Characterization of sulfur-oxidizing bacteria isolated from mustard (Brassica juncea L.) rhizosphere having the capability of improving sulfur and nitrogen uptake.

AIMS: The present investigation was carried out to isolate, screen and characterize potential sulfur-oxidizing bacteria (SOB) isolated from mustard field's soil. METHODS AND RESULTS: A total of 130 bacteria were isolated and after screening five maximum sulfate-producing isolates were optimized for culture conditions. The incubation time of 48 h was found optimum for all bacterial isolates and 30°C was the best temperature for the growth of SSD11, SSR1 and SSG8 whereas 35°C for SSF17. The pH 8 was found best for all four isolates except SSF17 (6 pH). Media having glucose as a carbon source and ammonium sulphate as an N-source were producing maximum sulphate. The isolates SSF17, SSR1 and SSG8 were identified as Burkholderia cepacia (accession no. MT559819), Enterobacter cloacae (accession no. MT559820) and Klebsiella oxytoca (accession no. MT372097), respectively, on the basis of morphological, biochemical and molecular characterization. The isolates were also found to increase N and S uptake efficiently in both wheat and mustard crops. CONCLUSION: This study strongly concludes that SOB isolated from the mustard field can oxidize sulfur in vitro and in vivo conditions. The three best isolates come out of the study were identified as Burkholderia, Enterobacter and Klebsiella strains. Also, inoculation of SOB increased the uptake of S and N nutrient in mustard and wheat crops and thus may be proved as an important plant growth-promoting bacteria having the biofertilization capability. SIGNIFICANCE AND IMPACT OF THE STUDY: As we know, our soil is continuously deteriorating day by day due to excessive utilization and immoderate use of chemical fertilizers. The SOB could minimize the application of chemical fertilizers thus reducing environmental deterioration by improving soil health in sustainable agricultural practices.