Some Properties of a Photodynamic Pigment From Blepharisma

Abstract

1. A pigment can be extracted from Blepharisma undulans by heat treatment of a concentrated suspension of the deeply pigmented animals. 2. In the presence of this pigment, various colorless protozoans are sensitized to light and killed if exposed long enough. The protozoans show a differential sensitivity, some being much more sensitive than others. 3. Bleached colorless blepharismas are not sensitized to their own pigment even after prolonged exposure in the most concentrated solutions available. 4. Blepharisma is also less sensitive than any of the protozoans tested to such photodynamic dyes as rose bengal. 5. The pigment is not extracted from wet blepharismas by non-polar solvents, but is readily extracted into such polar organic solvents as the alcohols. 6. When the alcohol extract is dried, the amorphous residue is readily soluble in a variety of organic solvents, but not in the most non-polar. 7. The pigment is highly stable in alcohol extract and has been kept in the dark for years. 8. The pigment is bleached by light in a photooxidation. 9. Absorption maxima are found at wave lengths 5800, 5400, 4800, and 3300 A, the latter being the largest. Similar peaks are found in alcohol and water solutions, although the heights are not exactly the same. In both alcoholic and aqueous solutions pH had an effect on the absorption spectrum. Heat has little effect but illumination with intense visible light or exposure to ultraviolet light bleaches the pigment with decreases in the characteristic peaks. 10. Preliminary absorption column experiments indicate a single pigment in the alcohol extract. 11. Experiments on the migration of zoopurpurin in agar and gelatin gels indicate that it diffuses at about the same rate as eosin and is therefore probably not a large molecule.

STUDIES ON THE RED AND BLUE FORMS OF THE PIGMENT OF BLEPHARISMA*

“…The pigment of Blepharisma called zoopurpurin by Archichovskij [ 5 ] is of general interest because it is one of the few endogenous photosensitizing pigments known and it is almost unique in the animal world. Only in the fluorescent strain of Srentor [7], and possibly in strains of Tetrahymena geleii [20] which produce protoporphyrin, is similar photosensitization observed, although other protozoans possess pigments; e.g., many dinoflagellates [21], and the ciliates Fabrea salina [22], and Holosticha rubra [23,24] -but in no other case has endogenous photosensitization been demonstrated [ 3 ] . Endogenous photosensitizers occur in bacteria and in many of them carotenoids serve to protect them against photosensitization [25].…”

“…BLEPHARISMA, which has been grown in the dark and is reddish in color, is killed by exposure to bright visible light (2700 fc) [l], but if it is first changed in color to bluegray by exposure to dim visible light (200 fc), it loses such photosensitivity [2,3]. Killing does not occur in the absence of oxygen; therefore, the process is one of photooxidation [l].…”

Exposure of natural Antarctic marine microbial assemblages to ambient UV radiation: effects on bacterioplankton

“…Sommaruga et al (1999) showed that, in high altitude lakes, the concentration and grazing rates of bactivores was reduced by exposure to UVB wavelengths. However, protozoans differ greatly in the sensitivity to UV exposure (Giese 1953, Maller 1962. Our results showed that prolonged exposure of planktonic communities to high UV irradiances increased microheterotroph concentrations.…”

Blepharismin produced by a protozoan Blepharisma functions as an antibiotic effective against methicillin-resistant Staphylococcus aureus

“…Although the solubility of BLR in water is low [17], the maximal absorption at 585 nm which specifies BLR, was clearly observed in the cytoplasmic fraction of MRSA K‐1 (data not shown), indicating that BLR is incorporated into the bacterial cell.…”