Improvement of rice plant productivity by native Cr(VI) reducing and plant growth promoting soil bacteria Enterobacter cloacae.

Rapid industrialization and anthropogenic activities have produced huge amount of noxious Cr(VI), which accumulate in the soil for longer period. As a consequence, that decreases rice plant productivity in contiguous agricultural field of Sukinda mining area, Odisha. Thus, the high Cr(VI) resistant native bacterial strain CTWI-06 was selected for the study, which depicted resistance to 3500 ppm of Cr(VI) and wide array of other metals. Under optimized condition, the multi-metal resistant bacteria reduced 94% Cr(VI) within 92 h and Cr(VI) reduction was confirmed by FTIR and XRD analysis. Plant growth promoting traits like N2 fixation; phosphate (146.87 ppm), potassium (12.55 ppm) and Zn solubilization; ammonification; IAA production (114 μg mL-1) and suppression of fungal phytopathogens such as Rhizoctonia solani (ITCC 2060) and Phytium debaryanum (ITCC 5488) were also recorded. The bacterial strain was identified as Enterobacter cloacae CTWI-06 by 16S rDNA sequence (Accession No. MG757378). It significantly improved growth traits as well as productivity of Mahalakshmi rice variety in pot culture. Thus, the potential Cr(VI) reducing and PGPB strain may be utilized for long term bioremediation of Cr(VI) in chromium contaminated soil and to maintain soil fertility.