Catabolic gene indices of hydrocarbon diminution in Ultisol treated with cropped Bacillus altitudinis-amendments

Abstract

This study evaluated catabolic gene expression as an index of hydrocarbon breakdown in ultisol treated with Bacillus altitudinis-Cropped Biofertilizers derived from Biosolid and Brewer Spent Grain (BSG) using phenotypic and molecular methods. We observed significant reductions in Total Petroleum Hydrocarbons (TPH) concentrations with both amendments, albeit the biosolid based amendment was markedly more effective. Concurrently, there was a substantial increase in hydrocarbon-degrading bacteria. Notably, the bulk of Operational Taxonomic Units (OTUs) in biosolid (95.77 %) and BSG (93.00 %) amended Ultisol were Proteobacteria, Acidobacteria, Actinobacteria, and Planctomycetes, which are key players in hydrocarbon bioremediation. We observed the presence of eleven hydrocarbon-degrading genes through M5nr analysis. These genes encompass essential catalysts for aliphatic hydrocarbon degradation and hydrocarbon desulfurization. Notably, these enzymes/genes include Bacterial Flavin-bound Monooxygenase (AlmA), Alkane Monooxygenase (AlkM), Alpha Ketoglutarate Dependent Dioxygenase (alkB), Propane Monooxygenase (PrM), Cytochrome P450 (cP450), Methane Monooxygenase/Ammonia Monooxygenase (MMO/AMO) subunits A, B, and C, Alkane Sulfonate Monooxygenase (ssuD), Alkane Sulfonates Transport System Permease Protein (ssuC), Dibenzothiophene Monooxygenase (dszC), Dibenzothiophene-Sulfone Monooxygenase (dszA), and Dibenzothiophene-5,5-Dioxide Monooxygenase (dszB). These genes play pivotal roles in the degradation of aliphatic hydrocarbons and hydrocarbon desulfurization. Interestingly, unique gene expression patterns were observed for each amendment, with Actinomycetales and Bulkhoderiales orders expressing the majority of identified genes. These findings have revealed the amendment-specific microbial and genetic alterations and, the diversity and potential of the annotated genes induced by the Bacillus altitudinis-Cropped Biofertilizers (biosolid and BSG amendments) for effective remediation of hydrocarbon-contaminated soils.