Priestia megaterium reduces hydrogen sulfide level in swine manure potentially through an assimilatory mechanism and microbiota modulation

Noxious odors from swine farms pose significant health and environmental concerns. Hydrogen sulfide (H₂S) is one of the major compounds causing noxious odors. Using biological inoculants offers a promising, efficient, and cost-effective method to reduce H₂S emissions from these farms. Several studies have found that Priestia megaterium (formerly Bacillus megaterium) can help mitigate the production of H₂S. However, detailed knowledge regarding its mechanisms of action is still limited. In this study, the potential of novel strain of P. megaterium, strain S188, for the reduction of H₂S in swine manure has been demonstrated. The artificial manure-based assay revealed that P. megaterium S188 significantly reduced the headspace concentration of H₂S. Moreover, transcriptomic analysis revealed that exposure to H₂S upregulated the expression of several cysteine and methionine biosynthesis-related genes in P. megaterium S188. Furthermore, treatment of swine manure with P. megaterium S188 was associated with significant modulation of the microbiota in the manure. Overall, this study provides insights into the putative mechanisms underlying the reduction in H₂S levels mediated by P. megaterium S188 and its potential as a biological inoculant for H₂S mitigation in swine farms. KEY POINTS: • Priestia megaterium S188 has shown the ability to lower H₂S from swine manure. • Transcriptomic analysis revealed upregulation of H₂S-related biosynthesis genes. • P. megaterium S188 treatment is associated with changes in the manure microbiota.