H 2 accumulation and N 2 fixation variation by Ni limitation in Cyanothece

• Published in: Limnology and oceanography 2020-02, Vol.65 (2), p.377-386
• Main Authors: Tuo, Sing‐how, Rodriguez, Irene B., Ho, Tung‐Yuan
• Format: Article
• Language: English
• ISSN: 0024-3590; 1939-5590
• DOI: 10.1002/lno.11305

Ni is an essential cofactor in NiFe‐uptake hydrogenase, an enzyme regulating H 2 metabolism in diazotrophic cyanobacteria, the major H 2 producers in the surface ocean globally. Here, we investigated the effect of Ni supply on H 2 production and N 2 fixation by using a model marine cyanobacterial diazotroph, Cyanothece . By mediating total dissolved Ni concentrations from 100 to 0.03 nmol L −1 in a trace metal‐defined culture medium, we demonstrated that Ni deficiency results in H 2 accumulation, coupled with decreasing Ni quotas, growth rates, and occasionally relatively low N 2 fixation rates. These results indicate that Ni deficiency limits the growth of the Cyanothece to some extent, considerably decreases H 2 uptake by hydrogenase and leads to H 2 accumulation and N 2 fixation variation in the diazotroph. The findings show that Ni availability is a critical factor on controlling H 2 production and N 2 fixation in marine diazotrophic cyanobacteria. The information of Ni bioavailability for diazotrophic cyanobacteria is thus essential to evaluate the importance of Ni for H 2 cycling and N 2 fixation in oceanic surface waters.