Heavy metal tolerant Pseudomonas protegens isolates from agricultural well water in northeastern Algeria with plant growth promoting, insecticidal and antifungal activities

The application of plant growth promoting bacteria (PGPB) with biocontrol activities as inoculants of crop plants against phytopathogenic fungi and insect pests provide a biological alternative to the use of agrochemicals. Two Pseudomonas protegens strains were isolated from agricultural well water in a heavy metal contaminated area near Bejaia, northeastern Algeria. The isolates S4LiBe and S5LiBe had 16S rRNA gene sequence similarities of 99.4%–99.7% with P. protegens CHA0T and other P. protegens strains. The phenotypic profiles tested with BIOLOG-GN2-microplates showed differences in 12 of 95 carbon sources tested, as compared to the type strain P. protegens CHA0T. The isolates S4LiBe and S5LiBe showed plant growth promoting potential which is commonly associated with the production of the phytohormone indole acetic acid and siderophores and the solubilization of insoluble phosphate. In addition, they produce chitinase and other polymer degrading enzymes. As the strains S4LiBe and S5LiBe were isolated from heavy metal polluted well water, they are resistant against several heavy metals (2.0 mM K2Cr2O7 and 3.0 mM CoSO4, HgSO4, CdSO4 8H2O and PbCl2), while the reference strain P. protegens CHA0T was very sensitive to Hg2+ and Cd2+ and had lower tolerance towards Co2+ and Pb2+. The isolates S4LiBe and S5LiBe were active in mycelial growth inhibition assays against Botrytis cinerea, Verticillium dahliae, Fusarium graminearum, Aspergillus niger and Aspergillus flavus (growth inhibition between 88% and 48%). Furthermore, S4LiBe and S5LiBe showed effective insecticidal activities, when tested in the Galleria injection assay and they were tested positive for the insect toxin gene fitD alike the reference strain CHA0T. Finally, inoculation of barley seeds with S5LiBe in non-polluted agricultural soil significantly stimulated the germination rate and growth of seedlings, with increased shoot length (11.96 cm ± 0.59), shoot and root fresh weight (0.10 g ± 0.009, 0.04 g ± 0.006), shoot and root dry weight (0.075 g ± 0.003, 0.03 g ± 0.007) as compared to non-inoculated plants (10.23 cm ± 0.84, 0.06 g ± 0.007, 0.025 g ± 0.006, 0.047 g ± 0.006, and 0.016 g ± 0.004, respectively). In heavy metal contaminated soil, inoculation with strain S5LiBe resulted in similar increase of germination rate and growth parameters of barley like in the non-polluted soil, while P. protegens CHA0T inoculated plants were not stimulated. Thus, the heavy metal tolerant isolates S4LiBe and S5LiBe have a potential as beneficial bacteria for agricultural application even in heavy metal polluted soils, e.g. for the stimulation of biomass crops. The demonstration of successful isolation from agricultural well water may open more ready access for a wide variety of this kind of beneficial bacteria for agricultural application

Analyse et optimistation du r eseau distribution electrique de la Wilaya de Bouira par la m ethode de l'analyse matricielle

La demande en energie electrique est en progression constante il est donc imp eratif d'optimiser le r eseau de distribution de cette energie qui est fourni sous forme de puissance, cette derni ere exprim e sous forme produit v:i (v :volt, i :Amp ere) .il en d ecoule que deux ces param etres d eterminant tout l'optimisation, on doit donc se baser sur la relation qui est reli e ce deux param etres, cette derni ere se pr esent e sous la forme matricielle AX = b. A est la matrice d'incidence. X : la di erence du potentielle. B : le courant. En g en erale cette equation n'a pas de solution, on cherche alors la meilleure approximation. La m ethode matricielle nous permettant d'arriver a but et c'est r ev el e meilleure que la m ethode des moindres carr es, il est plus direct et exigent moins de temps de calcul, il pr esente aussi l'avantage de param etres proc ed es de simulation, car la m ethode r eduite consid erablement le temps de calcul

