Isolation of some BALOS (Bdellovibrio and Like Organisms) strains and evaluation of their ability to parasitize some fish pathogenic bacteria.

BALOs (Bdellovibrio And Like Organisms) are small, motile, monopolar-flagellated, aerobic Gram negative bacteria able to attack, penetrate and grow within the periplasmic space of Gram negative bacteria, killing at the end of the life cycle the pray cell. BALOs are widely distributed in nature and have been isolated from soil freshwater, seawater, plant roots, biofilms, sewage, shells, crab gills and in animals and human faeces. Considering their intrinsic ability to parasite and lyse pray cells, BALOs have been proposed as attractive potential biocontrol agents, useful to control Gram negative microbial populations living in systems as plants, animals and their products, humans, water and surfaces. The aim of this work consisted in isolating BALOs strains from different substrates, utilizing two different isolation procedures, and testing the isolates as potential biocontrol agents against some fish pathogenic Gram negative bacteria. Four BALOs strains have been isolated from river waters, sea waters and molluscs samples. By means of optic, phase contrast and electron transmission microscopy, some stages of the isolates life cycle (attack, attachment, bdelloplast formation, development, maturation and lysis) have been observed, whereas their ability to kill in vitro some fish pathogenic bacteria, such as Yersinia ruckeri, Vibrio anguillarum and Aeromonas salmonicida isolated from infected rainbow trout and European seabass, was demonstrated against two different strains of V. anguillarum and one of Y. ruckeri. The results suggest the prospective role of the BALOs as biocontrol agents, involving further applicative studies for setting up a chemio-therapeutic alternative approach.[...]