Magnetite nanoparticles enhance growing rate of Bradyrhizobium japanicum

摘要

The aim of this study was to investigate whether magnetite nanoparticles affect Bradyrhizobium growth rate (BGR) in liquid media, with a view to controlling sensitivity to high pH and, hence, survival in extreme conditions. Treatments were different concentrations of nanoparticles suspended in liquid medium (yeast mannitol broth, YMB) mixed with and adhering to the Histic strain of Braydrhizobium japanicum. Experimental design was a complete randomized block (CRB) with four replications. The most important variables were growth rate coefficient (GRC), mean generation time (MGT), and number of generations (NG) of bacteria before the stationary phase. The nanoparticles increased GRC and NG, and decreased MGT; the optimal quantity of nanoparticles determined. In the presence of these nanoparticles the pH of the culture remained almost constant from zero time to 96 hours of growth, but without nanoparticles the pH increased from 6.8 to 7.1 during the same interval.