Screening of potential biosurfactant-producing bacteria isolated from seawater biofilm

Seawater represents a specific environment harboring complex bacterial community which is adapted to harsh conditions. Hence, biosurfactant produced by these bacteria under these conditions have interesting proprieties. The screening of biosurfactant producing strains isolated from seawater biofilm was investigated. Specific media, which have been reported to induce biosurfactant production, were used to prepare bacterial cultures and four methods; drop collapse, blue agar, blood-agar lysis and emulsification index, were applied to screen for biosurfactant production. 16 culturable, aerobic bacterial strains were isolated from biofilm in this study. Among these isolates, nine strains were Gram-positive and seven were Gram-negative. However the majority of the biosurfactant producer strains were Gram-negative belonging to different genera according to " a multitube micromethod for identification of bacteria (API system gallery)". Some of the isolated genera such as: Bacillus, Pseudomonas, Micrococcus, Neisseria, and Aeromonas are well known as biosurfactant producers, while other genera, mainly Staphylococcus, Chrysomonas and Photobacterium, were described for the first time as biosurfactant producers in this work.Keywords: Biosurfactant, seawater biofilm, bacteri

Isolation of four hydrocarbon effluent-degrading Bacillaceae species and evaluation of their ability to grow under high-temperature or high-salinity conditions

Four bacterial strains belonging to the family Bacillaceae were isolated from a polluted site and tested for their efficiency in degrading a refinery effluent highly polluted with hydrocarbons. Among 13 strains isolated, four were selected for their efficiency. Each of these four strains demonstrated a strong ability to grow as a single strain on a hydrocarbon effluent (HCE) as sole carbon source. In batch assays using clarified wastewater as diluent, the strains achieved high-percentage decreases in total hydrocarbon concentration within 18 days: 98% with Bacillus licheniformis STK08, 87% with Geobacillus stearothermophilus STM04, 80% with Lysinibacillus sphaericus STZ75 and 72% with Bacillus firmus STS84. The decreases were greater during the first three days of treatment, with 73, 66, 39 and 47% recorded for Bacillus licheniformis STK08, G. stearothermophilus STM04, L. sphaericus STZ75 and B. firmus STS84, respectively. Growth assays run under different conditions showed that B. licheniformis STK08 and G. stearothermophilus STM04 were able to grow at salinities of up to 120 g/L and at 55°C. Potential biosurfactant production tested using two methods namely modified drop collapse (MDC) and blue agar plate (BAP) demonstrated that the four Bacillaceae species are biosurfactant producers.Keywords: Hydrocarbons, biodegradation, pure culture, high salinity, high temperatureAfrican Journal of Biotechnology Vol. 12(14), pp. 1636-164

Anaerosalibacter bizertensis gen. nov., sp. nov., a new halotolerant bacterium isolated from sludge.

International audienceA strictly anaerobic, halotolerant and thermotolerant strain designated C5BELT was isolated from storage tanks holding wastes generated by the recycling of discarded motor oils located in north Tunisia. Cells of strain C5BELT stained Gram-positive, were motile by laterally inserted flagella, straight, and spore-forming. Their two major fatty acids were iso-C15:0 (60.1 %) and iso-C15:0 dimethyl acetal (22.0 %). Growth was observed at temperatures ranging from 25 to 55 °C (optimum 40 °C) and at pH 6 to 9 (optimum 7.5). The salinity range for growth was 0-100 g l-1 of NaCl (optimum 5 g l-1). Yeast extract is required for growth. Strain C5BELT was heterotrophic, able to use glucose, pyruvate, succinate, yeast extract, bio-trypcase and peptone, but was unable to grow on casamino acids. Sulfate, thiosulfate, sulfite, elemental sulfur, fumarate, nitrate and nitrite were not reduced. The DNA G + C content was 31.1 mol%. 16S rRNA gene sequence analysis indicated that strain C5BELT was a member of the family Clostridiaceae, class Clostridia, phylum Firmicutes and was most closely related to Sporanaerobacter acetigenes DSM 13106T (92.4 % similarity). On the basis of 16S rRNA gene sequence comparisons and physiological characteristics, strain C5BELT can be classified as a new species of a new genus, for which the name Anaerosalibacter bizertensis gen. nov., sp. nov. is hereby proposed. The type strain is C5BELT (= DSM 23801 = JCM 17239)

Dossier : Femmes, famille et droit

Quelle place occupent les femmes aujourd’hui ? Comment déchiffrer les dynamiques politiques et les conservatismes propres à chacun des pays de la région ? Le dossier, coordonné par Karima Dirèche-Slimani, s’attache à décrypter les évolutions de mœurs et de mentalités à l’œuvre dans les sociétés maghrébines à partir des codes de la famille. Une analyse riche et pertinente. Car si le Maroc tend à consacrer l’égalité juridique entre homme et femme depuis 2004, l’Algérie demeure plus réservée en la matière. Quant à la Tunisie, elle a célébré en 2006 le cinquantenaire du code de statut personnel abolissant la polygamie et la répudiation. Un dossier essentiel qu’accompagnent, à côté des habituels Gros Plans, Notes, Points de vue, Rubriques d’analyse, Études thématiques, des sujets à la pointe de l’actualité : qu’en est-il du pouvoir médiatique au Maghreb ? Qu’en est-il des Maghrébins en Europe ? Éric Gobe, rédacteur en che