The ability of bacteria to regulate synthesis of a photosystem was initially observed in 1887 by Erwin Esmarch who described the first successful isolation of a photosynthetic bacterium in pure culture. In his essay, he noted that "the spirillum only produces pigment if the air is completely or almost completely excluded from the colony". (A review of this work has recently been published by Gest, 1995). This observation was later extended to include light regulation of the …showed first 75 words of 576 total…

…showed last 75 words of 576 total…frame, designated hvrA, that appears to be responsible for light regulation of the puf and puh operons (Buggy et al., 1994) (Figure 2c). Disruption of hvrA results in an inability to stimulate puf and puh expression in response to a reduction in light intensity, suggesting that HvrA functions as a dim light activator. HvrA contains a putative helix-turn-helix DNA binding domain and DNA footprint experiments have demonstrated that HvrA binds to the puf and puh promoters.