The mitigating effects and mechanisms of Bacillus cereus on chronic cadmium poisoning in Litopenaeus vannamei based on histopathological, transcriptomic, and metabolomic analyses.

ABSTRACT

Shrimp are non-negligible victims of cadmium (Cd) contamination, and there is still a lack of strategies for mitigating Cd toxicity in shrimp. Bacillus cereus, with its significant heavy metal (HM) tolerance and chelating effects, is a representative beneficial bacterium to be investigated for mitigating the toxicity of Cd exposure. This study revealed the effects and potential mechanisms of B. cereus in mitigating chronic Cd toxicity in shrimp by analyzing growth performance, hepatopancreatic Cd accumulation, pathology, as well as comprehensive hepatopancreatic transcriptomics and metabolomics in Litopenaeus vannamei. The results showed that shrimp's growth inhibition, hepatopancreatic Cd accumulation and physiological structure damage in B. cereus+chronic Cd group were effectively alleviated compared with the chronic Cd treatment group. The pathways related to amino acid metabolism, glycolipid metabolism, immune response, and antioxidant stress were significantly activated in the B. cereus+chronic Cd group, including glycolysis, pentose phosphate pathway, oxidative phosphorylation, biosynthesis of amino acids, and biosynthesis of unsaturated fatty acids pathways. The key differentially expressed genes (e.g., macrophage migration inhibitory factor, glycine cleavage system H protein, glycine dehydrogenase, phosphoglucomutase-2, asparaginase, ATP synthase subunit, cytochrome c, and 4-hydroxyphenylpyruvate dioxygenase) and metabolites (e.g., L-leucine, D-ribose, gluconic acid, 6-Phosphogluconic acid, sedoheptulose 7-phosphate, 1-Kestose, glyceric acid, arachidic acid, prostaglandins, 12-Keto-tetrahydro-leukotriene B4, and gamma-glutamylcysteine) associated with the above pathways were significantly altered. This study demonstrated that B. cereus is an effective mitigator for the treatment of chronic Cd poisoning in shrimp. B. cereus may play a role in alleviating the toxicity of Cd by enhancing the antioxidant performance, immune defense ability, metabolic stability, and energy demand regulation of shrimp. The study provides reference materials for the study of B. cereus in alleviating Cd toxicity of shrimp and broadens the application of probiotics in treating HM toxicity.