RESUMEN
The huge biological diversity of the Brazilian Cerrado is an important source of economically interesting microbial agents. The phylum Actinobacteria plays an important role in nutrient cycling, potentially improving their availability to plants. In this study, we isolated an actinobacteria (strain 3AS4) from wheat rhizospheres of crops cultivated in the Cerrado biome. Strain 3AS4 was identified as belonging to the genus Streptomyces and had phosphorus mobilization ability, mineralizing approximately 410 µg ml-1 from phytate, 300 µg ml-1 from calcium phosphate, and 200 µg ml-1 from rock phosphate. The analysis of the actinobacteria crude extract by spectrometric techniques revealed the presence of gluconic and 2-ketogluconic acid, and a greenhouse experiment was carried out to evaluate its plant growth promotion activity in soybean. Soil in its natural condition (with no phosphorus addition), 40 kg ha-1 rock phosphate from Bayovar (RP) added to soil, and triple super phosphate (SPT) added to soil were used. Significant differences in plant height were observed at 6 weeks when the plants were inoculated with the 3AS4 strain. The growth of inoculated plants in natural condition was promoted in 17% compared with the RP and SPT non-inoculated conditions, suggesting that inoculation can enable plants to grow with lower chemical P fertilizers. In the plants that were inoculated with the 3AS4 strain in the RP condition, the plant height increased by approximately 80% and the shoot:root ratio was approximately 30% higher compared to control conditions (non-inoculated plants in natural conditions). 3AS4 has P-solubilizing potential and can be exploited as an inoculant for soybean cultivation. These results suggest that this actinobacterium is a valuable resource for sustainable agriculture and will allow the reduction of phosphate fertilization in the future.
RESUMEN
Cyanobacteria dwelling on the salt-excreting leaves of the mangrove tree Avicennia schaueriana were isolated and characterized by ecological, morphological and genetic approaches. Leaves were collected in a mangrove with a history of oil contamination on the coastline of São Paulo state, Brazil, and isolation was achieved by smearing leaves on the surface of solid media or by submerging leaves in liquid media. Twenty-nine isolated strains were shown to belong to five cyanobacterial orders (thirteen to Synechococcales, seven to Nostocales, seven to Pleurocapsales, one to Chroococcales, and one to Oscillatoriales) according to morphological and 16S rRNA gene sequence evaluations. More detailed investigations pointed six Rivulariacean and four Xenococcacean strains as novel taxa. These strains were classified as Phyllonema gen. nov. (type species Phyllonema aviceniicola sp. nov. with type strain CENA341T) and Foliisarcina gen. nov. (type species Foliisarcina bertiogensis sp. nov. with type strain CENA333T), according to the International Code of Nomenclature for Algae, Fungi, and Plants. This investigation shows some of the unique cyanobacteria inhabiting the phyllosphere of Avicennia schaueriana can be retrieved by culturing techniques, improving current taxonomy and providing new insights into the evolution, ecology, and biogeography of this phylum.