Many reef aquarists and coral farmers are (understandably) wary of microbial aquarium products. More often than not, the manufacturer declines to identify the major component species in the product. This certainly might cause one to wonder if there really are any beneficial microbes present and, if so, whether or not they’re even alive. And these concerns only set the stage for the big question: If there truly is a large number of viable microbes in here, will they actually survive in my reef tank…Do they really originate from a healthy, natural coral reef habitat?’
In search of the real deal
In 2022, Hydrospace decided to take a stab at addressing these issues by introducing a functional group of indigenous reef microbes to the aquarium community. We were particularly excited about the possibility of obtaining reef-associated anaerobic phototrophs. So, we started the project by organizing an expedition to a wild reef!
The remote island of Mo’orea near Tahiti in French Polynesia was to be that place. There, we visited three relatively oligotrophic, shallow water sites around the island that were characterized by large, healthy Porites sp. bommies on a sandy bottom. At each site, we not only collected substrate samples, but also collected physical, metagenomic and chemical (including ICP) data. We even met with a lead biologist from Coral Gardeners, a highly reputed reef restoration organization, to gain more insight into the current state of health of the island’s reefs with a focus on the sites we investigated.
Though we had obtained volumes of data and immeasurable insight, the only physical material we returned with was a mere three pinches of sand. Thankfully, soon after inoculating a mixture of the three substrate samples into our proprietary marine culture medium, growth of bacteria was clearly evident–phototrophic bacteria!
We’ve since determined through DNA sequencing that this consortium is actually comprised of several phototrophic species, including Rhodovolum sp. (purple nonsulfur bacteria), Marichromatium purpuratum (purple sulfur bacteria) and Prosthecochloris sp. (green sulfur bacteria). Roseospira sp. (purple nonsulfur bacteria) makes a smaller, but nevertheless significant, appearance as well. At maturity, these cultures present as a golden green suspension (primarily Rhodovolum and Prosthecochloris).
What is so notable about this consortium is its stability. This remarkable stability owes mainly to syntrophy. Syntrophy is best described as a complex set of relationships where multiple species efficiently feed off of each other’s metabolic waste products in a cyclic fashion. Collected from the wild together–and subsequently cultivated together–the keystone members of this mutualistic microbial community are conserved in these cultures.
Bacterial team in a bottle
Astounded by the ease with which this consortium is cultured and maintained, as well as the varied probiotic qualities of each of the three major constituents, we’re proud to share this resource with the aquarium and aquaculture community as PNS Deep Cycle™.
PNS Deep Cycle™ contains a functionally complete community of marine anaerobes that are prominent in natural coral reef microbiomes, but are nevertheless poorly represented in most reef aquaria. Rather than competing with each other, the species in this consortium exchange metabolic intermediates to facilitate an otherwise energetically unfavorable process, thereby promoting each other’s survival as a coherent unit. In addition to breaking down organic wastes and inhibiting the growth of less desirable anaerobes, the three major components in this unique product perform the following ecological services:
Rhodovolum sp. improves water quality through the consumption of dissolved organic matter (1), whereafter it becomes a nutritious live food due in part to its probiotic properties (2, 3, 4) and relatively high content of fatty acids (5, 6, 7, 8).
Marichromatium purpuratum improves water quality by consuming dissolved organic matter, reducing nitrate and sulfide concentrations (9, 10, 11) and providing probiotic benefits (12).
Prosthecochloris sp. plays important roles in nitrogen and sulfur cycling (13, 14, 15, 16) and likely forms a symbiotic relationship with stony corals as an endolithic diazotroph (17, 18).
Special applications
PNS Deep Cycle™ contains several obligately anaerobic species; therefore, protecting the cultures from oxygen exposure may promote successful colonization of the substrate. One simple means of carrying out an oxygen-free transfer is by injection. Any syringe with a long needle or tube is suitable for this purpose. Slowly inject the pre-measured dose as deeply, and across as many injection sites, as possible into the substrate.
Similarly, direct transfer to dry rock and porous biomedia can promote colonization of these bacteria. This is accomplished simply by soaking the material in the product under anaerobic conditions (i.e., no aeration). Place the rock/media in a clean, sealed container that is just large enough to contain the material. Add to the container a sufficient volume of PNS Deep Cycle™ to thoroughly soak the material. Add a sufficient volume of clean saltwater to displace any remaining air to the rim of the container. Place lid on the container and allow material to condition for 24 hours. After the conditioning period, the material may be added (along with the water in the container) to the tank, filter system, etc.
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