Marine probiotics: increasing coral resistance to bleaching through microbiome manipulation

Abstract

Although the early coral reef-bleaching warning system (NOAA/USA) is established, there is no feasible treatment that can minimize temperature bleaching and/or disease impacts on corals in the field. Here, we present the first attempts to extrapolate the widespread and well-established use of bacterial consortia to protect or improve health in other organisms (e.g., humans and plants) to corals. Manipulation of the coral-associated microbiome was facilitated through addition of a consortium of native (isolated from Pocillopora damicornis and surrounding seawater) putatively beneficial microorganisms for corals (pBMCs), including five Pseudoalteromonas sp., a Halomonas taeanensis and a Cobetia marina -related species strains. The results from a controlled aquarium experiment in two temperature regimes (26 °C and 30 °C) and four treatments (pBMC; pBMC with pathogen challenge – Vibrio coralliilyticus , VC; pathogen challenge, VC; and control) revealed the ability of the pBMC consortium to partially mitigate coral bleaching. Significantly reduced coral-bleaching metrics were observed in pBMC-inoculated corals, in contrast to controls without pBMC addition, especially challenged corals, which displayed strong bleaching signs as indicated by significantly lower photopigment contents and F v / F m ratios. The structure of the coral microbiome community also differed between treatments and specific bioindicators were correlated with corals inoculated with pBMC (e.g., Cobetia sp.) or VC (e.g., Ruegeria sp.). Our results indicate that the microbiome in corals can be manipulated to lessen the effect of bleaching, thus helping to alleviate pathogen and temperature stresses, with the addition of BMCs representing a promising novel approach for minimizing coral mortality in the face of increasing environmental impacts.

A Zeaxanthin-Producing Bacterium Isolated from the Algal Phycosphere Protects Coral Endosymbionts from Environmental Stress

“…Although the antibiotic treatment definitely brought about an artificial effect on the bacterial community of the control algae, which showed low bacterial diversity, this enabled us to disentangle the complex interactions between Symbiodiniaceae and bacteria. Since, compared with that of corals, the bacterial communities of algal cultures are simple and amenable to manipulation through antibiotic treatment and bacterial inoculation, as shown in the present and previous studies (17,40,45), cultured Symbiodiniaceae can be used as a platform for initial screenings and functional assessments of bacteria that are beneficial or harmful to Symbiodiniaceae and the coral holobiont.…”

“…These functions include defense against pathogens (12,13) and the cycling of nutrients such as nitrogen (14) and sulfur (15). Moreover, coral-associated bacteria have been proposed to be involved in coral resistance to bleaching (16,17), which has a devastating impact on reefs worldwide (4). Although some bacterial species are intimately associated with corals and cultured Symbiodiniaceae (18)(19)(20), suggesting their importance in the coral holobiont, functional and molecular assessments of such bacteria are still in their infancy, partly because corals are limited in their amenability to microbiome manipulation (6).…”

The roles of age, parentage and environment on bacterial and algal endosymbiont communities in Acropora corals

“…In contrast to corals that have comparatively long generation times, microbes are capable of more rapid changes and their roles in assisting host climate change adaptation and acclimatization within the host's reproductive lifetime are increasingly being recognized (van Oppen et al, 2017;van Oppen, Oliver, Putnam, & Gates, 2015;Rosenberg et al, 2007;Theis et al, 2016). The manipulation of microbial communities in corals via inoculation with resilient microbial strains may serve as a tool to increase coral stress tolerance (Damjanovic, Blackall, Webster, & van Oppen, 2017; van Oppen et al, 2017;Rosado et al, 2019). Our findings point towards early recruits as the life stages where such interventions may be most successful, and testing this is an important new avenue of research.…”

Symbiodiniaceae‐bacteria interactions: rethinking metabolite exchange in reef‐building corals as multi‐partner metabolic networks

“…Gammaproteobacteria in the genus Endozoicomonas are a ubiquitous endosymbiont for corals (Bayer et al ., ), and comparative genomic analysis of different strains of Endozoicomonas from different hosts suggests a common role in carbohydrate cycling and potential specificities in amino acid synthesis (Neave et al ., ). Recent advances have allowed a better understanding of the functional significance of coral‐associated bacterial communities, their roles in resource provision and nutrient cycling (Rädecker et al ., ; Bourne et al ., ; Raina et al ., ), their responses to shifts in environmental conditions (Brener‐Raffalli et al ., ), and their potential ‘probiotic' role in mediating holobiont health and survival (Damjanovic et al ., ; Peixoto et al ., ; Webster and Reusch, ; Rosado et al ., ; van Oppen and Blackall, ).…”