Isolation of Plant Growth Promoting Rhizobacteria from Spartina densiflora and Sarcocornia perennis in San Antonio polluted salt marsh, Patagonian Argentina

Abstract

With the purpose of Plant Growth Promoting Rhizobacteria (PGPR) isolation, several authors have sampled different wetlands in the northern half of Argentina. However, to date, we do not know the existence of microbiological studies conducted in the Patagonian salt marshes, and concretely, concerning isolation of PGPR. The present work was conducted in the heavy metal polluted San Antonio salt marsh, in two areas with different grade of pollution. In those areas, we isolated cultivable bacteria from the rhizosphere of the halophytes Spartina densiflora and Sarcocornia perennis, and look for several plant growth promoting (PGP) properties among them. In total, 60 different cultivable bacteria were isolated. 50% of the rhizobacterial strains demonstrated at least one of the PGP properties assayed, 25% of them produced siderophores, 16% were able to solubilize phosphate, 11% were able to produce auxins and 7% chitinase. We could observe that PGP properties were more abundant among bacteria growing in polluted soils. Also, bacteria inhabiting S. densiflora rhizosphere showed more PGP properties related to heavy metal phytostabilization mechanisms, in line with the phytoremediation strategy of this halophyte. Overall, these findings support the idea that coastal hazardous scenarios may be a good opportunity to seek for PGPR. Indeed, some of the strains isolated in this work presented more than one PGP property, so they may be selected for further formulation of inoculants for different applications. For further research, it would be interesting to analyse other PGP properties in these strains, as well as to isolate rhizobacteria from other halophytes in diverse Patagonian salt marshes.