AUTHOR=Faridy Nastaran , Torabi Ehssan , Pourbabaee Ahmad Ali , Osdaghi Ebrahim , Talebi Khalil 

TITLE=Unveiling six novel bacterial strains for fipronil and thiobencarb biodegradation: efficacy, metabolic pathways, and bioaugmentation potential in paddy soil

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1462912

DOI=10.3389/fmicb.2024.1462912

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p>Soil bacteria offer a promising approach to bioremediate pesticide contamination in agricultural ecosystems. This study investigated the potential of bacteria isolated from rice paddy soil for bioremediating fipronil and thiobencarb, common agricultural pesticides.</p></sec><sec><title>Methods</title><p>Bacterial isolates capable of degrading fipronil and thiobencarb were enriched in a mineral salt medium. A response surface methodology with a Box-Behnken design was utilized to optimize pesticide degradation with the isolated bacteria. Bioaugmentation tests were performed in paddy soils with varying conditions.</p></sec><sec><title>Results and discussion</title><p>Six strains, including single isolates and their mixture, efficiently degraded these pesticides at high concentrations (up to 800 µg/mL). <italic>Enterobacter</italic> sp., <italic>Brucella</italic> sp. (alone and combined), and a mixture of <italic>Stenotrophomonas</italic> sp., <italic>Bordetella</italic> sp., and <italic>Citrobacter</italic> sp. effectively degraded fipronil and thiobencarb, respectively. Notably, a single <italic>Pseudomonas</italic> sp. strain degraded a mixture of both pesticides. Optimal degradation conditions were identified as a slightly acidic pH (6-7), moderate pesticide concentrations (20-50 µg/mL), and a specific inoculum size. Bioaugmentation assays in real-world paddy soils (sterile/non-sterile, varying moisture) demonstrated that these bacteria significantly increased degradation rates (up to 14.15-fold for fipronil and 5.13-fold for thiobencarb). The study identifies these novel bacterial strains as promising tools for bioremediation and bioaugmentation strategies to tackle fipronil and thiobencarb contamination in paddy ecosystems.</p></sec>