“…In this case, POR operates under both aerobic and micro-oxic conditions, but it requires light for its reaction. On the other hand, the Chl BLN complex catalyzes the same reaction only under microoxic conditions, regardless of illumination (28). In contrast, in the case of slr1790, HemY, and HemG homologs, it is difficult to assume any reasons for the presence of slr1790, HemY, or HemG in the bacterial kingdom, as these genes coexist in the same class of bacteria.…”