Isolation and characterization of symbiotic N2-fixing Rhizobium meliloti from soils contaminated with aromatic and chloroaromatic hydrocarbons: PAHs and PCBs

Influence of Rhizobium meliloti on phytoremediation of polycyclic aromatic hydrocarbons by alfalfa in an aged contaminated soil

“…It therefore follows that enhancement of plant metabolic activities by inoculation with rhizobia may lead to stimulation of the growth of PAH-degrading bacteria. Some studies have indicated that rhizobia, either as free living cells or in symbiosis with host plants, have the ability to transform PCBs and PAHs [12,14,16,25]. In the present study, inoculation with Rhizobium significantly enhanced depletion of 3-and 4-ring PAHs in the soil.…”

“…Rhizobia colonize the roots of legumes where they fix atmospheric N 2 , some of which can be utilized for plant growth [11]. Rhizobia are found in contaminated environments where various toxic chemicals are present [12,13]. Several bacterial species in the genus Rhizobium are able to utilize PAHs, polychlorinated biphenyls (PCBs), or heterocyclic aromatic compounds [14][15][16][17] but little is known about the ability of Rhizobium to further degrade PAHs in soils.…”

Potential for biodegradation of polychlorinated biphenyls (PCBs) by Sinorhizobium meliloti

“…The hallmark of rhizobial studies has always been focused on their agricultural significance, e.g. in competition and survival as inocula, in N 2 -fixation and nodulation, in cross-talk between microbe and plant symbiont [13]. Expecting Rhizobia to inhabit environments with aromatic pollutants is not surprising since they have long been known to metabolize simple aromatic compounds like flavones and other phenolic root exudates [9][10][11], and to possess ring-cleavage enzymes such as catechol 1,2-dioxygenase and protocatechuate 3,4-or 4,5-dioxygenase [8,9,24,25].…”

“…Expecting Rhizobia to inhabit environments with aromatic pollutants is not surprising since they have long been known to metabolize simple aromatic compounds like flavones and other phenolic root exudates [9][10][11], and to possess ring-cleavage enzymes such as catechol 1,2-dioxygenase and protocatechuate 3,4-or 4,5-dioxygenase [8,9,24,25]. Recent studies suggest that free-living Rhizobia can also tolerate and biotransform soil contaminants, such as PCBs, PAHs, TNT, atrazine and halobenzoates [13,15,[26][27][28].…”

“…Damaj and Ahmad [12] reported the capability of PCB degradation by a rhizobial strain Rhizobium meliloti Zb57 in resting-cell cultures for the first time. Then the indigenous rhizobial strains were isolated from soils contaminated with PAHs and PCBs [13]. Mehmannavaz et al [14] investigated the effects of plant-Rhizobia-soil interactions on the biotransformation of PCBs in the soil.…”