Symbiont-host relationships in chemosynthetic mussels: A comprehensive lipid biomarker study

Author(s)

Matthias Kellermann, Florence Schubotz, Marcus Elvert, Julius Lipp, Daniel Birgel-Rennebeck, Xavier Prieto-Mollar, Nicole Dubilier, Kai-Uwe Hinrichs

Abstract

Symbiosis with chemosynthetic microorganisms allows invertebrates from hydrothermal vents and cold

seeps, such as mussels, snails and tubeworms, to gain nutrition independently of organic input from photosynthetic

communities. Lipid biomarkers and their compound specific stable carbon isotopes (d13C)

have greatly aided the elucidation of chemosynthetic symbiosis. Due to recent methodological advances

in liquid chromatography it is now possible to obtain a more holistic view of lipid biomarkers, including

the analysis of intact polar membrane lipids (IPLs) and bacteriohopanepolyols (BHPs). This study provides

an extensive examination of polar and apolar lipids in combination with stable carbon isotope analysis of

three Bathymodiolus mussels (Bathymodiolus childressi, Bathymodiolus cf. thermophilus, Bathymodiolus

brooksi) hosting different types of bacterial symbiont (methane-oxidizing, sulfur-oxidizing and a dual

symbiosis with methane- and sulfur-oxidizing symbionts, respectively). We propose that IPLs with

C16:1 acyl side chains, and phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and phosphatidylethanolamine

(PE) head groups, which were only detected in the gill tissue, can be used as symbiont-characteristic

biomarkers. These putative symbiont-specific IPLs provide the opportunity to detect and

quantify the methanotrophic and thiotrophic symbionts within the gill tissue. Additional characteristic

markers for methanotrophic symbionts were found in B. childressi and B. brooksi, including the BHP derivatives

aminotriol and aminotetrol, 4-methyl sterols and diagnostic fatty acids (FAs), such as C16:1x9,

C16:1x8, and C18:1x8. In general, the d13C values of FAs, alcohols and BHP-derived hopanols were in accordance

with carbon assimilation pathways of the respective methanotrophic or thiotrophic symbionts in

all three Bathymodiolus mussels. Differences in BHP distribution as well as d13C values in the two mussels

hosting a methanotrophic symbiont may indicate the presence of different methanotrophic symbionts

and/or changes in the nutritional status. In all three mussel species the d13C values of lipid biomarkers

assigned to the symbionts were similar to those of the hosts, indicating the importance of the bacterial

symbionts as the main carbon source for the mussel tissue.

Organisation(s)

Department of Geology

External organisation(s)

Universität Bremen, Max-Planck-Institut für marine Mikrobiologie

Journal

Organic Geochemistry

Pages

112-124

No. of pages

13

ISSN

0146-6380

Publication date

2012

Peer reviewed

Yes

Austrian Fields of Science 2012

105105 Geochemistry

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