Identification of lactobacilli residing in chicken ceca with antagonism against Campylobacter

Bacteriocins produced by Lactobacillus salivarius have been recently recognized as a natural means to control Campylobacter and Salmonella in live poultry. This finding is of relevance since Campylobacter jejuni and Campylobacter coli are the predominant species isolated from poultry that are associated with human campylobacteriosis. In the present work, lactic acid bacteria (LAB) isolated from the cecum of twenty Tunisian chickens were identified and those isolates with antagonism against Campylobacter were further characterized. Following their preliminary confirmation as LAB, 150 strains were identified by combining morphological criteria, biochemical tests, and molecular methods, the latter inluding intergenic 16S- 23S PCR, specific lactobacilli PCR, and a biphasic approach. Most of the LAB isolated belonged to the genus Lactobacillus, among them Lb. sakei (33.3%), Lb. salivarius (19.4%), Lb. reuteri (8.6%), and Lb. curvatus (8.6%). The other LAB strains included those of the genus Weissella (16.7%), Enterococcus faecalis (5.3%), Leuconostoc mesenteroides (2.7%), Lactococcus graviae (2.7%), and Streptococcus sp. (2.7%). The Lactobacilli strains were tested for their antagonism against C. jejuni and C. coli. The activity of three of them, Lb. salivarius SMXD51, Lb. salivarius MMS122, and Lb. salivarius MMS151, against the aforementioned target strains could be ascribed to the production of bacteriocins.     

Diversity of terrestrial isopods in the northern Tunisian wetlands

To evaluate the influence of wetland types on the distribution of terrestrial isopods, species richness, relative abundance and diversity indices were studied in the supralittoral zone of 95 wetlands in the north‐western of Tunisian dorsal, belonging to six types: lagoon, hill reservoir, river, dam, lake and sebkha. We tested the following hypothesis: (i) is isopod diversity influenced by wetland types? (ii) is isopod diversity influenced by bioclimatic zones? and (iii) what are the environmental factors influencing isopod distribution? A total of 3255 individuals belonging to twenty species of terrestrial isopods were captured. Species richness differs significantly between wetland types. A highly significant positive relationship between species richness and both humidity and altitudinal gradient was described. The dendrogram of similarities showed a divergence of the lagoons compared to the remaining wetland types.     

QTLs mapping of morphological traits related to salt tolerance in <Emphasis Type="Italic">Medicago truncatula</Emphasis>

To understand the complex inheritance of tolerance to salt stress in Medicago truncatula, quantitative trait loci (QTLs) analysis was performed using a set of recombinant inbred lines (RILs) derived from a cross between the tolerant line Jemalong A17 and susceptible line F83005.5. The RILs and parental lines were grown in individual pots filled with sterilized sand in a greenhouse under 0 and 50 mM NaCl. Plants were harvested after a period of 60 days. Fourteen quantitative traits related to aerial and root growths were measured. Broad-sense heritability of measured traits ranged from 0.21 to 0.83 and from 0.05 to 0.62 in control and in salt-stressed conditions, respectively. Established correlations between measured traits are dependent on treatment effect. We identified and mapped 10 QTLs in control conditions and 19 in salt stress. No major QTL was identified indicating that tolerance to salt stress is governed by several genes with low effects. The QTLs detected under control and under salt-stressed conditions almost did not share the same map locations suggesting that the loci that are not stable across treatments reflect adaptation to this constraint. The maximum of QTLs was observed on the chromosome 8. The usefulness of these QTLs, identified in greenhouse conditions, for marker-assisted selection should therefore be evaluated under field conditions, and validated in other genetic backgrounds.     

The anti-inflammatory effect of paraoxonase 1 against oxidized lipids depends on its association with high density lipoproteins

