Intergenerational Transfer of Specific Bacteria in Corals and Possible Implications for Offspring Fitness

Abstract

Diverse and abundant bacterial populations play important functional roles in the multi-partite association of the coral holobiont. The specificity of coral-associated assemblages remains unclear, and little is known about the inheritance of specific bacteria from the parent colony to their offspring. This study investigated if broadcast spawning and brooding corals release specific and potentially beneficial bacteria with their offspring to secure maintenance across generations. Two coral species, Acropora tenuis and Pocillopora damicornis, were maintained in 0.2 μm filtered seawater during the release of their gametes and planulae, respectively. Water samples, excluding gametes and planulae, were subsequently collected, and bacterial diversity was assessed through a pyrosequencing approach amplifying a 470-bp region of the 16S rRNA gene including the variable regions 1-3.Compared to the high bacterial diversity harboured by corals, only a few taxa of bacteria were released by adult corals. Both A. tenuis and P. damicornis released similar bacteria, and the genera Alteromonas and Roseobacter were abundant in large proportions in the seawater of both species after reproduction. This study suggests that adult corals may release bacteria with their offspring to benefit the fitness in early coral life stages.

Diazotrophs: Overlooked Key Players within the Coral Symbiosis and Tropical Reef Ecosystems?

“…Both horizontal (environmental) and vertical (genetic) transmission has been reported for zooxanthellae and prokaryotic associates (Harrison and Wallace, 1990;Chen et al, 2010;Ceh et al, 2013b). If one or the other transmission predominates may depend -at least to some degree-on the reproduction strategy of the coral species under study, i.e., brooding vs. broadcasting corals (Apprill et al, 2009;Littman et al, 2009a;Ceh et al, 2013a).…”

“…Nevertheless, the dominant associated diazotrophs may also vary depending on the health of the coral (Yang et al, 2015). Bacterial diversity decreases as corals grow, and the dominant groups also change with each life stage, likely reflecting a fine tuning of the hosted microbial community upon changes in metabolic needs in different life stages and/or when experiencing environmental stress or disease (Nissimov et al, 2009;Ceh et al, 2013b;Lema et al, 2014b;Santos et al, 2014 see Section Does Diazotrophy Enhance Coral Resilience? ).…”

Responses of Coral-Associated Bacterial Communities to Local and Global Stressors

“…Similar to humans, compartmentalization of the microbiome generates distinct microbial communities in the coral animal, within the surface mucus layer, tissues, skeleton, and gut (Sweet et al, 2010;Ainsworth et al, 2015;Apprill et al, 2016) and some particularly associated with Symbiodinium (Ainsworth et al, 2015). Coral-associated bacteria can be transferred vertically from parent to larva (Sharp et al, 2012) or they can be horizontally acquired from the environment (Apprill et al, 2009;Sharp et al, 2010), including when adult corals release bacteria (e.g., Altermonas and Roseobacter) as a by-product of broadcast spawning (Ceh et al, 2013b). Although recent research has focused on the role of microbiomes in coral adaptation (Gilbert et al, 2012;Glasl et al, 2016), coral reef management still largely ignores the role of microbial communities, with the exception of Symbiodinium, in coral resilience .…”

Nitrogen cycling in corals: the key to understanding holobiont functioning?

“…Symbiosome: the multiple-layer host-derived membrane complex that surrounds Symbiodinium when in symbiosis with the coral host. functioning of the coral holobiont, a variety of mechanisms have evolved to enable an effective intergenerational transfer of specific microbes to ensure coral offspring fitness [12,13]. This vertical transfer presumably facilitated the evolution of host-specific and persistent microbial communities in many corals [14][15][16][17][18].…”