Intact polar lipids of Thaumarchaeota and anammox bacteria as indicators of N cycling in the eastern tropical North Pacific oxygen-deficient zone

[摘要] In the last decade our understanding of the marine nitrogen cycle hasimproved considerably thanks to the discovery of two novel groups ofmicroorganisms: ammonia-oxidizing archaea (AOA) and anaerobicammonia-oxidizing (anammox) bacteria. Both groups are important in oxygen-deficient zones (ODZs), where they substantially affect the marine N budget.These two groups of microbes are also well known for producing specificmembrane lipids, which can be used as biomarkers to trace their presence inthe environment. We investigated the occurrence and distribution of AOA andanammox bacteria in the water column of the eastern tropical North Pacific(ETNP) ODZ, one of the most prominent ODZs worldwide. Suspended particulatematter (SPM) was collected at different depths of the water column in high resolution, at both a coastal and an open-ocean setting. The SPM was analyzedfor AOA- and anammox bacteria-specific intact polar lipids (IPLs), i.e.,hexose-phosphohexose (HPH)-crenarchaeol and phosphatidylcholine(PC)-monoether ladderane. Comparison with oxygen profiles reveals that boththe microbial groups are able to thrive at low (< 1 μM)concentrations of oxygen. Our results indicate a clear niche segregation ofAOA and anammox bacteria in the coastal waters of the ETNP but a partialoverlap of the two niches of these microbial species in the open-watersetting. The latter distribution suggests the potential for an interactionbetween the two microbial groups at the open-ocean site, although the natureof this hypothetical interaction (i.e., either competition or cooperation)remains unclear.

[学科分类] 地球化学与岩石