Data from: 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.