Characterization of GP21 and GP12: Two Potential Probiotic Bacteria Isolated from the Gastrointestinal Tract of Atlantic Cod

Abstract

This study evaluated the probiotic potential of GP21 (Pseudomonas sp.) and GP12 (Psychrobacter sp.), two bacteria isolated from the intestinal tract of a cold-water fish, Atlantic cod. The antagonistic activity of the two intestinal bacteria against two fish pathogens (Vibrio anguillarum and Aeromonas salmonicida subsp. salmonicida) was studied under different physical conditions. Further, their resistance to physiological barriers and their ability to form biofilms were examined. In addition, a test was conducted to confirm that the isolates were not pathogenic to the host fish. The two bacteria exhibited differences in their antagonism to the pathogens. Both were active against V. anguillarum at mildly acidic conditions over a 5-day period. The activity of GP21 against A. salmonicida was greater at pH 7-8. The maximum antagonistic activity was observed at a temperature of 15°C and at a salt concentration of 15 ppt for both the isolates. They did not produce acids, could release siderophores and tolerated both the acidic environment and the bile salts. Their ability to form biofilms was high around 15°C and when iron was supplemented in the medium at 5 μmol l(-1). There was no mortality of fish during the pathogenicity experiment, confirming the safety of both isolates for further applications. Considering the favorable characteristics identified here, it could be concluded that GP21 and GP12 isolated from the gastrointestinal tract of Atlantic cod are potential probiotic candidates.

Teleost intestinal immunology

“…Despite this down-regulation of cytokine expression increased survival, increased weight gain, decreased cortisol levels and improved stress responses were monitored [192]. In Atlantic cod autochthonous intestinal bacteria also appeared to be potential probionts [193] and proteomic analysis of probiotic stimulated cod indicated a lower level of immune stimulation but an up-regulation of proteins involved in growth and development [194]. It will be clear that the data given on probiotic stimulation are fragmentary and probably bacterial strain or fish species dependent and hence much more research is necessary to explain the protection reported after feeding probiotics.…”

Nutritional impacts on fish mucosa: immunostimulants, pre- and probiotics

“…Several host-derived candidate probiotics have been characterized both from coldwater (Lazado et al, 2010c;Brunt et al, 2007;Spanggaard et al, 2001;Robertson et al, 2000;Gildberg and Mikkelsen, 1998;Jöborn et al, 1997) and warm-water fish species (Lara-Flores and Olvera-Novoa, 2013; Chantharasophon et al, 2011;Ghosh et al, 2007;Kumar et al, 2006). On the course of exploring new probiotic microorganisms, the attention was directed to the commensal microorganisms of the host.…”

“…LAB isolates from the gut of tilapia had higher antagonistic activity from extra cellular protein (ECP), putatively bacteriocin compared to the intracellular protein (ICP) against A. hydrophila (Vijayabaskar and Somasundaram, 2008). ), candidate probiotics from the intestinal microbiota of Atlantic cod (Lazado et al, 2010c). Inhibitory activity of the extracellular supernatant was also identified in GP21 (Pseudomonas sp.)…”

“…Inhibitory activity of the extracellular supernatant was also identified in GP21 (Pseudomonas sp.) The siderophore-producing ability of a potential probiotic bacterium has been linked to its antagonistic activity (Lazado et al, 2010c) and the protection obtained during a pathogen challenge experiment (Gatesoupe, 1997). ), candidate probiotics from the intestinal microbiota of Atlantic cod (Lazado et al, 2010c).…”

“…There are several factors (e.g., temperature, salinity, pH) that could immensely influence the antagonistic activity of a candidate probiotic (Caipang et al, 2010;Lazado et al, 2010c) and these should be considered especially in extrapolating and making comparative deductions between the results from in vitro and in vivo studies. This approach is still relevant, but one must acknowledge that antagonism in a natural environment is a complex scenario.…”