AimThe aims of this study were to investigate whether purified PON1 can reduce the pro-inflammatory effect of oxidized phospholipids and whether the effect depended on its association with HDL.Main methodsLipid peroxidation was induced by copper ions and was measured using the conjugated diene method. Lysophosphatidylcholine (lyso-PC) formation was measured by HPLC with evaporative light scattering detection (ELSD) and ICAM-1 expression on Ea.hy926 endothelial cells was analyzed by flow cytometry.Key findingsPurified PON1 significantly inhibited copper-induced oxidation of LDL and HDL, causing a 60.5% and 77.7% decrease in conjugated diene formation, respectively. Incubating PON1 with oxLDL caused a significant increase in lyso-PC levels, while oxHDL caused a significant decrease. PON1 (12.5 to 50 μg/mL) had a pro-inflammatory effect in the presence of oxLDL, increasing ICAM-1 levels in Ea.hy926 cells by 33.0% and 40.6% (p < 0.001) respectively, and had an anti-inflammatory effect in the presence of oxHDL, causing a 3-fold reduction in ICAM-1 levels. PON1 also caused a significant decrease in TNFα? and purified lyso-PC-induced ICAM-1 expression. The results obtained with reconstituted HDL as well as LCAT and PAF-AH inhibitors suggested that the anti-inflammatory effect of PON1 against oxidized lipids is dependent on its association with HDL.SignificanceOur results clearly showed that PON1 is involved in the anti-inflammatory effect of HDL and that the effect appears to depend on its association with HDL.     

Analysis of Genetic Variation in Natural Populations of Medicago truncatula of Southern Tunisian Ecological Areas, Using Morphological Traits and SSR Markers

We used 19 quantitative traits and 14 microsatellite markers (SSRs) to analyze the genetic variation in four natural populations of the model legume Medicago truncatula sampled in southern Tunisia. The greatest genetic variation of quantitative traits and molecular markers occurred within populations (>71%). In contrast to quantitative population differentiation (Q _ST ?=?0.09), a high level of molecular differentiation (F _ST ?=?0.23) was found among populations. The majority of quantitative traits exhibited Q _ST values significantly less than F _ST values, suggesting that selection may be acting to suppress differentiation for these traits. There was no significant correlation between genetic variation of quantitative traits and molecular markers within populations. On the other hand, significant correlations were found between measured quantitative characters and the site-of-origin environmental factors. The eco-geographical factors with the greatest influence on the variation of measured traits among populations were altitude, followed by soil texture, assimilated phosphorus (P₂O₅) and organic matter. Nevertheless, there were no consistent patterns of associations between gene diversity (He) and eco-geographical factors.     

Sec1/Munc18 protein stabilizes fusion-competent syntaxin for membrane fusion in Arabidopsis cytokinesis

Intracellular membrane fusion requires complexes of syntaxins with other SNARE proteins and regulatory Sec1/Munc18 (SM) proteins. In membrane fusion mediating, e.g., neurotransmitter release or glucose-stimulated insulin secretion in mammals, SM proteins preferentially interact with the inactive closed, rather than the active open, conformation of syntaxin or with the assembled SNARE complex. Other membrane fusion processes such as vacuolar fusion in yeast involve like membranes carrying cis-SNARE complexes, and the role of SM protein is unknown. We investigated syntaxin-SM protein interaction in membrane fusion of Arabidopsis cytokinesis, which involves cytokinesis-specific syntaxin KNOLLE and SM protein KEULE. KEULE interacted with an open conformation of KNOLLE that complemented both knolle and keule mutants. This interaction occurred at the cell division plane and required the KNOLLE linker sequence between helix Hc and SNARE domain. Our results suggest that in cytokinesis, SM protein stabilizes the fusion-competent open form of syntaxin, thereby promoting trans-SNARE complex formation.     

Parasitoids of chickpea leafminer Liriomyza cicerina (Diptera: Agromyzidae) and their parasitism rate on chickpea fields in North Tunisia

In recent years, as a consequence of climatic changes, the leafminer Liriomyza cicerina had emerged as a serious pest in chickpea crops causing considerable damage in Tunisia. Thus, the search of control methods is necessary. The aim of this research was to monitor and identify the naturally occurring parasitoids of the chickpea leafminer Liriomyza cicerina in insecticide-free chickpea-growing areas located in North-Western Tunisia. Chickpea leaves with mines were weekly sampled from Beja and Kef sites during 2016 and 2017 and kept to observe and count emerging leafminer and parasitoid adults in the laboratory. Results revealed that L. cicerina parasitoids complex species included three hymenopteran parasitoids namely Opius monilicornis (Fisher, 1962) (Braconidae); Diglyphus isaea (Walker, 1838) (Eulophidae) and Diaulinopsis arenaria (Erdös, 1951) (Eulophidae). These parasitoids were identified and recorded for the first time in Tunisia on L. cicerina with parasitism rate varied between 13% and 52.5%. The most common species was O. monilicornis. The correlation between infestation rate on chickpea plants and number of emerged three parasitoids was calculated revealing high significant and positive correlations. The diversity index (H′) was also calculated. The three parasitoids were found in two sites Beja and Kef; while the diversity differed during the developmental stage of chickpea crops.