A Caltech Library Service

The coral symbiont Candidatus Aquarickettsia is variably abundant in threatened Caribbean acroporids and transmitted horizontally

Baker, Lydia J. and Reich, Hannah G. and Kitchen, Sheila A. and Klinges, J. Grace and Koch, Hanna R. and Baums, Iliana B. and Muller, Erinn and Vega Thurber, Rebecca (2021) The coral symbiont Candidatus Aquarickettsia is variably abundant in threatened Caribbean acroporids and transmitted horizontally. . (Unpublished)

[img] PDF - Submitted Version
Creative Commons Attribution Non-commercial No Derivatives.

[img] Archive (ZIP) - Supplemental Material
Creative Commons Attribution Non-commercial No Derivatives.


Use this Persistent URL to link to this item:


The aquatic symbiont Candidatus Aquarickettsia rohweri infects a diversity of non-bilaterian metazoan phyla. In the threatened coral Acropora cervicornis, Aquarickettsia proliferates in response to increased nutrient exposure, resulting in suppressed growth and increased disease susceptibility and mortality. This study evaluated the extent, as well as the ecology and evolution of Aquarickettsia infecting the Caribbean corals: Ac. cervicornis and Ac. palmata and their hybrid (Ac. prolifera). The bacterial parasite Aquarickettsia was found in all acroporids, with host and sampling location impacting infection magnitude. Phylogenomic and genome-wide single nucleotide variant analysis found Aquarickettsia clustering by region, not by coral taxon. Fixation analysis suggested within coral colonies, Aquarickettsia are genetically isolated to the extent that reinfection is unlikely. Relative to other Rickettsiales, Aquarickettsia is undergoing positive selection, with Florida populations experiencing greater positive selection relative to the other Caribbean locations. This may be due to Aquarickettsia response to increased nutrient stress in Florida, as indicated by greater in situ replication rates in these corals. Aquarickettsia did not significantly codiversify with either coral animal nor algal symbiont, and qPCR analysis of gametes and juveniles from susceptible coral genotypes indicated absence in early life stages. Thus, despite being an obligate parasite, Aquarickettsia must be horizontally transmitted via coral mucocytes, an unidentified secondary host, or a yet unexplored environmentally mediated mechanism. Importantly, the prevalence of Aquarickettsia in Ac. cervicornis and high abundance in Florida populations suggests that disease mitigation efforts in the US and Caribbean should focus on preventing early infection via horizontal transmission.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Baker, Lydia J.0000-0002-1453-421X
Reich, Hannah G.0000-0002-8622-8801
Kitchen, Sheila A.0000-0003-4402-8139
Klinges, J. Grace0000-0003-3172-133X
Baums, Iliana B.0000-0001-6463-7308
Muller, Erinn0000-0002-2695-2064
Additional Information:The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license. This version posted January 29, 2021. Thanks to Dr. Tory Hendry for feedback on evolutionary methods employed and Dr. Hanna Koch for permits facilitating the movement of corals between Mote’s field and land coral nurseries; Florida Keys National Marine Sanctuary under permit # FKNMS-2015-163-A3. Funding: This work was funded by an NSF Biological Oceanography grant to RVT and EM (#1923836) and an NSF CAREER award to EM (#1452538-OCE). Funding for the S. ‘fitti’ genomes was provided by NSF OCE-1537959 to IBB. Data accessibility: All sequences used are available in the SRA in PRJNA473816, assembled A. rohweri genomes are accessible under PRJNA66646, and coral mitochondrial genomes are MW246489-MW246565. Author Contributions: LB conducted the research, analyzed and interpreted the data, and wrote the manuscript. EM and RVT assisted in the conceptualization of the work, financially supported the project, and assisted in the writing and editing of the manuscript. HRG, SAK, JGK, HRK, and IBB provided data, analysis, and resources and assisted in the editing of the manuscript. Competing interests: The authors have nothing to disclose.
Funding AgencyGrant Number
Subject Keywords:metagenome assembled genomes, symbiont, transmission, evolution, aquatic bacteria
Record Number:CaltechAUTHORS:20210129-095514933
Persistent URL:
Official Citation:The coral symbiont Candidatus Aquarickettsia is variably abundant in threatened Caribbean acroporids and transmitted horizontally. Lydia Jeanne Baker, Hannah G. Reich, Sheila A. Kitchen, J. Grace Klinges, Hanna R. Koch, Iliana B. Baums, Erinn Muller, Rebecca Vega Thurber. bioRxiv 2021.01.28.428674; doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107802
Deposited By: Tony Diaz
Deposited On:29 Jan 2021 18:16
Last Modified:03 Mar 2021 21:47

Repository Staff Only: item control page