Discovery of the heliobacteria.

The first photosynthetic bacterium obtained in pure culture wasRhodospirillum rubrum, isolated by Erwin Esmarch in 1887. The organism appeared to be an aerobic heterotroph, and Esmarch was unaware of its photosynthetic 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 anoxygenic phototrophs increased greatly through the systematic study of numerous 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 technique required ability to use N2 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 photosynthetic bacteria (Gest 1992).