Abstract
Bacillus aryabhattai AB211 is a plant growth promoting, Gram-positive firmicute, isolated from the rhizosphere of tea (Camellia sinensis), one of the oldest perennial crops and a major non-alcoholic beverage widely consumed all over the world. The whole genome of B. aryabhattai AB211 was sequenced, annotated and evaluated with special focus on genomic elements related to plant microbe interaction. It’s genome sequence reveals the presence of a 5,403,026 bp chromosome. A total of 5226 putative protein-coding sequences, 16 rRNA, 120 tRNA, 8 ncRNAs, 58 non-protein coding genes, and 11 prophage regions were identified. Genome sequence comparisons between strain AB211 and other related environmental strains of B. aryabhattai, identified about 3558 genes conserved among all B. aryabhattai genomes analyzed. Most of the common genes involved in plant growth promotion activities were found to be present within core genes of all the genomes used for comparison, illustrating possible common plant growth promoting traits shared among all the strains of B. aryabhattai. Besides the core genes, some genes were exclusively identified in the genome of strain AB211. Functional annotation of the genes predicted in the strain AB211 revealed the presence of genes responsible for mineral phosphate solubilization, siderophores, acetoin, butanediol, exopolysaccharides, flagella biosynthesis, surface attachment/biofilm formation, and indole acetic acid production, most of which were experimentally verified in the present study. Genome analysis and experimental evidence suggested that AB211 has robust central carbohydrate metabolism implying that this bacterium can efficiently utilize the root exudates and other organic materials as an energy source. Genes for the production of peroxidases, catalases, and superoxide dismutases, that confer resistance to oxidative stresses in plants were identified in AB211 genome. Besides these, genes for heat shock tolerance, cold shock tolerance, glycine-betaine production, and antibiotic/heavy metal resistance that enable bacteria to survive biotic/abiotic stress were also identified. Based on the genome sequence information and experimental evidence as presented in this study, strain AB211 appears to be metabolically diverse and exhibits tremendous potential as a plant growth promoting bacterium.
Highlights
Plant growth promoting rhizobacteria (PGPR) are a heterogeneous group of bacteria that are present in the rhizosphere and exert beneficial effects on plant development (Kloepper et al, 1980; Lugtenberg and Kamilova, 2009)
The present study aims at the thorough elucidation of the plant growth promoting traits and to identify other metabolic features of B. aryabhattai AB211, rhizobacteria isolated from tea rhizosphere
Plant roots host a wide variety of microorganisms, many of them cooperating with the plant by providing support for plant nutrition, stress tolerance, and health
Summary
Plant growth promoting rhizobacteria (PGPR) are a heterogeneous group of bacteria that are present in the rhizosphere and exert beneficial effects on plant development (Kloepper et al, 1980; Lugtenberg and Kamilova, 2009). A variety of rhizobacteria, including Pseudomonas and Bacillus spp. are commonly found in the rhizosphere of a wide variety of plant species and stimulate plant growth through direct or indirect mechanisms (Podile and Kishore, 2006). There exist several indirect mechanisms as well, through which many rhizobacteria promote plant growth Such mechanisms involve events like: synthesis of antibiotics, antifungals, and biopesticides (Hammer et al, 1997; Lugtenberg and Kamilova, 2009; Perez et al, 2011; Ahemad and Khan, 2012), production of biocides such as hydrogen cyanide and fungal cell wall degrading enzymes, e.g., chitinase and β-1,3-glucanase (Zhang and Yuen, 2000; Haas and Keel, 2003; Malfanova et al, 2011), and production of iron chelating small molecules, siderophores to compete for iron in the rhizospheric environment to achieve better selection (Lemanceau et al, 2009; Schalk et al, 2011). Compared to plant growth promoting Pseudomonas, relatively little is known about the growth promotion features of plant associated Bacillus spp
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