PHOTOGENIN AND PHOTOPHELEIN.
As we have just seen, the light of a mass of bacteria disappears almost instantly if they are broken up by any of the usual cytolytic agents. This result is no doubt due to the fact that they continually burn their light-producing substances as soon as they manufacture them. The substances are therefore present in very small quantity. For this reason we might expect to fail in demonstrating the existence of photogenin and photophelein, although we must remember that forms like Cavernularia, which contain a large amount of luminous material, also fail in showing the photogenin-photophelein reaction.
Since it is practically impossible to grind the luminous bacteria in sea-water and so prepare an extract of photogenin, we are forced to prepare our extract by cytolyzing with distilled water and thus obtain a dark solution containing swollen suspended bacteria. This fluid will give no light, however, on adding a suspension of bacteria heated to boiling. Thinking that bacterial photophelein as well as photogenin might be destroyed by boiling temperature, I tried heating to lower temperatures, 90°, 80°, 70°, 60°, and 50°, for 2 minutes, but in no case did light appear on mixing with photogenin. Neither did these solu tions give light on mixing with firefly photogenin, but we can obtain light from a bacterial photophelein prepared in the following way: by adding absolute alcohol to a dense mass of the bacteria, then remov ing the alcohol by centrifuging, and quickly drying by evaporation in vacuo. The resultant powder gives no light with water, but does
cause firefly photogenin to phosphoresce very faintly. Similar material prepared with acetone instead of alcohol gave no light with firefly photogenin. In order to obtain a bacterial powder which will give light with firefly photogenin it is necessary to remove the alcohol and dry as quickly as possible; otherwise the photophelein is destroyed.
Addition of ether to a mass of luminous bacteria causes the light to disappear rapidly and it is possible that the photogenin is destroyed by ether and not the photophelein; but bacteria so treated, after the ether had been evaporated by a current of air, gave no light with firefly photogenin. Negative results were obtained also with an alka line (m/12 KOH) extract of luminous bacteria neutralized with HCI. A precipitate of nucleoprotein (?) is produced on neutralization. Apparently the bacterial photophelein is formed in such small quan tities from its precursor or is so unstable that all methods of obtaining it have failed, with the exception of the rapid precipitation by alcohol.