In Situ Spawning of Hydrothermal Vent Tubeworms (Riftia pachyptila)

Genome and proteome data predict the presence of both the reductive citric acid cycle (rCAC; also called the reductive tricarboxylic acid cycle) and Calvin-Benson-Bassham cycle (CBB) in “ Candidatus Endoriftia persephonae”, the autotrophic sulfur-oxidizing bacterial endosymbiont from giant hydrothermal vent tubeworm Riftia pachyptila. We tested whether these cycles were differentially induced by sulfide supply, since the synthesis of biosynthetic intermediates by the rCAC is less energetically expensive than the CBB. R. pachyptila were incubated under in situ conditions in high-pressure aquaria under low (28-40 μmol hr −1 ) or high (180 - 276 μmol hr −1 ) rates of sulfide supply. Symbiont-bearing trophosome samples excised from R. pachyptila maintained under either condition were capable of similar rates of CO 2 fixation. Activities of rCAC enzyme ATP-dependent citrate lyase and CBB enzyme RubisCO did not differ between the two conditions, though transcript abundances for ATP-dependent citrate lyase were 4 to 5-fold higher under low sulfide conditions. δ 13 C values of internal dissolved inorganic carbon pools were variable, and did not correlate with sulfide supply rate. In samples taken from freshly collected R. pachyptila, δ 13 C values of lipids fell between those collected for organisms using either the rCAC or CBB cycles exclusively. These observations are consistent with co-occurring activities of rCAC and CBB cycles in this symbiosis. IMPORTANCE Previous to this study, the activities of the rCAC and CBB in R. pachyptila had largely been inferred from –omics studies of R. pachyptila without direct assessment of in situ conditions prior to collection. In this study, R. pachyptila were maintained and monitored in high-pressure aquaria prior to measuring their CO 2 -fixation parameters. Results suggest that ranges in sulfide concentrations similar to those experienced in situ do not exert a strong influence on the relative activities of the rCAC and CBB. This observation highlights the importance of further study of this symbiosis and other organisms with multiple CO 2 -fixing pathways, which recent genomics and biochemical studies suggest are likely to be more prevalent than anticipated.

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Development of an Easy-to-Operate Underwater Raman System for Deep-Sea Cold Seep and Hydrothermal Vent In Situ Detection

Sensors ◽

10.3390/s21155090 ◽

2021 ◽

Vol 21 (15) ◽

pp. 5090

Author(s):

Qingsheng Liu ◽

Jinjia Guo ◽

Wangquan Ye ◽

Kai Cheng ◽

Fujun Qi ◽

...

Keyword(s):

Deep Sea ◽

Hydrothermal Vent ◽

Methane Hydrate ◽

Sulfur Cycle ◽

Cold Seep ◽

Remotely Operated Vehicle ◽

Bacterial Mats ◽

Optical Module ◽

In Situ Detection

As a powerful in situ detection technique, Raman spectroscopy is becoming a popular underwater investigation method, especially in deep-sea research. In this paper, an easy-to-operate underwater Raman system with a compact design and competitive sensitivity is introduced. All the components, including the optical module and the electronic module, were packaged in an L362 × Φ172 mm titanium capsule with a weight of 20 kg in the air (about 12 kg in water). By optimising the laser coupling mode and focusing lens parameters, a competitive sensitivity was achieved with the detection limit of SO42− being 0.7 mmol/L. The first sea trial was carried out with the aid of a 3000 m grade remotely operated vehicle (ROV) “FCV3000” in October 2018. Over 20,000 spectra were captured from the targets interested, including methane hydrate, clamshell in the area of cold seep, and bacterial mats around a hydrothermal vent, with a maximum depth of 1038 m. A Raman peak at 2592 cm−1 was found in the methane hydrate spectra, which revealed the presence of hydrogen sulfide in the seeping gas. In addition, we also found sulfur in the bacterial mats, confirming the involvement of micro-organisms in the sulfur cycle in the hydrothermal field. It is expected that the system can be developed as a universal deep-sea survey and detection equipment in the near future.

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Polyclonal symbiont populations in hydrothermal vent tubeworms and the environment

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.1281 ◽

2019 ◽

Vol 286 (1896) ◽

pp. 20181281 ◽

Cited By ~ 8

Author(s):

Julia Polzin ◽

Philip Arevalo ◽

Thomas Nussbaumer ◽

Martin F. Polz ◽

Monika Bright

Keyword(s):

Hydrothermal Vent ◽

Low Frequency ◽

Gene Sequencing ◽

Housekeeping Genes ◽

Partner Choice ◽

Sequence Variability ◽

Riftia Pachyptila ◽

Free Living ◽

High Coverage ◽

Dominant Genotype

Horizontally transmitted symbioses usually house multiple and variable symbiont genotypes that are acquired from a much more diverse environmental pool via partner choice mechanisms. However, in the deep-sea hydrothermal vent tubeworm Riftia pachyptila (Vestimentifera, Siboglinidae), it has been suggested that the Candidatus Endoriftia persephone symbiont is monoclonal. Here, we show with high-coverage metagenomics that adult R. pachyptila house a polyclonal symbiont population consisting of one dominant and several low-frequency variants. This dominance of one genotype is confirmed by multilocus gene sequencing of amplified housekeeping genes in a broad range of host individuals where three out of four loci ( atpA , uvrD and recA ) revealed no genomic differences, while one locus ( gyrB ) was more diverse in adults than in juveniles. We also analysed a metagenome of free-living Endoriftia and found that the free-living population showed greater sequence variability than the host-associated population. Most juveniles and adults shared a specific dominant genotype, while other genotypes can dominate in few individuals. We suggest that although generally permissive, partner choice is selective enough to restrict uptake of some genotypes present in the environment.

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