Isolation and Characterization of Rhizobacteria Screened from Roots of <i>Limnobium laevigatum</i>

The quantity of wastewater is increasing globally due to accelerated urbanization, population growth, and economic development. This drives up the demand for methods to resolve the wastewater problem that has been in short supply. Limnobium laevigatum acts as a hyperaccumulator due to the high accumulation of heavy metals found in the roots of L. laevigatum, such as Zn, Cr, Pb, and Ni, thus showing potential for use in wastewater treatment. This study aims to identify the characteristics of rhizobacteria that screened from the roots of L. laevigatum. This study is randomized, in which 50 colonies are randomly selected from the origins of L. laevigatum. The roots of L. laevigatum are cultivated, and the isolation of the rhizobacteria strains is performed. The characterization of the rhizobacteria is determined by gram staining and biochemical testing. The biochemical testing is evaluated to determine the unidentified rhizobacteria species with catalase activity. 58% of the isolates are found in gram-positive, and 42% of them are gram-negative. The sphere-shaped rhizobacteria arrangements are found in single streptococcus and staphylococcus. In contrast, the rod-shaped rhizobacteria arrangements are observed as single, Diplo, and palisades. The biochemical test resulted in 23 colonies, of which 46% were catalase-positive, and 27 colonies, 54% were observed as catalase-negative. In this study, Fourier transform infrared (FTIR) spectroscopy is performed to identify the different characteristic peak values of various functional compounds in the roots of L. laevigatum. It analyzes the prominent peaks at 56.2454 in 696 cm-1 that showed strong C-Br stretching, indicating the presence of a halo compound, which can efficiently degrade certain specific aromatic compounds present in wastewater. The rhizobacteria play a vital role in wastewater treatment by decomposing organic matter and pollutants into less toxic or non-toxic substances, reducing biological oxygen demand (BOD), and promoting plant growth by the interaction between plant growth-promoting rhizobacteria and the aquatic plants. In short, this study is expected to advocate sustainable and eco-friendly wastewater treatments by using rhizobacteria that screened in the roots of L. laevigatum.