Molecular characterization of Arsenic resistant rhizospheric bacterial strains

WEVAR OLLER AL; PEREIRA, PAOLA P.; BESSOPIANETO G; TALANO MA; AGOSTINI, E

San Luis

Congreso; XIII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL (SAMIGE 2018), San Luis, 8-10 de Agosto de 2018; 2018

Contamination of soils with arsenic constitutes a global environmental problem with significant negative impact on human health and agriculture. Rhizospheric microbial populations are known to affect plant growth and metal(loid) mobility and availability through the release of chelating agents, acidification, phosphate solubilization and redox changes. Biological treatments, based on inoculation with appropriate metal(loid)-resistant rhizobacteria, are receiving increasing attention in order to alleviate plant stress and develop sustainable soil management. In this work, we have further characterized six bacterial strains with plant growth promoting (PGP) properties isolated from soybean rhizosphere. The aims of this work were to update bacterial nomenclature and distinguish selected bacterial strains from different rhizospheric strains to improve genetic traceability in co-inoculation microcosms assays. Initially, based on 16S rDNA sequence similarity (NCBI database), these strains were identified as Enterobacter cloacae AW1, Pseudomonas fluorescens AW2, Rhodococcus erytropolis AW3, P. putida AW4, P. poae AW5 and P. poae AW6. In the last years, new species have been described, many others have been renamed and databases are constantly being updated. By using a ?cured? database (RDB) for 16S rDNA sequences bacterial similarity changed, P. fluorescens AW2 was 99,2% similar to P. extremorientalis, P. putida AW4 was 95,3% similar to P. taiwanensis, while the other two Pseudomonas strains previously identified as P. poae showed 99% similarity with P. extremorientalis strain BS2774. Enterobacter and Rhodococcus strains 16S rDNA closest relative also changed. Furthermore, ERIC and BOX-PCR profiles were performed. Also, some morphological, cultural and physiological characteristics were tested (pigment production, hydrolysis of gelatin, growth in differential media, among others) under aerobic conditions. Considering the results, we constructed new phylogenetic trees. Typification of PGP bacteria is necessary, not only to determine their level of kinship with pathogenic strains but also to achieve genetic traceability that allows post-inoculation monitoring of microorganisms.