC system under stressful climate conditions. Furthermore, legumes’ rhizosphere microbiome possessed a higher resilient capacity than cereals. We also identified different fungal keystones involved in litter decomposition and drought tolerance within AF systems facing the water-scarce condition and promoting crop production within the SC system. Overall, we showed that AF reduces cereal and legume rhizosphere microbial diversity, enhances network complexity, and leads to more stable beneficial microbial communities, especially in severe drought, thus providing more accurate predictions to preserve soil diversity under unfavorable environmental conditions.This research was carried out as part of the D4DECLIC Project, ARIMNet 2 Young Scientists Call 2017 (ERA-NET program), and Grant agreement no. 618127

201: Are QT intervals correlated to apnea-hypopnea index in obstructive sleep apnea?

IntroductionSeveral studies proved that obstructive sleep apnea (OSA) is associated with cardio-vascular diseases such as cardiac arrhythmia. QT duration and dispersion reflect the heterogeinity of ventricular repolarization and are considered as precursors of ventricular arrhythmiaAimThe aim of this study is to assess the relation between the severity of OSA parameters as apnea hypopnea index and QT intervals.MethodsForty patients (18 men and 22 women) who were diagnosed with OSA by overnight polysomnography were included in this prospective study. The mean age was 56±10 years old. They were all in sinus rhythm. Before initiating continuous positive airway pressure therapy, we calculated on a 12 lead ECG : QT duration (QTend) corrected to Bazett formula and QT dispersion (QT end max -QT end min).ResultsTwenty four patients had severe OSA (AHI >30), 4 had moderate OSA (AHI between 15 and 30) and 12 had a mild OSA (AHI between 5 and 15). There was a significant positive correlation between QT dispersion and AHI (r=0.48, p=0.001)ConclusionThe severity of OSA seems to be correlated with ventricular repolarization heterogeinity These results suggest that the higher is the AHI the higher is the risk of ventricular arrhythmia occurence. Further studies are needed to validate these results

A year of genomic surveillance reveals how the SARS-CoV-2 pandemic unfolded in Africa.

The progression of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in Africa has so far been heterogeneous, and the full impact is not yet well understood. In this study, we describe the genomic epidemiology using a dataset of 8746 genomes from 33 African countries and two overseas territories. We show that the epidemics in most countries were initiated by importations predominantly from Europe, which diminished after the early introduction of international travel restrictions. As the pandemic progressed, ongoing transmission in many countries and increasing mobility led to the emergence and spread within the continent of many variants of concern and interest, such as B.1.351, B.1.525, A.23.1, and C.1.1. Although distorted by low sampling numbers and blind spots, the findings highlight that Africa must not be left behind in the global pandemic response, otherwise it could become a source for new variants

Isolation and Characterization of Hydrocarbon-Degrading Yeast Strains from Petroleum Contaminated Industrial Wastewater

Two yeast strains are enriched and isolated from industrial refinery wastewater. These strains were observed for their ability to utilize several classes of petroleum hydrocarbons substrates, such as n-alkanes and aromatic hydrocarbons as a sole carbon source. Phylogenetic analysis based on the D1/D2 variable domain and the ITS-region sequences indicated that strains HC1 and HC4 were members of the genera Candida and Trichosporon, respectively. The mechanism of hydrocarbon uptaking by yeast, Candida, and Trichosporon has been studied by means of the kinetic analysis of hydrocarbons-degrading yeasts growth and substrate assimilation. Biodegradation capacity and biomass quantity were daily measured during twelve days by gravimetric analysis and gas chromatography coupled with mass spectrometry techniques. Removal of n-alkanes indicated a strong ability of hydrocarbon biodegradation by the isolated yeast strains. These two strains grew on long-chain n-alkane, diesel oil, and crude oil but failed to grow on short-chain n-alkane and aromatic hydrocarbons. Growth measurement attributes of the isolates, using n-hexadecane, diesel oil, and crude oil as substrates, showed that strain HC1 had better degradation for hydrocarbon substrates than strain HC4. In conclusion, these yeast strains can be useful for the bioremediation process and decreasing petroleum pollution in wastewater contaminated with petroleum hydrocarbons

Isolation of bacterial strains from compost teas and screening of their PGPR properties on potato plants

The beneficial effect of compost and compost tea on plant growth and protection is mainly associated with the microbial diversity and the presence of bacteria with plant growth–promoting effect. PGPR are considered as eco-friendly bio-fertilizers that may reduce the use of chemical pesticides and fertilizers. Three composts (AT, A10, and A30) were previously prepared from industrial wastes (olive mill wastewater, olive pomace, coffee ground, and phosphogypsum). In the present study, we isolated three bacterial strains from the compost teas. The phylogenetic identification of these bacterial strains (B.AT, B.A10, and B.A30) showed that they correspond to Serratia liquefaciens (B.AT and B.A10) and Achromobacter spanius (B.A30) species. A further characterization of the PGPR traits of these bacteria showed that they produce siderophore, exopolysaccharides, and IAA. Their effect on potato plant growth, yields, and tuber quality was performed under field culture conditions. Results showed that these strains can be characterized as PGPR, the best effect on potato plant growth was observed with Serratia liquefaciens (B.AT), the best yield and tuber quality was observed with Serratia liquefaciens (B.A10) while bacterial treatment with Achromobacter spanius (B.A30) is a Cd-tolerant PGPR.This work was financially supported by the Tunisian Ministry of High Education and Scientific Research