As we continue to learn about aquarium probiotics, it’s clear that they have a huge impact on the health of diverse plant and animal species. That is no longer in question. Most recent research has focused on exactly how these beneficial microbes work to aid their host’s digestive and immune systems. This recently published paper “Preparation and biological activities of an extracellular polysaccharide from Rhodopseudomonas palustris” in the International Journal of Biological Macromolecules reveals one such mechanism that involves the highly valuable probiotic purple non-sulfur bacterium (PNSB), R. palustris.
As the principle investigator Peng Zhang explains, “The photosynthetic bacterium, Rhodopseudomonas palustris has been widely used as probiotics in aquaculture, while the molecular basis underlying the probiotic properties of this organism remains largely unknown.” His team successfully purified a novel extracellular polysaccharide from the fermentation of R. palustris. It was further discovered that this substance, termed RPEPS-30, serves to promote mRNA expression of certain microbial gene clusters, thereby promoting the growth of fellow, widely used, probiotics such as Lactobacillus.
Commercial fish and shrimp farmers have for long noticed the synergistic effects of using certain probiotic cocktails. Now, we are closer to understanding how these diverse gut flora combine their efforts to best protect and nourish their host. The possibilities for purple non-sulfur bacteria do not end with aquaculture–home aquarists also may use these microbes to their advantage. Just consider how many prepared aquarium feeds, marketed to hobbyists, contain sporiform (i.e., may be dried) probiotics such as Lactobacillus. It is exciting that we now know, at least in part, why mixing these probiotic bacteria together produces such good results.
Reef aquarists have been using PNS ProBio, which contains R. palustris, with generally great results, for several years now. Perhaps this new revelation will cause some users to try introducing these bacteria with their fish foods, particularly those that are known to be enhanced with probiotics such as Lactobacillus. This is as easy as allowing the dry or thawed frozen food items to soak in the PNS ProBio (maybe with a little bit of tank water if needed) for a few minutes prior to offering them to the fish. This could be a PNS ProBio dose that would have otherwise been intended for the corals. Indeed, most of the ‘food soak’ will disperse throughout the tank and become available to corals, clams and other filter-feeders to consume–all while some passes through the fish’s gut, thereby encouraging good general health, increasing food absorption and reducing wastes.
Without a doubt, these nutritious PNS bacteria can do a lot to improve aquarium animals’ diets all the way down the food chain–from protists to copepods to fish and corals. But new scientific knowledge, as it passes down to us hobbyists, will no doubt help us continue to increase these benefits!