M. Kern et al., EVIDENCE FOR A REGULATORY LINK OF NITROGEN-FIXATION AND PHOTOSYNTHESIS IN RHODOBACTER-CAPSULATUS VIA HVRA, Journal of bacteriology, 180(7), 1998, pp. 1965-1969
A Rhodobacter capsulatus reporter strain, carrying a constitutively ex
pressed nifA gene and a nifH-lacZ gene fusion, was used for random tra
nsposon Tn5 mutagenesis to search for genes required for the NtrC-inde
pendent ammonium repression-of NifA activity. A mutation in hvrA, whic
h is known to be involved in low-light activation of the photosyntheti
c apparatus, released both ammonium and oxygen control of nifH express
ion in this reporter strain, demonstrating a regulatory link of nitrog
en fixation and photosynthesis via HvrA In addition, a significant inc
rease in bacteriochlorophyll a (BChla) content was found in cells unde
r nitrogen-fixing conditions. HvrA was not involved in this up-regulat
ion of BChla. Instead, the presence of active nitrogenase seemed to be
sufficient for this process, since no increase in BChla content was o
bserved in different nif mutants.