X-Ray Survival Studies on the Alga Brachiomonas submarina Bohlin

Abstract

Brachiomonas submarina Bohlin, a member of the Chlamydomonadaceae, is a free-swimming unicellular alga which grows readily either in liquid medium or on agar and is capable of growth in a defined medium, as well as in peptone media. The cells are approximately 10 to 20 i., so they may be counted or examined cytologically under high power of the microscope without resort to oil immersion optics. These properties suggest that Brachiomonas might be a useful subject in radiobiological investigations, since it would be amenable to nutritional manipulation, and both total and viable cell counts could be performed on the same sample. Another intriguing feature of this alga is its mode of division. As described by Hazen (1), the protoplast goes through two or three successive divisions, and about 2 hours later the 4 or 8 new cells are liberated from the mother-cell wall. During the course of this investigation, we observed that on a regimen of alternating light and dark periods the release of new daughters is confined to the dark period; this permits partial synchronization and is an additional useful and interesting property.