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).