Hydrocarbons have been shown to both inhibit and stimulate soil ureolysis, indicating under certain pollution conditions indigenous ureolytic communities perform better than in absence of contaminants, pointing to an unresolved adaptation mechanism. In this study we conducted a molecular investigation on ureC gene expression of model Microbial-Induced Calcite Precipitation (MICP) bacterium Sporosarcina pasteurii during growth under increasing concentrations of hydrocarbon water extracts obtained from a coal tar polluted soil to ensure environmental relevance. Results indicated S. pasteurii ability to carry out ureolysis from low initial cell concentration (OD 600, initial = 0.01). Flow cytometry showed insignificant differences in growth despite undergoing significant cell membrane damage at the highest hydrocarbon concentration. Quantification of ureC gene revealed a significant increase in urease transcription per unit cell with increasing hydrocarbon concentration, indicating higher urease synthesis to maintain similar ureolysis rates. We postulate this adaptation mechanism was in response to the nitrogen deficiency caused by intracellular urease inhibition by hydrocarbons. The temporal dynamics in ureC gene expression indicated urease transcription in S. pasteurii was inductive rather than constitutive. This gene up-regulation mechanism resulted in earlier ureolysis and achievement of environmental conditions favourable for calcium carbonate precipitation compared to the absence of hydrocarbons. The results of this study could elucidate the underlying mechanism leading to enhanced soil ureolysis observed under certain hydrocarbon pollution scenarios. • Sporosarcina pasteurii thrives in heavily polluted hydrocarbon environments. • Cellular urease enzyme synthesis increases with increasing hydrocarbon concentration to compensate for urease activity inhibition • Cellular response maintains bulk ureolysis rates and achieves conditions for MICP earlier
Comadran-Casas et al. (2026) studied this question.