Dynamics, Diversity and Function of Endophytic Siderophore-Producing Bacteria in Rice

Abstract

Siderophore production confers to bacteria competitive advantages to colonize plant tissues and to exclude other microorganisms from the same ecological niche. This work shows that the community of endophytic siderophore-producing bacteria (SPB) associated to Oryza sativa cultivated in Uruguayan soils is dynamic and diverse. These bacteria were present in grains, roots, and leaves, and their density fluctuated between log(10) 3.44 and log(10) 5.52 cfu g(-1) fresh weight (fw) during the plant growth. Less than 10% of the heterotrophic bacteria produced siderophores in roots and leaves of young plants, but most of the heterotrophic bacteria were siderophore-producers in mature plants. According to their amplified restriction DNA ribosomal analysis (ARDRA) pattern, 54 of the 109 endophytic SPB isolated from different plant tissues or growth stages from replicate plots, were unique. Bacteria belonging to the genera Sphingomonas, Pseudomonas, Burkholderia, and Enterobacter alternated during plant growth, but the genus Pantoea was predominant in roots at tillering and in leaves at subsequent stages. Pantoea ananatis was the SPB permanently associated to any of the plant tissues, but the genetic diversity within this species-revealed by BOX-PCR fingerprinting- showed that different strains were randomly distributed along time and plant tissue, suggesting that a common trait of the species P. ananatis determined the interaction with the rice plant. Several isolates were stronger IAA producers than Azospirillum brasilense or Herbaspirillum seropedicae. In vitro inhibition assays showed that SPB of the genus Burkholderia were good antagonists of pathogenic fungi and that only one SPB isolate of the genus Pseudomonas was able to inhibit A. brasilense and H. seropedicae. These results denoted that SPB were selected into the rice plant. P. ananatis was the permanent and dominant associated species which was unable to inhibit two of the relevant plant growth-promoting bacteria.

Characterization of biofilm and corrosion of cast iron pipes in drinking water distribution system with UV/Cl2 disinfection

“…The compositions of bacteria related with iron cycling underwent great changes in different ARs and different stages. In the AR with UV/Cl 2 , at stage I, the relative abundance of nitrate-reducing bacteria (NRB) was 9.9%, and among them, 3.9% NRB were related to redox cycling of iron, such as Hyphomicrobium (3.7%) (Stein et al, 2001), and 6% NRB produced siderophores, including Sphingomonas (Duckworth et al, 2009), Brucella (Roop, 2012), Acinetobacter (Proschak et al, 2013) and Azospirillum (Loaces et al, 2011). The ironrespiring bacteria were 11.7%, predominantly including ironreducing bacteria (IRB) Acidobacterium (10.2%) (Nancucheo and Johnson, 2010) and iron-oxidizing bacteria (IOB) Pedomicrobium (1.3%) (Braun et al, 2009).…”

Trace Element Management in Rice

“…Soil microbes also secrete compounds having metal binding ligands such as siderophores, which enhance plant uptake of TEs [71,72]. Plant growth promoting bacteria also promote both mobilization of TEs from paddy soils and root growth by hormonal activities [73][74][75].…”

Inside the Plants: Endophytic Bacteria and their Functional Attributes for Plant Growth Promotion

“…They reported that approximately 10% of the heterotrophic bacteria were able to produce siderophores in roots and leaves of young plants, but most of the heterotrophic bacteria were actively produced siderophore in mature plants. Siderophore production provides competitive advantages to endophytic bacteria for colonization of plant tissues and hence, excludes other microorganism from the colonization for the same ecological niche (Loaces et al, 2011). Siderophore production in nodule forming bacteria was investigated by Verma et al, (2012), they inoculate the nodule forming bacteria in the YEM media and conducted Chrome AzurolSulfonate (CAS) assay for formation of orange halos in blue agar plate.…”

“…It is one of the mechanisms used to compete with the plant pathogens. Loaces et al, (2011) studied the communities of siderophore producing endophytic bacteria from the grains, roots, and leaves of Oryza sativa cultivated on Uruguayan soils. They reported that approximately 10% of the heterotrophic bacteria were able to produce siderophores in roots and leaves of young plants, but most of the heterotrophic bacteria were actively produced siderophore in mature plants.…”