DISCOVERY OF THE HELIOBACTERIA

The first photosynthetic bacterium obtained in pure culture was Rhodos pirillum rubrum, isolated by Erwin Esmarch in 1887. The organism appea red to be an aerobic heterotroph, and Esmarch was unaware of its photo synthetic capability. The overall general characteristics of a number of major species of photosynthetic bacteria were described by Molisch and van Niel before 1945. Subsequently, our knowledge of the anoxygeni c phototrophs increased greatly through the systematic study of numero us new species isolated from enrichment cultures in which capacity for anaerobic (and anoxygenic) growth with light as the energy source was a primary selective factor. A further refinement of the enrichment te chnique required ability to use N-2 as the sole source of nitrogen for growth under anaerobic photosynthetic conditions, and this led to the isolation of additional new species, including the heliobacteria. The first recognition of the heliobacteria was facilitated by serendipity , which was a significant factor in a number of other researches on ph otosynthetic bacteria (Gest 1992).