The porphin requirements of the Hemophilus organisms have been studied. Organisms of the parainfluenzae group show quantitative differences in their ability to synthesize heme. The ability of the parainfluenzae organisms to grow appears to depend on the rate with which they synthesize heme and in part at least on the properties of the medium to protect the heme from peroxidative breakdown.
Quantitative studies of the growth of H. influenzae Turner on various iron porphins have been made. Iron protoporphin gives greatest growth when supplied in excess, although iron mesoporphin appears more efficient at lower concentrations. Iron deutero- and iron hematoporphin are much less effective. This suggests that although the vinyl groups are not essential for growth of the Turner organism they may be required for some particular enzymes which aid in attaining maximum growth.
A number of substances potentiate the growth-promoting properties of iron porphins. These substances include reducing agents and agents which destroy H2O2.
E. influenzae Turner appears to require heme for anaerobic as well as aerobic growth. The possibility of an essential heme enzyme functioning under anaerobic conditions must therefore be considered.
