Delivering Beneficial Microorganisms for Corals: Rotifers as Carriers of Probiotic Bacteria

Abstract

The use of Beneficial Microorganisms for Corals (BMCs) to increase the resistance of corals to environmental stress has proven to be effective in laboratory trials. Because direct inoculation of BMCs in larger tanks or in the field can be challenging, a delivery mechanism is needed for efficient transmission of the BMC consortium. Packaged delivery mechanisms have been successfully used to transmit probiotics to other organisms, including humans, lobsters, and fish. Here, we tested a method for utilizing rotifers of the species Brachionus plicatilis for delivery of BMCs to corals of the species Pocillopora damicornis. Epifluorescence microscopy combined with a live/dead cell staining assay was used to evaluate the viability of the BMCs and monitor their in vivo uptake by the rotifers. The rotifers efficiently ingested BMCs, which accumulated in the digestive system and on the body surface after 10 min of interaction. Scanning electron microscopy confirmed the adherence of BMCs to the rotifer surfaces. BMC-enriched rotifers were actively ingested by P. damicornis corals, indicating that this is a promising technique for administering coral probiotics in situ. Studies to track the delivery of probiotics through carriers such as B. plicatilis, and the provision or establishment of beneficial traits in corals are the next proof-of-concept research priorities.

Harnessing the microbiome to prevent global biodiversity loss

“…[10][11][12][13][14] . Despite the challenges of applying microbes to surfaces beneath the saltwater ocean, coral microbiomes have been manipulated ex situ through the introduction of probiotic strains by incubation, topical application 11,13,14,119,120 or direct feeding 121 . Microbiome transplantation using resistant donor corals from the wild has also demonstrated thermal protective effects on coral populations 10 , such as increased growth 120 and reduced stress responses under heat (including mortality evasion following thermal stress bleaching) 11,13,119 , oil exposure 12,14 and pathogen challenges 11,116 , all of which are accompanied by microbiome restructuring.…”

Antibiotics Alter Pocillopora Coral-Symbiodiniaceae-Bacteria Interactions and Cause Microbial Dysbiosis During Heat Stress

“…This has been shown to be feasible in cnidarian model systems such as Hydra, Nematostella, and Aiptasia (Murillo-Rincon et al, 2017;Domin et al, 2018;Medrano et al, 2019;Costa et al, 2021;Dungan et al, 2021), but is only beginning to be explored in reefbuilding corals and other cnidarians (Lin et al, 2019;Cunning and Baker, 2020;Weiland-Bräuer et al, 2020). Experiments that apply a combination of antibiotics treatments followed by targeted probiotic delivery or "microbiome recovery" treatments will yield insights into whether disturbed coral-associated bacteria communities and host stress response phenotypes can be "rescued" by the re-introduction of one or several beneficial microbes (Peixoto et al, 2017(Peixoto et al, , 2021Rosado et al, 2018;Damjanovic et al, 2019;Assis et al, 2020;Santoro et al, 2021). Future work would also benefit from the inclusion of baseline samples and additional time points to track the temporal changes in bacteria community composition and transcriptome responses across coral colonies.…”

Exploring microbiome engineering as a strategy for improved thermal tolerance in Exaiptasia diaphana

“…Although there was evidence for increased relative abundance of some consortium members in the host microbiome, the key limitation of the present study was the inability of the bacteria to persist after inoculation. Bacteria delivery via bioencapsulation in A. salina is used in aquaculture to ensure dosed bacteria are ingested (Hai et al 2010 ), and a method for corals using rotifers has been reported (Assis et al 2020 ). Researchers using probiotics to treat stony coral tissue loss disease (SCTLD) in the field have also tested strategies such as weighted enclosures, paste applied directly to SCTLD lesions, and slow release beads to improve bacteria‐coral contact and maintain probiotic concentrations in the open marine environment (Smithsonian Marine Station 2020 ).…”