Antimicrobial Activities of Bacteria Associated with the Brown Alga Padina pavonica

General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Macroalgae belonging to the genus Padina are known to produce antibacterial compounds that may inhibit growth of human-and animal pathogens. Hitherto, it was unclear whether this antibacterial activity is produced by the macroalga itself or by secondary metabolite producing epiphytic bacteria. Here we report antibacterial activities of epiphytic bacteria isolated from Padina pavonica (Peacocks tail) located on northern coast of Tunisia. Eighteen isolates were obtained in pure culture and tested for antimicrobial activities. Based on the 16S rRNA gene sequences the isolates were closely related to Proteobacteria (12 isolates; 2 Alpha-and 10 Gammaproteobacteria), Firmicutes (4 isolates) and Actinobacteria (2 isolates). The antimicrobial activity was assessed as inhibition of growth of 12 species of pathogenic bacteria (Aeromonas salmonicida, A. hydrophila, Enterobacter xiangfangensis, Enterococcus faecium, Escherichia coli, Micrococcus sp., Salmonella typhimurium, Staphylococcus aureus, Streptococcus sp., Vibrio alginoliticus, V. proteolyticus, V. vulnificus) and one pathogenic yeast (Candida albicans). Among the Firmicutes, isolate P8, which is closely related to Bacillus pumilus, displayed the largest spectrum of growth inhibition of the pathogenic bacteria tested. The results emphasize the potential use of P. pavonica associated antagonistic bacteria as producers of novel antibacterial compounds

Destruction photodynamique des oeufs de Taeniidés et de Toxocara sp. dans l'eau

Dans le but de mettre en évidence l'effet de la photosensibilisation sur les formes de résistance de parasites, qui se retrouvent dans des eaux partiellement épurées ou brutes à des concentrations variables, nous avons été amenés à les isoler dans de l'eau distillée. Ceci nous a permis de rendre compte des effets directs qu'ils peuvent contracter lors de la photosensibilisation et de mieux gérer les différents paramètres qui y interviennent. Dans le présent travail, nous nous sommes intéressés à l'étude des mécanismes photodynamiques de la photosensibilisation sur des formes infectantes de parasites (notamment oeufs de Taeniidés et Toxocara sp.), par photosensibilisants (RB, BM, T4MPyP) libres dans la solution ou fixés sur support par une résine. Ainsi, nous avons contribué à élucider les processus photoinactivateurs des oeufs d'helminthes en fonction des différentes conditions expérimentales. Nous avons étudié dans un premier temps, l'effet photosensibilisant notamment selon le mécanisme Type I de la photosensibilisation (autres espèces réactives de l'oxygène tel que le radical hydroxyle -OH), Type II (production de l'1O2) et par effet contact, de 3 composés appartenant à différents groupes de colorants [rose bengale (RB), bleu de méthylène (BM), porphyrine tétracationique (T4MPyP)], mis en solution dans de l'eau distillée en présence d'une suspension d'oeufs de parasites. L'observation microscopique a montré que les pourcentages d'oeufs de Taeniidés fracturés dans de l'eau distillée, atteignaient 31,5 % pour une concentration relativement élevée de l'ordre de 450 ± 49 oeufs par ml en suspension avec la T4MPyP (20 µM), après 120 min d'exposition à la lumière visible artificielle sous une intensité lumineuse instantanée de 500 W.m2. Le pourcentage le plus élevé est obtenu en présence de la T4MPyP, suivi du RB et du BM. Ces mêmes résultats ont montré que les oeufs de Taeniidés sont plus sensibles à la photosensibilisation que les oeufs de Toxocara sp. Par ailleurs, pour distinguer la prédominance des réactions de Type II faisant intervenir l'oxygène singulet des autres entités radicalaires, des expérimentations ont été entreprises avec des Ps fixés sur support (photosensibilisation indirecte). Les Ps sont fixés par une résine sur les parois du réacteur. Les résultats ont montré que la T4MPyP fixée permet d'enregistrer des pourcentages de fracturation des oeufs de Taeniidés de l'ordre de 30 ± 2 % après 60 min d'exposition à la lumière visible artificielle (500 W.m2), suivie du RB et du BM. Dans les mêmes conditions, des pourcentages de fracturation moins importants ont été obtenus pour les oeufs de Toxocara sp. notamment durant les trois premières heures d'exposition aux irradiations visibles artificielles. Les Ps fixés sur les parois du réacteur, sans entrer en contact direct avec la cible, arrivent à endommager les oeufs de Taeniidés et de Toxocara et à provoquer leur cassure. Ces observations dans l'eau distillée, pourraient mettre en évidence le deuxième mécanisme de réaction de la photosensibilisation (Type II). En plus, les oeufs de Toxocara étaient devenus plus sensibles par rapport aux oeufs de Taeniidés et ceci à la suite d'une prolongation du temps d'exposition à la lumière

