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Plant growth promoting rhizobacteria (PGPR) are one class of beneficial bacteria inhabiting the soil ecosystem (Kloepper et al 1989). PGPR are found in association with roots of many different plants. The high concentration of these bacteria around the roots, ie in the rhizosphere; presumably occurs because of the presence of high levels of nutrients (especially small molecules such as amino acids, sugars and organic acids) that are exuded from roots of most plants and can thus be used to support bacterial growth and metabolism (Whipps 1990). The effects of PGPR on plant growth can be mediated by direct or indirect mechanisms (Glick 1995). The direct effects have been most commonly attributed to the production of plant hormones such as auxins, gibberellins and cytokinins, or by supplying biologically fixed nitrogen. These PGPR affect growth by indirect mechanisms such as suppression of bacterial, fungal and nematode pathogens by the production of siderophores, HCN, ammonia, antibiotics, volatile metabolites etc., by induced systemic resistance and/or by competing with the pathogen for nutrients or for colonization space (Glick 1995). A particular bacterium may affect plant growth and development using any one or more of these mechanisms (Montesinos, 2003). A relatively recent discovery implicates the