PROSPECTING FOR COLD WATER PROBIOTICS

Production of cold water (CW) fish species including trout and salmon are an important part of aquaculture.  In large scale production facilities for CW fish species stressful conditions, disease and poor water quality can occur and result in significant economic loss to the industry.  Often chemicals, antibiotics, and vaccination are used to improve fish health.  Research efforts are looking for ecologically friendly alternatives to chemotherapeutics to improve the conditions in fisheries and to ensure that the effluent from rearing facilities are environmentally friendly.

Historically, probiotics have been used successfully in aquaculture to improve water quality, to produce inhibitory metabolites, and to competitively exclude pathogens from space, nutrients, and adhesion sites.  Since, many of the Bacillus strains used in aquaculture products have an optimal growth temperature of 37°C they work well in warm water applications.  However, salmonids grow in CW.    For example, trout are reared at 15°C and Atlantic salmon grow best between 6°C and 16°C.  We tested a number of our beneficial microbes and found that the supernatant from cultures grown at 30°C inhibited Flavobacterium psychrophilum, our warm water isolates from Ecuador and Malaysia had no activity against psychrophilum.  Also, not every isolate of a particular species had the same activity.

Since we are looking for beneficial microbes for CW applications, it makes sense to prospect for beneficial microbes from Polar Regions and from salmonids.   We have mined for beneficial microbes from temperate and polar ocean waters, cold water lakes and streams by plating the water samples and incubating the plates at 15°C.  Thus far, we have isolated 9 microbes that grow well at 15°C-22°C and that have activity against F. psychrophilum at 15°C.  Information concerning these microbes will be presented.