HYDROGENASES IN NOSTOC SP STRAIN PCC-73102, A STRAIN LACKING A BIDIRECTIONAL ENZYME

The present study was carried out in order to examine and characterize the bidirectional hydrogenase in the cyanobacterium Nostoc sp. strain PCC 73102, Southern hybridizations with the probes Av1 and Av3 (hoxY and hoxH, bidirectional hydrogenase small and large subunits, respecti vely) revealed the occurrence of corresponding sequences in Anabaena v ariabilis (control), Anabaena sp. strain PCC 7120, and Nostoc muscorum but not in Nostoc sp. strain PCC 73102, As a control, hybridizations with the probe hup2 (hupL, uptake hydrogenase large subunit) demonstra ted the presence of a corresponding gene in all the cyanobacteria test ed, including Nostoc sp. strain PCC 73102, Moreover, with three differ ent growth media, a bidirectional enzyme that was functional in vivo w as observed in N. muscorum, Anabaena sp. strain PCC 7120, and A. varia bilis, whereas Nostoc sp. strain PCC 73102 consistently lacked any det ectable in vivo activity, Similar results were obtained when assaying for the presence of an enzyme that is functional in vitro, Native poly acrylamide gel electrophoresis followed by in situ hydrogenase activit y staining was used to demonstrate the presence or absence of a functi onal enzyme, Again, bands corresponding to hydrogenase activity were o bserved for N. muscorum, Anabaena sp. strain PCC 7120, and A. variabil is but not for Nostoc sp. strain PCC 73102, In conclusion, me were una ble to detect a bidirectional hydrogenase in Nostoc sp. strain PCC 731 02 with specific physiological and molecular techniques, The same tech niques clearly showed the presence of an inducible bidirectional enzym e and corresponding structural genes in N. muscorum, Anabaena sp. stra in PCC 7120, and A. variabilis. Hence, Nostoc sp. strain PCC 73102 see ms to be an unusual cyanobacterium and an interesting candidate for fu ture biotechnological applications.