The ability of Pseudomonas to grow and to produce siderophores is dependent on the iron content and the type of carbon sources in the medium. Under conditions of low-iron concentration the Pseudomonas isolates studied produced yellow-green fluorescent iron-binding peptide siderophores and the biosynthesis of this siderophores was affected by several different environmental parameters. Four basal media, supplemented with different concentration of iron, were employed to study the effect of iron and different organic carbon sources on siderophore production in Pseudomonas fluorescens. The highest siderophores concentration was obtained in succinate medium. Ferric iron increased the growth yield and completely repressed siderophores production above 200 g/l, but had a positive effect below 160 g/l. Penicillin and lead elicited the production of siderophores in the presence of excess iron. Pre-treatment of the standard succinate medium with α α α α,α α α α-dipyridyl and 8-hydroxyquinoline to reduce the concentration of iron diminished both the growth yield and siderophore production, but α α α α,α α α α-dipyridyl increased significantly the amount of siderophores produced in the presence of 0.20 mg/l of the chelating ion.

Several strains of environmental Pseudomonas aeruginosa have been used in biotechnology to produce beneficial metabolites in medicine and agriculture. Many secondary metabolites are secreted throughout their growth where phenazines are one among the most known stronger metabolites. The phenazines are antimicrobial substances inhibiting a wide range of pathogenic bacteria. In order to exploit the antimicrobial effect of P. aeruginosa and its pheanzines we do isolate the studied bacteria from saline soil collected from Mina river region (Relizane, Algeria). Ten isolates belonged to Pseudomonas were selected by an antagonistic test, one of isolates was identified as P. aeruginosa and selected for phenazines production. Phenazines were produced using King A broth medium, extracted by ethyl acetate and purified by silica gel chromatography. The antimicrobial activity of crude extract containing phenazines was evaluated by the disc diffusion method against a number of pathogen microorganisms and the minimal inhibitory concentrations (MIC) were determined. The results indicated that the crude phenazines solution was effective against Escherichia coli, Staphylococcus aureus, Bacillus cereus, Shigella sonnei and Candida albicans. The characterization of purified phenazines extract by HPLC showed a peak similar to the standard. The results of this study will contribute in the identification of the potential of phenazines naturally-occurring substances as antimicrobial agents.

<p>Artemisia, one of the larger genera in the family Asteraceae, comprises from 200 to more than 500 taxa at the specific or subspecific level. Artemisia herba-alba Asso (Shih) is grown in North Africa and certain parts of Asia and Middle East. It is one of the most widely used plants in the Algerian folk medicine. The antioxidant and free radical scavenging activities of the methanolic extracted materials were tested together with their antibacterial effects against isolated bacterial strains causing food poisoning. In summary, <em>A. herba-alba</em> Asso represent a good phenolic and flavonoid content (161, 64 mg/g and 16,83mg/g, respectively) in comparison with <em>T. capitatus</em> L which represent a phenolic content of 131, 48 mg/g and 14, 96 of flavonoid content. The results shows also that the methanolic extracts of the two plants possess a strong antioxidant (DPPH, FRAP assays) and antibacterial activities, which supports their ethnopharmacological use and <em>A. herba alba</em> represent the highest values (IC 50: 2, 35 mg/ml and OD 1, 13 at 700nm). Our results show the interest of <em>A. herba-alba</em> Asso and <em>T. capitatus</em> L, among other medicinal plants, in search of new chemo-preventive agents against biofilm and planktonic growth of food spoilage pathogens. Further studies are envisaged to target the most interesting molecules responsible for these activities. It is concluded that organic extracts from <em>Artemisia herba alba</em> Asso, exert strong antioxidant activities which are related to their polyphenol contents. </p>

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