DETERMINATION OF ACC DEAMINASE, NITROGENASE AND ANTAGONISTIC ACTIVITIES OF GRAM NEGATIVE BACTERIA ISOLATED FROM WHEAT FIELDS AND THEIR SALT TOLERANCE

Abstract

1-aminocyclopropane-1-carboxyl ate (ACC) deaminase activity is an important marker for bacteria to support plant growth by lowering ethylene levels in plants. The enzyme has been found in limited numbers of bacteria and plays an important role in supporting plant growth and development under environmental stress conditions, by reducing stress induced ethylene production in plants. The aim of this study is to investigate strains with ACC deaminase, nitrogenase and antagonistic activities. In the present study, bacteria isolated from rhizosphere soils and wheat seedlings from Canakkale were screened for ACC deaminase activity, and eight isolates were determined to be ACC deaminase positive. The results of traditional methods showed that eight bacteria were identified as Pseudomonas, Enterobacter and Serratia strains. ACC deaminase activity was determined by measuring the production of a-ketobutyrate. Nitrogenase activity was analyzed by Acetylene Reduction Assay (ARA). According to the results, there are some differences in ACC deaminase activities among all strains isolated from wheat fields. ACC deaminase activity was analyzed on eight bacteria. The highest ACC deaminase activity was found on Pseudomonas sp. CKB55 (2833 nmol alpha-ketobutyrate.mg(-1).h(-1))). The highest nitrogenase activity was determined on Pseudomonas sp. CKB10 (808 nmol ethylene/mg.h). In antagonistic activity studies, Pseudomonas sp. CKB52 has shown an maximum inhibition zone against Erwinia caratovora ECC100, and the zone was 11 mm. Most of the isolates have shown tolerance to 1000 mM NaCl concentration. It can be said that ACC deaminase-contaning bacteria could be an environment-friendly and promising potential strategy to promote plant growth, alleviate biotic and abiotic stresses and provide sustainable agriculture, especially for ethylene-sensitive plants production. As a conclusion, Gram negative bacteria, isolated from wheat fields, have high ACC deaminase, nitrogenase and antagonistic activities. Additionally, these bacteria have a high salt tolerance.