BIODEGRADABLE POTENTIAL OF RHIZOBACTERIA FROM TOMATO PLANT ON TETRACHLOROETHANE

ABSTRACT Environmental contamination by tetrachloroethane, a highly persistent chlorinated hydrocarbon, poses major ecological and public health concerns. This study assessed the biodegradation potential of rhizobacteria isolated from the tomato (Solanum lycopersicum) rhizosphere on tetrachloroethane. Rhizospheric soil samples were collected and processed using serial dilution and spread-plate techniques on Nutrient Agar and Plate Count Agar. A total bacterial load ranging from 49–191 CFU (log 1.69–2.28) was recorded, indicating high microbial abundance. Isolates were characterized using cultural, morphological, and biochemical tests, followed by molecular confirmation through PCR amplification of the 16S rRNA gene. Clear PCR bands were obtained for isolates T10⁻³B2 and T10⁻²B2, and BLAST results showed 99.76–100% identity with Pseudarthrobacter and Arthrobacter species. Biodegradation screening was conducted in Mineral Salt Medium (MSM) supplemented with tetrachloroethane (50–200 mg/L). Isolates were inoculated and incubated for 14 days, during which growth was monitored using optical density at 600 nm and degradation was assessed using gas chromatography. Results showed distinct variations in degradation ability: isolates TA² (0.484 OD), TB⁻²(A) (0.409), T10⁻³B2 (0.402), and T10⁻³A1 (0.395) exhibited the highest growth in tetrachloroethane medium, indicating strong tolerance and active utilization of the compound. In contrast, isolates T10⁻²A3 (0.131) and TB⁻³(A) (0.145) showed limited growth, suggesting low biodegradative capability. Gas chromatographic analysis confirmed a significant reduction in tetrachloroethane concentration across cultures inoculated with high-performing isolates, demonstrating true biological degradation rather than abiotic loss. Overall, the study establishes that tomato rhizosphere bacteria particularly the Pseudarthrobacter/Arthrobacter isolate T10⁻³B2 possess efficient enzymatic systems for dehalogenation and oxidative breakdown of tetrachloroethane. These findings highlight the potential of tomato-associated rhizobacteria as sustainable, eco-friendly agents for bioremediation of chlorinated hydrocarbon-contaminated soils. Further optimization and enzyme level studies are recommended to enhance field-scale application