Purple non sulfur bacteria (PNSB) are gram negative anoxygenic phototrophic prokaryotes predominantly living in anoxic environments exposed to light and are known to play important role in many ecological processes. Earlier studies on the diversity of PNSB from various habitats of India contributed to the discovery of 31 novel species. The present thesis focused on exploring the unseen majority of this metabolically diverse group and the description of novel species of PNSB based on the polyphasic taxonomic approach. Based on distinct morphological, physiological, chemotaxonomic and genetic...