Isolation of cold tolerant and ACC Deaminase producing Plant Growth Promoting Rhizobacteria from High Altitudes

It is well known that certain plant growth promoting rhizobacteria having 1-aminocyclopropane-1-carboxylate (ACC) deaminase enzyme activity that reduce the level of stress ethylene and stimulating growth of plants under various biotic and abiotic stresses. On the other hand, cold environments are characterized by short growing seasons and temperatures below the optimal values for growth of PGPR. So, isolation of novel cold tolerant and ACC deaminase containing bacteria is very important. Keeping all this in view, thirty two 1-aminocyclopropane-1-carboxylic acid deaminase-producing cold tolerant bacteria were isolated from the 20 rhizospheric soils of wild plants collected from high altitudes (17602724 m) in different mountains in Erzurum, Eastern Anatolia, Turkey. They were screened in their ACC deaminase producing potentials and 8 of them were selected. It was found that these eight bacteria may grow and produce ACC deaminase at sub-optimal temperatures (5, 15 and 20 degrees C). The most effective four species in alpha-ketobutyrate producing potential from ACC were Stenotrophomonas maltophilia GBK 4 (1.207 mg(-1) h(-1)), Leucobacter iarius GBK 2 (0.993 mg(-1) h(-1)), Pseudomonas fluorescens GBK 3 (0.962 mg(-1) h(-1)) and Pseudomonas migulae GBK 1 (0.951 mg(-1) h(-1)), respectively. Results show that these isolates have a great plant growth promoting potential at cold climatic conditions.