A novel cohabitation between two diazotrophic cyanobacteria in the oligotrophic ocean.

摘要: The cyanobacterial genus Trichodesmium is biogeochemically significant because of its dual role in nitrogen and carbon fixation the oligotrophic ocean. species form colonies that can be easily enriched from water column used for shipboard rate measurements to estimate their contribution oceanic budgets. During a July 2010 cruise near Hawaiian Islands North Pacific Subtropical Gyre, specific morphology puff-form were examined under epifluorescent microscopy found harbor colonial endobiont, morphologically identified as heterocystous diazotrophic cyanobacterium Calothrix. Using unialgal enrichments obtained this cruise, we show these Calothrix-like cyanobionts (hetDA ‘Trichodesmium-associated diazotroph’) fix on diurnal cycle (maximally middle light with detectable minimum dark). Gene sequencing nifH revealed was likely not quantified using currently described quantitative PCR (qPCR) primers. Guided by sequence isolate, new hetDA-specific primers designed subsequent qPCR environmental samples detected diazotroph surface depth 150 m, reaching densities up ∼9 × 103 l−1. Based phylogenetic relatedness 16S rRNA gene sequences, it predicted distribution cyanobiont limited subtropical but reaches South Atlantic Oceans. Therefore, previously unrecognized cohabitation, if beyond Pacific, could potentially influence Trichodesmium-derived budgets world