Rhizosphere colonization and arsenic translocation in sunflower (Helianthus annuus L.) by arsenate reducing Alcaligenes sp. strain Dhal-L

Abstract

In the present study, six arsenic-resistant strains previously isolated were tested for their plant growth promoting characteristics and heavy metal resistance, in order to choose one model strain as an inoculum for sunflower plants in pot experiments. The aim was to investigate the effect of arsenic-resistant strain on sunflower growth and on arsenic uptake from arsenic contaminated soil. Based on plant growth promoting characteristics and heavy metal resistance, Alcaligenes sp. strain Dhal-L was chosen as an inoculum. Beside the ability to reduce arsenate to arsenite via an Ars operon, the strain exhibited 1-amino-cyclopropane-1-carboxylic acid deaminase activity and it was also able to produce siderophore and indole acetic acid. Pot experiments were conducted with an agricultural soil contaminated with arsenic (214 mg kg -1 ). A real time PCR method was set up based on the quantification of ACR3(2) type of arsenite efflux pump carried by Alcaligenes sp. strain Dhal-L, in order to monitor presence and colonisation of the strain in the bulk and rhizospheric soil. As a result of strain inoculation, arsenic uptake by plants was increased by 53 %, whereas ACR3(2) gene copy number in rhizospheric soil was 100 times higher in inoculated than in control pots, indicating the colonisation of strain. The results indicated that the presence of arsenate reducing strains in the rhizosphere of sunflower influences arsenic mobilization and promotes arsenic uptake by plant.

Arsenic Metabolism and Toxicity Influenced by Ferric Iron in Simulated Gastrointestinal Tract and the Roles of Gut Microbiota

“…Moreover, our results also showed that some OTUs affiliated with Clostridium XlVa , Bacteroides , Alistipes , Bilophila , Alcaligenes , Cloacibacillus , and Bordetella had potential As resistance (Figure A). Similarly, the As resistance of species of Clostridium , Bacteroides , Alcaligenes , and Bordetella had been reported in other previous studies. ,,, …”

“…To our knowledge, few studies have been conducted to 53 investigate how the normal environmental concentrations of Fe affect the 54 bioaccessibility and toxicity of As, which is very important to characterize the actual 55 risk of As in drinking water. 56 Page 4 of 33…”

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“…The members of Actinobacteria play a major role in agricultural soil quality and soil fertility. Actinobacteria represents a large fraction of microbiomes in the root systems and is well established that they are dominant fraction of the microbial community in soils of wild and agricultural plant species [47][48][49][50][51]. Together with other phyla, the members of actinobacteria account for a large proportion in the rhizosphere of numerous plants including wheat (Triticum aestivum) [9,17,44,52,53]; rice (Oryza sativa) [48,54,55]; maize (Zea mays) [50,56,57]; Sugarcane (Saccharum officinarum) [58][59][60]; soybean (Glycine max) [51,[61][62][63]; pea (Pisum sativum) [51,64,65]; sunflower (Helianthus annuus) [49,66,67] and chickpea (Cicer arietinum) [68,69].…”