Plant growth-promoting bacteria that decrease heavy metal toxicity in plants

Abstract

Kluyvera ascorbata SUD165 and a siderophore-overproducing mutant of this bacterium, K. ascorbata SUD165/26, were used to inoculate tomato, canola, and Indian mustard seeds which were then grown in soil for 25-42 days in the presence of either nickel, lead, or zinc. The parameters that were monitored included plant wet and dry weight, protein and chlorophyll content in the plant leaves, and concentration of heavy metal in the plant roots and shoots. As indicated by a decrease in the measured values of these parameters, in all instances, plant growth was inhibited by the presence of the added metal. Both bacterial strains were effective, although not always to a statistically significant extent, at relieving a portion of the growth inhibition caused by the metals. In most cases, the siderophore overproducing mutant K. ascorbata 165/26 exerted a more pronounced effect on plant growth than did the wild-type bacterium K. ascorbata SUD165. The data suggest that the ability of these bacteria to protect plants against the inhibitory effects of high concentrations of nickel, lead, and zinc is related to the bacteria providing the plants with sufficient iron.

Potential of Plant Growth Promoting Traits by Bacteria Isolated from Heavy Metal Contaminated Soils

“…The exact mechanism behind the improved plant growth is ambiguous (Dell'Amico et al 2008;Tica et al 2011). These PGPRs have a special ability to grow in heavy metal contaminated environment (Barakat 2011;Burd et al 2000;Belimov et al 2005). Heavy metals are regarded as serious pollutants in environment including agricultural soils (Wei and Yang 2010).…”

“…These bacteria can promote plant growth by producing siderophore production, indole acetic acid production, phosphate solubilisation and hydrogen cyanide production (Dell'Amico et al 2008;Sheng and Xia 2006). Recent studies have revealed that these PGPRs could promote plant growth and protect plants against heavy metals toxicity in heavy metal-contaminated soils (Barakat 2011;Burd et al 2000;Belimov et al 2005;Dell'Amico et al 2008;Idris et al 2004).…”

Role of plant growth promoting rhizobacteria in the remediation of metal contaminated soils

“…These organisms affect plant growth in three different ways-(1) by synthesizing and providing particular compounds to the plants (Glick 1995) (2) facilitating the uptake of certain nutrients from environment (Ç akmakçi et al 2006) and (3) protecting plants from certain diseases . Generally, rhizobacteria improves plant growth by synthesizing phytohormones precursors (Perveen et al 2002;Ahmad et al 2008), vitamins, enzymes, siderophores, antibiotics (Burd et al 2000;Glick 2001) and inhibiting ethylene synthesis. In addition, the rhizobacterial strains can solubilize inorganic P Khan 2005, 2007;, mineralizing organic P (Ponmurugan 2006;, improve plant stress tolerance to drought, salinity and metal toxicity, leading thereby to increased plant growth.…”

“…P-solubilization Canbolat et al (2006) Variovorax paradoxus, Rhodococcus sp. and Flavobacterium (Cd tolerant) IAA and siderophores Belimov et al (2005) Kluyvera ascorbata Siderophore Burd et al (2000) Pseudomonas fluorescens IAA, siderophore and P-solubilization Gupta et al (2005) Pseudomonas putida Siderophore Tripathi et al (2005) Sphingomonas Bacillus, Pseudomons, Azotobacter, and Azospirillum P-solubilization and IAA Tank and Saraf (2003) Pseudomonas sp. IAA, siderophore and P-solubilization Gupta et al (2002) under metal-free environment, the synthesis of these compounds by metal-tolerant rhizobia are limited.…”

Bacillus thuringiensis beyond insect biocontrol: plant growth promotion and biosafety of polyvalent strains

“…This enzyme enables these microorganisms to utilise ACC as a sole N source or both N and C sources (Belimov et al 2005). In addition to facilitating the growth of plant roots by lowering the level of ethylene (Glick, 1995;Glick et al, 1998), plant growth-promoting bacteria expressing ACCD were shown to protect plants from the deleterious effects of some environmental stresses including heavy metals (Burd et al, 2000;Belimov et al, 2005), flooding (Grichko and Glick, 2001), salt (Mayak et al, 2004a), drought (Mayak et al, 2004b) and phytopathogens (Wang et al, 2000).…”