Isolation and screening for plant growth-promoting (PGP) actinobacteria from Araucaria angustifolia rhizosphere soil

Abstract

Actinobacteria are capable of playing several different roles in soil ecosystems. These microorganisms affect other organisms by producing secondary metabolites and are responsible for the degradation of different complex and relatively recalcitrant organic compounds. In our survey of actinobacteria isolated from the rhizosphere of Araucaria angustifolia, five culture media (AI, WYE, YCED, MSSC and LNMS) were compared for their effectiveness in isolating these microorganisms. When summing up all the isolates randomly obtained, we got 103 isolates. After isolation, the phosphate-solubilizing ability and the "in vitro" production of indole-acetic acid and chitinases were evaluated. The AI medium was ineffective for actinobacteria isolation, when it was compared with the other four culture media. Indole-acetic acid and chitinase were produced by respectively 36% and 24% of the strains tested. However, only 2% of the 103 strains presented some phosphate-solubilizing ability. These results demonstrate the biotechnological potential of these microorganisms. Key words: Brazil Pine, selective culture media, indole-acetic acid, chitinase, phosphate solubilization Isolamento e seleção de actinobactérias promotoras do crescimento de plantas de solo rizosférico de Araucaria angustifolia RESUMO: Actinobactérias são capazes de desenvolver diferentes funções no ecossistema edáfico. Esses microrganismos, além de interagir com outros grupos de microrganismos e plantas, ao produzir metabólitos secundários, são responsáveis pela degradação de diferentes compostos orgânicos. Com intuito de facilitar os estudos envolvendo actinobactérias encontradas em sistemas florestais, cinco meios de cultura (AI, WYE, YCED, MSSC e LNMS) foram avaliados quanto à eficiência em isolar estes microrganismos. Além disso, foi analisada a capacidade dos diferentes isolados em solubilizar fosfato de cálcio, produzir ácido indol-acético e quitinases. Dos cinco meios de cultura testados, somente o AI foi ineficiente em isolar actinobactérias. A produção de ácido indol-acético e quitinases foi observada em 36% e 24% dos isolados analisados, respectivamente. Contudo, apenas 2% dos 103 isolados foram capazes de solubilizar fosfato de cálcio. Estes resultados comprovam o potencial biotecnológico desses microrganismos. Palavras-chave: Pinheiro Brasileiro, meios de cultura seletivos, ácido indol-acético, quitinase, solubilização de fosfato

Phenotypic, Stress Tolerance and Plant Growth Promoting Characteristics of Rhizobial Isolates from Selected Wild Legumes of Semiarid Region, Tirupati, India

“…The range of IAA produced by these isolates is in agreement with soybean isolates [34]. Most of the isolates can be considered as high IAA producing rhizobia, according to Hynes et al [35] report, where 5 -10 µg/ml of IAA production is more common among rhizobia, Variation in the production of IAA by different rhizobial species/strains and influence of cultural conditions on the amount of IAA produced reported by many workers [36] [37]. Variation in IAA production by different isolates could be due to variation in utilization of L-Tryptophan.…”

Corrosive Lesions at Concrete Infrastructures as Promising Source for Isolating Bioactive Actinobacteria

“…Most of the actinomycetes strains were isolated from soil and aquatic environment appeared to have the ability of solubilizing sparingly available inorganic P sources or mineralizing some P from the organic P sources in soil. Actinomycetes developed several potential mechanisms for phosphate solubilization those involving the production of chelating compounds, like organic acids or by means of a modification of pH of the medium by the secretion of organic acids or protons (Richardson et al, 2009;Vasconcellos et al, 2010). Also they produced acid or alkaline phosphatases would be able to mineralize organic P sources (Richardson et al, 2009;Ghorbani-Nasrabadi et al, 2012).…”

Antimicrobial potential of actinobacteria isolated from the rhizosphere of the Caatinga biome plant Caesalpinia pyramidalis Tul.

“…These filamentous bacteria are aerobic and synthesize volatile compounds, such as geosmin, which gives soil its characteristic "wet earth" odor. Streptomyces sp are very valuable, as they produce several commercial antibiotics, including streptomycin (Vasconcellos et al, 2010;Madigan et al, 2012). Given this, the aim of the present study was to evaluate the antimicrobial activity of actinobacteria isolated from the rhizosphere of the plant Caesalpinia pyramidalis Tul.…”