THE USE OF SPECTROPHOTOMETRY IN AN ECOLOGICAL INVESTIGATION OF THE FACULTATIVELY ANAEROBIC PURPLE PHOTOSYNTHETIC BACTERIA

Abstract

Diverse habitats were surveyed for the presence of Athiorhodaceae, using isolation techniques that permitted the development of only the facultatively anaerobic species of this family: Rhodopseudomonas capsulata, Rhodopseudomonas gelatinosa, Rhodopseudomonas palustris, Rhodopseudomonas spheroides, and Rhodospirillum rubrum. Of the 150 samples of soil, mud, sand, and water inoculated into enrichment media, 125 initiated cultures of photosynthetic bacteria, as indicated by spectrophotometric examination of the cultures. Subsequently, eight of these cultures were intensively investigated and isolates of the four species of Rhodopseudomonas were identified. Attempts to isolate Rhodospirillum rubrum from the cultures were unsuccessful. Species identifications were based on spectral examinations of aqueous cell-free preparations of the photosynthetic bacterial pigments. The species determinations based on the spectral evidence agreed with those based on the morphological and physiological criteria currently used for the identification of the Athiorhodaceae.