Biological Control of Botrytis cinerea by Bacillus sp. Strain S7LiBe Under Abiotic Stress

In this investigation, the isolate S7LiBe isolated from trefoil rhizosphere in Barbacha, Bejaia (northern Algeria), was selected on the basis of plant growth promoting attributes. This isolate identified as Bacillus sp. based on 16SrDNA sequence analysis, exhibits the highest similarity of 99.1% with Bacillus pichinotyi AF519463 andAF519460 and Bacillus sp. JX152775. Bacillus sp. S7LiBe has been subjected to the study of its antifungal activity against Botrytis cinerea in vitro and in vivo on the detached lettuce leaves. The effect of some abiotic factors on the performance of this bacterial strain as biocontrol agent and the production of some antifungal metabolites (siderophores, ammonia, hydrogen cyanide and chitinase) were also carried out. The results showed that Bacillus sp. S7LiBe strain inhibit the mycelial growth in high level (70%±1,33) and the fungal spores germination (82,54%±3,58 ). The strain produce siderophores, ammonia, hydrogen cyanide and chitinase. Its antagonistic activity was found to be optimal on CZA modified medium at a pH of 6.5 and a temperature of 30 ° C. The antagonist activity on the detached lettuce leaves showed that the bacterial strain inhibit 57.0% of the lesion extension

Chapter 13 - Knock, knock-let the bacteria in: enzymatic potential of plant associated bacteria

Beneficial bacteria associated with plants have evolved for thousands of years together with their hosts to an intricate communication system that allow the recognition and penetration into plant tissues without harming them. Within the molecules involved in this communication system, the enzymes produced by the bacteria have an important role and some of them have been shown essential at first steps of plant colonization. In this chapter, we analyze the implication of some of the most well-known enzymes related to plant probiotic bacteria and their hosts, the steps at which these enzymes participate to allow the recognition by the plants and the bacterial penetration into their inner tissues. Between these enzymes we will examine the importance of (i) cellulases, produced by important plant growth promoters to penetrate plant tissues; (ii) chitinases, implicated in the defense of the plant against fungi and recognition by the plants; (iii) lectins, implicated in the attachment and first recognition steps; (iv) pectinases, which are usually expressed early during infection, in the penetration steps; and (v) xylanases, implicated in the recycling at senescence, amongst others. The upregulated expression of some of these enzymes in plant growth promoting bacteria was surprising at first, as they would be expected in pathogens, not in mutualistic microorganisms. However, as more data are available, the implication of hydrolytic enzymes in beneficial plant colonization is become clear

Cours de microbiologie générale destiné aux étudiants L2 Ecologie et Environnement

107 p. : ill. ; 30 cm. (+ CD-Rom)Les micro-organismes aussi appelés microbes forment un ensemble d’organismes vivants microscopiques, invisibles à l’œil nu. C’est leurs seul points communs car ils diffèrent et varient par leur morphologie, leur physiologie, leur mode de reproduction et leur écologie. Les micro-organismes sont les plus petits des êtres vivants et les derniers à être découverts, ils n’ont pu être observés qu’avec l’avènement des premiers instruments optiques grossissants. Après une introduction générale, le présent manuscrit est scindé en sept principaux chapitres, à savoir ; une introduction générale au monde des microbes, suivie d’un chapitre détaillant la structure et la morphologie de la cellule bactérienne, les chapitres trois et quatre sont focalisés sur la nutrition et la croissance de la cellule bactérienne. Un chapitre sur la classification détaillée des bactéries, suivis d’un autre sur les agents antimicrobiens, le dernier chapitre est consacré à quelques notions de Mycologie et de Virologie, pour en finir par une liste de références bibliographique. Ce travail est un appui pour les étudiants de deuxième année Biologie de différentes spécialités. Les différents chapitres détaillés sont accompagnés avec des illustrations et des figures permettent de bien assimiler le contenu