Arsenic Resistance and Biosorption by Isolated Rhizobacteria from the Roots of <i>Ludwigia octovalvis</i>

Abstract

Certain rhizobacteria can be applied to remove arsenic in the environment through bioremediation or phytoremediation. This study determines the minimum inhibitory concentration (MIC) of arsenic on identified rhizobacteria that were isolated from the roots of <i>Ludwigia octovalvis</i> (Jacq.) Raven. The arsenic biosorption capability of the was also analyzed. Among the 10 isolated rhizobacteria, five were Gram-positive (<i>Arthrobacter globiformis</i>, <i>Bacillus megaterium, Bacillus cereus, Bacillus pumilus</i>, and <i>Staphylococcus lentus</i>), and five were Gram-negative (<i>Enterobacter asburiae, Sphingomonas paucimobilis, Pantoea</i> spp.<i>, Rhizobium rhizogenes</i>, and <i>Rhizobium radiobacter</i>). <i>R. radiobacter</i> showed the highest MIC of >1,500 mg/L of arsenic. All the rhizobacteria were capable of absorbing arsenic, and <i>S. paucimobilis</i> showed the highest arsenic biosorption capability (146.4 ± 23.4 mg/g dry cell weight). Kinetic rate analysis showed that <i>B. cereus</i> followed the pore diffusion model (<i>R</i> ² = 0.86), <i>E. asburiae</i> followed the pseudo-first-order kinetic model (<i>R</i> ² = 0.99), and <i>R. rhizogenes</i> followed the pseudo-second-order kinetic model (<i>R</i> ² = 0.93). The identified rhizobacteria differ in their mechanism of arsenic biosorption, arsenic biosorption capability, and kinetic models in arsenic biosorption.