Deciphering Rhizosphere Soil System for Strains Having Plant Growth Promoting and Bioremediation Traits

Abstract

The rhizosphere is an important region of microbial interactions where exudates released by plant roots are the main source of food for microorganisms, which play a vital role in increasing their population density and activities. An isolate of bacterium Pseudomonas sp., designated as KS51, that expressed plant growth-promoting traits and antagonistic activity was isolated from the rhizospheric soil of Calotropis sp., grown in the northern and central regions of India. The isolate was recognized as Gram negative rod (0.67 9 2.89 lm) shaped bacterium. It grew at optimum temperature ranging from 25 to 30°C, exhibited tolerance to a wide pH range of 6-10 and tolerated salt concentrations up to 5 % (wt/vol). Though, it was sensitive to chloramphenicol, ampicillin, tetracycline, gentamicin, ceftriaxone, and erythromycin, it showed resistance to co-trimoxazole, cefuroxime, ciprofloxacin, penicillin G, augmentin, fusidic acid and vancomycin. The bacterium was biochemically characterized and examined in vitro for their plant growth-promoting traits like production of indole acetic acid (IAA) (8 lg ml -1 day -1 ), hydrogen cyanide (HCN), siderophore and phosphate solubilization (268 lg ml -1 after 144 h). The mean growth rate constant (K) of isolate was found to increase with successive increments in substrate concentration of naphthalene and anthracene (0.5-1.0 mg/50 ml). KS51 was also found to be a good degrader for naphthalene (78.44 %) and anthracene (63.53 %) as determined by HPLC analysis. Based on the 16S rRNA analysis, KS51 showed the maximum similarity with Pseudomonas sp. On the basis of its growth-promoting, biocontrol and bioremediation potential properties, KS51 could be applied in biotechnological applications.

Potential of Polycyclic Aromatic Hydrocarbon-Degrading Bacterial Isolates to Contribute to Soil Fertility

“…Such combination of attributes is indispensable for sustainable agricultural production and environmental protection particularly in the mining and agroforestry sectors. Very few studies have been reported in this respect [ 18 , 20 ]. The present study aimed to evaluate, in vitro , the potential roles of PAH-degrading isolates to solubilize phosphates, fix atmospheric nitrogen, and produce IAA as an exploration of their ability to contribute to soil fertility and restorative bioremediation.…”

Microbial Diversity in Soil under Potato Cultivation from Cold Desert Himalaya, India

“…Potato, being valuable food crop worldwide, has received attention in view of the colonization of plant growth promoting microbes in potato fields [39,40]. Plant growth promoting microbes are also receiving attention for their associated importance in bioremediation [41,42].…”

Toluene Degrading Bacteria from the Rhizosphere of Solanum melongena Contaminated with Polycyclic Aromatic Hydrocarbon

“…Agrawal et al, (2011) reported PGPB isolate MFB-1 R-3 produced highest level of IAA in liquid broth (33.55 µg ml -1 ) and FA 2 K100 3 , the least (1.75 µg ml -1 ). In a study carried by Shukla et al, (2012) showed maximum phosphate solubilization after 2 days of incubation whereas the isolate BRB-2 showed maximum solubilization after 5 days of incubation (Fig 4). Studies revealed that several bacterial strains (Pseudomonas, Bacillus, Rhizobium and Enterobacter) and fungal strains (Aspergillus and Penicillium) have been recognized as powerful phosphate solubilizers and potential bioremediation agents as well (Jain and Khichi, 2014).…”