Cultured Diversity of Purple Anoxygenic Phototrophic Rhizobacteria of Paddy and their plant Growth promoting Attributes

Abstract

The Anoxygenic phototrophic bacteria (APB) encompasses an extremely heterogeneous group of prokaryotes that are capable of newlineconverting radiant energy into chemical energy under anaerobic conditions but release no oxygen. The heterogeneity of APB is newlinedemonstrated by great variations they show in their habitats, morphology, physiology, radiation capturing pigments and phylogeny. In contrast to oxygenic cyanobacteria and plants, they posses only one photosystem (PSI or PSII). Instead of water, they use electron donors which are more reduced than water such as reduced sulfur compounds (sulfide, thiosulfate, sulfite, tetrathionate), hydrogen, a number of small organic compounds [acetate, pyruvate; (Imhoff, 1995)], or ferrous iron (Fe 2+ ) (Heising et al ., 1999; Heising and Schink, 1998). APB are widely distributed in various aquatic and terrestrial habitats, which include rice fields (Arunasri, 2004; Harada et al ., 2001; Elbadry et al ., 1999; Habte and Alexander 1980; Matsuguchi and Tangcham, 1974; newlineKobayashi et al ., 1967). The rice fields which are characterized by the diurnal light irradiance, eutrophic environment and oxic-anoxic interface (Liesack et al ., 2000 ), provide purple phototrophic bacteria (a major newlinephysiological group of APB) with an ideal niche for their growth (Feng et al ., 2009). The purple bacteria were found to be repeatedly enriched and found in high numbers at different stages of the rice plant (Archana, Lakshmi KVNS, Ph.D Thesis, 2012