Rapid screening and phylogenetic analysis of plastic-oxidizing Bacillus relatives from agricultural soil

Abstract Background Plastic pollution is an escalating environmental and public health concern, particularly in agricultural and landfill settings where oxygen levels fluctuate. While numerous bacteria have been implicated in plastic biodegradation, few studies have explored the diversity and phylogenetic basis of plastic-oxidizing bacteria enriched directly from soil environments under redox gradients. Results We used a modified Winogradsky column to enrich microbial communities from agricultural soil, embedding low-density polyethylene (LDPE) strips at different oxygen depths. Biofilms were harvested and screened for plastic oxidation ability using a tetrazolium-based redox assay. Ten Bacillus and Bacillus -related isolates were selected for whole-genome sequencing and phenotypic testing under aerobic and anaerobic conditions. The assay revealed significant variation in plastic oxidation potential across strains. Closely related species typically exhibited similar phenotypes, suggesting evolutionary conservation of plastic-degrading capacity. However, outliers were identified, suggesting possible horizontal gene transfer or independent acquisition. Notably, several strains displayed plastic-oxidizing activity under anoxic conditions, highlighting previously underappreciated anaerobic plastic degradation potential. Conclusions This study demonstrates that agricultural soils harbor diverse Bacillus relatives with variable but often phylogenetically patterned plastic-oxidizing abilities. The use of Winogradsky columns enabled enrichment of both aerobic and anaerobic degraders, providing insight into ecological versatility. The results underscore the potential of these strains in developing context-specific bioremediation strategies for oxygen-variable environments such as landfills and contaminated soils. Graphical Abstract