Five types of non-sulfur purple bacteria, which differed from one another in their pigment content, were exposed to ultraviolet radiation while in various environments and physiological states. The resulting effects upon their respiration and photosynthesis were observed by manometric methods. Tentative conclusions were that carotenoid pigments do not protect cells from inactivation by ultraviolet (protein-absorbed) radiation and that the observed effects do involve indirect action. Absorption spectra of the five types of bacteria, obtained in a medium which minimized light scattering, are presented. The writers express their sincere appreciation to Dr. Roderick K. Clayton, under whose direction this research was accomplished, for his instructions and patient assistance, and to their own families who have so graciously submitted to two years of the rigors which accompany education.

http://archive.org/details/radiationprotect1094514542

First Lieutenant, United States Air Force

Major, United States Air Force

Captain, United States Army