Incursion of Bluetongue in Tunisia: Molecular Characterization of Viral Strains

In December 1999, the bluetongue was declared in Tunisia. Other cases of the disease have also been reported in other countries in the Mediterranean basin. The aim of this work was to characterize viral isolates obtained during the epizootic, which occurred from December 1999 to March 2000, and to perform serotype determination. The three genomic segments, 2, 7 and 10, corresponding to the proteins VP2, VP7 and NS3/NS3A, were amplified by PCR and sequenced. Sequences of the various genomic segments obtained from Tunisian viral isolates were compared with the Corsican vaccinal and wild-type strain, as well as with other bluetongue virus strains published in GenBank. The results are presented in the form of phylogenetic trees and tables in which nucleotide sequences are compared, thus showing the common origin of the Tunisian viral strain (serotype 2) and the Corsican strain that was responsible for the October 2000 epizootic

Antimicrobial Activities of Bacteria Associated with the Brown Alga Padina pavonica

Macroalgae belonging to the genus Padina are known to produce antibacterial compounds that may inhibit growth of human- and animal pathogens. Hitherto, it was unclear whether this antibacterial activity is produced by the macroalga itself or by secondary metabolite producing epiphytic bacteria. Here we report antibacterial activities of epiphytic bacteria isolated from Padina pavonica (Peacocks tail) located on northern coast of Tunisia. Eighteen isolates were obtained in pure culture and tested for antimicrobial activities. Based on the 16S rRNA gene sequences the isolates were closely related to Proteobacteria (12 isolates; 2 Alpha- and 10 Gammaproteobacteria), Firmicutes (4 isolates) and Actinobacteria (2 isolates). The antimicrobial activity was assessed as inhibition of growth of 12 species of pathogenic bacteria (Aeromonas salmonicida, A. hydrophila, Enterobacter xiangfangensis, Enterococcus faecium, Escherichia coli, Micrococcus sp., Salmonella typhimurium, Staphylococcus aureus, Streptococcus sp., Vibrio alginoliticus, V. proteolyticus, V. vulnificus) and one pathogenic yeast (Candida albicans). Among the Firmicutes, isolate P8, which is closely related to Bacillus pumilus, displayed the largest spectrum of growth inhibition of the pathogenic bacteria tested. The results emphasize the potential use of P. pavonica associated antagonistic bacteria as producers of novel antibacterial compounds

遠山景晋『未曽有記』について : 蝦夷紀行がもたらしたもの

Marine macroalgae surfaces constitute suitable substrata for bacterial colonization which are known to produce bioactive compounds. Thus, hereby we focused on heterotrophic aerobic bacteria species associated with coralline red alga (northern coast of Tunisia, southern Mediterranean Sea) and their inhibition against several microbial marine and terrestrial species. The whole collection (19 isolates, J1 to J19) was identified, based on their 16S ribosomal RNA gene sequences as Proteobacteria (14 strains), Bacteroidetes (4 strains) and Firmicutes (1 strain). Thirty-six percent of the isolates (J2, J9, J11, J13, J16, J17 and J18) were antibiotic-like producers with in vitro inhibition against Gram + and Gram - bacteria and the yeast . Highest level of inhibition was revealed for the isolates J2, J9 and J13 identified respectively as , and , with strong activity against , and , with inhibition diameters of 25 to 35 mm shown by drop test assay on T soy agar plates. Furthermore, we tested inhibition of crude organic extracts against human and marine bacteria as well as against all isolates, in order to determine the degree of affinity of the epibionts to their proper host. The recovery of strains with antimicrobial activity suggests that represent an ecological niche which harbors a specific microbial diversity worthy of further secondary metabolites investigation

Heterotrophic bacteria associated with the green alga <i>Ulva rigida</i>: identification and antimicrobial potential

Heterotrophic bacteria associated with the green alga <i>Ulva rigida</i>, collected from the coast of Tunisia, were isolated andsubsequently identified by their 16S rRNA gene sequences and by phylogenetic analysis. The 71 isolates belong to four phyla:Proteobacteria (Alpha-and Gamma- subclasses), Bacteroidetes, Firmicutes, and Actinobacteria. Most of the isolates belong toProteobacteria. The Gram-positive Firmicutes and especially the genus Bacillus were well-represented at the surface of <i>U. rigida</i>,collected from the coast as well as from the lagoon, while Actinobacteria were represented only at the surface of algae collectedfrom the coast of Cap Zebib. Bacteroidetes were more represented at the surface of algae collected from the Ghar El Melh lagoon.The bacterial community of the water surrounding the algae was different from that associated with the surface of the algae.Moreover, the abundance of bacteria in the surrounding water was much lower compared to the density of bacteria associatedwith the surface of the algae. Bacteria isolated from the algal surface were tested for their antimicrobial potential. The resultsshow that ~ 36%of the algae-associated bacterial isolates possess antibacterial activity whereas free-living bacteria, isolated fromthe surrounding water, did not show such activity. The surface of <i>U. rigida</i> was colonized by a high diversity of culturable andpossibly novel epiphytic bacteria that may be an important source of antimicrobial compounds and are therefore ofbiotechnological interest