Diversity and function of prevalent symbiotic marine bacteria in the genus Endozoicomonas

Abstract

Endozoicomonas bacteria are emerging as extremely diverse and flexible symbionts of numerous marine hosts inhabiting oceans worldwide. Their hosts range from simple invertebrate species, such as sponges and corals, to complex vertebrates, such as fish. Although widely distributed, the functional role of Endozoicomonas within their host microenvironment is not well understood. In this review, we provide a summary of the currently recognized hosts of Endozoicomonas and their global distribution. Next, the potential functional roles of Endozoicomonas, particularly in light of recent microscopic, genomic, and genetic analyses, are discussed. These analyses suggest that Endozoicomonas typically reside in aggregates within host tissues, have a free-living stage due to their large genome sizes, show signs of host and local adaptation, participate in host-associated protein and carbohydrate transport and cycling, and harbour a high degree of genomic plasticity due to the large proportion of transposable elements residing in their genomes. This review will finish with a discussion on the methodological tools currently employed to study Endozoicomonas and host interactions and review future avenues for studying complex host-microbial symbioses.

Dominance of Endozoicomonas bacteria throughout coral bleaching and mortality suggests structural inflexibility of the Pocillopora verrucosa microbiome

“…Similarly, in our current study the stable bacterial community of P. verrucosa was driven by the prevalence and dominance of two Endozoicomonas OTUs. Importantly, the same two Endozoicomonas phylotypes were previously shown to prevail in the microbiome of P. verrucosa across its entire global distribution range with little geographic partitioning, suggesting a particularly intimate and conserved host‐microbe relationship (Neave, Apprill, Ferrier‐Pagès, & Voolstra, 2016). …”

“…More generally, Endozoicomonas are commonly assumed to provide an important role in coral holobiont functioning due to their widespread prevalence and high abundance in many coral species (Bayer et al., 2013; Gignoux‐Wolfsohn, Aronson, & Vollmer, 2017; Glasl et al., 2016; Jessen et al., 2013; Meyer, Gunasekera, Scott, Paul, & Teplitski, 2016; Neave et al., 2016; Neave, Rachmawati, et al., 2017) and apparent metabolic versatility (Ding, Shiu, Chen, Chiang, & Tang, 2016; Hyun et al., 2014; Neave, Michell, et al., 2017; Yang et al., 2010). Further, reductions in the abundance of Endozoicomonas in stressed, diseased, or bleached corals are reported in a number of studies, suggesting that pervasive abundance of Endozoicomonas might be an indicator of habitat suitability (Bourne et al., 2008; Cárdenas et al., 2012; Gignoux‐Wolfsohn et al., 2017; Meyer et al., 2016; Morrow et al., 2014; Roder et al., 2015; Röthig et al., 2016; Ziegler et al., 2016).…”

“…This is in contrast to our findings here, where we see a quasi‐invariant association with Endozoicomonas that makes up on average 90% of the bacterial community, despite the severe nutrient treatments and distinct stress phenotypes, (coral bleaching and progressed tissue sloughing, respectively). Hence, our data suggest a near‐obligate association, much like the association with Symbiodinium , although the specific functional importance of this relationship still needs to be defined (Neave et al., 2016; Neave, Michell, et al., 2017). …”

Quorum Sensing Interference and Structural Variation of Quorum Sensing Mimics in Australian Soft Coral

“…"Spongiobacter, " now recognized as belonging to the genus Endozoicomonas (Neave et al, 2016), was originally recovered from a marine sponge (Pike et al, 2013) but is also present in many gorgonian (Sunagawa et al, 2010;La Rivière et al, 2013) and scleractinian corals (Raina et al, 2009;Blackall et al, 2015;Bourne et al, 2016). "Spongiobacter" strains have been attributed a number of ecological roles; "Spongiobacter" strains from A. millepora demonstrated a dependence on DMSP and consequently a role in the biogeochemical sulfur cycle was postulated (Raina et al, 2009), whereas, "Spongiobacter" strains from the sponge Suberites carnosus demonstrated antibacterial activity (Flemer et al, 2012).…”

Ultra-Violet Radiation Has a Limited Impact on Seasonal Differences in the Acropora Muricata Holobiont

“…In summer, we also observed a lower abundance of Thalassospira, known as potential symbionts of ctenophores (Hao, 2014), and four OTUs of Endozoicomonas, a genus commonly found in healthy corals (Bayer et al, 2013a,b;Neave et al, 2017;van de Water et al, 2017van de Water et al, , 2018b, as well as in a wide range of other marine invertebrates (Forget and Juniper, 2013;Fiore et al, 2015;Katharios et al, 2015). Although their exact functions are unknown, both Thalassospira and Endozoicomonas may be involved in host health through nutrient acquisition and provision, and in structuring of the host microbial community (Hao, 2014; reviewed by Neave et al, 2016). Our results on the abundance of Endozoicomonas, and the observed changes in host physiology between summer and winter, however, do not appear to provide additional insights into the potential role of Endozoicomonas in corals.…”