Femtosecond and picosecond fluorescence of native bacteriorhodopsin and a nonisomerizing analog

The spectrally and temporally resolved fluorescence properties of native bacteriorhodopsin (bR) and bR reconstituted with a nonisomerizing analog of the retinal Schiff base (bR5.12) are examined. The first attempt to experimentally monitor the excited state relaxation processes in both type of pigments using ultrafast fluorescence spectroscopy is reported. The fluorescence is emitted from retinal molecules in an all-trans configuration. Substantial energy relaxation involves very fast intramolecular and intermolecular vibrational modes and these are shown to occur on a time scale faster than isomerization. The possible contribution of dielectric interaction between the retinal Schiff base and the protein environment for the excited state energy relaxation is discussed.     

Toxin-based in-vitro selection and its potential application to date palm for resistance to the bayoud Fusarium wilt

Date palm (Phoenix dactylifera L.) is qualified as a 'tree' of great ecological and socio-economical importance in desert oases. Unfortunately, it is being decimated, especially in Morocco and Algeria, by a fusariosis wilt called bayoud and caused by Fusarium oxysporum f. sp. albedinis (Fao). Controlling this disease requires the implementation of an integrated management program. Breeding for resistance is one of the most promising component strategies of this program. Few naturally resistant cultivars with a mediocre fruit quality (dates) are known. Conventional and non-conventional methods are under development and have to use the simplest and easiest methods to screen for resistant individuals. The use of pathogen toxins as selective agents at the tissue culture step might be a source of variability that can lead to the selection of individuals with suitable levels of resistance to the toxin and/or to the pathogen among the genetic material available. Foa produces toxins such as fusaric, succinic, 3-phenyl lactic acids and their derivatives, marasmins and peptidic toxins. These toxins can be used bulked or separately as selective agents. The aim of this contribution was to give a brief overview on toxins and their use as a mean to select resistant lines and to initiate a discussion about the potential use of this approach for the date palm-Foa pathosystem. This review does not pretend to be comprehensive or exhaustive and was prepared mainly to highlight the potential use of Foa toxins for selecting date palm individuals with a suitable resistance level to bayoud using toxin-based selective media.     

Genotype identification of Enterocytozoon bieneusi isolates from stool samples of HIV-infected Tunisian patients

The microsporidian species Enterocytozoon bieneusi is a major cause of chronic diarrhea and malabsorption in patients with AIDS. Genotyping was performed on seven E. bieneusi strains for the first time in Tunisia. All the strains were isolated from stool samples of humans with immunodeficiency virus (HIV) infection. Analysis of the ribosomal RNA gene internal transcribed spacer (rDNA ITS) allowed the identification of three distinct genotypes previously described in other studies. Genotypes D and B were characterized in four and two respectively. The Peruvian genotype (Peru 8) was detected in the last isolate. These results indicate a genetic diversity in E. bieneusi strains from HIV Tunisian patients and suggest the coexistence of both zoonotic and anthroponotic route of transmission.     

Estimation of Canine Leishmania Infection Prevalence in Six Cities of the Algerian Littoral Zone Using a Bayesian Approach

A large-scale study on canine Leishmania infection (CanL) was conducted in six localities along a west-east transect in the Algerian littoral zone (Tlemcen, Mostaganem, Tipaza, Boumerdes, Bejaia, Jijel) and covering two sampling periods. In total 2,184 dogs were tested with an indirect fluorescent antibody test (IFAT) and a direct agglutination test (DAT). Combined multiple-testing and several statistical methods were compared to estimate the CanL true prevalence and tests characteristics (sensitivity and specificity). The Bayesian full model showed the best fit and yielded prevalence estimates between 11% (Mostaganem, first period) and 38% (Bejaia, second period). Sensitivity of IFAT varied (in function of locality) between 86% and 88% while its specificity varied between 65% and 87%. DAT was less sensitive than IFAT but showed a higher specificity (between 80% and 95% in function of locality or/and season). A general increasing trend of the CanL prevalence was noted from west to east. A concordance between the present results and the incidence of human cases of visceral leishmaniasis was observed, where also a maximum was recorded for Bejaia. The results of the present study highlight the dangers when using IFAT as a gold standard.     

Fungal and Bacterial Colonisation of Salix pedicellataLeaves Decaying in Permanent and Intermittent Streams in Eastern Morocco

Leaf degradation was investigated at four sites in the Zegzel/Cherraa river system (Oueds). Two sites (Upper Zegzel and Lower Zegzel) carry water throughout the year and two (Upstream and Downstream Cherraa) are dry for 5–7 months each year. The dynamics of leaf weight loss and microorganisms associated with Salix pedicellata leaves decaying at the four sites were compared for the first time during the same period over this permanent and intermittent system. Overall decay rates of leaves were significantly higher in the permanent Zegzel stream sections (k = 0.0094 d^–1 upstream and 0.0056 downstream) than in the intermittently flowing Cherraa sites (k = 0.0046 upstream, and 0.0036 downstream). In the latter, decay was much slower during dry than during wet periods (Upstream Cherraa: k = 0.0028 and 0.0446, respectively; Downstream Cherraa, k = 0.0008 and 0.0357, respectively). Similar gradients from permanent to intermittent sites were observed in numbers of bacteria per unit area or per weight of decaying leaves (direct counts by epifluorescence microscopy), in numbers of fungal species and in sporulation rates, from leaves recovered at the four sites. Ten hyphomycete species were new for Morocco.     

Optimization of citric acid production by Aspergillus niger using two downgraded Algerian date varieties

In the present work, the GHARS and the MECH DEGLA downgraded date varieties were used in a fermentation medium in order to produce citric acid by the Aspergillus niger. The biochemical characteristics of the dates were investigated, along with the chemical and physical characteristics of the solutions of both samples. The analyzed parameters included the moisture and sugar content, the ash residual, the pH values, and the electrical conductivity. The effect of the following fermentation parameters was studied: initial pH, temperature, incubation period, and methanol. For the GHARS and MECH DEGLA date varieties respectively, the ash residual measured at 1.90% and 2.47%. For each date variety, the moisture and total sugars were measured at 11.59% and 85%, for the GHARS, and 12.82% and 80.47% for the MECH DEGLA. Citric acid production using either of the two varieties of dates showed a high yield in a short time.The obtained results showed that the highest production of citric acid by both medium of dates was achieved at the initial pH value of 3.0, temperature 30 °C, and an incubation period of 8 days. Also, the maximum amount of citric acid was produced when both mediums contained 4% of methanol. Both varieties of dates showed a good yield for the citric acid and can be used as a culture medium since they are economic and ensure good growth for the Aspergillus niger.     

Distribution de Megaporellaboulangeri Deloffre et Beun, 1986 (algue dasycladale) dans le Jurassique du bassin atlantique marocain

The recent biostratigraphic and micropaleontologic works permitted to specify the distribution of Megaporellaboulangeri Deloffre and Beun in the Jurassic of the Moroccan Atlantic basin. The lower limit of the extension of this dasycladale alga, earlier attribued to the Early Kimmeridgian by Deloffre and Beun (1986), is currently placed in the Early Callovian, on the basis of the age provided by Megaporellaboulangeri biozone. The Otternstellaarabica biozone dates the upper limit of the extension of the species of the Early Oxfordian. Megaporellaboulangeri proliferates in the borders of the basin where the internal lagoons facies dominate, however it is absent in the western parts with open sea facies.