Characterizing the plasticity of nitrogen metabolism by the host and symbionts of the hydrothermal vent chemoautotrophic symbioses Ridgeia piscesae.
Chemoautotrophic symbionts of deep sea hydrothermal vent tubeworms are known to provide their hosts with all their primary nutrition. While studies have examined how chemoautotrophic symbionts provide the association with nitrogen, fewer have examined if symbiont nitrogen metabolism varies as a function of environmental conditions. Ridgeia piscesae tubeworms flourish at Northeastern Pacific vents, occupy a range of microhabitats, and exhibit a high degree of morphological plasticity [e.g. long-skinny (LS) and short-fat (SF) phenotypes] that may relate to environmental conditions. This plasticity affords an opportunity to examine whether symbiont nitrogen metabolism varies among host phenotypes. LS and SF R. piscesae were recovered from the Axial and Main Endeavour Field hydrothermal vents. Nitrate and ammonium were quantified in Ridgeia blood, and the expression of key nitrogen metabolism genes, as well as stable nitrogen isotope ratios, was quantified in host branchial plume and symbiont-containing tissues. Nitrate and ammonium were abundant in the blood of both phenotypes though environmental ammonium concentrations were, paradoxically, lowest among individuals with the highest blood ammonium. Assimilatory nitrate reductase transcripts were always below detection, though in both LS and SF R. piscesae symbionts, we observed elevated expression of dissimilatory nitrate reductase genes, as well as symbiont and host ammonium assimilation genes. Site-specific differences in expression, along with tissue stable isotope analyses, suggest that LS and SF Ridgeia symbionts are engaged in both dissimilatory nitrate reduction and ammonia assimilation to varying degrees. As such, it appears that environmental conditions -not host phenotype-primarily dictates symbiont nitrogen metabolism.
Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave, Cambridge, MA, 02138-2020, USA.|SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, 200136, China.
Li
L
Liao
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 266 Woods Hole Rd., MS 25, Woods Hole, MA, 02540, USA.
Scott D
SD
Wankel
College of Life Sciences, Zhejiang University, 388 Yuhangtang Road, Hangzhou, 310058, China.
Min
M
Wu
Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave, Cambridge, MA, 02138-2020, USA.
Colleen M
CM
Cavanaugh
Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave, Cambridge, MA, 02138-2020, USA.
Peter R
PR
Girguis
D064751:Ammonium Compounds / Q000097:blood; D000818:Animals; D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D052837:Chemoautotrophic Growth; D060086:Hydrothermal Vents; D050901:Nitrate Reductase / Q000235:genetics; D009566:Nitrates / Q000097:blood; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis; D010641:Phenotype; D011077:Polychaeta / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D013559:Symbiosis
D064751:Ammonium Compounds; D009566:Nitrates; D009587:Nitrogen Isotopes; D050901:Nitrate Reductase; D009584:Nitrogen
Ridgeia; hydrothermal vent; nitrogen; symbiosis; tubeworm