Characterization of Newly Isolated and Established Strains of the Acidophilic Phototrophic Bacterium Rhodoblastus acidophilus

Norbert Pfennig, a German microbiologist, isolated the first true acidophilic purple bacterium in 1969. He named the organism Rhodoblastus acidophilus. Since the original work of Pfennig, no study has examined the phylogeny and physiology of the original strains of R. acidophilus or isolated any new strains. In this thesis six new strains of acidophilic purple nonsulfur bacteria were isolated from a Canadian Sphagnum peat bog. Moreover, three original Pfennig strains of R. acidophilus and two uncharacterized strains (previously isolated by Michael Madigan) were included in experiments aimed to describe the new isolates and further our understanding of the species Rhodoblastus acidophilus. Although pigmentation varied, all of the strains studied were very similar. The 16S rRNA genes of the new bog isolates and the original strains of R. acidophilus and Rhodoblastus sphagnicola, another acidophilic purple phototroph isolated from a Sphagnum peat bog in Russia, showed a 16S rRNA gene sequence similarity greater than or equal to 97%. All isolates were acidophilic and grew best photoheterotrophically on certain organic or fatty acids, or alcohols as carbon sources. Despite subtle physiological differences, all of the strains shared many characteristics. This indicates that R. acidophilus is a reasonably homogenous species and suggests that diversity of the acidophilic phototrophs may be low