The iron-regulated isiA gene of Fischerella muscicola strain PCC 73103 is linked to a likewise regulated gene encoding a Pcb-like chlorophyll-binding protein

Abstract

The expression of the chlorophyll a‐binding, iron stress‐induced protein IsiA is part of the cyanobacterial response to iron deficiency. A new isiA gene from the filamentous heterocystous cyanobacterial strain, Fischerella muscicola PCC 73103, was identified using standard and inverse PCR. While in unicellular cyanobacterial strains isiA is organized in an operon with isiB (encoding flavodoxin), in Fischerella not an isiB gene but another chlorophyll‐binding protein encoding gene was identified downstream of isiA, which shows significant similarities to Pcb‐like protein encoding genes known from prochlorophytes. The expression of both genes was clearly activated under iron deficiency. Although isiA and pcbC were independently transcribed, the size of the pcbC transcript indicates a large iron‐regulated operon. Beside a 10‐fold increase of isiA transcript content iron‐starved cells of Fischerella showed a blue‐shift in the red chlorophyll a absorption peak. In addition, chlorophyll fluorescence at 77 K was dominated by an emission peak at 685 nm. These features are in accordance with the characteristics of IsiA accumulation in iron‐starved unicellular cyanobacteria, suggesting identical IsiA function in heterocystous strains in spite of different genetic organization.

Development of a hybrid cell for energy production

“…To enhance their properties as an energy source, silver nanoparticles (AgNPs) were added to their culture medium in order to generate a new hybrid material, which from now on we will call Cy-AgNPs (F. muscicola+AgNPs). These developed hybrid cells can use these nanostructures as antennas to enhance the transport of electric charge [22] since cyanobacteria, by the mechanism of photosynthesis, release electric charge but their transport is delimited by the interface between cyanobacteria and their culture medium [23][24][25][26]. AgNPs were synthesized by green chemistry using extract of the fruit of Berberis hallii (carrasquilla) species following the protocol described in [27][28][29][30][31][32].…”