AUTHOR=Pérez-Ramos Adrián , Mohedano Maria L. , Pardo Miguel Á. , López Paloma 

TITLE=β-Glucan-Producing Pediococcus parvulus 2.6: Test of Probiotic and Immunomodulatory Properties in Zebrafish Models

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01684

DOI=10.3389/fmicb.2018.01684

ISSN=1664-302X

ABSTRACT=<p>Lactic acid bacteria synthesize exopolysaccharides (EPS), which could benefit the host’s health as immunomodulators. Furthermore, EPS could protect bacteria against gastrointestinal stress, favoring gut colonization, thus protecting the host against pathogenic infections. <italic>Pediococcus parvulus</italic> 2.6, produces a 2-substituted (1,3)-β-<sc>D</sc>-glucan and, in this work, its probiotic properties as well as the immunomodulatory capability of its EPS have been investigated using <italic>Danio rerio</italic> (zebrafish). To this end and for a comparative analysis, <italic>P. parvulus</italic> 2.6 and its isogenic β-glucan-non-producing 2.6NR strain were fluorescently labeled by transfer of the pRCR12 plasmid, which encodes the mCherry protein. For the <italic>in vivo</italic> studies, there were used: (i) a gnotobiotic larvae zebrafish model for bacterial colonization, pathogen competition, and evaluation of the β-glucan immunomodulation capability and (ii) a transgenic (<italic>mpx:GFP</italic>) zebrafish model to determine the EPS influence in the recruitment of neutrophils under an induced inflammation. The results revealed a positive effect of the β-glucan on colonization of the zebrafish gut by <italic>P. parvulus</italic>, as well as in competition of the bacterium with the pathogen <italic>Vibrio anguillarum</italic> in this environment. The larvae treatment with the purified β-glucan resulted in a decrease of expression of genes encoding pro-inflammatory cytokines. Moreover, the β-glucan had an anti-inflammatory effect, when it was evaluated in an induced inflammation model of <italic>Tg</italic>(<italic>mpx:GFP</italic>) zebrafish. Therefore, <italic>P. parvulus</italic> 2.6 and its EPS showed positive health properties in <italic>in vivo</italic> fish models, supporting their potential usage in aquaculture.</p>