Effect of Biocides on MS2 and K Coliphages

Several biocides commonly used in disinfection processes as antibacterial and antifungal agents were tested for activity against MS2 and K coliphages. MS2 was resistant to most biocides; only glutaraldehyde (0.5%) and peracetic acid (1%) achieved a 4-log₁₀ titer reduction in 20 min. In contrast, K phage was sensitive to most biocides, being resistant only to phenol (2%) and chlorhexidine (1%).     

Experimental evolution of nodule intracellular infection in legume symbionts

Soil bacteria known as rhizobia are able to establish an endosymbiosis with legumes that takes place in neoformed nodules in which intracellularly hosted bacteria fix nitrogen. Intracellular accommodation that facilitates nutrient exchange between the two partners and protects bacteria from plant defense reactions has been a major evolutionary step towards mutualism. Yet the forces that drove the selection of the late event of intracellular infection during rhizobium evolution are unknown. To address this question, we took advantage of the previous conversion of the plant pathogen Ralstonia solanacearum into a legume-nodulating bacterium that infected nodules only extracellularly. We experimentally evolved this draft rhizobium into intracellular endosymbionts using serial cycles of legume-bacterium cocultures. The three derived lineages rapidly gained intracellular infection capacity, revealing that the legume is a highly selective environment for the evolution of this trait. From genome resequencing, we identified in each lineage a mutation responsible for the extracellular–intracellular transition. All three mutations target virulence regulators, strongly suggesting that several virulence-associated functions interfere with intracellular infection. We provide evidence that the adaptive mutations were selected for their positive effect on nodulation. Moreover, we showed that inactivation of the type three secretion system of R. solanacearum that initially allowed the ancestral draft rhizobium to nodulate, was also required to permit intracellular infection, suggesting a similar checkpoint for bacterial invasion at the early nodulation/root infection and late nodule cell entry levels. We discuss our findings with respect to the spread and maintenance of intracellular infection in rhizobial lineages during evolutionary times.     

The opecoelidae (Digenea) of sparid fishes of the western Mediterranean. II. Pycnadenoides yamaguti, 1938 and Pseudopycnadena Saad-Fares & Maillard, 1986

The genera Pycnadenoides Yamaguti, 1938 and Pseudopycnadena Saad-Fares & Maillard, 1986 are redefined and their validity discussed. Two forms, currently considered to be Pycnadenoides senegalensis Fischthal & Thomas, 1972, one from Lithognathus mormyrus and Diplodus vulgaris off Corsica (Scandola) and one from Sparus aurata off Provence and Languedoc, are described separately, as some preliminary biochemical studies suggest that they might be distinct. This species is commented upon in relation to Distomum mormyri Stossich, 1885, D. umbrinae Stossich, 1885, Pycnadenoides pagrosomi Yamaguti, 1938 and P. ghanensis Fischthal & Thomas, 1968. Pseudopycnadena fischthali Saad-Fares & Maillard, 1986 is redescribed from Diplodus vulgaris, D. annularis and D. sargus off Corsica (Scandola).

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Résumé Les auteurs redéfinissent et discutent la validité des genres Pycnadenoides Yamaguti, 1938 et Pseudopycnadena Saad-Fares & Maillard, 1986. Deux formes considérées actuellement comme Pycnadenoides senegalensis Fischthal & Thomas, 1972, l'une parasite de Lithognathus mormyrus et de Diplodus vulgaris des côtes de Corse (Scandola), l'autre parasite de Sparus aurata des côtes de Provence et du Languedoc, sont décrites séparément. Des études biochimiques préliminaires suggèrent qu'il pourrait s'agir de deux espèces différentes. Cette espèce est discutée par rapport à Distomum mormyri Stossich, 1885, D. umbrinae Stossich, 1885, Pycnadenoides pagrosomi Yamaguti, 1938 et P. ghanensis Fischthal & Thomas, 1968. Pseudopycnadena fischthali Saad-Fares & Maillard, 1986 est redécrit à partir d'exemplaires provenant de Diplodus vulgaris, D. annularis et D. sargus des côtes de Corse (Scandola).

     

Effect of biocides on Pseudomonas aeruginosa phage F116

Pseudomonas aeruginosa phage F116 is of interest in understanding the virucidal mechanisms of disinfectant action. Phage F116 has been used to test several disinfectants. The bacteriophage was relatively resistant to several biocides commonly used in disinfection processes. Only 0.05% cetylpyridinium chloride, 0.1% peracetic acid and 2% phenol were highly active against the phage.