Effects on growth and nitrogen metabolism of Synechococcus elongatus PCC 7942 expressing recombinant nitric oxide synthase from Synechococcus PCC 7335

ESPINOSA JAVIER; CONTRERAS ASUNCION; CORREA ARAGUNDE NATALIA; SALINAS PALOMA; LAMATTINA LORENZO

Alicante

Congreso; 23rd European Nitrogen Cycle Meeting; 2018

Nitric oxide synthases (NOSs) are oxidoreductase enzymes that catalyze the oxidation of arginine to citrulline and nitric oxide (NO). Recently, we characterized the first NOS enzyme in the marine cyanobacteria from the nitrogen-fixing Synechococcus PCC 7335 (SyNOS). SyNOS possesses a canonical mammalian NOS architecture that consist of the oxygenase and reductase domains, with the addition of an unusual globin domain of unknown function at the N-terminus. Expression of the recombinant SyNOS in E. coli allows the bacteria reach a higher OD600 at stationary phase when growing in LB medium. Moreover, cultures expressing recombinant SyNOS and growing in deficient nitrogen media, display almost similar growth rate compared to sufficient nitrogen conditions. In this study, we have focused in the expression of SyNOS in Synechococcus elongatus PCC 7942 (hereafter S. elongatus), a freshwater and nitrogen-non fixing cyanobacterium that lacks a NOS gene and allows easy genetic manipulation. A copy of the coding gene for SyNOS, fused to the IPTG-inducible promoter Ptrc, was introduced into S. elongatus chromosome. Detection of both transcripts and SyNOS protein was confirmed by RT-PCR and western blot analysis. The effects of SyNOS expression on S. elongatus growth in different nitrogen regimes, nitrate transport and pigment degradation will be discussed in the context of the role of nitric oxide synthases in cyanobacterial nitrogen metabolism.