Role of Bacillus cereus in Improving the Growth and Phytoextractability of Brassica nigra (L.) K. Koch in Chromium Contaminated Soil

Abstract

Plant growth-promoting rhizobacteria (PGPR) mediate heavy metal tolerance and improve phytoextraction potential in plants. The present research was conducted to find the potential of bacterial strains in improving the growth and phytoextraction abilities of Brassica nigra (L.) K. Koch. in chromium contaminated soil. In this study, a total of 15 bacterial strains were isolated from heavy metal polluted soil and were screened for their heavy metal tolerance and plant growth promotion potential. The most efficient strain was identified by 16S rRNA gene sequencing and was identified as Bacillus cereus. The isolate also showed the potential to solubilize phosphate and synthesize siderophore, phytohormones (indole acetic acid, cytokinin, and abscisic acid), and osmolyte (proline and sugar) in chromium (Cr+3) supplemented medium. The results of the present study showed that chromium stress has negative effects on seed germination and plant growth in B. nigra while inoculation of B. cereus improved plant growth and reduced chromium toxicity. The increase in seed germination percentage, shoot length, and root length was 28.07%, 35.86%, 19.11% while the fresh and dry biomass of the plant increased by 48.00% and 62.16%, respectively, as compared to the uninoculated/control plants. The photosynthetic pigments were also improved by bacterial inoculation as compared to untreated stress-exposed plants, i.e., increase in chlorophyll a, chlorophyll b, chlorophyll a + b, and carotenoid was d 25.94%, 10.65%, 20.35%, and 44.30%, respectively. Bacterial inoculation also resulted in osmotic adjustment (proline 8.76% and sugar 28.71%) and maintained the membrane stability (51.39%) which was also indicated by reduced malondialdehyde content (59.53% decrease). The antioxidant enzyme activities were also improved to 35.90% (superoxide dismutase), 59.61% (peroxide), and 33.33% (catalase) in inoculated stress-exposed plants as compared to the control plants. B. cereus inoculation also improved the uptake, bioaccumulation, and translocation of Cr in the plant. Data showed that B. cereus also increased Cr content in the root (2.71-fold) and shoot (4.01-fold), its bioaccumulation (2.71-fold in root and 4.03-fold in the shoot) and translocation (40%) was also high in B. nigra. The data revealed that B. cereus is a multifarious PGPR that efficiently tolerates heavy metal ions (Cr+3) and it can be used to enhance the growth and phytoextraction potential of B. nigra in heavy metal contaminated soil.

Improved chromium tolerance of Medicago sativa by plant growth-promoting rhizobacteria (PGPR)

“…The detrimental effects of Cr (VI) on plant growth obtained in this study were also reported in previous works [ 18 , 20 , 61 – 63 ]. Chen et al [ 64 ] reported that 20 mg of Cr (VI) per kilogram in soil can significantly reduce plant dry weight and root length of wheat.…”

Biosurfactant producing multifarious Streptomyces puniceus RHPR9 of Coscinium fenestratum rhizosphere promotes plant growth in chilli

“…According to Javee et al [ 54 ] fatty acids (octadecanoic acids, petadecanoic methyl ester, palmitic acid and oleic acid) are produced from Staphylococcus saprophyticus SBPS15. Application of any bacteria for plant growth needs to be screened for various PGP traits like indole, ammonia, and solubilization of phosphate [ 55 ]. IAA is known to improve adventitious roots that assist the plant in nutrient and water absorption; in turn, bacteria benefit from increased plant root exudates [ 56 – 60 ].…”

Production, Purification, and Characterization of Bacillibactin Siderophore of Bacillus subtilis and Its Application for Improvement in Plant Growth and Oil Content in Sesame

“…Bacillus sp. is known to stimulate plant growth and prevent pathogen infection [77] and also plays a significant role against biotic stresses through the production of phytohormones, volatile organic compounds, exopolysaccharides, siderophores, and P solubilization [78][79][80]. Application of B. subtilis has been reported to improve crop productivity.…”