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 characteristics, strains JA490, JA590, JA737 and JA755 isolated from the present study were classified as representatives of novel species for which the names Rhodopseudomonas harwoodiae, Phaeospirillum tilakii, Rhodobacter viridis and Rhodomicrobium udaipurense respectively was proposed. The type strains from the study were deposited at international culture collection centers for public accessibility.