Plant Growth Promotion by ACC Deaminase-Producing Bacilli Under Salt Stress Conditions

Salinity in soils is widely recognized as one of the major problems that affect agricultural plant growth and production. Fortunately, different plant growth-promoting bacteria (PGPB) can help plants to tolerate such stressful circumstances. In this chapter, we review the pioneering and recent works of PGPB, particularly those species of the bacilli group that contains the enzyme 1-aminocyclopropane-1-carboxylate deaminase or ACC deaminase. The ACC deaminase can degrade the ACC precursor of the ethylene, so that an increase in ethylene synthesis under salt stress is avoided. The distribution of the bacterial ACC deaminase enzyme in soil microorganisms, as well as the plant growth promotion by ACC deaminase-producing Bacilli, and the potential employment of naturally halotolerant Bacilli as bio-inoculants in agroecosystems with salinity problems are discussed.