Microbiologist Diane Kapareiko of the Northeast Fisheries Science Center's Aquaculture and Enhancement Division Laboratory in Milford, Connecticut, said that OY15 helped boost survival of larvae in her lab by 20-35%.
Probiotics have become commonplace in salmon and shrimp aquaculture and now biologists at the National Oceanic and Atmospheric Administration (NOAA) have developed a probiotic bacterial strain to help oyster hatchery managers improve survival of their larvae and protect them from dangerous bacteria.
Probiotic OY15 was developed by microbiologist Diane Kapareiko and her team at the Northeast Fisheries Science Center’s Aquaculture and Enhancement Division Laboratory in Milford, Connecticut to help oyster hatchery managers boost survival of Eastern Oyster (Crassostrea virginica) larvae and seed and improve defenses against Vibrio bacteria.
“Well, Vibrio bacteria are common in waters off the East Coast, and there are good and bad Vibrio strains” Kapareiko told Hatchery International. “We started work on our probiotic strain, with a pathogenic Vibrio to challenge the oyster larvae during bioassays. This pathogenic Vibrio had been isolated from a bay scallop mortality outbreak we had here in our lab back in the day. This strain proved to be pathogenic to oyster larvae as well.”
Because the shellfish probiotic was a first and there wasn’t an established protocol for identifying and screening probiotic candidates for bivalves, Kapareiko and her colleagues adapted a method they found in agriculture journals covering dairy cows, where the use of probiotics has a longer history.
Over a seven-year period, the Milford Lab team collected bacteria that occur naturally in the digestive glands of healthy adult Eastern oysters. Then they grew those candidate strains in Petri dishes along with a pathogenic strain of Vibrio bacteria that caused the disease outbreak in the lab years before. The strains most effective at inhibiting the growth of the pathogen in the Petri dish advanced to the next stage of testing – the guts of live oyster larvae.
The most effective strain ended up being the 15th tested, thus the name OY15.
Many probiotics are thought to work by competitive exclusion of potential pathogens. For instance, if your gut has plenty of beneficial bacteria that aid in digestion, then detrimental bacteria are less likely to gain a foothold because the beneficial bugs would consume the majority of nutrients. Scientists initially expected they would see the same mechanism at work with oyster probiotics.
Instead, OY15 appeared to boost the larval immune system so they could fight off the pathogenic Vibrio.
“We know it’s benign, but it could be a former pathogen that ramps up the oyster immune system,” explained Kapareiko. “The larval immune system recognizes probiotic OY15 as a threat and is stimulated, yet OY15 is totally harmless to the larvae.”
Over the summer, shellfish biologists at the University of Rhode Island (URI) have been field testing the new probiotic, as well as two other strains university staff have developed separately. Kapareiko’s team hopes their OY15 can be commercialized in a couple years if all goes well with the URI field tests this summer.
Kapareiko said that OY15 helped boost survival of larvae in her lab by 20-35%.
— Erich Luening