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Functional and molecular characterization of plant growth promoting Bacillus isolates from tomato rhizosphere.

ABSTRACT: The rhizosphere offers a quintessential habitat for the microbial communities and facilitates a variety of plant-microbe interactions. Members of the genus Bacillus constitute an important group of plant growth promoting rhizobacteria (PGPR), which improve growth and yield of crops. In a total of 60 bacterial isolates from the tomato rhizosphere, 7 isolates were selected based on distinct morphological characteristics and designated as tomato rhizosphere (TRS) isolates with a number suffixed viz., TRS-1, 2, 3, 4, 5, 7, and TRS-8. All the seven isolates were Gram positive, with in vitro plant growth promoting (PGP) traits like phosphate and zinc solubilization, and also produced indoleacetic acid (IAA), phytase, siderophore, hydrogen cyanide (HCN), and 1-aminocyclopropane-1-carboxylate (ACC) deaminase, besides being antagonistic to other microbes and formed biofilm. The seven isolates belonged to the genus Bacillus as per the 16S rDNA sequence analysis. Phylogenetic tree grouped the isolates into four groups, while BOX-PCR fingerprinting allowed further differentiation of the seven isolates. The PGP activity of the isolates was measured on tomato seedlings in plant tissue culture and greenhouse assays. A significant increase in root colonization was observed over 15 days with all the isolates. Greenhouse experiments with these isolates indicated an overall increase in the growth of tomato plants, over 60 days. Isolates TRS-7 and TRS-8 were best plant growth promoters among the seven isolates, with a potential as inoculants to increase tomato productivity.

SUBMITTER: Kalam S

PROVIDER: S-EPMC7452486 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Functional and molecular characterization of plant growth promoting <i>Bacillus</i> isolates from tomato rhizosphere.

Kalam Sadaf S Basu Anirban A Podile Appa Rao AR

Heliyon 20200819 8

The rhizosphere offers a quintessential habitat for the microbial communities and facilitates a variety of plant-microbe interactions. Members of the genus <i>Bacillus</i> constitute an important group of plant growth promoting rhizobacteria (PGPR), which improve growth and yield of crops. In a total of 60 bacterial isolates from the tomato rhizosphere, 7 isolates were selected based on distinct morphological characteristics and designated as tomato rhizosphere (TRS) isolates with a number suffi ...[more]

PMID: 32904284

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Project description:The use of plant growth-promoting rhizobacteria (PGPR) as a bioremediation enhancer in plant-assisted phytoremediation requires several steps, consisting of the screening, selection, and characterization of isolates. A subset of 50 bacterial isolates representing a wide phylogenetic range were selected from 438 morphologically different bacteria that were originally isolated from a petroleum hydrocarbon (PHC)-polluted site of a former petrochemical plant. Selected candidate bacteria were screened using six conventional plant growth-promoting (PGP) traits, complemented with the genetic characterization of genes involved in alkane degradation, as well as other pertinent functions. Finally, the bacterial isolates were subjected to plant growth promotion tests using a gnotobiotic approach under normal and stressed conditions. Our results indicated that 35 bacterial isolates (70%) possessed at least four PGP traits. Twenty-nine isolates (58%) were able to utilize n-hexadecane as a sole carbon source, whereas 43 isolates (86%) were able to utilize diesel as the sole carbon source. The presence of catabolic genes related to hydrocarbon degradation was assessed using endpoint PCR, with the alkane monooxygenase (alkB) gene found in 34 isolates, the cytochrome P450 hydroxylase (CYP153) gene found in 24 isolates, and the naphthalene dioxygenase (nah1) gene found to be present in 33 isolates. Thirty-six strains (72%) promoted canola root elongation in the growth pouch assay. After several rounds of screening, seven bacterial candidates (individually or combined in a consortium) were tested for canola root and shoot growth promotion in substrates amended by different concentrations of n-hexadecane (0%, 1%, 2%, and 3%) under gnotobiotic conditions. Our results showed that Nocardia sp. (WB46), Pseudomonas plecoglossicida (ET27), Stenotrophomonas pavanii (EB31), and Gordonia amicalis (WT12) significantly increased the root length of canola grown in 3% n-hexadecane compared with the control treatment, whereas Nocardia sp. (WB46) and Bacillus megaterium (WT10) significantly increased shoot length compared to control treatment at the same concentration of n-hexadecane. The consortium had a significant enhancement effect on root length compared to all isolates inoculated individually or to the control. This study demonstrates that the combination of PGPR traits and the PHC degradation potential of bacteria can result in an enhanced beneficial effect in phytoremediation management, which could lead to the development of innovative bacterial inoculants for plants to remediate PHC-contaminated soils.

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Dataset Information

Functional and molecular characterization of plant growth promoting Bacillus isolates from tomato rhizosphere.

Publications

Functional and molecular characterization of plant growth promoting <i>Bacillus</i> isolates from tomato rhizosphere.

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