which produces 1-aminocyclopropane-1-carboxylate (ACC)deaminase, conferred IST to drought stress in pepper(Capsicum annuum L.) and tomato (Solanum lycopersicumL.) plants [7] . Under stress conditions, including drought,the plant hormone ethylene endogenously regulates plant homeostasis and results in reduced root and shoot growth[8] . However, degradation of the ethylene precursor ACCby bacterial ACC deaminase releases plant stress andrescues normal plant growth [8] . Recent efforts to apply these results to greenhouse and field situations include using mixtures of PGPR strains with symbiotic nitrogen-fixing rhizobia [9] or with mycorrhizal fungi [10] . The rhizobia are sensitive to drought stress, resulting in a significant decrease of N2 fixation when faced with low soil-water content. Under drought stress, co-inoculation of bean (Phaseolus vulgaris L.) with Rhizobium tropici and two strains of P. polymyxa resultedin augmented plant height, shoot dry weight and nodule number [9] . Interestingly, the effect on IST and increased nodule number was greater when a mix of two strains of P.polymyxa was applied than when one strain was applied,suggesting some synergistic effects from the use of strain mixtures.Investigations into how drought stress affects plant hormone balance revealed an increase in abscisic acid(ABA) content in the leaves, indicating that the reduction of endogenous cytokinin levels magnifies ABA content,eliciting stomata closure [9,11] (Figure 1). The cytokinin –ABA antagonism might be the result oftaboli metabolic interactions because they share a common biosynthetic origin [11] . It will be interesting to determine whether cytokinin produced by P. polymyxa affects ABA signaling of plants or rhizobia-elicited nodulation [6,9] .Co-inoculation of lettuce (Lactuca sativa L.) with PGPR pseudomonas mendocina and arbuscular mycorrhizal fungi (Glomus intraradices or G. mosseae) augmented an antioxidant catalase under severe drought conditions,suggesting that they can be used in inoculants to alleviate the oxidative damage elicited by drought [10] (Figure 1).