The Volatilomes of Symbiodiniaceae-Associated Bacteria Are Influenced by Chemicals Derived From Their Algal Partner

Abstract

Biogenic volatile organic compounds (BVOCs) are a large group of molecules involved in trophic interactions, stress response and atmospheric chemistry. Although they have been extensively studied in terrestrial ecosystems, their identity and prevalence in the marine environment remains largely unexplored. Here we characterized the volatilome of two abundant marine bacteria that were previously identified as members of the core microbiome of Symbiodiniaceae (phylum: Dinoflagellata), the photosynthetic endosymbionts of reef building corals. To determine the influence of Symbiodiniaceae exudate on their associated bacteria, we incubated isolates of Marinobacter adhaerens HP15 and Labrenzia sp. 21p with Symbiodiniaceae culture filtrate or culture medium (control) and investigated their volatilomes using GC-MS. The volatilome of Labrenzia sp. incubated in Symbiodiniaceae filtrate was significantly different and more diverse relative to the control. In contrast, the overall composition of the M. adhaerens volatilomes were consistent between treatment and control. Among the 35 compounds detected in both bacterial species, the dominant chemical functional groups were halogenated hydrocarbons, aromatic hydrocarbons and organosulfurs, some of which are known to play roles in inter-organism signaling, to act as antioxidants and as antimicrobials. This study provides new insights into the potential sources and diversity of marine BVOCs, uncovering a wide range of molecules that may play important physiological and ecological roles for these organisms, while also revealing the role of Symbiodiniaceae-associated bacteria in the emission of important atmospheric gases.

Heat stress decreases the diversity, abundance and functional potential of coral gas emissions

“…Chambers were placed in a water bath, with temperature and light matching their experimental conditions (HYDRA; Aquaillumination). Samples for characterization of the volatilome were then collected (as per Lawson et al, 2019Lawson et al, , 2020, whereby chambers were purged for 30 min with instrument grade air (BOC Gases, Linde Group) while the outlet was collected on thermal desorption (TD) tubes (200 mg Tenax TA; Markes International Ltd; see Figure S3), that were capped immediately post-purge and stored at 4°C. Blanks containing seawater from the setup (from control and heat treated conditions) and hardened Selleys epoxy were run in conjunction with all analyses.…”

“…We carried out a targeted quantification of isoprene, one of the most commonly emitted BVOCs in higher plants, as this compound can scavenge harmful reactive oxygen species (ROS) produced during stressful conditions (Sharkey & Singsaas, 1995;Velikova et al, 2006;Vickers et al, 2009) and enhanced isoprene emission is frequently correlated with temperature increases in many plant species (Guidolotti et al, 2019). Isoprene had not previously been detected with our GC-MS set up (see Lawson et al, 2019Lawson et al, , 2020, potentially due to its high reactivity and because of its very low concentration. Given the ubiquitous nature of isoprene in terrestrial systems and its potential roles in stress tolerance, additional samples were taken for targeted analysis to investigate if heat stress affected its concentration in reefbuilding corals.…”

“…Our previous work has demonstrated that coral microbial endosymbionts can produce diverse, species-specific volatilomes that are influenced by environmental factors (Lawson et al, 2019(Lawson et al, , 2020. In our examination of the coral holobiont, we therefore hypothesized that (a) the two species have distinct volatilomes while sharing some 'core' compounds and (b) that these volatilomes shift in response to heat stress.…”

“…Here we describe the BVOC emissions of two common reef‐building corals from the GBR, Acropora intermedia and Pocillopora damicornis , during an experimentally simulated heat stress event. Our previous work has demonstrated that coral microbial endosymbionts can produce diverse, species‐specific volatilomes that are influenced by environmental factors (Lawson et al., 2019, 2020). In our examination of the coral holobiont, we therefore hypothesized that (a) the two species have distinct volatilomes while sharing some ‘core’ compounds and (b) that these volatilomes shift in response to heat stress.…”

Holobiont Nitrogen Control and its Potential for Eutrophication Resistance in an Obligate Photosymbiotic Jellyfish

“…xamachana is a model for the marine cnidarian-symbiodinian association, but currently lacking data on its prokaryotic associates and their function [28]. This is an essential shortcoming as bacteria also directly interact with Symbiodiniaceae [82,86]. Further corroborating a functional importance of these associations, coral holobionts host conserved algal-bacterial partnerships [83] and bacteria derived carotenoids have been shown to protect the algal endosymbionts (and thereby the holobiont) from environmental stress [87].…”