Selected bacterial strains protect Artemia spp. from the pathogenic effects of Vibrio proteolyticus CW8T2

In this study Vibrio proteolyticus CW8T2 has been identified as a virulent pathogen for Artemia spp, Its infection route has been visualized with tran smission electron microscopy, The pathogen affected microvilli and gut epit helial cells, disrupted epithelial cell junctions, and reached the body cav ity, where it devastated cells and tissues, In vivo antagonism tests showed that preemptive colonization of the culture water with nine selected bacte rial strains protected Artemia juveniles against the pathogenic effects. Tw o categories of the selected strains could be distinguished: (i) strains pr oviding total protection, as no mortality occurred 2 days after the experim ental infection with V, proteolyticus CW8T2, with strain LVS8 as a represen tative, and (ii) strains providing partial protection, as significant but n ot total mortality was observed, with strain LVS2 as a representative. The growth of V, proteolyticus CW8T2 in the culture medium was slowed down in t he presence of strains LVS2 and LVS8, but growth suppression was distinctly higher with LVS8 than with LVS2. It was striking that the strains that gav e only partial protection against the pathogen in the in vivo antagonism te st showed also a restricted capability to colonize the Artemia compared to the strains providing total protection. The in vivo antagonism tests and th e filtrate experiments showed that probably no extracellular bacterial comp ounds were involved in the protective action but that the living cells were required to protect Artemia against V. proteolyticus CW8T2.